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Listening to Fish
Passive Acoustic Applications in Marine Fisheries
8-10 April 2002
An International Workshop on the Applications of
Passive Acoustics in Fisheries
Massachusetts Institute of Technology
Cambridge, MA
Conference Proceedings
TABLE OF CONTENTS
Listening to Fish: Proceedings of the International Workshop on the
Applications of Passive Acoustics to Fisheries
Rodney Rountree, Cliff Goudey, and Tony Hawkins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Locating sciaenid spawning aggregations in anticipation of harbor modifications,
and reactions of spotted sea trout spawners to acoustic disturbance
Mark Collins, Bridget Callahan, Bill Post, and Amanda Avildsen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Characterization of sounds and their use in two sciaenid species: weakfish and Atlantic croaker
Martin A. Connaughton, Michael L. Lunn, Michael L. Fine, & Malcolm H. Tayor. . . . . . . . . . . . . . . . . . . . 15
Detection and characterization of yellowfin and bluefin tuna using passive acoustical techniques
Scott Allen and David A. Demer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Acoustic Competition in the Gulf Toadfish Opsanus beta:Crepuscular Changes & Acoustic Tagging
Michael L. Fine and Robert F.Thorson . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Passive Acoustic Field Research on Atlantic Cod, Gadus morhua L. in Canada
Susan B. Fudge and George A. Rose. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Passive Acoustic Transects: Mating Calls and Spawning Ecology in East Florida Sciaenids
R. Grant Gilmore, Jr.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
The Use of Passive Acoustics to Identify a Haddock Spawning Area
Anthony D. Hawkins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Using a Towed Array to Survey Red Drum Spawning Sites in the Gulf of Mexico
Scott A. Holt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Fish Courtship and Mating Sounds
Phillip S. Lobel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Using Passive Acoustics to Monitor Spawning of Fishes in the Drum Family (Sciaenidae)
Joseph J. Luczkovich and Mark W. Sprague . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Are acoustic calls a premating reproductive barrier between two northeast Atlantic cod (Gadus
morhua) groups—a review
Jarle Tryti Nordeide and Jens Loss Finstad . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
Applications of underwater acoustics data in fisheries management for
spotted seatrout, Cynoscion nebulosus, in estuaries of South Carolina
Bill Roumillat and Myra Brouwer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
Soniferous Fishes of Massachusetts
Rodney Rountree, Francis Juanes, and Joseph E. Blue. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
The mating behaviour of Atlantic cod (Gadus morhua).
Sherrylynn Rowe and Jeffrey A. Hutchings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
Spotted Seatrout Spawning Requirements and Essential Fish Habitat: A Microhabitat
Approach Using Hydrophones
Donald M. Baltz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
Creating a Web-based Library of Underwater Biological Sounds
Jack W. Bradbury and Carol A. Bloomgarden. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
Potential for coupling of underwater TV monitoring with passive acoustics
Charles A. Barans, David Schmidt, Myra C. Brouwer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
Application of Passive Acoustic Methods for Detection, Location and Tracking of Whales
Christopher W. Clark. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
Passive Detection and Localization of Transient Signals from Marine Mammals using
Widely Spaced Bottom Mounted Hydrophones in Open Ocean Environments
Susan Jarvis and David Moretti . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
Multihydrophone localization of low frequency broadband sources
Stephen E. Forsythe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
Synchronized underwater audio-video recording
Phillip S. Lobel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
New technologies for passive acoustic detection of fish sound production
David A. Mann . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
A remote-controlled instrument platform for fish behaviour studies and sound monitoring
Ingvald Svellingen, Bjørn Totland and Jan Tore Øvredal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
Potential for the use of Remotely Operated Vehicles (ROVs) as a platform for passive acoustics.
Rodney Rountree, Francis Juanes, and Joseph E. Blue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
Quantifying Species-Specific Contributions to the Overall Sound Level
Mark W. Sprague and Joseph J. Luczkovich. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147
Classifying Fish Sounds Using Wavelets
Mark Wood. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154
A summary report on the Biology Session and Biology Working Group from the International
Workshop on the Application of Passive Acoustics in Fisheries.
Joseph J. Luczkovich . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
Working Group on Technology Issues
David Mann . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168
Acknowledgements
Edited by Rodney Rountree
1
,Cliff Goudey
2
,Tony Hawkins
3
,Joeseph J. Luczkovich
4
and David Mann
5
1
School for Marine Science and Technology,UMASS Dartmouth,706 South Rodney French Blvd.,New
Bedford,MA 02744
2
Center for Fisheries Engineering Research,MIT Sea Grant College Program,Bldg.NE20-376,3
Cambridge Center,Cambridge,MA 02139
3
Environment & Society at the University of Aberdeen,St Mary's,Kings College,Aberdeen,AB24 3UF,
UK
4
Institute for Coastal and Marine Resources (Old Cafeteria Complex) Department of Biology (Howell
Science Complex N-418),East Carolina University,Greenville,NC 27858
5
USF College of Marine Science,140 Seventh Avenue South, St.Petersburg,FL 33701-5016
Special thanks to Diane Rittmuller and Frank "Chico" Smith,School for Marine Science and
Technology (SMAST),UMASS Dartmouth for additional editing support.
Based on the International Workshop on the Applications of Passive Acoustics to Fisheries,
April 8-10,2002,sponsored by MIT Sea Grant College Program,Office of Naval Research (ONR Code
342,Marine Mammal S&T Program),and National Undersea Research Program,with additional sup-
port from SMAST,UMass-Dartmouth, Connecticut Sea Grant,Florida Sea Grant,Hawaii Sea Grant,
Louisiana Sea Grant,North Carolina Sea Grant,South Carolina Sea Grant Consortium,Texas Sea Grant
and Woods Hole Sea Grant.
Listening to Fish: Proceedings of the International Workshop on the
Applications of Passive Acoustics to Fisheries
Rodney Rountree
1
,Cliff Goudey
2
, and Tony Hawkins
3
1
School for Marine Science and Technology, UMASS Dartmouth, 706 South Rodney French Blvd, New
Bedford, MA 02744
2
Center for Fisheries Engineering Research, MIT Sea Grant College Program, MIT Bldg. NE20-376,
3 Cambridge Center, Cambridge, MA 02139
3
Kincraig, Blairs, Aberdeen, Scotland AB12 5YT
Workshop Objectives
1. Convene an international conference to assess the potential of passive acoustics as a tool with
applications in fisheries and marine conservation in estuarine, coastal and oceanic ecosystems.
2. To promote the use of passive acoustics for exploring the oceans, surveying marine biodiversity,
and assessing the impact of man’s activities upon the oceans.
3. Develop an international research initiative to explore and extend the use of passive acoustics
in the marine sciences in both applied and non-applied fields, and to develop potential
research theme areas for future funding.
Introduction
On April 8-10, 2002, MIT Sea Grant hosted an international workshop on the application of passive
acoustics in fisheries in Dedham, Massachusetts.The ‘hands-on’ workshop drew over 40 European
and North American experts from fisheries, fish biology, acoustics, signal processing, underwater
technology and other related fields. The workshop was divided into 4 sessions and 2 working
groups with a total of 29 presentations delivered.The first session entitled:“Passive Listening for
fishes - what has been done?” reviewed past and current research activities, while the second ses-
sion “Future developments and applications” examined recommendations for future research and
examples where existing programs could be enhanced by passive acoustic technology. The third
session “Acoustic technology” reviewed the state of the art and future developments for underwater
acoustic and related technologies. A special session included demonstrations of hardware and soft-
ware. The workshop was caped off by a working group on the biological and ecological aspects of
passive acoustic research, moderated by Joe Luczkovich of East Carolina University, and a working
group on technology and software issues moderated by David Mann of the University of Southern
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Florida in St. Petersburg. A web page was constructed to document the findings of the workshop
(http://web.mit.edu/seagrant/acoustics/index.html).
The workshop was a great success at bringing together an outstanding group of international
researchers to exchange research results, knowledge and ideas related to the application of passive
acoustics to fisheries, census of marine life and related issues. The workshop demonstrated the high
potential of passive acoustics as a research tool for fisheries and related fields through the presenta-
tion of the results of a number of successful research projects. One of the important outcomes of
the workshop was the exchange of information about ongoing and past research projects that have
successfully used passive acoustics. Previously, many of these scientists had been working in isola-
tion with little interaction with their colleagues working across North America and overseas. The
fisheries biologists participating in the workshop also gained valuable insight from exchange of
information with scientists with well-established backgrounds in the use of passive acoustics to
study marine cetaceans (see Clark, Jarvis and Moretti, herein). Another important result was the
exchange of hardware and software technologies among the participants. The workshop has
already fostered renewed enthusiasm among the participants for this field of research and has
resulted in new domestic and international collaborations. In addition, the workshop brought
researchers together with administrators, staff and scientists from several funding agencies and with
the media (e.g., NURP, National Geographic, etc.). Finally, extensive discussion of the future research
priorities for passive acoustics, and development of both domestic and international collaborations,
are expected to go a long way towards promoting the application of passive acoustic technology to
fisheries and related fields. Some of the most important research initiatives identified by the work-
shop participants were: 1) the importance of developing a national database of historic underwater
sound archives (see Bradbury and Bloomgarden, herein), 2) the importance of establishing a
National/International Reference Library of fish sounds, which would be guided by an international
panel of scientists drawn in part from the workshop participants, 3) the importance of establishing
an international research and training center for passive acoustics applications to fisheries and
marine census (potentially at Grant Gilmore’s Laboratory at the Kennedy Space Center), and 4) the
importance of active promotion of the technology through publications of the workshop proceed-
ings and related articles. Many more specific research needs in biology and technology were
addressed and are presented throughout these proceedings.
Background
Fish are difficult to see and study in the ocean. SCUBA techniques can help in shallow waters and a
range of active acoustic and optical techniques can assist in deep water, but we are still largely igno-
rant of the distribution and behavior of the great majority of marine fish. Possibly one of the great-
est challenges to researchers attempting to study the behavioral ecology of fishes is that of finding
the fish in the first place. Often a scientist must go to great lengths conducting expensive and time
consuming biological surveys simply to determine the locations or habitats where a fish can be
found, before any attempt to study its biotic and abiotic interactions can be made. After all, you
can’t study something you can’t find. Any tool that can help scientists to locate fish is therefore
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
valuable. Fish too face the problem of assessing their environment, navigating through it, and com-
municating with others of their kind. A surprisingly large number use sound to overcome the prob-
lem of living in a visually opaque medium.
Over 800 species of fishes from 109 families worldwide are known to be vocal, though this is likely
to be a great underestimate. Of these, over 150 species are found in the northwest Atlantic (Fish
and Mowbray 1970
1
). Amongst the vocal fishes are some of the most abundant and important com-
mercial fish species, including cod, haddock and the drum fishes (sciaenidae).
Passive acoustics offers a unique tool to study these fishes, which often live in dark and turbid
waters and are difficult to observe by other means. Passive acoustic techniques can be used to
locate concentrations of particular species, especially during their vulnerable spawning stage. This
in turn allows spawning habitat to be identified, mapped, and protected. It can allow the numbers
of fish to be assessed. And it can be used to gain a better understanding of fish behaviour, includ-
ing fish migrations. Passive acoustics can also be used to simultaneously monitor sources of noise
pollution, and to study the impact of man’s activities on marine communities. Anthropogenic
sources include noise generated by boating activity, seismic surveys, sonars, fish-finders, depth find-
ers, drilling for oil and gas, and military activities. These all have an unknown but potential impor-
tant impact on marine fauna. We believe that passive acoustic technologies hold special promise
and will become important tools in the coming years. However, it has been largely ignored in the
northwest Atlantic in the study of fishes important in the marine food chain. It is also a technique
that is amenable to cooperative research with commercial fishermen, who can bring their own
knowledge to such studies.
Applications to Fisheries
Sounds travel much farther in water than light and underwater sounds, including fish calls, can
often be heard over much greater distances than fish can be seen. Listening to fish can contribute a
great deal to our knowledge of their abundance, distribution and behavior. Passive acoustics stud-
ies using relatively simple techniques have been successful in locating concentrations of important
fish species, opening the way for further, more detailed studies of their behavior, distribution and
habitat use. As reflected in the various research programs described within this proceedings,
already significant strides have been taken in the application of passive acoustics to fisheries:
* in an Arctic fjord in northern Norway, workers from the FRS Marine Laboratory, Aberdeen and
the University of Tromsø have located a spawning ground of haddock, Melanogrammus aeglefi-
nus.Passive listening has revealed that this species, previously thought to spawn offshore in
deep water, can also form large spawning concentrations close to shore (see Hawkins).
*Norwegian researchers are using passive acoustics to study spawning behavior of Atlantic cod
and other gadids (see Nordeide and Finstad, Svellingen et al.).
*a number of studies in the estuaries of the eastern United States have helped to localize the
spawning areas of drum fishes and demonstrating the usefulness of passive acoustics as a tool
for identification of essential fish habitat requirements, as well as a tool to provide fisheries
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
managers with information of sciaenid reproductive biology (see Collins et al., Gilmore, Holt,
Luczkovich and Sprague, Roumillat and Brower).
*for the first time in the United States passive acoustics are being explored as a tool to census
marine fishes on the continental shelf. In one study, a towed hydrophone array is being used to
identify spawning sites of red drum in the western Gulf of Mexico (see Holt). In another study,
passive acoustics are being used to catalogue soniferous fishes in the Stellwagen Bank National
Marine Sanctuary (see Rountree et al., Rountree and Juanes). One goal of the study is to deter-
mine the feasibility of using passive acoustics as a supplemental tool in the census of fish diver-
sity and habitat use patterns in the sanctuary.
* an ongoing survey of soniferous fishes of Massachusetts has resulted in a significant range
extension for the cryptic estuarine and inshore fish, the striped cusk-eel, Ophidion marginatum
(see Rountree and Juanes). Extensive sampling over many decades with conventional gears in
the region had failed to recognize the importance of striped cusk-eel to the fauna, while pas-
sive acoustics revealed it to be widespread and abundant.This study demonstrates that even a
low-budget, low-tech, approach to passive acoustics can contribute significantly to the census
of marine life.
New Technology
Studies described at the workshop have pushed technology to new levels that will allow researchers
to expand the frontiers of fisheries science and ocean exploration:
* the potential for combining hydrophone arrays with other underwater census technologies is
being explored, including ROVs (see Rountree et al., Luczkovich and Sprague), underwater video
(see Svellingen et al., Lobel, Barans et al.) and active acoustics (Fudge and Rose). Lobel has pio-
neered the use of advanced SCUBA technologies for studies of fish vocal behavior.
* researchers are beginning to look towards existing acoustic arrays maintained by the Navy and
other agencies for applications to fishes (see Jarvis and Moretti).
* Advances are being made in the development of modeling tools and software for tracking
vocal fish (see Forsythe) and identifying individual fish (see Wood).
* New technologies for detecting and recording underwater sounds are rapidly evolving (see
Mann).
* Historic archives of fish sounds are being assembled and rescued from deterioration and will be
made available to researchers and the public through the internet (see Bradbury and
Bloomgarden). The establishment of internet access to libraries of fish sounds is an important
step to more widespread use of passive acoustics in fisheries science and related fields.
The Future of Passive Acoustics
Although studies described during the workshop reflect the rapid growth of research on passive
acoustics applications to fisheries and marine census, there are many areas where technical devel-
opments are needed to promote future research:
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Software
* the development of sound recognition systems, based on wavelet analysis and other new tech-
niques to enable the automatic discrimination of different species. For a north Atlantic species,
the haddock, it has already proved possible to distinguish the voices of individual male fish (see
Wood).
* automatic event detection/analysis software to quantify temporal patterns of sounds over long
time periods.
* localization/tracking software (see Forsythe).
* software allowing simultaneous analysis of video and audio data in behavior studies (i.e., click
on the sound wave of a fish call and view the corresponding video frame in a second window).
This capability would allow rapid correlations of individual sounds and sound components with
behavior and functional morphology.
The improvement of passive listening technology for systematically detecting and recording sounds
at sea, including:
* ship based listening systems, with dangling and towed hydrophones.
* bottom mounted listening systems based on underwater vehicles and pop-up buoys.
* drifting sonobuoy systems, either storing the data, or telemetering data to ships or shore-based
listening stations.
* large hydrophone arrays, capable of localizing sound sources.
* measurement of source levels, and calibration techniques for measuring the distance of sound
sources.
Back-yard science: Perhaps of equal importance to passive acoustics systems for use in the open
ocean is the development of technology to aid in small scale, low budget studies of marine fishes in
estuarine and inshore habitats. We feel that passive acoustics have a great potential as a tool to pro-
vide basic information on essential fish habitat use patterns, as it becomes more widely used in
classrooms and State and Federal sampling programs. Several studies presented at the workshop
demonstrate the usefulness of this type of research to fisheries. A good example of this is the dis-
covery, using passive acoustics, that striped cusk-eels are abundant in Massachusetts estuaries,
where despite a long history of conventional sampling in the region, the species was thought to be
a very rare straggler. Technologies to aid this type of research include:
* archival acoustic recorders - unmanned recorders for use on ships of opportunity in many types
of habitats.
* homing devices to locate sound sources (see Forsythe, Rountree et al.).
* devices that allow simultaneous recording of both audio and video data.
* hand-held devices for shore based, or small boat surveys in shallow water.
* miniature ROV designed for both video and audio recording of fish behavior from small boats
and from shore.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Application of passive acoustics in a wider range of habitats where fish may aggregate to spawn.
For example:
* mangrove areas, which are especially difficult to survey by conventional means, but where the
diversity of fishes may be especially high.
*coral reefs and rocky reefs, where again many species aggregate.
*oceanic and inshore banks, where the mass spawning of sound producing species, like cod and
haddock, takes place.
* the deep sea, where many species like the morids and macrourids are suspected to be vocal
from anatomical evidence.
* estuaries - the primary spawning grounds for many economically important fishes.
Development of local, regional, national and international networks of “listening posts” especially in
estuarine and inshore waters. Incorporation of listening posts into local and regional environmental
data networks like GoMOOS and the NOAA/OCRM/NERR’s System Wide Monitoring Program.
The Benefits of Passive Acoustics
* non-invasive, non-destructive census of marine life.
* works at night without bias (versus video and other techniques that require lights).
* can provide continuous monitoring of fishes.
* provides remote census capabilities.
* determine the daily and seasonal activity patterns of fishes including determination of discrete
daily spawning times.
* a better foundation for the management of exploited species by mapping their distribution
and pinpointing their spawning grounds.
* a better understanding of the habitat preferences of key fish species (e.g., Essential Fish Habitat
“EFH” assessment in the US), giving a better focus for their conservation.
* establishment of baselines for the abundance and distribution of key fish species, allowing
examination of the effects of future environmental change.
* obtaining a wider knowledge of the behavior of those fish that cannot readily be studied by
any other method.
* can be used to monitor environmental noise and determine their sources.
* can be used to examine the impact of anthropogenic noise on fish, especially on spawning
behaviors.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
* networks of listening posts can provide synoptic data on the occurrence of fishes and spawn-
ing activities on local, regional, national and global scales.
Conclusion
Research presented at this workshop underscores the great strides that have been made in the
application of passive acoustics to fisheries and related issues in the last two decades. It is clear
from this body of work, that although passive acoustics is currently largely overlooked as a research
tool, it is a rapidly “up-and-coming” field of research that holds great promise for the future. It is our
hope that publication of this proceeding will stimulate the growth of this field, and will encourage
funding agencies to support passive acoustics research.
Acknowledgements
This workshop and the publication of the proceedings benefited by contributions from many indi-
viduals. Grace Lee set up the web page and did much of the text and graphics layout for the pro-
ceedings. The staff of the Endicott House and Brooks Center provided outstanding conference facil-
ities and support for the workshop. The workshop and publication of the workshop proceedings
received major funding from MIT Sea Grant, the Office of Naval Research, and from the Northeast-
Great Lakes Center of the National Undersea Research Program. Travel for some workshop partici-
pants was funded in-whole, or in-part by: Connecticut Sea Grant, Florida Sea Grant, Hawaii Sea
Grant, Louisiana Sea Grant, North Carolina Sea Grant, the South Carolina Sea Grant Consortium,
Texas Sea Grant, and the Woods Hole Sea Grant Programs.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Locating sciaenid spawning aggregations in anticipation of harbor modifica-
tions, and reactions of spotted sea trout spawners to acoustic disturbance
Mark Collins, Bridget Callahan, Bill Post, and Amanda Avildsen
SC Marine Resources Research Institute, SCDNR, Charleston, SC, USA
Introduction
The estuarine-dependent sciaenids are by far the most recreationally (= economically) important
fishes in the Savannah River (SC/GA, USA) estuary. Regional populations of the primary species have
declined in abundance in recent years amid concerns about reduced spawning stock biomass. Most
southern states have responded by tightening harvest regulations.
Plans for major modifications and deepening of the Savannah Harbor and shipping channel have
generated special concerns about exacerbating sciaenid spawning stock reductions due to: 1) direct
dredging mortality; 2) acoustic disruption of spawning aggregations; or, 3) reducing the acceptabili-
ty to the fish of any presently utilized spawning sites through alterations to the bathymetry, flow
characteristics, etc.
The estuaries of SC, GA, and northern FL differ in a number of ways (e.g., higher tidal amplitudes, no
seagrasses) from those to the north and south, and there are reasons to believe that sciaenid
spawning behavior may also differ. Studies of sciaenid spawning in this central region have been
limited in number, producing for example only three red drum spawning locations: two in SC and
one in GA. No studies have been conducted in the Savannah River. Thus, a passive acoustic survey
was initiated to define the geographic and temporal distribution of spawning aggregations of the
recreationally important sciaenid species, determine site fidelity between years, characterize spawn-
ing habitats, and determine effects of dredging activity on aggregations.
Methods
An acoustic survey was conducted during August- November 2000 and February-November 2001 in
the Savannah River estuary, with some coverage of the shipping channel offshore. A directional
hydrophone, analog receiver, and audio recorder were used to detect and record signals, and specif-
ic locations of spawning sites were determined through triangulation. Signal strength (quantified
on a 1-5 scale), prominent bathymetric/structural characteristics, light phase, tide stage, current
velocity, depth, temperature, salinity, and dissolved oxygen were recorded for each location. Field
activities were conducted on average 3 days/week. Emphasis was on the lower estuary where salini-
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
ties were >15 ppt, but occasional broader surveys were conducted to ensure that no spawning
activity was occurring farther upriver.
During June 2001, preliminary dredging operations began in one turning basin in the lower harbor,
which had been identified as the location of one of the primary spawning aggregations of spotted
seatrout. The reaction of the spawning aggregation to dredging activity was monitored through
the end of the spawning season.
Results
Recreationally/economically important sciaenids encountered included red drum Sciaenops ocella-
tus,spotted sea trout Cynoscion nebulosus,black drum Pogonias cromis, and weakfish Cynoscion
regalis.Sporadic drumming of all species occurred in various locations of the lower estuary.
However, six primary spawning sites were identified for spotted seatrout, one for weakfish, and one
for black drum. All sites were in salinities > 16 ppt, and all were within 12.2 river km of the river
mouth.
Time of day of spawning varied somewhat among species, but in general it appeared to be
anchored around sunset with peak activity from about 1 hr before through about 3 hr after. This
was especially evident with spotted seatrout, which had the longest spawning season. As day
length shortened and sunset occurred progressively earlier at the end of the summer, spawning
activity began earlier.
Spotted seatrout spawning activity took place during May-September, peaking in July-August.
Water temperature apparently was a seasonal spawning cue, as activity ceased abruptly and did not
resume when there was a 2
o
C drop to 24
o
C over a 2-day period (although spawning in lower tem-
peratures has been previously reported). All six sites located in 2000 were again used in 2001, but
activity did not begin at all sites simultaneously.The sites had several characteristics in common:
they were in the main river channel rather than side-creeks, they were in or adjacent to deep water
(7-10 m), and they were associated with structure of some type. Structure varied among sites, but
was generally a large channel marker or a rocky area such as a submerged jetty. Drumming activity
appeared strongest when a high or early ebb tide occurred during the appropriate time of day.
Black drum spawned during late March to mid-June at river km 0 (the river mouth) in water temper-
atures of 14-19
o
C. Weakfish spawning activity was concentrated just upriver at river km 2 during
June to early October at temperatures of 23.9-29.0
o
C. Weakfish appeared to be less site-specific
than black drum or spotted seatrout, with the aggregation sometimes moving temporarily upriver
and then returning. Weakfish also tended to aggregate around structure like spotted seatrout,
although more weakly, while black drum aggregated in the middle of the channel where no struc-
ture could be detected.
No large red drum spawning aggregations were located. A number of times, individuals or very
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
small groups of drumming males were found. This was most consistently at the mouth of the river
and in the shipping channel outside the mouth. All activity noted was during August-September.
The active dredge in the vicinity of a large spotted seatrout aggregation began operations at the
upriver end of the turning basin, the opposite end from the aggregation, and moved slowly down-
river. No changes in drumming intensity or periodicity relative to the dredge were noted. However,
the spawning season ended (as confirmed by checking other known spawning sites) before the
dredge actually reached the fish; it was ~100 m away at that point. Large and small vessels transited
the area but did not disturb the fish. One acoustic disturbance that was dramatically apparent, how-
ever, was a total cessation of drumming when bottlenose dolphin Tursiops truncatus (which make a
pronounced acoustic signal) passed by. This behavior was also noticed on two occasions with red
drum.
Discussion
Passive acoustic mapping of sciaenid spawning sites in preparation for harbor modifications was
successful. It confirmed spawning of important sciaenid species within the harbor area, and it
defined the spawning temporally and spatially. There was considerable temporal overlap in spawn-
ing activity among species, and in the lower 2 river km there appeared to be spatial overlap.
However, on a finer scale (hundreds of meters) there was little or no overlap. It is obvious, however,
that the lower 2 river km can be considered the most important sciaenid spawning area in the
Savannah estuary, as all four species aggregated in that stretch of river. Aggregations of red drum
were very small. Comparing this behavior to previous reports from the region is problematic due to
the limited number of systems that have been studied; the aggregation in Charleston Harbor, SC
was quite large, while the aggregation detected in St. Helena Sound, SC was very small. Thus, it is
not known whether red drum typically form large aggregations in this region, or if in some systems
they generally spawn in small groups.
Despite the apparent importance of acoustic signals in spawning aggregations for these species,
noise from boats, dredges, etc. does not interfere with drumming behavior, even when the source of
the noise is close by. Certainly, these fish must be acclimated to vessel passage due to the fact that
the Savannah River is a major port. It is unknown whether fish in a less populous habitat would be
so impervious to anthropogenic noise. The only response to an acoustic signal was exhibited
toward bottlenose dolphin, which prey on these fishes; the cessation of drumming was apparently a
predator avoidance behavior.
While spotted seatrout males do not respond to dredging noise, it is unknown what effect a dredge
would have as it worked in the midst of the aggregation. Relatively large fishes (e.g., Atlantic stur-
geon Acipenser oxyrinchus) are reported with some regularity having been sucked up by dredges
elsewhere. Further, because two (and possibly three) of these species appear to cue in on struc-
tures, removal of these structures, as commonly occurs during deepening and channelization opera-
tions, may have a negative impact. Future research plans include statistical analyses of environmen-
tal variables as related to drumming activity, and re-examination in 2002 of spotted seatrout spawn-
ing behavior in the turning basin that was dredged in 2001.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Acknowledgments
Hayne von Kolnitz assisted extensively in both field and laboratory. Bruce Stender verified identifi-
cations of larval fishes. Joseph Luczkovich (East Carolina University), Mark Spraque (East Carolina
University), Archibald McCallum (University of Charleston), Grant Gilmore (Dynamac Corp.), and Bill
Roumillat provided invaluable assistance in verifying species identifications from acoustic record-
ings of aggregations. South Carolina Department of Natural Resources, Georgia Ports Authority, and
Southern Liquid Natural Gas provided funding.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Characterization of sounds and their use in two sciaenid species: weakfish and
Atlantic croaker
Martin A. Connaughton
1
,Michael L. Lunn
1
,Michael L. Fine
2
,& Malcolm H.Tayor
3
1
Washington College, 300 Washington Ave., Chestertown, MD 21620 mconnaughton2@washcoll.edu,
milunn@yahoo.com
2
Department of Biology, Virginia Commonwealth University, Richmond,VA 23284-2012, USA,
mfine@atlas.vcu.edu.
3
College of Marine Studies and Department of Biological Sciences, University of Delaware, Newark,
DE 19716, USA, mtaylor@udel.edu.
Introduction
Both weakfish Cynoscion regalis and Atlantic croaker Micropogonias undulatus are members of the
family Sciaenidae, a group of fish that have been known to produce sound since the turn of the
20th century. This family of fishes produces sound through the use of highly specialized, extrinsic
sonic muscles which lie in close proximity, but are not attached to, the swimbladder (Tower 1908,
Tavolga 1964). In weakfish and most sciaenids, sonic muscles are found only in the male; however, in
others, including Atlantic croaker, the muscles are found in both males and females (Tower 1908,
Fish and Mowbray 1970). Sound production has been linked to reproductive behavior in a number
of sciaenid species (Fish and Cummings 1972, Guest and lasswell 1978, Mok and Gilmore 1983,
Saucier and Baltz 1993) and with fright or warning behaviors in a few species, including Atlantic
croaker (Fish and Mowbray 1970). The purpose of this paper is to characterize the sounds produced
by two species of sciaenid and to discuss the roles of these sounds in the behaviors of these species.
Methods and Results
Weakfish experiments
Field recordings:Field recordings using a hydrophone (Edmund Scientific) were made near the
mouth of the Delaware Bay at three stations along an inshore-offshore transect ranging from 1.24
to 5.64km from shore and varying in depth from 3.5 to 7.8m. One-minute recordings were made at
hourly intervals over a 24hr period on eight dates from mid-April through mid-August, encompass-
ing the late spring-early summer spawning season. Recordings of drumming sounds were ranked
qualitatively from 0 - 4, with 0 representing no calls and 4 representing continuous calling by a cho-
rus of individuals (Connaughton and Taylor 1995).
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Drumming was highly seasonal, increasing dramatically from zero in mid-April to nearly maximal
levels in early May. Activity remained at near maximal levels throughout May and June, and
decreased gradually in intensity through July and into August. Physiological indicators of reproduc-
tive readiness, including plasma androgen levels, male GSI, and the presence of hydrated eggs were
all high during the period of maximal drumming activity. Drumming activity also expressed diel
trends, reaching maximal levels between 20:00 and 24:00hr (sunset was between 19:50 - 20:40) and
declining to a minimum between 05:30 and 10:30hr. Drumming activity, whether seasonal or diel,
was most intense inshore, declining in intensity as one moved offshore (Connaughton and Taylor,
1995). The seasonality, evening timing, and inshore location of sound production all coincide with
the known reproductive activity of weakfish in this area (Villoso 1989,Taylor and Villoso 1994).
Captive spawning recordings: Captive weakfish held in a 1500L tank were induced to spawn with
two injections of 1000 IU hCG/kg body weight administered in the early afternoon on two succes-
sive days. Fish spawned during the evening of the second day of injections. Spawning activity was
documented on standard VHS tape with video (Ikegami CCD camera, ICD 4224) and audio (Edmund
Scientific) input (Connaughton and Taylor 1996). Field and captive sounds, staccato bursts of 6-10
individual pulses, were identical (Connaughton and Taylor 1996). It was also determined that domi-
nant frequency and repetition rate vary with temperature and fish size (Connaughton et al. 2000).
During courtship, only pair spawning was observed, though larger groups in larger enclosures
might behave differently. Drumming activity was most often initiated after the first spawning event,
but based on the timing of sound production and spawning in the field (Taylor and Villoso 1994,
Connaughton and Taylor 1995) this observation may be due to a tank effect. The number of drum-
ming bursts per minute varied somewhat between males, but remained relatively constant for a
given male for the duration of the evening’s sonic activity, i.e. number of bursts per minute did not
drop off as time passed after a spawning event. Sound production ceased prior to gamete release,
which was apparently synchronized by body contact.
Croaker experiments
Captive spawning recordings: As above, field caught Atlantic croaker were maintained in laboratory
tanks and induced to spawn following hormone injections, and video/audio recordings (B&W CCD
camera, OS-40D,World Precision Instruments; model C21 hydrophone, Cetacean Research
Technology) were made. To date, only a single successful trial, involving one male and two females,
has been conducted. The courtship behavior of the croaker was similar to that exhibited by the
weakfish: drumming began after the first spawning event, was maintained for several hours there-
after, and ceased just prior to gamete release.
Only the male produced courtship sounds, bursts of 1-3 pulses, with a mode of two pulses.
Dominant frequency for the single recorded male (33cm total length) was 300Hz and the repetition
rate of pulses within a burst was 5.4Hz. Courtship sounds were lower in frequency and repetition
rate than fright response sounds (see below). In addition, the number of drumming bursts per
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
minute decreased steadily following each spawning event, a behavioral characteristic not shared
with weakfish (Fig. 1).
Fright response recordings: Fright response recordings were made in a rectangular 1250L tank.
Sound production was elicited by casting a shadow over the surface of the holding tank, or moving
a dip net through the water. Thirteen fish, ranging in total length from 22.5 to 30cm were recorded,
and both male and female croaker called readily. The number of pulses per burst for fright response
calls varied more widely that in courtship calls,ranging from 1-9, though the mode was still two. In
contrast, the repetition rate of pulses within a burst was greater in fright response calls, ranging
from 7.87 to 33.56 pulses/sec and expressing a mean of 18.09. Repetition rate was more variable in
shorter bursts (2 or 3 pulses per burst) than in longer bursts (Fig. 2). Even given that dominant fre-
quency appears to vary with fish size (650 to 540Hz for 22.5 to 29cm total length fish), courtship
sounds appear to have a lower dominant frequency (approximately 100Hz lower for a 33cm fish)
(Fig. 3).
Discussion
Sound production in weakfish and croaker may be involved in the formation of spawning aggrega-
tions and/or attracting a mate, though because of the small tank size, this could not be determined
in our laboratory experiments (Connaughton and Taylor 1996). It may also play a role in female
mate selection, since larger individuals of each species produce a sound with a lower dominant fre-
quency (Connaughton et al. 2000). Though weakfish will produce sounds if drawn to the surface
when caught hook and line, or when removed from a tank into the air, we have never recorded a
fright response call from weakfish like those so easily elicited from Atlantic croaker. In-air ‘distur-
bance’ calls elicited from weakfish when they are removed from the water were identical to
courtship calls except for having a wider range of pulses in each burst of sound (Connaughton et al.
2000). In contrast, our data suggest that fright response and courtship calls in croaker may be quite
distinct in dominant frequency and repetition rate, though more data needs to be collected.
Acknowledgements
This work was supported by the Wallop-Breaux Sport Fishing Act with funds administered through
the Delaware Department of Natural Resources and Environmental Control and by in-house funding
provided by Washington College.
Literature Cited
Connaughton, M. A. and Taylor, M. H. (1995). Seasonal and daily cycles in sound production associat-
ed with spawning in the weakfish, Cynoscion regalis.Env.Biol. Fish. 42, 233-240.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Connaughton, M. A. and Taylor, M. H. (1996). Drumming, courtship, and spawning behavior in captive
weakfish, Cynoscion regalis.Copeia 1996, 195-199.
Connaughton, M. A.,Taylor, M. H. and Fine, M. L. (2000). Effects of fish size and temperature on weak-
fish disturbance calls: implications for the mechanism of sound generation. J. Exp. Biol. 203, 1503-
1512.
Fish, J. F. and Cummings,W. C. (1972). A 50-dB increase in sustained ambient noise from fish
(Cynoscion xanthulus). J. Acoust. Soc. Am. 52, 1266-1270.
Fish, M. P. and Mowbray, W. H. (1970). Sounds of western North Atlantic fishes. Baltimore:The Johns
Hopkins Press.
Guest,W. C. and Lasswell, J. L. (1978). A note on courtship behavior and sound production of red
drum. Copeia 1978, 337-338.
Mok, H. K. and Gilmore, R. G. (1983). Analysis of sound production in estuarine aggregations of
Pogonias cromis, Bairdiella chrysoura, and Cynoscion nebulosus (Sciaenidae). Bulletin of the Institute
of Zoology, Academia Sinica 22, 157-186.
Saucier, M. H. and Baltz, D. M. (1993). Spawning site selection by spotted seatrout, Cynoscion nebulo-
sus, and black drum, Pogonias cromis, in Louisiana. Env. Biol. Fish. 36, 257-272.
Tavolga, W. N. (1964). Sonic characteristics and mechanisms in marine fishes. In Marine bio-acoustics,
vol. 1 (ed.W. N.Tavolga), pp. 195-211. New York: Pergamon Press.
Taylor, M. H. and Villoso, E. P. (1994). Daily ovarian and spawning cycles in weakfish.Trans. Am. Fish.
Soc. 123, 9-14.
Tower, R.W. (1908).The production of sound in the drumfishes, the sea-robin and the toadfish. Ann.
N.Y. Acad. Sci. 18, 149-180.
Villoso, E. P. (1989). Reproductive biology and environmental control of spawning cycle of weakfish,
Cynoscion regalis (Bloch and Schneider) in Delaware Bay: University of Delaware, Newark, Delaware.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Illustrations and Diagrams
Figure 3. Dominant frequency of individual sound pulses plotted across specimen total length from sounds pro-
duced by male and female croaker (N=13) during fright response behaviors. The shaded block represents the domi-
nant frequency of calls made by the single male (33 cm) during courtship sound production.
0
5
10
15
20
-50 0 50 100 150 200 250
Number of calls minute
-1
Time from first spawning (min)
0
10
20
30
40
012345678910
Repetition rate (pulses sec
-1
)
Number of pulses per call
Figure 1. Croaker courtship sound production expressed as number of calls min-
1
across time. Values were deter-
mined for one minute out of every five recorded over the course of the evening. The solid vertical line represents the
first spawning event (9:29PM) and the double vertical line, the second (10:29PM).
Figure 2. Repetition rate plotted across number of pulses per call from sounds produced by male and female croaker
(N=13) during fright response behaviors. The shaded block represents the repetition rate and number of pulses
observed during courtship sound production.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Detection and characterization of yellowfin and bluefin tuna using passive
acoustical techniques
Scott Allen
1
and David A. Demer
2
1
Scripps Institution of Oceanography (allen@sdsioa.ucsd.edu)
2
NOAA/NMFS/SWFSC/Fisheries Resources Division, 8604 La Jolla Shores Drive, La Jolla, CA 92037
(david.demer@noaa.gov)
Introduction
Underwater sounds generated by Thunnus albacares and Thunnus thynnus were recorded and stud-
ied to explore the possibility of passive-acoustical detection. Tuna vocalizations were recorded at
the Monterey Bay Aquarium, Monterey, California, and Maricultura del Norte in Ensensada, Baja
California, Mexico. At both locations, the most prevalent sounds associated with tuna were low-fre-
quency pulses varying from 20 to 130 Hz, lasting about 0.1 seconds, and usually single and unan-
swered (Fig. 1). A behavior similar to coughing was coincident with these sounds: the animal’s
mouth opened wide with its jaw bones extended and its abdomen expanded, then contracted
abruptly. On one occasion in Mexico, this behavior and associated noise were simultaneously
recorded (Fig. 2). The center frequencies of these vocalizations may vary as the resonant frequencies
of the tuna’s swim bladder, suggesting a passive-acoustical proxy for measuring the size of tuna.
Matched-filter and phase-difference techniques were explored as means for automating the detec-
tion and bearing-estimation processes.
Conclusion
This study shows that adult bluefin and yellowfin tuna, like many other fish, are capable of generat-
ing sound.The acoustical signals are short (~0.1 s), narrow-bandwidth pulses of low frequency (20-
130 Hz) and amplitude (~105 dB re 1 _Pa @ 1m).
Observations of these fish suggest that a coughing or yawning behavior causes muscular contrac-
tion about the swim bladder and an associated short-duration sound pulse of narrow-bandwidth
and low-frequency and intensity. If the recorded sounds are generated by swim bladder resonance,
then the size of the swim bladder determines the center frequency of the sound pulse. It is
unknown whether the tuna vocalizations are generated as a by-product of some biological function
such as clearing the gills, or an intentional form of communication.
Acknowledgements
We are thankful to Dr. Rennie Holt, Director of the United States Antarctic Marine Living Resources
Program and Dr. John Hunter, Head of the Fisheries Resources Division, SWFSC, for providing the lab-
oratory and equipment resources necessary to complete this study. We would also like to thank Dr.
Kenneth Baldwin of the University of New Hampshire Center for Ocean Engineering for allowing S.
Allen to conduct his Master’s Thesis research at SWFSC. Thanks also to Mr. Ted Dunn, founder of
Maricultura Del Norte of Ensenada, Mexico for graciously supporting this effort with access to his
fish pens. Thanks finally to Dr. Charles Farwell, the manager of pelagic displays at the Monterey Bay
Aquarium in Monterey, California.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Illustrations and Diagrams
Figure 1. Bluefin vocalization recorded at Maricultura del Norte, 18 November 2000 using two hydrophones (a) and
their power spectral densities (b). Signals were low-pass filtered (Order 4 Butterworth, fc=600 Hz). Estimated sound
pressure level is 105 dB re 1 mP.
Figure 2. A bluefin tuna vocalizing at Maricultura
del Norte Ensenada. During the vocalization, the
animal’s mouth opened wide with its jaw bones
extended and its abdomen expanded, then con-
tracted abruptly
Acoustic Competition in the Gulf Toadfish Opsanus beta: Crepuscular Changes
and Acoustic Tagging
Michael L. Fine
1
and Robert F. Thorson
2
1
Department of Biology, Virginia Commonwealth University, Richmond,VA 23284-2012
2
Present address: 133 Mockingbird Rd.,Tavernier, FL 33070
We quantified crepuscular variation in the emission rate and call properties of the boatwhistle
advertisement call of Gulf toadfish Opsanus beta from a field recording of a natural population of
nesting males in the Florida Keys. Their calls are more variable and complex than previously report-
ed (Fig. 1). A call typically starts with a grunt followed by one to five tonal boop notes (typically two
or three) and lasts for over a second. The first boop is considerably longer than later ones, and inter-
vals between boops are relatively constant until the final interval, which approximately doubles in
duration. Positions of fish are fixed for long periods, and calls are sufficiently variable that we could
discern individual callers in field recordings (Fig. 1). Calling rate increases after sunset when males
tend to produce shorter calls with fewer notes (Fig. 2). Analysis by number of notes per call indi-
cates some individuals decrease the number of initial grunts and the duration of the first note, but
most of the decrease results from fewer notes. To our knowledge this sort of call plasticity has not
been demonstrated before in fishes. We suggest that call shortening lowers the chances of overlap-
ping calls of other males and that the small amount of time actually spent producing sound (total
on time) is an adaptation to prevent fatigue in sonic muscles adapted for speed but not endurance.
Anomalous boatwhistles contain a short duration grunt embedded in the tonal portion of the boop
or between an introductory grunt and the boop (Fig. 3b, c). Embedded grunts have sound pressure
levels and frequency spectra that correspond with those of recognized neighbors, i.e. we are able to
identify individuals based on frequency spectrum of their grunts (Fig. 4). We therefore suggest that
one fish is grunting during another’s call, a phenomenon here termed acoustic tagging. Snaps of
nearby pistol shrimp may also be tagged, and chains of tags involving more than two fish occur (Fig.
5). The stimulus to tag is a relatively intense sound with a rapid rise time, and tags are generally pro-
duced within 100 ms of a trigger stimulus. Time between the trigger and the tag decreases with
increased trigger amplitude.Tagging is distinct from increased calling in response to natural calls or
stimulatory playbacks since calls rarely overlap other calls or playbacks. Tagging is not generally
reciprocal between fish suggesting parallels to dominance displays.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Illustrations and Diagrams
Fig.1. Sonagrams and oscillograms from five individual Opsanus beta.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Illustrations and Diagrams
Fig 2. Sonagrams from 4-, 3-, 2- and 1-boop calls from an individual Opsanus beta.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Illustrations and Diagrams
Fig. 3. Sounds of Opsanus beta illustrating acoustic tagging. (a) A typical boatwhistle with an initial grunt (G), a long
tonal boop B1 and two shorter boops (B2 and B3). (b) Sonagram and (c) oscillogram of a boatwhistle tagged by
another fish.The T marks the tag, which has lower frequency energy and greater amplitude than the boatwhistle.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
100 200 300 400 500 600 700 800
-45
-40
-35
-30
-25
-20
-15
-10
-5
0
F1
F2
F3
F4
Peak Frequency (Hz)
P
e
a
k
A
m
p
l
i
t
u
d
e
Fig. 4. Plot of peak amplitude in dB against the frequency of peak amplitude from grunt spectra for four toadfish
recorded at weekly intervals.
Fig. 5.Tags of shrimp snaps. (a) oscillogram of a pistol shrimp snap tagged by fish 1 with a latency of 41 ms shown in
real time. (b) Same selection expanded. (c) Chain of tags initiated by a shrimp snap that is tagged by fish 3. Fish 3’s
grunt is then tagged by fish 2, who in turn is tagged by fish 1.
Passive Acoustic Field Research on Atlantic Cod, Gadus morhua L. in Canada
Susan B. Fudge
1
and George A. Rose
2
1
Fisheries Conservation Chair, Fisheries and Marine Institute, Memorial University of Newfoundland,
155 Ridge Road, PO Box 4920, St. John’s, NF Canada, A1C 5R3
sfudge@caribou.mi.mun.ca.
2
Senior Chair of Fisheries Conservation, Fisheries and Marine Institute, Memorial University of
Newfoundland, 155 Ridge Road, PO Box 4920, St. John’s, NF Canada, A1C 5R3
grose@caribou.mi.mun.ca.
Introduction
The Atlantic cod is a very important commercial fish in Newfoundland and Atlantic Canada and has
been a part of the culture for centuries. In the past ten years, cod stocks have been drastically
depleted. In Newfoundland waters, cod is found from the coast to the continental shelf in water
temperatures ranging from approximately -0.5
0
C to 8.5
0
C.They are broadcast spawners and typical-
ly spawn in large aggregations (Robichaud, 2002). The spawning season typically occurs in the
spring but varies by area and is influenced by environmental factors, such as temperature (Scott and
Scott, 1988). Spawning begins in the north as early as February and ends in the south as late as
December. The depth at which spawning occurs varies among stocks; some may spawn in water as
shallow as 20m, while others at depths over 300m (Rose, 1993). Differences in spawning behaviours
among sub-stocks and among ages and sexes have been reported (Robichaud, 2002). Laboratory
studies have shown that cod have elaborate courtship behaviours with males being very territorial
and more aggressive males having the most success at spawning. Cod are also known to detect and
produce sound and this observation has long been recognized by lab experiments (e.g. Brawn,
1961).This study is the first attempt in Canada to document the sounds made during spawning and
to relate them to spawning behaviour in order to link active and passive acoustic research in behav-
ioural field studies.
Previous and future research on Atlantic cod behaviour
Two of the largest spawning components of Atlantic cod in Newfoundland waters have been stud-
ied using active acoustics for several years.These include Placentia Bay, located on the south coast
of Newfoundland (NAFO regulatory area 3Ps), and Trinity Bay, located on the north east coast (NAFO
regulatory area 3L). Annual acoustic surveys using SIMRAD EK 500 echo sounders, along with the
analyses of the data using FASIT (Fisheries Assessment and Species Identification Tool) (Lefeuvre et
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
al., 2000) have provided insights into stock migrations and spawning behaviours.The echogram in
Figure 1 is from April 2000 in Placentia Bay, Newfoundland, showing some of the pelagic behaviour
easily observed using an echo sounder. Cod in this area have a peak spawning period between April
and June.This spawning aggregation was found in a trench, over 300m deep.The image in the bot-
tom corner is an enlargement of the echogram where single cod targets (white arrow) are resolved.
The use of active acoustics has lead to observations of different spawning aggregation structures.
Figure 2 is an echogram of spawning columns observed in shallow waters of Placentia Bay in 1997
at a depth of approximately 50m (Rose, 1993). In section A, several columns are shown. Section B is
an enlargement of one of these columns, which extends approximately 20m off the ocean floor.
Throughout their range, cod occur in distinct stocks as well as sub-stocks, and spawning behaviour
within specific sub-stocks is of interest. Sonar tagging studies have been conducted to investigate
the homing ability of Atlantic cod to specific spawning grounds. Long-term sonar transmitting tags
(Lotek CAFT16_3 Acoustic Transmitters) were implanted in female and male cod at a spawning
ground in Placentia Bay, Newfoundland in April 1998. Homing of cod back to the spawning ground
from which they were taken was observed. Approximately 50% of the tagged cod returned to the
same spawning ground (capture site) in subsequent years and 25% of the tagged cod returned 3
years in a row (Robichaud and Rose, 2001). This study provides some of the first direct evidence that
cod undertaking long-distance feeding migrations may home to a specific spawning location in
consecutive years. Present tagging work that has begun this year also will involve the identification
of distinct spawning populations using acoustic surveys; cod have been released within their
“home”populations as well as within other groups. Results of this study hope to provide valuable
insight into the Atlantic cod’s homing properties.
Using active acoustics in surveys and sonar tagging studies, we have learned a great deal about cod
spawning aggregations and migratory behaviour. As spawning is the first step towards recruitment
and rebuilding cod stocks, there is a continuing interest in the specific behaviour of spawning.
Brawn (1961) documented many interesting features of cod spawning behaviour. Cod are known to
have specific social behaviours related to spawning. Brawn (1961) observed distinct courtship
behaviours performed by males toward females, as well as aggressive behaviour of males toward
males. Both sexes in cod have been observed to produce sound, although it is the males whose
sound production is thought to play an important role in spawning, such as attracting females and
holding territories (Brawn, 1961). In cod, the drumming muscles surrounding the swim bladder are
thought to be related to sound production.
Present field studies will observe the acoustic properties of spawning aggregations over two
spawning seasons.These studies are interested in both the production and reception of sound by
cod, its role in spawning behaviour, and also the influence of ambient noise in the ocean environ-
ment on these behaviours.We have chosen two main research areas, which have been studied for
the past number of years using active acoustics and sonar tracking. Placentia Bay and Trinity Bay
both have relatively large coastal spawning populations. However, Placentia Bay is becoming
increasingly industrialized while Trinity Bay is not. With use of a small vessel specially equipped for
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
the work, cod spawning aggregations will be located using a Biosonics DE 70 kHz echosounder with
digital data storage. Once located sounds from the aggregation are detected, they will be recorded
using a hydrophone (ITC 8212) with a Stanford Research System pre-amplifier (model SR560). Data
will be in the form of WAV files and stored on a hard drive of a lap-top computer and analyzed using
Avisoft SASLab Pro software. Video recordings will be made using an underwater video camera (J.W.
Fishers MFG. Inc., TOV-1). A parallel study will be conducted on fish from the same stocks kept in the
lab at the aquaculture facility at Memorial University of Newfoundland.
Summary
This study is the first of its kind in Canada, and is attempting to document the sounds that cod
make during spawning at sea and to relate these to spawning behaviour.The work attempts to link
active acoustic research with passive acoustics and to use real-time video to study cod spawning
behaviour. From past acoustic research, we have learned much about the state of cod stocks, spawn-
ing aggregations, migrations, and homing.With the addition of passive acoustic tools, we hope to
learn more about the spawning behaviour of individual cod.
Acknowledgments
Several people were instrumental in past and present studies.We would like to thank Dave
Robichaud,Wade Hiscock, Matt Windle, the crews of the CCGS Teleost and CCGS Shamook. Danny
Boyce of the Aquaculture Facility at Memorial University and all the participants and sponsors of the
International Workshop of Passive Acoustics in Fisheries.
References
Brawn,Vivien M. 1961. Aggressive behaviour in the cod (Gadus callarias L.). Behaviour 18: 108-145.
Brawn,Vivien M. 1961. Reproductive behaviour of cod (Gadus callarias L.). Behaviour 18: 177-198.
Brawn,Vivien M. 1961. Sound production by the cod (Gadus callarias L.). Behaviour 18: 239-245.
Chapman, C.J. and A. D. Hawkins. 1973. A hearing study in the cod, Gadus morhua L. Journal of
Comparative Physiology 85: 147-167.
Lefeuvre, P., G.A. Rose, R. Gosine, R. Hale, W. Pearson, and R. Khan. 2000. Acoustic species identification
in the northwest Atlantic using digital image processing.Fisheries Research 47: 137-147
Nordeide, J.T. and E. Kjellsby. 1999. Sound from cod at their spawning grounds.ICES Journal of Marine
Science. 56:326-332.
Robichaud, D. 2002. Homing, population structure and management of cod, with emphasis on cod
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
spawning at Bar Haven in Placentia Bay, Newfoundland. Ph. D. thesis. Biology Department, Memorial
University of Newfoundland.
Rose, G.A. 1993. Cod spawning on a migration highway in the north-west Atlantic. Nature 366: 458-
461.
Scott W.B., and M.G. Scott. 1988. Atlantic Fishes of Canada. University of Toronto Press, Toronto.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Illustrations and Diagrams
Figure 1: Echogram of a spawning cod aggregation in Placentia Bay, Newfoundland 2001.
Figure 2: Cod spawning column in Placentia Bay in 1997.
Passive Acoustic Transects: Mating Calls and Spawning Ecology in East Florida
Sciaenids
R. Grant Gilmore, Jr., Ph.D.
Dynamac Corporation, Mail Code: DYN-1, Kennedy Space Center, FL 32899, USA.
rggilmorej@aol.com
Introduction
Historical Acoustic Work with Sciaenid Fishes: Sciaenid fishes have been known to produce sound for
centuries (Aristotle, 1910; Dufossé, 1874a,b) and the association of sciaenid sounds with spawning
has been known nearly as long (Darwin, 1874; Goode, 1887). For hundreds of years the Chinese
have isolated sciaenid spawning sites from their water craft by listening to drumming sounds ema-
nating from the water through the hull of their boats (Han Ling Wu, Shanghai Fisheries Institute,
pers. comm.). The isolation of sciaenid spawning sites using underwater technology is recent and
dependent on the availability of underwater transducers, hydrophones, and acoustic recorders used
to access and study underwater sounds (Fish and Mowbray 1970). Hydrophone tape recordings of
vocalizations produced by large sciaenid aggregations during spawning was pioneered by Dobrin
(1947), Dijkgraaf (1947, 1949), Knudsen et al. (1948), Protasov and Aronov (1960), Schneider and
Hasler (1960),Tavolga (1960, 1981), Fish and Mowbray (1970), Fish and Cummings (1972).
The first isolation and description of soniferous sciaenid aggregations using mobile hydrophones
moving along a sound transect at spawning sites was conducted by Takemura et al. (1978), Mok and
Gilmore (1983) and Qi et al. (1984). A portable hydrophone and recording system was carried via a
boat from one site to another along a measured transect with recordings made along a preset grid
or in a linear series (Mok and Gilmore 1983; Gilmore 1994, 1996, 2002). Recordings were made for 30
- 300 seconds at each site depending on transect length. Recorded sounds were verified by record-
ing captured specimens identified to species and documenting specific sound types through sono-
graphic analyses.This technique allowed spatial-temporal isolation and identification of species-
specific sounds produced by sciaenid fishes, particularly under conditions of high sound attenua-
tion for large group sounds (low frequency high intensity sounds).
Using detailed sonographic analyses of field recordings made on transects Mok and Gilmore (1983)
described the characteristic sounds of black drum, Pogonias cromis,spotted sea trout, Cynoscion neb-
ulosus and silver perch, Bairdiella chrysoura. Subsequent to these observations considerable addi-
tional work has been done on sound characterization in these species as well as the weakfish, C.
regalis and the red drum, Sciaenops ocellata. Passive acoustic transect techniques have been used
by several investigators to isolate spawning sciaenid groups in the field (Sausier and Baltz, 1992,
1993; Connaughton and Taylor, 1994, 1995; Luczkovich et al., 1999, 2000).
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Recent East Florida research 1990-2002: Over the past twelve years the value of passive acoustic stud-
ies in determining spatial and temporal spawning activity in sciaenids has increased. East central
Florida studies have been supported by the Florida Fish and Wildlife Conservation Commission, U.S.
Geological Survey, National Aeronautics and Space Administration, Canaveral National Seashore and
NOAA/National Marine Fisheries Service. The major objectives of these studies have been to devel-
op new techniques and technologies to allow real time continuous monitoring of soniferous aquat-
ic organisms. This included a prototype neural network to identify species specific sounds (Lin
1996), and remotely deployed underwater computer systems (HBOI ALMS; NASA PAMS) with
hydrophones and physical sensors for environmental parameters to allow association of physical
oceanography with acoustic activity.
Future acoustic research at the Kennedy Space Center: The long term objectives of this work at the
Kennedy Space Center is to develop an acoustic and sensor array that will allow continuous moni-
toring of biotic acoustic activity in association with intra and interspecific interactions as well as cli-
matic and oceanographic phenomena. An experimental acoustic arena is being developed in the
marine protected areas within the secure zone of the NASA and U.S. Air Force launch complex at
Cape Canaveral.
Function of Sound Production in Sciaenids
The most predictable and robust sounds produced by many fishes are those associated with repro-
duction. As in many soniferous animals, it is the male that must attract a mate and induce her to
donate eggs for fertilization, and, therefore, it is often only the male that produces sound. Large
choral aggregations of male sciaenid species are formed by spotted seatrout, weakfish, red drum
and silver perch specifically to attract females with which to spawn. Since these male choral aggre-
gations contribute no significant resources required by females except the males themselves (no
male paternal care, no food, or nest sites) they are appropriately called seatrout “leks”, such as those
formed by aggregative birds and amphibians strictly for the purpose of reproduction (Höglund and
Alatalo 1995). A lek is an arena to which females come and on which most of the mating occurs. An
arena is a site on which several males aggregate but does not form the habitat normally used by the
species for other activities such as feeding. Sciaenid leks are seasonal and are associated with a wide
variety of environmental parameters that are favorable for egg, larval and adult survival. The
acoustic properties of lek sites are undoubtedly favorable for mating call transmission and must
have specific acoustic properties. Although many sciaenid spawning sites have been isolated to
date, their acoustic properties have not been studied in detail (Mok and Gilmore, 1983; Saucier et. al,
1992, Saucier and Baltz, 1993; Luczkovich et al., 1999; Gilmore 2002). Aggregative calling only occurs
at the appropriate time for spawning, facilitating successful mating, egg fertilization, egg/larval dis-
persal and survival.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Sciaenid Sound Production Mechanisms
The most robust and energetic sciaenid sounds are produced by sonic muscles indirectly or directly
vibrating the membrane of the gas bladder. When a freshly captured, recently calling, male seatrout
is dissected, the bright red sonic muscles surrounding the gas bladder can be easily differentiated
from the exterior lateral body muscles.The muscle vibratory rate is directly associated with the fun-
damental frequency of the characteristic seatrout call produced by the gas bladder.
Most of the 1,200 species in this family produce sound using sonic muscles associated with the gas
bladder. Using the species specific muscle contraction rates and the gas bladder shape sciaenids
produce diagnostic sounds that can be used to identify species within the family (Mok and Gilmore
1983), as has been demonstrated in amphibians and birds. The characteristic shape of the sciaenid
gas bladder is so conservative that it has been used as one of the primary characters to classify sci-
aenids and to determine their phyletic relationships (Chu 1963; Chao 1978, 1986).
Classification of Sciaenid Sounds
Figure 2 illustrate the diagnostic mating calls of sciaenids known to spawn in the Indian River
Lagoon system of east central Florida.
Sciaenid Acoustic and Spawning Ecology: When and Where do Sciaenids Produce Sound?
Mok and Gilmore (1983) demonstrated that sciaenid sound production was specifically associated
with crepuscular and nocturnal courtship and spawning activities. Pelagic eggs and larvae of the
spotted seatrout were collected with plankton nets at spawning sites during vocalization periods
(Mok and Gilmore, 1983; Alshuth and Gilmore, 1993, 1994, 1995). These same studies of soniferous
spawning aggregations have demonstrated long-term spawning site fidelity, with the principal
spawning sites identified by Mok and Gilmore (1983) being used for over twenty years (Gilmore,
1994, 1996, 2002).
As male spotted seatrout could be recognized by distinctive crepuscular calls their presence or
absence from specific locations could be determined and the percent occurrence of calls at all
acoustic listening sites derived. In addition, the approximate size of the calling group could be esti-
mated based upon sound intensity (dB level, re 1 µPa) and group size estimates using a three part
scale: 1 - small group or individual callers; 2 - moderate groups of several tens of callers; and 3 - a
large group of what appear to be hundreds of simultaneous callers. Unfortunately, mixed species
chorus behaviors were common with Arius felis and Bairdiella chrysoura joining in with spotted
seatrout calls, therefore, elevating site specific sound intensities and masking seatrout numbers
based on sound intensity. The percent occurrence of spotted seatrout calls at a site or time period is
the most objective data used to define site and period use by seatrout leks. However, Gilmore
(1994) found that spatial and temporal distributions of the estimated group size, egg and larval
abundance in the water column and percent occurrence of calling trout were highly correlated (r =
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
0.92 to 0.98 at α= 0.05). This indicates that group size estimates were a useful, independently
derived variable that could be used to verify calling trout distributions and relative use of specific
sites or particular times of the year. These two data types have been used to isolate spawning times
and locations.
Seasonal mating calls were directly associated with primary spawning activity in east central Florida
sciaenids. Figure 4 summarizes their seasonal call pattern at this latitude based on over 300
acoustic transects between 1978 and 2002.
Spatial distribution of sciaenid spawning calls: All soniferous spawning populations of sciaenids in the
upper Banana River Lagoon, a lagoon associated with the Indian River Lagoon system, within the
protected waters of the Kennedy Space Center have been mapped. Spawning sites are utilized only
from sunset to midnight during the spawning period with greater call activity on new and full
moon phases. Some sites within the Indian River Lagoon system have been known as favored
spawning sites with mating calls having been recorded from these sites for over 20 years. Figure 5
represents primary call sites for all sciaenids known to spawn in the upper Banana River Lagoon
basin north of the NASA Causeway at the Kennedy Space Center.
Future Technology Developments at KSC Relative to Acoustic studies of Sciaenid Fishes
Once locations and periods of acoustic activity and spawning have been isolated as they have at the
Kennedy Space Center, then a number of basic questions and hypotheses can be addressed relative
to the evolutionary significance of sound production in sciaenids and other soniferous fishes.
Examples are:
1. Does sciaenid sound production increase the probability of predation mortality?
2. What are the energetic costs of sonifery?
3. How does sciaenid foraging behavior relate to spawning and sound production and are there
sexual differences in foraging behavior as a result of differences in mating behavior, acoustic
energetics?
4. What are the benefits of sonifery to spawning aggregations?
With the installation of permanent acoustic arrays, portable acoustic systems, roving robotic
acoustic platforms and physical sensor arrays we believe it will be possible to address detailed
research objectives that will finally unravel the intimate mating, foraging and predatory escape
behaviors of regional estuarine sciaenid communities.
Acknowledgements
Sensor Web pod deployments (developed by Kevin Delin, NASA/JPL, Pasadena, CA) and our
NASA/KSC PAMS (Portable Acoustic Monitoring System) being deployed by the Clelia submarine
during a NOAA OE project August 2001.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Literature Cited
Alshuth, S. and R.G. Gilmore. 1993. Egg identification, early larval development and ecology of the
spotted seatrout, Cynoscion nebulosus C. (Pisces: Sciaenidae). ICES C.M. 1993/G 28, Dem. Fish Com: 18
pp.
Alshuth, S. and R.G. Gilmore. 1994. Salinity and temperature tolerance limits for larval spotted
seatrout, Cynoscion nebulosus C. (Pisces: Sciaenidae). ICES C.M. 1994/L:17, Biol. Oceanogr. Cttee., 19
pp.
Alshuth, S. and R.G. Gilmore. 1995. Egg and early larval characteristics of Pogonias cromis, Bairdiella
chrysoura, and Cynoscion nebulosus (Pisces: Sciaenidae), from the Indian River Lagoon, Florida. ICES
C.M. 1995/L:17, Biol. Oceanogr. Cttee., 21 pp.
Aristotle. Historia Animalium, IV, 9.Trans. by D.D’A.Thompson. 1910. Oxford. Clarendon Press.
Chu,Y.T., Y.L. Lo and H.L.Wu. 1963. A study on the classification of the sciaenoid fishes of China, with
description of new genera and species. 1972 Reprint, Antiquariaat Junk, Netherlands.
Chao, L.N. 1978. A basis for classifying western Atlantic sciaenidae (Teleostei: Perciformes). NOAA
Tech. Rept. NMFS Circ. 415.
Chao, L.N. 1986. A synopsis on zoogeography of the sciaenidae. Pp. 570-589, In T. Uyeno, R. Arai,T.
Taniuchi and K. Matsuura (eds.) Indo-Pacific Fish Biol.: Proceedings of the Second Internatl. Conf.
Indo-Pac. Fishes.
Connaughton, M.A. and M.H.Taylor. 1994. Seasonal cycles in the sonic muscles of the weakfish,
Cynoscion regalis.Fish. Bull. 92: 697-703.
Connaughton, M.A. and M.H.Taylor. 1995. Seasonal and daily cycles in sound production associated
with spawning in the weakfish,Cynoscion regalis.Envir. Biol. Fish. 42: 233-240.
Darwin, C. 1874. The descent of man. 2nd edition. N.Y.: H.H. Caldwell.
Dijkgraaf 1947. Ein tone erzeugender fisch in Neapler Aquarium. Experimenta, vol. 3, pp. 494-494.
Dijkgraaf 1949. Untersuchungen uber die funktionen des ohrlabyrinths bei meeresfischen. Physiol.
Comp. Oecolog., vol. 2, pp. 81-106.
Dobrin 1948. Measurements of underwater noise produced by marine life. Sci., Vol. 105: 19-23.
Dufossé, A. 1874a. Rescherches sur les bruts et les sons expressifs que font entendre les poissons
d’Europe et sur les organes producteurs de ces phenomenes acoustiques ainsi que sur les appareils
de l’audition de plusieurs de ces animaux. Annales des Sci. Naturelles ser 5, 19: 53 pp.
Dufossé, A. 1874b. Rescherches sur les bruts et les sons expressifs que font entendre les poissons
d’Europe et sur les organes producteurs de ces phenomenes acoustiques ainsi que sur les appareils
— 37 —
Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
de l’audition de plusieurs de ces animaux. Annales des Sci. Naturelles ser 5, 20: 134 pp.
Fish, J.F. and W.C. Cummings. 1972. A 50-dB increase in sustained ambient noise from fish
(Cynoscion xanthurus). J. Acoust. Soc. Amer. 52: 1266-1270.
Fish, M.P. and W.H. Mowbray. 1970. Sounds of western North Atlantic fishes. The Johns Hopkins
Press, Baltimore.
Gilmore, R.G.,, Jr. 1994. Environmental parameters associated with spawning, larval dispersal and
early life history of the spotted seatrout, Cynoscion nebulosus (Cuvier). Final Program Rev., Contract
No. LCD 347. Mar. Res. Inst., Fla. Dept. Environ. Protection, St. Petersburg, Fla.
Gilmore, R.G. , Jr. 1996. Isolation of spawning groups of spotted seatrout, Cynoscion nebulosus, using
passive hydroacoustic methodologies. Final Report, 21 November 1996, 12 pp., Fla. Dept. Environ.
Protection, Mar. Res. Inst., St. Petersburg, Fla. Subcontract to Dr. Roy Crabtree, Principal Investigator,
FMRI study entitled: The reproductive biology of spotted seatrout, Cynoscion nebulosus, in the Indian
River Lagoon.
Gilmore, R.G, Jr.. 2000. Spawning site fidelity, classification of spawning environments and evolu-
tionary stable strategies: Serranids versus Sciaenids. (Abstract) In Session 54: Fish Aggregation
Symposium. 80th Annual Meeting Am. Soc. Ichthy. And Herp., La Paz, Mexico, June 14-20, 2000.
Gilmore, R.G, Jr.. 2002. Sound production and communication in the spotted seatrout. Chapter 11.
pp. 177-195, in Biology of the Spotted Seatrout, S.A. Bortone, ed. CRC Press, Boca Raton.
Goode, G. B. 1887. American fishes: a popular treatise upon the game and food fishes of North
America with special reference to habits and methods of capture. L.C. Page Co., Boston.
Hoglund, J. and R.V. Alatalo. 1995. Leks. Princeton Univ. Press. 248 pp.
Knudsen, V.O. , R.S. Alfred and J.W. Emling. 1948. Underwater ambient noise. J. Mar. Res., Vol. 7: 410-
429.
Lin,Ya Di. 1996. A neural network for the isolation of fish sounds. Ph.D. Dissertation, Florida Institute
of Technology, Melbourne, Florida, USA.
Luczkovich, J. J., M.W. Sprague, S.E. Johnson and R.C. Pullinger. 1999. Delimiting spawning areas of
weakfish, Cynoscion regalis (family Sciaenidae), in Pamlico Sound, North Carolina usign passive
hydroacoustic surveys. Bioacoustics 10: 143-160.
Luczkovich, J.J., H.J. Daniel III, M. Hutchinson, T. Jenkins, S.E. Johnson, R.C. Pullinger and M.W. Sprague.
2000. Sounds of sex and death in the sea: bottlenose dolphin whistles suppress mating choruses of
silver perch. Bioacoustics 10. 323-334.
Protasov, V.R. and M.I. Aronov 1960. On the biological significance of sounds of certain Black Sea fish.
(In Russian). Biofizika, Vol. 5: 750-752.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Qi, M., S. Zhang and Z. Song. 1984. Studies on the aggregate sound production of most species of
croaker (sciaenoid fishes) in Bohai Sea, Yellow Sea and East China Sea. Studia Marina Sinica, Peking,
21: 253-264.
Saucier, M.H. and D.M. Baltz. 1992. Hydrophone identification of spawning sites of spotted seatrout
Cynoscion nebulosus (Osteichthys: Sciaenidae) near Charleston, South Carolina. N.E. Gulf Sci. 12(2):
141-145.
Saucier, M.H. and D.M. Baltz. 1993. Spawning site selection by spotted seatrout, Cynoscion nebulosus
and black drum, Pogonias cromis, in Louisiana. Env. Biol. Fishes 36: 257-272.
Schneider, H. and A.D. Hasler 1960. Laute and luerzeugung beim susswassertrommler Aplodinotus
grunniens Rafinesque (Scianenidae, Pisces), Zeitschr. Vergl. Physiol., Vol. 43: 499-517.
Takemura, A, T. Takita and K. Mizue. 1978. Studies on the underwater sound - VII: Underwater calls of
the Japanese marine drum fishes(Sciaenidae). Bull. Jap. Soc. Sci. Fish. 44: 121-125.
Tavolga, W. N. 1960. Sound production and underwater communication in fishes. pp. 93-136, in
Animal Sounds and Communication, Lanyon,W.E. and W. N. Tavolga, eds., AIBS 7.
Tavolga, W.N., A.N. Popper and R.R. Fay. (eds). 1981. Hearing and sound communication in fishes.
Springer Verlag, N.Y.: pp 395-425
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Illustrations and Diagrams
Fig. 1. Representative sciaenid internal anatomy revealing the gas bladder and sonic muscles of a male weakfish,
Cynoscion regalis.
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Illustrations and Diagrams
Fig. 2. Energy distribution patterns associated with harmonic frequency bands and fundamental frequencies are
species specific and were used to train a neural network to recognize sciaenid calls (Lin 1996).
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Illustrations and Diagrams
Figure 5
Figure 4. Croaker courtship sound production expressed as number of calls min-1 across time. Values were deter-
mined for one minute out of every five recorded over the course of the evening. The solid vertical line represents the
first spawning event (9:29PM) and the double vertical line, the second (10:29PM).
The Use of Passive Acoustics to Identify a Haddock Spawning Area
Anthony D Hawkins
FRS Marine Laboratory, PO Box 101, Victoria Road,Torry, Aberdeen AB11 9DB, Scotland, UK.
greenseas@btopenworld.com
Introduction
The haddock is an important food fish, widely distributed throughout the deeper shelf waters of the
North Atlantic. It is very heavily fished and in some areas is considered to be exploited beyond safe
biological limits. Fisheries management measures have included the closure of spawning areas
(Waiwood & Buzet, 1989). Haddock gather together close to the seabed to spawn (Boudreau, 1992).
Fertilization is external and the pelagic eggs hatch near the sea surface. The larvae drift in the
upper part of the water column before the young fish move down to the seabed.There is very little
detailed information, however, on where haddock spawn. The location of the spawning grounds
has to be inferred either from catches of mature fish, or from the distribution of pelagic eggs.
Haddock are generally believed to spawn offshore at depths of 200-500m or even deeper (Solemdal
et al, 1997), but oral evidence from fishermen suggests that in some areas haddock may spawn
inshore (Ames, 1998).
Like other members of the cod family (Gadidae), the haddock is a noisy fish. The male produces a
diversity of sounds over the spawning season, with distinctive sounds associated with particular
behavioural acts (Hawkins and Amorim, 2000). This behaviour offers the opportunity to detect the
presence of spawning fish simply by listening for sounds. A search was therefore carried out in
coastal waters by listening for the characteristic sounds of haddock. By this means an aggregation
of spawning haddock was located at the upper end of Balsfjord, a sub-arctic fjord in Northern
Norway.
Aquarium Observations on Spawning Haddock
Spawning of captive haddock was observed in a 10m diameter annular aquarium tank at the FRS
Marine Laboratory Aberdeen. Water depth was 1.5m and the water temperature was maintained at
8(C. The fish were observed from above by means of a low light level TV camera and their behav-
iour recorded on a time-lapse video tape recorder.
The sounds of the fish were detected with an omni-directional broad-band hydrophone (ITC,
6050C), amplified (Stanford SR560 pre-amplifier, bandwidth 30Hz to 10kHz), sampled at 8 kHz and
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
recorded directly as WAV files on the hard disk of a lap-top computer by means of Avisoft Recorder.
Sound analysis was performed with Avisoft SASLab Pro.
In the aquarium, individual female haddock spawned repeatedly over several weeks. Spawning was
accomplished through a close spawning embrace, and preceded by elaborate courtship behaviour.
Sounds were recorded in the aquarium from male and female haddock, and from juveniles.
However, during the spawning period sounds were predominantly made by the male fish.
Haddock sounds have been described as a series of ‘knocks’ (Hawkins & Chapman, 1966), repeated
regularly at different rates. It has since become apparent that each knock can be subdivided into
two short, low-frequency pulses of sound, spaced closely together (Hawkins & Amorim, 2000).
The individual knocks produced by male fish were regularly repeated at a range of different rates,
depending on the behaviour of the fish. Short sequences of repeated knocks were emitted during
agonistic encounters. At spawning time, male fish produced much longer sequences, lasting from
several seconds to several minutes, the knocks being produced at intervals varying from 500 ms to
30 ms. At the very fastest rates, with intervals of less than 50 ms, the sounds were heard as a contin-
uous humming. Different behavioural acts leading up to the spawning embrace were associated
with different repetition rates.This rich diversity of sounds produced by the male haddock appears
to be characteristic of this species.
Male haddock showed a distinctive solitary display. Dominant males adopted a characteristic pat-
tern of pigmentation, occupied a favoured area and showed a characteristic pattern of movement,
moving in tight circles or a figure of eight. During this behaviour the male uttered an almost contin-
uous train of regularly repeated knocks repeated at intervals of between 140 and 60 ms (Figure 1).
During the spawning season males spent much of their time in solitary display (9h out of 24, 75% at
night), interrupting the display only when other fish entered their territories.
Differences between the sounds of individual male haddock were analysed by measurements on
the waveform or through wavelet analysis (see Wood, these proceedings). In most instances the
knocks were composed of two pulses separated by intervals of 10-20ms. The two pulses often dif-
fered in frequency, the first being higher than the second. Within a given call, or from day to day,
there was little variation in the waveform for an individual fish. From month to month, however,
there was a significant change in the detail of the waveform, though the double pulse structure was
usually retained. There were often striking differences between the sounds of individual males
(Figure 2).
The characteristic sounds described from haddock in the aquarium provided clear criteria for the
location of spawning male haddock in the sea. The short low frequency sounds (below 1kHz), made
up of two pulses separated by intervals of 10 - 20 ms, regularly repeated at intervals of 300 - 30 ms,
often for more than several seconds, provided unequivocal evidence of the presence of haddock.
Moreover, changes in the repetition rate of the sounds were indicative of different stages in the
behaviour of the haddock. The sounds were quite different from those described for other gadoid
fish (Hawkins & Rasmussen (1978).
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Observations at Sea
Searching took place in Balsfjord, Tromsø, Northern Norway from a small research vessel (the FF
Hyas, Norges Fiskerihøgskole, Tromsø, length 12m). Balsfjord is a subarctic fjord (90 km2) with a 30m
sill at its entrance, with depths in the inner fjord dropping to 190m. Trawling surveys have shown a
preponderance of cod (Gadus morhua), but also significant catches of haddock. There is a small
local fishery for cod and haddock in the spring, and reports from fishermen suggested that haddock
spawned at the head of the fjord.
Sampling took place when individual fish echoes were detected on or close to the seabed on the
echo-sounder.The ship was stopped, anchored by the bow, and the hydrophone hung 2m above a
weight on the seabed by a cord attached to a small submerged buoy. Sound recordings were made
for a minimum of 15 minutes at each station with the main engine and auxiliary generator of the
ship shut down. The position of the ship was determined by GPS.
Four surveys were carried out at Balsfjord (17-19 April 2000; 10-12 May 2000; 9-10 December 2000;
3-7 April 2001).The distinctive sounds of haddock were detected at some time during each of the 4
surveys, though not at all stations and with varying incidence. In the first survey, 12 stations were
examined. Distinctive haddock sounds were recorded at the majority of stations within the main
basin, especially close to the head of the fjord. Slowly repeated knocks, made up of double pulses,
were the most common (Figure 3). Some were short (a few seconds), others extended over several
minutes. Occasionally, sounds with a faster repetition rate were recorded, suggesting that the had-
dock were engaging in agonistic and courtship activities. At one station in the main part of the
fjord, repeated grunts were recorded which lacked the double pulse structure characteristic of had-
dock. These were tentatively identified as coming from cod.
Sounds were recorded at all times of the day and night. However, in two areas a continuous low fre-
quency rumbling was detected at night, within which individual haddock knocks could be detected.
During the second survey, sounds were recorded at four of the five stations surveyed. All stations at
the head of the fjord yielded haddock sounds, and at three of them, the low frequency rumbling
sound was audible at night. At one station it proved possible to record for 10 minute periods every
hour over a 24 hour period. This revealed a 10 dB increase in ambient noise level at night, which
was attributable to the simultaneous production of sound by many haddock.
The third survey was carried out at the beginning of winter. At three stations long slow knocking
sounds were detected, made up of double and occasionally triple pulses, confirming the presence of
haddock. The sounds were rare, however, and no low frequency rumbling was detected, suggesting
that spawning had not yet begun. The fourth survey investigated 22 stations at the head of
Balsfjord during Spring. Many haddock sounds were detected at stations close to the head of the
fjord. Low frequency rumbling was detected at night at three stations. No haddock sounds were
detected at stations along the eastern edge of the fjord.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Discussion
By listening, it proved possible to locate concentrations of spawning haddock at the head of
Balsfjord during Spring over two successive years, confirming that passive acoustics provide a reli-
able non-invasive technique for identifying the precise areas where haddock spawn. The method
may greatly assist in the search for the spawning areas of commercially important food fishes.
Sound production was most intense at night.
Acknowledgments
These studies were collaborative and depended on the efforts of others. Research at the FRS Marine
Laboratory was conducted with Licia Casaretto, Marta Picciullin, & Mark Wood, all of the University of
Aberdeen. Studies at sea involved Licia Casaretto, Marta Picciullin and also Kjell Olsen and Captain
Eilert Halsnes from the University of Tromso.
References
Ames, E.P. (1998) Cod and haddock spawning grounds in the Gulf of Maine. In: The implications of
localized fishery stocks (eds. von Herbing, I.H., Tupper, M., & Wilson, J.) 55(64. NRAES, Ithaca, New York.
Boudreau, P.R. (1992) Acoustic observations of patterns of aggregation in haddock (Melanogrammus
aeglefinus) and their significance to production and catch. Can. J. Fish. Aquat. Sci. 49, 23(31.
Hawkins, A.D. & Amorim, M.C.P. (2000) Spawning sounds of the male haddock, Melanogrammus
aeglefinus. Env. Biol. Fish. 59, 29(41.
Hawkins, A.D. and Chapman, C.J. (1966) Underwater sounds of the haddock Melanogrammus
aeglefinus (L.). J. mar. biol. Ass. U.K. 46, 241-247.
Hawkins, A.D. and Rasmussen, K.J. (1978) The calls of gadoid fish. J. mar. biol. Ass. U.K. 58, 981-911.
Solemdal, P., Knutsen, T., Bjørke, H., Fossum, P., & Mukhina, N. (1997) Maturation, spawning and egg
drift of Arcto-Norwegian haddock (Melanogrammus aeglefinus). J. Fish. Biol., 51 (Suppl. A), p 419.
Waiwood, K.G. & Buzeta, M.I. (1989) Reproductive biology of Southwest Scotian Shelf haddock
(Melanogrammus aeglefinus). Can. J. Fish. Aquat. Sci. 46, 153(170.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Illustrations and Diagrams
Figure 3.Sounds recorded from Balsfjord, identified as haddock.
Figure 1. Repetitive knocks from a male haddock during solitary display.
Figure 2. Waveforms of ‘knocks’ from three individual males (A, B & C).
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Using a Towed Array to Survey Red Drum Spawning Sites in the Gulf of Mexico
Scott A Holt
University of Texas at Austin Marine Science Institute, 750 Channel View Drive, Port Aransas TX
78373 USA.
sholt@utmsi.utexas.edu
Introduction
The red drum (Sciaenops ocellatus) is an important recreational and, in some locations, commercial
species throughout its range. Juveniles generally live in estuaries and move to nearshore oceanic
waters as they reach maturity (Pearson 1929). Adults range widely over the nearshore continental
shelf waters throughout the year but apparently move to coastal waters to spawn (Overstreet 1983).
Spawning is generally thought to take place in coastal waters near inlets (Jannke 1971, Holt et al.
1985) although Lyczkowski-Shultz et al. (1988) found eggs and larvae out to 34 km from shore in
the eastern Gulf of Mexico.There is also evidence of limited spawning activity within estuaries in
Florida (Murphy and Taylor 1990, Johnson and Funicelli 1991) and in North Carolina (Luczkovich et
al.1999).
The location of spawning areas has typically been inferred through capture of fish with mature
gonads or the distribution of eggs and larvae. Red drum make loud, characteristic sounds during
spawning (Guest and Lasswell 1978). Listening for the characteristic sound production has recently
been used to locate red drum spawning sites in Indian River Lagoon, Florida (Johnson and Funicelli
1991), and in Plamico Sound, North Carolina (Luczkovich et al.1999), and at tidal inlets in South
Carolina (Collins et al., these proceedings).These surveys have been done with both hand-held
hydrophones and remotely placed sonobuoys.
Over a four-year period from 1998-2001, a hydrophone mounted on a pier in the Aransas Pass, Texas
tidal inlet has been use to record sounds of red drum spawning activity every evening during the
September through October spawning period. Recordings were made for 20 s every 15 m from
1700 to 0100 hours and spanned the 4-5 hour evening spawning period of red drum (Holt et al.
1985). Red drum produced characteristic spawning sounds from about one hour before sunset to
about three hours after sunset with the most intense activity occurring during the two hours follow-
ing sunset (S. Holt, unpublished data). These data, along with collections of red drum eggs and lar-
vae at the site, confirmed that red drum spawn actively in the vicinity of the tidal inlet. The spatial
extent of red drum spawning was still unknown but it was clear that surveying sound production
during spawning was an effective means of locating spawning sites.
This paper reports on a survey of potential spawning sites in the nearshore western Gulf of Mexico
using a towed hydrophone array.
Study Area and Methods
The survey was conducted in the northwestern Gulf of Mexico along the central portion of the
Texas, USA, coast. Preliminary surveys with a hand-held hydrophone in the area revealed that red
drum spawning sounds were more commonly observed along the 10 m contour than in either shal-
low water near the surf zone or farther offshore in deeper water. Hence, for this initial survey, three
transects were established roughly parallel to the coastline along the 10 m contour.Transects were
sampled on three consecutive nights (one transect per night) in late September 2000. Sampling
commenced about 30 - 45 min before sunset, which was about 1925, and ran for about 3.5 hours.
The towed array was composed of eight hydrophones in an 80 meter cable connected to a 200
meter towing cable and was towed at approximately 4.5 kts from a 105 foot stern trawler.The array
is spectrally flat (i.e. no peaks in sensitivity) from 6Hz to 18 kHz, with a sensitivity of approximately -
191 dB re 1 volt per µPa at 7.2 kHz.The signals from each of the eight separate hydrophones were
saved to an eight-track digital recorder (Tascam DA-88) sampling at 44 kHz. The combination of a
temporal window of spawning vocalizations (about 3.5 hours) and optimum towing speed for the
array of (4.5 kts) limited each nightly transect to about 20 km.
Red drum produce low frequency sounds described as knocks (Fish and Mowbray 1970) or drum-
ming (Guest and Lasswell 1978). Although Guest and Lasswell (1978) found the “dominant energy”
of their recordings from a tank was around 240 Hz - 1000 Hz, I have found the fundamental frequen-
cy of red drum calls obtained from unconstrained fish in the field to consistently be around 140 Hz -
160 Hz (Fig. 1). Each call consists of a variable number of pulses, or knocks, that are repeated at a
range of pulse repetition rates (Guest and Lasswell 1978, laboratory observations; S Holt unpub-
lished data, field observations). Whether there are specific behaviors associated with specific call
types is unknown but the existence of numerous variants in call pattern suggests individual variabil-
ity. Despite variation in call duration and pulse repetition rate, the consistency in fundamental fre-
quency and general character of the call pattern make recognition by ear relatively easy.
Recorded signals from the array were analyzed by listening to the tapes while observing the real-
time power spectra and real-time sonogram on a computer screen (SpectraPro 3.32, Sound
Technology Inc.). Two classes of red drum sounds could be distinguished. One was a low frequency
rumble with a prominent energy peak in the 150 Hz range.This was presumed to be from large
numbers of red drum producing sounds simultaneously but at some distance from the hydrophone.
(The sound produced by the ship and the hydrophone itself was determined to have dominant
energy in the range of 250 Hz - 300 Hz.) The other class of sounds was clearly distinguishable calls
made by an individual or small group of red drum.
The occurrence of background rumble indicates spawning activity in the vicinity of the hydrophone
but more work is needed before the spatial scale over which those sounds travel can be meaning-
fully interpreted. For this paper, I will describe only the distribution of individual or small-group calls.
From our observations and the work of Luczkovich et al. (1999), it appears that the drumming of an
individual red drum can be distinguished over a distance of about 100 m.Thus, we can roughly
define the spatial distribution of individual red drum detected by the hydrophones as a 200 m
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
swath along the transect. The physical location of each observation was determined by comparing
the underway data recorded from the ship’s SAIL system (which included time and latitude/longi-
tude as well as several physical parameters) and the clock time on the digital recorder which was
carefully synchronized with the ships clock. The data set was initially constructed by recording the
hour/minute/second of each identifiable call.The data was then summarized by counting the num-
ber of calls heard in each one-minute segment (the ships location was recorded once per minute so
that was our finest scale of spatial resolution).The number of calls/minute was arbitrarily divided in
two groups: <16 per minute and 16 or more per minute.This division was set to separate the typi-
cally lower occurrence of drumming (5-10 per minute was typical) from the relatively rarer higher
rate (we rarely heard more than 20-30 per minute). Finally the drumming rate (i.e. none, low, or high)
was plotted on the cruise track.
Results
Red drum calls were detected along most sections of the three transects (Figs. 2 & 3). Calls were
detected both in extensive clusters and in isolated occurrences along the transects. For example, on
the San Jose “A” transect (Fig. 3), there are two occurrences of near continuous calling that extend
over several kilometers. On the same transect, there are several isolated occurrences of red drum
calls and extensive segments (up to 4 km) where there are no calls.Transect segments were domi-
nated by the absence of red drum calls.There was a total of 474 minutes of observations over all
transects. Of those, 330 minutes (70%) had no red drum calls, 109 minutes (23%) had low drumming
rates (<16
per min
), and 35 minutes (7%) had high drumming rates (>15
per min
). High drumming activity
was concentrated in two segments along the San Jose “A” transect and in one segment of the
Matagorda transect. One segment, on the east end of the transect, spanned 5 minutes of towing
time and covered 600 m.The other, farther to the west on that transect, spanned 14 minutes of tow-
ing time and covered 2.2 km. Only 4 of the 14 minutes in this segment were low level drumming
and none were without drumming.
The most intense drumming activity occurred between 1830 and 2130. Little drumming was heard
after 2130 on the Matagorda or San Jose “A” transects (data for the later part of the San Jose “B” tran-
sect was lost due to an audio tape malfunction). Low and high drumming rates were distributed
throughout this time period without any temporal pattern.
Discussion
Based on the distribution of sound production, red drum appear to spawn all along the nearshore
region of the central Texas coast. This survey was not spatially comprehensive enough to fully delin-
eate the spawning area, but it is clear from this initial survey that spawning activity is widespread.
Spawning was not concentrated at inlets as suggested by earlier authors (Simmons and Breuer
(1962), Jannke (1971). Areas of the coastline far removed from the inlets had relatively intense drum-
ming activity and confirms suggestions of Murphy and Taylor (1990) that spawning also occurs over
the nearshore continental shelf.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
It is still not exactly clear how drumming by male red drum should be interpreted.There are at least
three possibilities: 1) the drumming male will engage in spawning at that location on that evening;
2) the drumming male is calling from a potential spawning site but will spawn at that site on that
day only if joined (or selected) by a cooperative female; or 3) the drumming male may move to
another place before engaging in spawning. Luczkovich et al. (1999) observed instances of red drum
drumming without finding eggs and Johnson and Funicelli (1991) found red drum eggs without
hearing drumming. In both instances, short-term observations were made in shallow water with a
hand held hydrophone and the observers may have disturbed the fish or missed part of the spawn-
ing process. At this point, it is assumed that drumming roughly equates to spawning but the issue
needs more investigation.
The distribution of drumming male red drum suggest that some, if not most, of the spawning takes
place among widely distributed individuals as opposed to highly aggregated groups. Only 7% of
the one-minute summaries recorded high drumming rates of more than 15 calls per minute. Guest
and Lasswell (1978) reported a call rate of about 2-16 calls per minute for captive red drum in
courtship. Our subjective impression from listening to the tapes was that many of the low drum-
ming rates were produced by a single fish.There were, however, at least two large aggregations of
drumming fish. Both were in the vicinity of Cedar Bayou, a relatively small but historically persistent
tidal inlet. One of these aggregations spanned a linear distance of over 2 km and its breath was
undetermined.The number of calls per minute (up to 40) indicates that several red drum were call-
ing simultaneously within the roughly 100 meter detection range of the hydrophones and this “den-
sity” was consistent over most of the 2 km stretch.
The full extent of the offshore spawning area of red drum is yet to be determined and much
remains to be learned about their reproductive strategies, but the use of towed hydrophone arrays
offers promise of an efficient means to achieve those goals.
Acknowledgments
I thank John Keller for processing the audio data and Cameron Pratt for preparing the figures. The
crew of the R/V Longhorn was instrumental in acquiring the recordings.This work was funded
through a grant from the Sid W. Richardson Foundation.
References
Fish, M. P., and W. H. Mowbray. 1970. Sounds of western North Atlantic fishes; a reference file of bio-
logical underwater sounds. Johns Hopkins Press, Baltimore.
Guest,W. C., and J. L. Lasswell. 1978. A note on courtship behavior and sound production of red
drum. Copeia 1978: 337-338.
Holt, G. J., S. A. Holt, and C. R. Arnold. 1985. Diel periodicity of spawning in sciaenids. Marine Ecology
Progress Series 27: 1-7.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Jannke,T. E. 1971. Abundance of young sciaenid fishes in Everglades National Park, Florida, in relation
to season and other variables. University of Miami Sea Grant Technical Bulletin 11: 128p.
Johnson, D. R., and N. A. Funicelli. 1991. Spawning of the red drum in Mosquito Lagoon, East-Central
Florida. Estuaries 14: 74-79.
Luczkovich, J. J., H. J. Daniel, III, and M. W. Sprague. 1999. Characterization of critical spawning habitats
of weakfish, spotted seatrout and red drum in Pamlico Sound using hydrophone surveys. Pages 128.
North Carolina Department of Environment and Natural Resources, Morehead City, NC.
Lyczkowski-Shultz, J., J. P. Steen, Jr., and B. H. Comyns. 1988. Early life history of red drum (Sciaenops
ocellatus) in the northcentral Gulf of Mexico. Pages 148. Mississippi-Alabama Sea Grant Consortium.
Murphy, M. D., and R. G. Taylor. 1990. Reproduction, growth, and mortality of red drum Sciaenops
ocellatus in Florida waters. Fishery Bulletin, US 88: 531-542.
Overstreet, R. M. 1983. Aspects of the biology of the red drum, Sciaenops ocellatus, in Mississippi.
Gulf Research Reports Supplement 1: 45-68.
Simmons, E. G., and J. P. Breuer. 1962. A study of redfish, Sciaenops ocellata Linnaeus and black drum,
Pogonias cromis Linnaeus. Publications of the Institute of Marine Science 8: 184-211.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Illustrations and Diagrams
Figure 3.Location of the Matagorda hydrophone transect. See Fig.2 legend for details.
Figure 1.Sonogram of a red drum call from an unconstrained individual in the field.This particular call consists of
three widely spaced knocks followed by two pairs of closely spaced knocks.
Figure 2.Location San Jose “A” and “B” hydrophone transects.The line indicates the cruise track. Bars above the line
indicate low one-minute drumming rates at that location. Bars below the line indicate high one-minute drumming
rates. Sampling time is indicated randomly along the track.
Reef Fish Courtship and Mating Sounds: unique signals for acoustic monitoring
Phillip S. Lobel
Boston University Marine Program, Marine Biological Laboratory
Woods Hole, MA 02543
The following text is extracted from:
Lobel, P. S. 2002 Diversity of fish spawning sounds and the application of passive acoustic monitor-
ing. Bioacoustics 12:286-289.
The table is reprinted from:
Lobel, P.S. (2001) Acoustic behavior of cichlid fishes. J. Aquaculture & Aquatic Sci. 9, 167-186.
Introduction
Marine bioacoustics is a multidisciplinary field with practical applications to economically important
global fisheries issues. One application of bioacoustics uses passive acoustic technology to record
temporal and spatial patterns of fish reproduction by detecting sounds associated with spawning
(Mann and Lobel 1995).The applicability of this tool depends upon whether specific species pro-
duce reliably identifiable sounds during courtship and spawning (Lobel 2001a). Monitoring
courtship and spawning sounds can be used to define important breeding habitats (a priority in
planning marine protected areas) and to understand the relationships between fish reproduction
and the fate of larvae in ocean currents. Mating is the crucial biological event to monitor in order to
understand the life history tactics of fishes, especially coastal marine species with a pelagic larval
phase. Mating is also a critical endpoint measurement in pollution impact studies. Measuring a
decrease in reproduction may be an early indication of subtle adverse affects of pollution. It is well
known that many fishes produce sounds associated with courtship. However, which fishes produce
specific sounds during spawning is not as well known.
A strong case for the value of bioacoustic monitoring is made by the discoveries that two of the
world’s most valuable fishes, cod and haddock, produce distinct courtship and spawning sounds
(Nordeide and Kjellsby 1999, Hawkins and Amorim 2000). This paper documents the spawning
sounds of four coral reef fishes and illustrates different types of acoustic patterns.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Examples of Spawning Sounds
Methods are reported by Lobel (2001a) and spawning behaviors with sounds are described in refer-
ences cited below for each species.
Ostracion meleagris (Family Ostraciidae) produces a clear tonal sound with one harmonic (Figure 1a,
Lobel 1996).
Dascyllus albisella (Family Pomacentridae) produces a spawning sound composed of a simple series
of one to four pulses (Figure 1b). This spawning sound differs from its courtship sound only by hav-
ing fewer pulses (Lobel and Mann 1995). A spawning sound was not found in another pomacentrid
(Abudefduf sordidus) or in related freshwater cichlids (Lobel 1998, 2001b, Lobel and Kerr 1999), even
though these other fishes produce courtship sounds similar to D. albisella.
Hypoplectrus nigricans (Family Serranidae) produces a distinct two-part spawning sound (Figure 1c).
A short downward frequency sweep is followed by a short silence and then followed by a broad-
band sound, which is made as the fish disperse gametes (Lobel 1992). This sound may be a combi-
nation of swimbladder sound and hydrodynamic noise from rapid fin fluttering.
Scarus iserti (Family Scaridae) spawns in aggregations of about 20 to 40 individuals.These fish gather
in groups over the reef surface and then suddenly and with great speed, rush upwards a few meters,
turn rapidly while releasing gametes and dart back to the reef shelter (Lobel 1992). This spawning
sound is hydrodynamic noise produced by the fish's swimming movements (Figure 1d).
Discussion
Why do some fishes make spawning sounds? By the time mating has started, mate selection has
already taken place. Such sounds may have originated as a mere by-product of movements associ-
ated with swimming and gamete extrusion. Furthermore, these sounds are in the low frequency
range that has been shown to be highly attractive to predators, e.g. sharks (Myrberg et al. 1972).
Spawning fishes may be less responsive to predatory threats once they are completely preoccupied
with mating (Lobel and Neudecker 1985, Sancho et al. 2000). The possibility that spawning sounds
may be an attracting signal to predators on adults or newly spawned embryos is a significant
potential cost in terms of natural selection.This implies that spawning sounds must also provide
some evolutionary advantage as well. Spawning sounds may have evolved to behaviorally synchro-
nize gamete release in order to maximize external fertilization.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Table 1. (reprinted from Lobel 2001b)
Possible information transmitted by sound patterns (in order of increasing complexity of signal
interpretation)
Message Acoustic clue
Mate location sound occurrence
Readiness to spawn sound occurrence
synchonization of gamete release (= mating or spawning sound)
Vigor / aggressiveness duration of call &/ call repetition rate
Individual size dominant frequency
Species identity variation in pulse repetition rate in a call, number of pulses in a
call, variation in pulse amplitude, call duration , plus color
patterns & behavior
Individual identity combination of all above clues, plus other features of behavior
Acknowledgement
Research funded by the Army Research Office (DAAG-55-98-1-0304 and DAAD19-02-1-0218). My
participation in this meeting was supported by the Woods Hole Sea Grant office.
References
Hawkins, A. D. & Amorim, M. C. P. (2000) Spawning sounds of the male haddock, Melanogrammus
aegelfinus. Environ. Biol. Fishes 59, 29-41.
Lobel, P. S., (1992) Sounds produced by spawning fish. Environ. Biol. Fishes 33, 351-358.
Lobel, P. S. (1996) Spawning sound of the trunkfish, Ostracion meleagris (Ostraciidae). Biol. Bul. 191,
308-309
Lobel, P. S. (1998) Possible species specific courtship sounds by two sympatric cichlid fishes in Lake
Malawi, Africa. Environ. Biol. Fishes 52, 443-452.
Lobel P. S. (2001a) Fish bioacoustics and behavior: passive acoustic detection and the application of
a closed-circuit rebreather for field study. Marine Technology Society Journal 35(2)19-28
Lobel, P. S. 2002 Diversity of fish spawning sounds and the application of passive acoustic monitor-
ing. Bioacoustics 12:286-289.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Lobel, P.S. (2001b) Acoustic behavior of cichlid fishes. J. Aquaculture & Aquatic Sci. 9, 167-186.
Lobel, P. S. 2002 Diversity of fish spawning sounds and the application of passive acoustic monitor-
ing. Bioacoustics 12:286-289.
Lobel, P. S. & Kerr, L. M. (1999) Courtship sounds of the Pacific Damselfish, Abudefduf sordidus
(Pomacentridae). Biol. Bul. 197, 242-244.
Lobel P. S. & Mann, D. A. (1995) Spawning sounds of the damselfish, Dascyllus albisella
(Pomacentridae), and relationship to male size. Bioacoustics 6, 187-198.
Lobel, P. S. & Neudecker, S. (1985) Diurnal periodicity of spawning activity by the hamlet fish,
Hypoplectrus guttavarius (Serranidae). In: The Ecology of Coral Reefs, Vol. 3, Symposia Series for
Undersea Research, (M. L. Reaka, ed), NOAA, Rockville, MD, pp. 71-86
Myrberg, A. A., Ha S. J., Walewski S. & Branbury J. C.. 1972. Effectiveness of acoustic signals in attract-
ing epipelagic sharks to an underwater source. Bull. Marine Sci. 22, 926-944. Sci. 56, 326-332.
Sancho, G., Petersen, C. W. & Lobel, P. S. (2000) Predator-prey relations at a spawning aggregation site
of coral reef fishes. Mar. Eco. Prog. Ser., 203, 275-288.
Nordeide, J.T. & Kjellsby, E. (1999) Sound from spawning cod at their spawning grounds. ICES J. Mar.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Illustrations and Diagrams
Figure 1. Sonograms produced using the hamming window function and an FFT size of 2048 points (Canary soft-
ware). Frequency scale is the same in all graphs, but time scale differs in each.a) Ostracion meleagris, duration 6213
ms, dominant frequency, DF 258 Hz, b) Dascyllus albisella, 3 pulses, duration 130 ms, DF 328 Hz, c) Hypoplectrus nigri-
cans, duration 1581 ms, DF 656 Hz, d) Scarus iserti, duration 329 ms, DF (two peaks) 492 & 211 Hz. Size range of these
fishes is about 10 – 20 cm SL. (reprinted from Lobel 2002).
Using Passive Acoustics to Monitor Spawning of Fishes in the Drum Family
(Sciaenidae)
Joseph J. Luczkovich
1,2
and Mark W Sprague
3
1
Institute for Coastal and Marine Resources,
2
Department of Biology,
3
Department of Physics,
East Carolina University, Greenville, NC, USA 27858 A
luczkovichj@mail.ecu.edu
spraguem@mail.ecu.edu
Introduction
Drum fish (Family Sciaenidae) are known for their sound production during mating, from which the
family derives its name (Fish and Mowbray 1970). Members of the drum family are dominant
species in the large and valuable commercial and recreational fisheries in North Carolina and the
Southeastern USA. Recently, concerns have been raised about the decline in the population and
spawning stock of some sciaenids, especially the red drum, Sciaenops ocellatus (Ross et al. 1995).
One management option that has been suggested is to create spawning reserves, but spawning
areas must be surveyed first in order to protect them. Sciaenid fishes held in captivity produce
species-specific sounds associated with spawning behavior (Guest & Laswell 1978; Connaughton
and Taylor 1996, Sprague et al. 2000) and recently spawned eggs and sounds co-occur in field sam-
ples (Mok and Gilmore 1983, Luczkovich et al. 1999). Spectral analysis of these sounds allows us to
identify each sciaenid species based on their sound production, even when they co-occur in the
same area (see Sprague et al 2000, Sprague and Luczkovich these proceedings). Because sounds are
produced by male fishes in the Sciaenidae in communication during courtship and spawning, we
are able to use these sounds as an indicator of spawning areas. Here we report on how we used
passive acoustic survey techniques for mapping spawning areas of red drum, weakfish (Cynoscion
regalis), spotted seatrout (C. nebulosus) and silver perch (Bairdiella chrysoura) in Pamlico Sound, NC.
Methods
Sounds of sciaenid fishes were recorded in two ways: 1) a hydrophone and recording system
deployed from a small boat that was able to move from station to station; and 2) a hydrophone
array system on a remotely operated vehicle (ROV) with low-light video capabilities. From May
through September during 1997 and 1998, we used an InterOcean (902) Calibrated Acoustic
Listening System [consisting of a gain-adjustable pre-amp, a hydrophone, and an overall sound
pressure level meter] and a Sony (TCD-D8) Digital Audio Tape recorder to record from a small boat
at fixed stations in Pamlico Sound for up to 5 min per station after sunset on monthly intervals. The
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
hydrophone was suspended over the side of the boat at a depth of 1 m. In order to confirm that the
sites where we recorded sounds were spawning areas, we conducted ichthyoplankton surveys at
the hydrophone stations immediately after each sound recording ended. A 28-cm diameter bongo
net with 500 µm mesh was towed at the surface for 5 min to capture the buoyant eggs. In May of
2001, we used a Phantom S2 ROV with low-light video and a calibrated International Transducer
Corporation (ITC-4066) hydrophone array to record the sound production of a silver perch in situ.
The hydrophone array was mounted on the ROV on a 1.5 m long boom.The pre-amplified signal
from the hydrophone array was sent up the 900-foot ROV umbilical cord to an audio and video
recorder on board the boat. Although we used a four-hydrophone array, which was originally
intended to help localize fish sounds, only one hydrophone (hydrophone number 4 located on the
far right side of the boom as viewed from the point of view of the video camera) was selected for
recording in this study. All sound recordings were resampled at 24 kHz from the original tapes
using a National Instruments A/D board. We used 1024-point Fast-Fourier-Transforms (FFTs) to
obtain spectrograms and estimates of overall sound pressure levels. To generate the spectrograms,
we used Virtual Instruments written for use with LabView data acquisition software and
Mathematica for creating plots. Statistical analysis was done using Systat 10 (Sprague et al. 2000).
Results
We detected the spawning aggregations of silver perch, weakfish, spotted seatrout, and red drum in
Pamlico Sound during both 1997 and 1998. Male silver perch were detected on both the eastern
and western side of Pamlico Sound, but were loudest at the inlet stations during May and June of
both years (Figure 1a). The male weakfish were detected making their characteristic “purring”
sounds only at stations on the eastern side of Pamlico Sound, near Ocracoke and Hatteras Inlets in
May through August of both years, but the peak calling was in May and June (Figure 1b). Spotted
seatrout were found producing their grunts at stations on both sides of the sound from June
through September, but were more regularly recorded near the Bay River on the western side of
Pamlico Sound in July of both years (Figure 1c). Red drum were heard both at the inlets and on the
western side of the sound in August through September both years, but they were loudest in
September near the mouth of the Bay River in the western side of the sound (Figure 1d).The overall
picture is one of a seasonally shifting use of specific areas near river mouths and inlets by the four
species, with distinct peak spawning times for each species.To demonstrate that these sounds are
associated with spawning activity, we collected sciaenid type eggs in the areas where we had
recorded fish sounds. The overall sound pressure level (in dB re 1 µPa) at each station was directly
correlated with the log
10
transformed sciaenid type egg density (Figure 2, r = 0.61). This suggests
that the sounds (produced by male fish) and the recently spawned sciaenid eggs (produced by
female fish) are associated in space and time, an indication that the sounds are associated with
spawning.
The low-light capabilities of the video camera of the Phantom S2 ROV allowed us to see fish as they
made their sounds.Thus, we were able to measure the sound production by silver perch when they
were a known distance from the hydrophone. In this way, we were able to determine the sound
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
source level for an individual fish in situ, which is a necessary first step for modeling sound produc-
tion and propagation. In May 2001, we had the opportunity to capture a single silver perch on video
while it passed in front of the ROV and the hydrophone, producing some of the loudest sounds that
we had recorded during our surveys. The ROV was deployed in Wallace Channel, near Ocracoke
Inlet, at a depth of 28 feet, in an area where we had previously recorded loud vocalizations of both
silver perch and weakfish. Poor water clarity and strong currents at this site limited the camera’s
ability to see and the mobility of the ROV, which was deployed with a down-weight rig to hold near
to the bottom during the tidal current shifts. On May 5, 2001 at 21:18:05, we recorded a calling male
silver perch and measured the sound pressure level at hydrophone #4 when the fish was swimming
through (from left to right) the viewing field of the low-light video (Figure 3). At this point, the
sound pressure level was 126 dB re 1µPa.At 21:18:15, after the fish swam across the video field of
view, and closer to hydrophone # 4, which was on the boom to the right, the sound pressure level
was measured at 129 dB re 1µPa.Thus, the overall sound pressure level increased as the fish (sound
source) got closer to the hydrophone.
Discussion
The passive acoustic approach we have described is limited to soniferous fishes, but almost all sci-
aenids fall into this category. Soniferous sciaenid fishes produced sounds during spawning in
Pamlico Sound, and these general areas have been mapped. Weakfish and silver perch call com-
monly near Hatteras and Ocracoke inlets, peaking in May and June, whereas spotted seatrout were
commonly detected calling throughout the summer in both eastern and western Pamlico Sound,
peaking in July. Red drum were less commonly detected by passive acoustics than the other
species of sciaenids, perhaps due to their declining spawning stocks; they were only detected at the
inlets and in western Pamlico Sound in August and September, with the greatest sound production
at the mouth of the Bay River in September. Sciaenid-type egg abundance was correlated to over-
all sound pressure level (loudness) of sciaenid drumming in field surveys, suggesting that egg pro-
duction could be estimated from sound production. This passive acoustic approach to estimating
spawning stock relative abundance would be useful to fishery biologists attempting to verify the
variations in spawning stock sizes from year to year. No estimates of absolute fish abundance can
be made at the present time; but biomass estimation may be possible in the future if active
acoustics were also used.
From the ROV hydrophone measurement of sound source levels, we can now estimate the distance
over which fish sounds can be detected. For an individual silver perch calling 1 m from the
hydrophone at 129 dB re 1 µPa, (assuming a cylindrical spreading model, where rmax is the radius
of the cylinder, see Luczkovich et al. 1999), we can now estimate r
max
= 10
(SPL source - SPL background)/10
= 79 m.
However, this cylindrical spreading model assumes that sound waves will propagate through water
with constant temperature and salinity and a uniform depth, conditions that are unlikely to occur at
the inlets. Consequently, we may be over-estimating the distance which we can detect sounds. It is
also possible that sound may be channeled further than this due to particular bathymetric and
water stratification conditions peculiar to Pamlico Sound and the inlets.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
References
Connaughton, M. A. and M. H. Taylor. 1996. Drumming, courtship, and spawning behavior in captive
weakfish, Cynoscion regalis.Copeia 1996, 195-199
Fish, M. P. and W. H. Mowbray. 1970. Sounds of Western North Atlantic Fishes, The Johns Hopkins
Press, Baltimore and London, 194 pp.
Guest,W. C. and J. L. Lasswell. 1978. A note on courtship behavior and sound production of red drum.
Copeia 1978, 337-338.
Luczkovich, J. J., M.W. Sprague, S. E. Johnson, and R. C. Pullinger. 1999. Delimiting spawning areas of
weakfish, Cynoscion regalis (Family Sciaenidae) in Pamlico Sound, North Carolina using passive
hydroacoustic surveys. Bioacoustics 10, 143-160.
Luczkovich, J. J., H. J. Daniel III, M. Hutchinson, T. Jenkins, S. E. Johnson, R. C. Pullinger, and M.W.
Sprague. 2000. Sounds of sex and death in the sea: bottlenose dolphin whistles silence mating cho-
ruses of silver perch. Bioacoustics 11, 323-334.
Mok, H. K. and R. G. Gilmore. 1983. Analysis of sound production in estuarine aggregations of
Pogonias cromis, Bairdiella chrysoura, and Cynoscion nebulosus (Sciaenidae). Bulletin of the Institute
of Zoology, Academia Sinica. 22, 157-186.
Sprague, M.W., J.J. Luczkovich, R. C. Pullinger, S. E. Johnson, T. Jenkins, and H. J. Daniel III. 2000. Using
spectral analysis to identify drumming sounds of some North Carolina fishes in the family
Sciaenidae. Journal of the Elisha Mitchell Society 116, 124-145.
Ross, J. L., Stevens,T. M. and Vaughan, D. S. 1995. Age, growth, reproductive biology, and population
dynamics of red drum (Sciaenops ocellatus) in North Carolina waters.Transactions of the American
Fisheries Society 124, 37-54.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Illustrations and Diagrams
Figure 3. Spectrogram of 24-s segment of the ROV audio track from hydrophone #4, recorded 5 May 2001, beginning
at 21:18:00. The sound source levels (in sound pressure in dB re 1 µPa) are shown for two times at which the silver
perch first appears in the ROV video camera field of view (at 5-6 s) and just after it passed out of view of the camera,
when it was the loudest (at 16-17 s)
Figure 1 Maps of Pamlico Sound sciaenid species’ spawning areas and times as determined by hydrophone surveys:
a) silver perch (triangles), peaking in May and June; b) weakfish (circles) peaking in May and June; c) spotted seatrout
(squares) peaking in July; and red drum (pentagons) peaking in September.
Figure 2 Log 10 transformed sciaenid-type
egg production plotted versus sound pressure
level (db re 1 µPa). Line fitted with a locally
weighted regression (LOWESS).
Is acoustic calls a premating reproductive barrier between two northeast
Atlantic cod (Gadus morhua) groups—a review
Jarle Tryti Nordeide
1
and Jens Loss Finstad
2
1
Faculty of Fisheries and Natural Sciences, Bodø Regional University, N-8049 Bodø, Norway.
2
Master student at: Department of Fisheries and Marine Biology, University of Bergen, Norway
Summary
This paper reviews the first attempts to test the hypothesis that spawning calls of male migratory
“Arctic” and a stationary “Coastal”cod group, which are sympatric during the spawning season, is a
premating behavioural reproductive barrier. As predicted from the hypothesis, a hushed hubbub of
sound with a transient character, band-width and harmonic spacing typical of cod calls, was
revealed at a major spawning ground during the spawning period but not six months later.
Moreover, individual calls from male cod kept in tanks varied a lot both in harmonic spacing and
duration, from 42 to 79 Hz and 0.11 to 1.25 s, respectively. Such individual variation in calls is expect-
ed if females choose mate on the basis of their calls. However, the results so far has failed to support
the third prediction, since no differences have been found between the calls of the two groups, nei-
ther in harmonic spacing, duration, or temporal structure of the calls.
Introduction
Northeast Atlantic cod consist of two stocks, the Northeast Arctic, or “Arctic” cod, and the Norwegian
coastal cod, or “Coastal” cod (Rollefsen 1934). Arctic cod migrate from the feeding areas in the
Barents Sea to the spawning areas along the Norwegian coast and the most important spawning
area is off the Lofoten Islands where the main spawning occurs in March and April (Bergstad & al.
1987). Coastal cod inhabit coastal areas and fjords, migrate short distances and spawns in a large
number of fjords along the Norwegian coast (Rollefsen 1954), including off the Lofoten Islands
(Hylen 1964). Both cod groups spawn in March and April and mature speciemens are sympatric dur-
ing spawning at the major spawning grounds off the Lofoten Islands (Nordeide 1998). A controver-
sial topic during decades has been whether or not the two cod groups interbreed, and a majority of
studies conclude that they rarely do (see references in Nordeide & Pettersen 1998). If so, active part-
ner choice is required, and lekking has recently been suggested to best describe the cod’s mating
system (Hutchings & al. 1999; Nordeide & Folstad 2000).
Møller (1968) suggested that active partner choice based on acoustic calls may be an behavioural
mechanism which prevents interbreeding between the two cod groups.The aim of this paper is to
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
summarize the first attempts to test predictions derived from Møller’s hypothesis.The predictions
are that (i) recordings from major cod spawning grounds should reveal sound with characteristics
typical of cod whereas much less sound should be revealed outside the spawning season, (ii) calls
from individual cod should show considerable variation, and (iii) calls from Arctic and Coastal cod
should differ.
Material and methods
To study sound at a major spawning ground, recordings were carried out during the night at five
stations off the Lofoten Islands at 68
o
13.0’N 14
o
38.7’E in Northern Norway, during the spawning sea-
son 8 and 9 April 1997, and half a year later on 4 September 1997 (Nordeide & Kjellsby 1999).The
measuring hydrophone with a 32 dB gain built-in preamplifier had a total sensitivity of -152 dB re 1
V/µPa within the frequency range of 16 Hz to 2 kHz. In order to emphasize the transient character of
the sound the digital recordings were analysed with Short-time Fourier Techniques (STFT), at the
Norwegian Defence Research Establishment (Nordeide & Kjellsby 1999).
To compare the calls from the two groups, recordings were carried out in land-based tanks in 1998
to 2001 (Finstad, 2002.). Speciemens of the Arctic and Coastal cod were caught by trawl and trans-
ferred to tanks where recordings were carried out during the spawning period in 1998 - 2001.The
smallest male used was 53 cm and the largest male was 94 cm long, whereas the smallest and
largest females were 51 cm and 104 cm long, respectively.The average length of the five cod groups
varied from 74.2 cm to 84.0 cm for males, and from 68.8 cm to 90.5 cm for females. Most recordings
were from three 6 m diameter fibreglass tanks, but a 3 m diameter fibreglass tank was also used.
Water level was 1.4 - 1.5 m in all tanks. Recording equipment was a 1 inch piezoceramic spherical
hydrophone with a sensitivity of -198 dB ref 1V 1µPa,a Levell preamplifier type TA 601 with 60 dB
gain, and a Sony TCD-D100 digital tape recorder. In 1998, the recordings were carried out with 12
speciemens (six Coastal males) in the experimental tank, whereas seven Arctic cod (5 males) where
present in 1999. After the first years of experience we had identified two major problems: (i) we
were not able to identify which cod produced the calls, and (ii) relatively few grunts had been
recorded. In 2000 and 2001 we therefore chose to first record grunts with all cod in each group kept
together, to increase the number of grunts.Thereafter, we split the groups of fish into a total of 10
smaller sub-groups to increase the minimum number of individual cod which could possibly pro-
duce the grunts.The groups in 2000 and 2001 consisted of 8 (3 males), 25 (19 males) and 22 (7
males) cod, respectively.The sub-groups consisted of from 4 (2 males) to 16 (11 males) cod.Towards
the end of the spawning season the fish were killed. Examination of their otoliths by the Institute of
Marine Research in Bergen, revealed that the recordings were carried out with groups and sub-
groups consisting of (i) only male Coastal cod with or without the presence of Arctic females, (ii)
only male Arctic cod with or without the presence of Coastal females, and (iii) a mixture of Coastal
and Arctic males and females.These three alternative combinations are referred to as “Coastal-vocal”,
“Arctic-vocal” and “Mix-vocal” groups respectively, since only males produce sound during the
spawning period (Brawn 1961c, Hawkins & Rasmussen 1978, see also Templeman & Hodder 1958,
Engen & Folstad 1999).The number of individual cod (statistical “N”) which could have produced the
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
recorded grunts were minimum 3 and maximum 12 in the “Coastal-vocal”group, minimum 2 and
maximum 7 in the “Arctic-vocal”, and minimum 4 and maximum 22 in the “Mix-vocal”groups.
Analysis by Avisoft-SASLabPro v. 3.74 provided estimates of harmonic spacing and duration of the
grunts.Temporal structure of 78 recorded high quality grunts were analysed from oscillograms.
Parameters included were number of downward peaks, time-intervals between peaks, and duration
of the grunt.These parameters were analysed by Principal Component Analysis by the software “The
Unscrambler” v. 7.5.
Results and Discussion
Field recordings provide support for the hypothesis that acoustic communication is important dur-
ing cod spawning. Sound recordings at the major spawning ground off the Lofoten Islands revealed
a hushed hubbub of sound, at approximately 40 - 500 Hz during the spawning period (Fig. 1a). Much
less sound was revealed in September (Fig. 1b) when no cod spawn and migratory cod had emigrat-
ed to the Barents Sea. Nordeide & Kjellsby (1999) argues that this sound most likely is made by
spawning cod since (1) The sound activity is highest in the frequency range where it has been sug-
gested cod communicate (Chapman & Hawkins 1973; Hawkins & Rasmussen 1978). (2) The sound
above 50 Hz had a transient character as expected for cod grunts. (3) More than ca. 50 million male
cod spawned off the Lofoten Islands in April 1997, and recordings were made where the Institute of
Marine Research in Bergen located the highest densities of spawning cod. (4) Cod totally dominat-
ed, by constituting more than 98 % by wet weight, the experimental and commercial catches in the
area the seven days before, during and after the recordings (Nordeide & Kjellsby 1999).
Variation in calls between individual cod kept in tanks is as expected under the hypothesis that
acoustic communication is important during female mate choice. Grunts from cod kept in tanks
vary in harmonic spacing from 42 Hz to 79 Hz, and in duration from 0.11 s to 1.25 (Table 1). The two
grunts with the lowest and highest harmonic spacing came from two different individuals, since
they were recorded from two different sub-groups.The shortest and longest calls were also pro-
duced by two different individuals. This shows that different cod individuals may grunt at different
frequencies and durations, but we cannot tell anything about each individual cod’s possibility to
vary their calls.
Frequency (Hz) Duration (s)
NMean Min Max N Mean Min Max
CC-vocal
1
18 53.4 47 60 11 0.33 0.13 0.94
NAC-vocal
2
11 55.7 50 60 11 0.31 0.11 0.74
MIX-vocal
3
126 51.5 42 79 95 0.22 0.13 1.25
All grunts 155 52.1 42 79 116 0.24 0.11 1.25
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Table 1 (above). Mean, minimum and maximum values of frequency and duration of grunts from CC-
vocal
1
,NAC-vocal
2
and the MIX-vocal
3
group. Number of grunts (N) of frequency measurements and dura-
tion measurements differ because some of the duration measurements were difficult to perform due to
background noise.The table is from Finstad (2002.).
1
Grunts from groups and sub-groups consisting of CC males and CC and NAC females, based on
otolith analyses
2
Grunts from groups and sub-groups consisting of only NAC individuals, based on otolith analy-
ses
3
Grunts from groups and sub-groups consisting of both CC and NAC, both males and females,
based on otolith analyses
The average harmonic spacing of grunts from the Coastal-vocal groups and Arctic-vocal groups
were 53.4 Hz and 55.7 Hz, respectively, and the calls from the two cod groups lasted on average 0.33
s and 0.31 s, respectively (Table 1). The difference of 2.3 Hz in harmonic spacing and 0.02 s in dura-
tion between the two groups, is probably negligible.The difference cannot be tested statistically
because the grunts are not independent events, since we were not able to tell which cod produced
each call. Moreover, the calls from the Mix-vocal groups show no bimodal distribution in harmonic
spacing or duration, as is expected if Coastal and Arctic cod call at two separate frequencies or dura-
tions. In the multivariate analysis of the temporal structure of the grunts, the first and second princi-
pal component explained 45 and 20%, respectively, of the total variation. However, the analysis did
not cluster the grunts from Arctic-vocal and Coastal-vocal cod into two separate groups, as should
be expected if the temporal structure of the two cod-groups differed (Finstad, 2002.). The hypothesis
thus failed to pass the third test, since we have not been able to separate the calls from the two cod
groups. However, analysis of temporal structure will continue with less rough analytical tools.
References
Bergstad, O.A.,T. Jørgensen, O. Dragesund 1987. Life history and ecology of the gadoid resources of
the Barents Sea. - Fisheries Research 5:119-161.
Brawn,V.M. 1961c. Sound production by the cod (Gadus callarias L.).- Behaviour 18:239-255.
Chapman, C.J. & A.D. Hawkins 1973. A field study of hearing in the cod, Gadus morhua L. - Journal of
Comparative Physiology. 85: 147-167.
Engen, F. & I. Folstad 1999. Cod courtship song: a song at the expense of dance?- Canadian Journal of
Zoology 77:542-550.
Finstad, J.L. 2002. Acoustic calls of Norwegian coastal cod and North-East Arctic cod (Gadus
morhua). Cand. scient. thesis at the Departure of Fisheries and Marine Biology, University of Bergen,
Bergen.
Hawkins, A.D. & K.J. Rasmussen 1978. The calls of Gadoid fish. - Journal of the Marine Biology
Association of U.K. 58:891-911.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Hutchings, J.A., T.D. Bishop & C.R. McGregor-Shaw 1999. Spawning behaviour of Atlantic cod, Gadus
morhua:evidence of mate competition and mate choice in broadcast spawner.- Canadian Journal
of Fisheries and Aquatic Sciences 56:97-104.
Hylen, A. 1964. Coastal cod and skrei in the Lofoten area. - Fiskeridirektoratets Skrifter Serie
Havundersøkelser, 13:27-42.
Møller, D. 1968. Genetic diversity in spawning cod along the Norwegian coast.- Hereditas 60:1-32.
Nordeide, J.T. 1998. Coastal cod and north-east Arctic cod - do they mingle at the spawning grounds
in Lofoten?- Sarsia 83:373-379.
Nordeide, J.T. & I. Folstad 2000. Is cod lekking or a promiscuous group spawner?- Fish and Fisheries
1:90-93.
Nordeide, J.T. & E. Kjellsby 1999. Sound from spawning cod at their spawning grounds.- ICES Journal
of Marine Science 56:326-332.
Nordeide, J.T. & I.H. Pettersen 1998. Haemoglobin frequencies and vertebrae numbers of cod (Gadus
morhua L.) off northern Norway - test of a population structure hypotheses.- ICES Journal of Marine
Science 55:134-140.
Rollefsen, G. 1934. The cod otolith as a guide to race, sexual development and mortality.- Rapports et
Proces-Verbaux des Reunions du Conseil International Pour l’Exploration de la Mer 88:1-6.
Rollefsen, G. 1954. Observations on the cod and cod fisheries of Lofoten.- Rapports et Proces-
Verbaux des Reunions du Conseil International Pour l’Exploration de la Mer, 136:40-47.
Templeman, W. & V.M. Hodder 1958. Variation with fish length, sex, stage of sexual maturity, and sea-
son in the appearance and volume of the drumming muscles of the swimbladder in the haddock,
Melanogrammus aeglefinus (L.).- Journal of the Fisheries Research Board of Canada. 15:355-390.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Illustrations and Diagrams
Figure 1. Recordings from a major spawning ground off the Lofoten Islands, (a) during the spawning period in April
and (b) in September when no cod spawn. Reprinted from ICES Journal of Marine Science,Vol. 56, Nordeide, J.T. & E.
Kjellsby, Sound from spawning cod at their spawning grounds, 326-332, 1999, by permission of the publisher
Academic Press.
Applications of underwater acoustics data in fisheries management for
spotted seatrout, Cynoscion nebulosus, in estuaries of South Carolina
Bill Roumillat and Myra Brouwer
Marine Resources Research Institute, South Carolina Department of Natural Resources,
217 Ft. Johnson Rd., Charleston, SC 29412.
roumillatb@mrd.dnr.state.sc.us
brouwerm@mrd.dnr.state.sc.us
Introduction
The spotted seatrout, Cynoscion nebulosus, is an estuarine-dependent member of the family
Sciaenidae. Spotted seatrout are year-round residents of estuaries along the South Atlantic coast
and spawning takes place inshore and in coastal areas (McMichael and Peters, 1989; Luczkovich et
al., 1999). During summer months, male spotted seatrout produce “drumming”sounds, this resulting
from the contraction of the swimbladder by specialized muscles which are seasonally hypertro-
phied from the abdominal hypaxialis muscle mass (Fish and Mowbray, 1970; Mok and Gilmore,
1983). Direct involvement of sound production with spawning has been shown for this and other
sciaenids (Mok and Gilmore, 1983; Saucier et al., 1992; Saucier and Baltz, 1993; Luczkovich et al.,
1999). By listening to these sounds during evening hours (Holt et al. 1985) using hydrophone equip-
ment we determined the locations, seasonality and diurnal periodicity of spawning aggregations in
Charleston Harbor (Saucier et al., 1992; Riekerk et al., unpublished data).
Spotted seatrout are group-synchronous spawners with indeterminate fecundity. As such, they
release gametes in several batches over a protracted spawning season and total fecundity is not
fixed prior to the onset of spawning (Wallace and Selman, 1981). The spawning season extends
from April through September along the South Atlantic and Gulf of Mexico coasts (Overstreet, 1983;
Brown-Peterson et al., 1988; McMichael and Peters, 1989; Wenner et al., 1990; Saucier and Baltz,
1993). As in other indeterminate spawning fish, annual fecundity in this species is dictated by the
number of oocytes released during each spawning event (batch fecundity, BF) and the number of
such spawning events during the course of the season (spawning frequency, SF). Estimation of
annual fecundity (AF) is intuitively necessary to determine the contribution of an entire spawning
season, and is made even more useful for fisheries management purposes if separated by size class
or age cohort within a population (Prager et al., 1987; Zhao and Wenner, 1995).
Behavior patterns based on acoustic data enabled us to target females in imminent spawning con-
dition, then carry out oocyte counts for batch fecundity estimation. Additional random sampling in
other estuarine areas of the SC coast provided the data necessary to estimate spawning frequency
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
for each of the three dominant age classes (ages 1-3) in our waters. Ultimately, our annual fecundity
estimates for each age class will facilitate management of this species in South Carolina.
Estimation of batch fecundity
We conducted sampling for batch fecundity studies during two consecutive afternoons fortnightly
from the middle of April through the first week of September 1998, 1999 and 2000. We deployed a
trammel net from a shallow water boat at pre-selected sites in Charleston Harbor. Sites were chosen
based on proximity to known spawning locales established through hydrophone work. Water
depth at the sampling sites ranged from 0.3 to 1.5 meters and sampling was conducted during the
afternoon (1400-1800h) high tide. Male spotted seatrout, identified by their drumming sounds, were
measured and released on site. Females were brought back to the laboratory for processing. We
recorded standard life-history parameters for each specimen, preserved sagittal otoliths for aging
and removed sections of the posterior portion of each ovary for histological work. In addition, whole
ovaries that evidenced oocyte maturation were fixed in 10% buffered seawater formalin for enu-
meration of hydrated oocytes (Hunter and Macewicz, 1985).
One hundred and thirty-five ovaries were used to estimate batch fecundity of spotted seatrout aged
1-3. We re-weighed preserved ovaries to the nearest 0.01 g and randomly extracted 130-150 mg
aliquots from three of eight possible regions in the ovary (four per lobe). We counted hydrated
oocytes and used their mean number per subsample to estimate the total number of oocytes in the
ovary.To investigate the relationships between batch fecundity and length, somatic weight (ovary-
free body weight), and age we used linear regression on log-transformed data.We used ANOVA on
ranked data for comparisons of mean batch fecundity among ages, months and years.
As expected, we found a significant difference in mean batch fecundity among age classes (Kruskal-
Wallis test, P< 0.05). Age 1 spotted seatrout, produced an average of 145,452 oocytes per spawn.
Fish aged 2 and 3 spawned an average of 291,123 and 529,976 oocytes per batch, respectively.
Therefore, mean batch fecundity was compared among months and years for each age class sepa-
rately. There were no significant inter-annual or monthly variations in mean batch fecundity for any
of the three age classes.
Pooling data across years, total length explained 69% of the variability in spotted seatrout batch
fecundity. Batch fecundity showed a similarly strong relationship to female somatic (ovary-free)
weight but did not relate quite as strongly to age. The equations below describe these relation-
ships:
Log BF = 3.134(Log TL) - 2.653 (r
2
= 0.686) P<0.05
Log BF = 1.011(Log OFWT) + 2.709 (r
2
= 0.675) P<0.05
Log BF = 0.288(Age) + 4.844 (r
2
= 0.586) P<0.05
Calculation of spawning frequency
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
We obtained samples for spawning frequency determination during the course of stratified random
trammel net sampling in several estuaries along the SC coast. Each stratum was sampled once a
month throughout the year during ebbing tide. However, we only used spotted seatrout samples
obtained during summer months (1 May through 31 August) for this study.
We calculated monthly spawning frequencies for age classes 1-3 using the postovulatory follicle
method of Hunter and Macewicz (1985) where spawning frequency is the inverse of the proportion
of ovaries with postovulatory follicles (POF) < 24 h old among mature and developing females.
Over a decade of sampling the Charleston Harbor estuarine system we have observed that, among
females captured in shallow water during the spawning season, oocyte maturation begins at about
1200h. From mid to late afternoon these females leave the marsh edge for deeper water to spawn.
Our hydrophone surveys have indicated that spawning typically begins around 1800h and ceases
around 2200h. Females then return to feeding grounds near the marsh where they are available to
our sampling gear. Knowledge of this reproductive behavior enabled us to target spotted seatrout
in the mid-late afternoon specifically to capture fish with late-maturing oocytes for batch fecundity
estimation. Females that were back in the shallows after having spawned the previous evening were
available for capture during daytime sampling. In addition, we carried out round-the clock sampling
on two occasions during the 2000-spawning season. Samples from this effort allowed for the cali-
bration of criteria used to age POFs.
A total of 941 female spotted seatrout, captured during the spawning seasons of 1998,1999 and
2000 was examined to determine spawning frequency. Females used to determine SF ranged in
length from 240 mm to 542 mm (mean 340 mm) and in age from 1 to 5. However, 97% of the speci-
mens belonged to age classes 1-3.Thus, reproductive parameters are presented only for these age
classes.
Small sample sizes prevented calculation of monthly spawning frequencies for each age class by
year. Thus, data for all three years were pooled to obtain a single monthly spawning frequency esti-
mate by age class (Table 1). Overall, spotted seatrout ages 1-3 in South Carolina spawned every 4.4
days or roughly 28 times during the reproductive season.
Estimation of annual fecundity
We calculated monthly egg production (MEP) by multiplying the monthly spawning frequency by
the mean monthly batch fecundity for each specimen. Because not all age-1 female trout were
mature at the beginning of the spawning season, the fraction of mature age-1 females obtained
from a previous study (Wenner, unpublished data) was used to refine the MEP estimate. MEP esti-
mates were then summed to arrive at an annual fecundity estimate for each age class (Table 1). We
used linear regression on log-transformed data to investigate the relationship between annual
fecundity and age and thus predict annual fecundity for spotted seatrout aged 4 and 5. Age
explained 98% of the variability in annual fecundity for age classes 1-3. From this relationship, the
predicted annual fecundities for age classes 4 and 5 were 43,752,211 and 101,157,945, respectively.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
AgeMonth Mean BF SF % mature Mean MEP
1May 117,760 (12) 4.18 (89) 78.6 386,897
June 135,403 (16) 9.40 (166) 94.0 1,196,418
July 141,237 (16) 6.54 (185) 97.0 895,978
August 176,594 (18) 4.57 (129) 100 807,035
Annual fecundity = 3,286,328
2May 280,724 (34) 6.80 (114) 100 1,908,926
June 307,322 (10) 7.60 (79) 100 2,335,650
July 370,170 (1) 9.04 (48) 100 3,346,337
August 307,195 (7) 6.34 (44) 100 1,947,620
Annual fecundity = 9,538,533
3May 487,475 (13) 7.42 (46) 100 3,617,061
June 519,630 (4) 9.12 (23) 100 4,739,027
July 765,911 (2) 3.1 (10) 100 2,374,325
August 590,994 (2) 11.61 (8) 100 6,861,439
Annual fecundity = 17,591,852
Table 1. Fecundity parameters for C. nebulosus ages 1 - 3 from South Carolina estuaries.BF= batch fecundity in num-
bers of oocytes; SF= spawning frequency expressed as the number of spawns per month; MEP= monthly egg produc-
tion= (BF*SF)%mature. Annual fecundity is the sum of mean monthly MEP values for each year class and represents
the total number of oocytes produced by any given female from 1 May to 31 August. Numbers in parentheses indi-
cate sample size.
We expanded annual fecundities relative to the abundance of each age class in our samples for the
three years of the study. We estimated that the overall average contribution from age 1 fish to the
reproductive output for the season was approximately 25% whereas fish aged 2 and 3 contributed
34% and 19% of oocytes, respectively. Ages 4-5, which comprised less than 3% of specimens sam-
pled, each contributed about 11% based on predicted annual fecundity values.
Discussion
Attempts at estimating the spawning potential of a species have rarely incorporated spawning
behavior into the methodology used in capturing the animals primarily due to limitations of the
sampling gear. Moreover, estimates of fecundity (batch numbers and spawning frequencies) have
relied on the assumption that the collection of a reasonable size range of adult females during
established spawning periods should be sufficient to cover all phases of reproductive activities
(DeMartini and Fountain,1981;Lisovenko and Adrianov, 1991). Our choice not to use the relative
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
occurrence of hydrated oocytes to estimate spawning frequencies was based on our knowledge of
the spawning behavior of this species. Previous work conducted in the study area (Riekerk et al.,
unpublished data) established the location and timing of spawning activities allowing us to focus
our sampling efforts in shallow waters near known spawning locations to collect females with late
maturing oocytes. This constant loss of late maturing females from the fish available to our nets in
shallow water would have decreased the relative abundance of this maturity stage in our samples.
Therefore, using the relative number of late maturing oocytes for spawning frequency calculations
would have resulted in an underestimate of spotted seatrout reproductive potential.
Because obtaining representative numbers of animals with late-maturing oocytes is not often feasi-
ble, researchers have relied on the relative abundance of postovulatory follicles to calculate spawn-
ing frequencies (i.e.Hunter and Goldberg, 1980; Hunter et al.,1986; Brown-Peterson et al., 1988;
Fitzhugh et al., 1993; Taylor et al., 1998; Macchi and Acha, 2000; Brown-Peterson and Warren, 2001;
Nieland et al., 2002). This method has depended on the ability to time the disappearance of these
structures. Our diurnal sampling of reproductively active spotted seatrout during warm water condi-
tions allowed us to establish criteria to accurately estimate the age of POFs throughout the spawn-
ing season. Furthermore, we were able to verify our assessments by sampling around the clock on
two occasions to collect fish over the time period immediately following a spawn.This would not
have been possible had we failed to establish and verify the location of spawning aggregations with
the use of passive acoustics.
The main impetus behind this study was to establish realistic annual fecundity estimates by age
class that could be used in predictive modeling of the spotted seatrout population in coastal South
Carolina. Herein, we present equations relating fecundity to length and age that can be used to esti-
mate the reproductive potential for each age class of spotted seatrout along the South Carolina
coast.The average season-long oocyte output of age 1 fish was one-third that of age 2 (~3.28 M vs.
9.5 M).When analyzed in relation to the abundance of the other age classes, age 2 fish were predict-
ed to contribute more overall fertilizable oocytes to the environment. Even though the average age
3 fish produced almost twice as many oocytes (17.5 M) than the average age 2, the abundance of
age 3 trout in our estuarine samples was low enough to make their overall contribution to a sea-
son’s spawning effort only half that of 2 year-olds.This exemplifies the potential for error in estimat-
ing reproductive output based on the abundance of year classes, especially that of younger fish.
Acknowledgements
We thank members of the Inshore Fisheries Section of the South Carolina Department of Natural
Resources for assisting in field data collection throughout this study (Dr. C. Wenner, J. Archambault,
H. von Kolnitz, W. Hegler, E. Levesque, L. Goss, C. McDonough, C. Johnson, A. Palmer). Dr. C. Wenner, H.
von Kolnitz and E. Levesque conducted age assessments. Histological processing was provided by C.
McDonough, R. Evitt, A. Palmer and W. Hegler. C. McDonough, T. Piper, K. Maynard and R. Evitt assist-
ed with oocyte counts. J. Archambault coordinated data management and Dr. C. Wenner and E.
Levesque provided helpful suggestions on the manuscript. Funding for this study was provided by
the National Marine Fisheries Service under MARFIN grant #NA77FF0550.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
References
Brown-Peterson, N., P. Thomas, and C. Arnold. 1988. Reproductive biology of the spotted seatrout,
Cynoscion nebulosus, in South Texas. Fish. Bull. 86:373-387.
Brown-Peterson, N. J. and J. W. Warren. 2001. The reproductive biology of spotted seatrout,
Cynoscion nebulosus, along the Mississippi Gulf coast. Gulf. Mex. Sci. 2001(1):61-73.
DeMartini, E. E., and R. K. Fountain. 1981. Ovarian cycling frequency and batch fecundity in the
queenfish, Seriphus politus: attributes representative of spawning fish. Fish. Bull. 79:547-560.
Fish, M. P., and W. H. Mowbray. 1970. Sounds of western North Atlantic fishes. A reference file of bio-
logical underwater sounds.The Johns Hopkins Press, Baltimore and London.
Fitzhugh, G. R., B. A. Thompson, and T. G. Snider. 1993. Ovarian development, fecundity and spawning
frequency of black drum, Pogonias cromis, In Louisiana. Fish. Bull. 91:244-253.
Holt, G.J., S. A. Holt, and C. R. Arnold. 1985. Diel periodicity of spawning in sciaenids. Mar. Ecol. Prog.
Ser. 27:1-7.
Hunter, J. R., and S. R. Goldberg. 1980. Spawning incidence and batch fecundity in northern anchovy,
Engraulis mordax.Fish. Bull. 77:641-652.
Hunter, J. R., and B. J. Macewicz. 1985. Measurement of spawning frequency in multiple spawning
fishes. In: An egg production method for estimating spawning biomass of pelagic fish: application to
the northern anchovy Engraulis mordax (R. Lasker, ed.) p. 79-94. U. S. Dep. Commer., NOAA Tech. Rep.
NMFS 36.
Hunter, J. R., B. J. Macewicz, and H. R. Sibert. 1986. The spawning frequency of skipjack tuna,
Katsuwonus pelamis,from the South Pacific. Fish. Bull. 84:895-903.
Lisovenko, L. A., and D. P. Andrianov. 1991. Determination of absolute fecundity of intermittently
spawning fishes.Voprosy ikhtiologii 31:631-641.
Luczkovich, J. J., H. J. Daniel III and M. W. Sprague. 1999. Characterization of critical spawning habi-
tats of weakfish, spotted seatrout and red drum in Pamlico Sound using hydrophone surveys. Final
report and annual performance report F-62-2 and F-62-2. North Carolina Department of
Environment and Natural Resources, Division of Marine Fisheries, Morehead City, NC 28557.
Macchi, G. J., and E. M. Acha. 2000. Spawning frequency and batch fecundity of Brazilian menhaden,
Brevoortia aurea, in the Rio de la Plata estuary off Argentina and Uruguay. Fish. Bull. 98:283-289.
McMichael, R. H., and K. M. Peters. 1989. Early life-history of spotted seatrout, Cynoscion nebulosus
(Pisces: Sciaenidae), in Tampa Bay, Florida. Est. 12:98-110.
Mok, H. K., and R. G. Gilmore. 1983. Analysis of sound production in estuarine aggregations of
Pogonias cromis, Bairdiella chrysoura, and Cynoscion nebulosus (Sciaenidae). Bull. Inst. Zool., Acad.
Sinica (Taipei) 22:157-186.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Nieland, D. L., R. G.Thomas, and C. A.Wilson. (2002). Age, growth and reproduction of spotted
seatrout in Barataria Bay, Louisiana. Trans. Am. Fish. Soc. 131:245-259.
Overstreet, R. M. 1983. Aspects of the biology of the spotted seatrout, Cynoscion nebulosus,in
Mississippi. Gulf Res. Rep. Suppl. 1:1-43.
Prager, M. H., J. F. O’Brien, and S. B. Saila. 1987. Using lifetime fecundity to compare management
strategies: a case history for striped bass. Am. J. Fish. Manag. 7:403-409.
Riekerk, G. H. M., S. J. Tyree, and W. A. Roumillat. 1997. Spawning times and locations of spotted
seatrout in the Charleston Harbor Estuarine System from acoustic surveys. Final Report to
Charleston Harbor Project, Bureau of Ocean and Coastal Resources Management, South Carolina
Department of Health and Environmental Control, Charleston.
Saucier, M. H., D. M. Baltz, and W. A. Roumillat. 1992. Hydrophone identification of spawning sites of
spotted seatrout Cynoscion nebulosus (Osteichthys: Sciaenidae) near Charleston, South Carolina. N.
Gulf Sci.12:141-145.
Saucier, M. H., and D. M. Baltz. 1993. Spawning site selection by spotted seatrout, Cynoscion
nebulosus, and black drum, Pogonias cromis, in Louisiana. Env. Biol. Fish. 36:257-272.
Taylor, R. G., H. J. Grier, and J. A.Whittington. 1998. Spawning rhythms of common snook in Florida. J.
Fish Biol. 53:502-520.
Wallace, R. A. and K. Selman. 1981. Cellular and dynamic aspects of oocyte growth in teleosts. Amer.
Zool. 21: 325-343.
Wenner, C. A., W. A. Roumillat, J. E. Moran Jr., M. B. Maddox, L. B. Daniel III and J. W. Smith. 1990.
Investigations on the life history and population dynamics of marine recreational fishes in South
Carolina: part 1. Final Report F-37. Marine Resources Research Institute, MarineResources Division,
South Carolina Department of Natural Resources, 217 Ft. Johnson Rd., Charleston, SC 29412.
Wenner, C. A. and B. Zhao. 1995. Stock assessment and fishery management of the spotted seatrout,
Cynoscion nebulosus, on the South Carolina coast. Marine Resources Research Institute, Marine
Resources Division, South Carolina Department of Natural Resources, 217 Ft. Johnson Rd.,
Charleston, SC 29412
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Soniferous Fishes of Massachusetts
Rodney Rountree
1
,Francis Juanes
2
, and Joseph E. Blue
3
1
School for Marine Science and Technology, UMASS Dartmouth, 706 Rodney French Blvd., New
Bedford, MA 02744-1221 rrountree@UMassD.Edu
2
Department of Natural Resources Conservation, University of Massachusetts, Amherst, MA 01003
3
President, Leviathan Legacy, Inc., 3313 Northglen Drive, Orlando, FL 32806 jblue46498@aol.com
Introduction
Since the seminal work of Fish and Mowbray (1970), little advancement has been made towards the
study of soniferous fishes from the marine waters of the Northeastern United States. A review of the
literature suggests at least 51 fishes are vocal in New England waters (Table 1), although many of
these species are uncommon stragglers to these waters. Spontaneous sound production is known
from only about half of these species. However, laboratory studies are often hampered by the diffi-
culty of maintaining healthy specimens, and the difficulty of inducing natural behaviors such as
spawning under confinement. This is further complicated by the fact that many fish are primarily
vocal during the spawning season, and may not vocalize until maturity, and because vocal behavior
is usually limited to males (e.g., haddock and weakfish). The objectives of this study were to conduct
a pilot field survey of soniferous fishes in Massachusetts’s waters to determine what species are
vocal and examine temporal patterns in vocal behavior. However, because of the unexpected find-
ing of widespread calls of the striped cusk-eel on Cape Cod, this paper will focus on this enigmatic
species.
Table 1(below). Partial list of species known to be capable of sound production based on field and/or laboratory
studies, and which occur at least seasonally in New England (Long Island to Maine) estuarine and shelf waters (Fish
et al. 1952, Fish and Mowbray 1970, Hawkins and Rasmussen 1978,Tavolga 1980, Mann et al. 1997). *Sound produc-
tion capability assumed based on the presence of anatomical structures usually associated with vocalization. (All
species were not necessarily subjected to both mechanical and electrical stimulation in the Fish et al. 1952 and Fish
and Mowbray 1970 studies).
Scientific name Common name Sounds produced spontaneous
ly (S) or under either mechanical
(M) or electrical (E) stimulation
Anguillidae American eel Weak: M,E and S
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Anguilla rostrata American eel Weak: M,E and S
Clupeidae American eel Weak: M,E and S
Brevoortia tyrannus Atlantic menhaden Weak: M
Clupea harengus Atlantic herring Weak: M, E
Opisthonema oglinum Atlantic thread herring Weak: M,E
Gadidae
*Brosme brosme Cusk ?
Gadus morhua Atlantic cod Strong: M, S
Melanogrammus aeglefinus Haddock Strong: S
Merluccius bilinearis Silver hake Weak: M
Pollachius virens Pollock Weak: M
Urophycis chuss Red hake Weak: E
Urophycis regia Spotted hake Weak: E
Ophidiidae
*Lepophidium profundorum Fawn cusk-eel ?
Ophidion marginatum Striped cusk-eel Strong: S
Batrachoididae
Opsanus tau Oyster toadfish Strong: S
Dactylopteridae
Dactylopterus volitans Flying gurnard Strong: M
Triglidae
Prionotus carolinus Northern searobin Strong: M, S
Prionotus evolans Striped searobin Strong: S
Cottidae
Myoxocephalus aenaeus Grubby Weak: M,E
Myoxocephalus Longhorn sculpin Strong: M,S
octodecemspinosus
Percichthyidae
Morone saxatilis Striped bass Moderate: M,E
Serranidae
Centropristis striata Black sea bass Weak: M,E
Pomatomidae
Pomatomus saltatrix Bluefish Weak: M,E
Carangidae
Alectis ciliaris African pompano Strong: M
Caranx crysos Blue runner Moderate: M,S
Caranx hippos Crevalle jack Strong: M,S
Caranx latus Horse-eye jack Strong: M,E,S
Caranx ruber Bar jack Strong: M,S
Chloroscombrus chrysurus Atlantic bumper Moderate: M,E
Selene setapinnis Atlantic moonfish Strong: M
Selene vomer Lookdown Strong: M
Seriola dumerili Greater amberjack Moderate: S
Lutjanidae
Ocyurus chrysurus Yellowtail snapper Weak: M,E,S
Lutjanus griseus Gray snapper Weak M,E
Haemulidae
Orthopristis chrysoptera Pigfish Strong: M,S
Sparidae
Stenotomus chrysops Scup Weak: M
Sciaenidae
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Bairdiella chrysoura Silver perch Strong: M,S
Cynoscion nebulosus Spotted seatrout ?
Cynoscion regalis Weakfish Strong: M,S
Leiostomus xanthurus Spot Moderate: M,E,S
Menticirrhus saxatilis Northern kingfish Weak: M
Micropogon undulatus Atlantic croaker Strong: M,S
Pogonias cromis Black drum Strong: M,S
Labridae
Tautoga onitis Tautog Moderate: E,S
Tautogolabrus adspersus Cunner Weak: E
Balistidae
Aluterus schoepfi Orange filefish Moderate: M,E,S
Balistes capriscus Gray triggerfish Moderate: M,E,S
Monacanthus hispidus Planehead filefish Moderate: M,E
Ostraciidae
Lactophrys quadricornis Scrawled cowfish Moderate: M
Tetraodontidae
Chilomycterus schoepfi Striped burrfish Moderate: M,E
Sphoeroides maculatus Northern puffer Moderate: M
Molidae
Mola mola Ocean sunfish Strong: M
Methods
Recordings of fish sounds were made at 12 different sites across Cape Cod at least once between
June and October 2001. However, the primary sampling location was the Cotuit town landing
which was sampled on 18 different dates, including 5 dates on which monitoring was conducted
over the diel cycle. Except for the diel studies, most sampling was conducted around sunset, usually
beginning 1 to 2 hours before sunset and continuing for 2 to 3 hours after sunset. To obtain infor-
mation on the daily pattern of fish calls, diel studies were conducted on five different dates at Cotuit
town landing. For these studies, sounds were recorded approximately from 1300-1400, 1900-2300,
0100-0200, and 0400-0600, corresponding to afternoon, sunset, night, and sunrise periods, respec-
tively. Low cost hydrophones (Arretec, PB 3098 Bletchley, Milton Keynes MK2 2AD, United Kingdom)
were deployed from docks, piers, jetties and small boats and recorded to a hi-fi VCR. Occasionally,
recordings were made to a Sony hand-held tape recorder (model TCM-929). In addition, whenever
possible, video recordings were made simultaneously to the VCR using a hand-deployed underwa-
ter video camera equipped with infrared lights (models made by Vista Cam, 9911 Goodhue St. NE,
Blaine MN 55449, and Aqua vu, Nature Vision Inc., 213 NW 4th St., Brainerd, MN 56401). Sounds were
captured to a PC while playing back from a VCR using Cool Edit 2000 (made by Syntrillium Software
Corporation). Some spectral analyses were also conducted using Signal for Windows (Engineering
Design, 43 Newton St, Belmont, MA 02478). To quantify call frequency, 1-4 hour sound samples were
divided into 10-minute segments and a randomly selected 2 minute sound clip was obtained from
each. Calls for toadfish, striped cusk-eel and searobins were identified and counted. Reference
sound clips of unknown calls were made and used to make counts of unknown sounds by type
(e.g.,“grunt-A”,etc.).
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Results
Over 53 VHS and 12 cassette tapes comprising over 160 hours of recordings were collected. Calls of
striped cusk-eels, Ophidion marginatum,oyster toadfish, Opsanus tau, and striped searobin, Prionotus
evolans, dominated the observations. Several unidentified calls were also common. We are continu-
ing our efforts to identify these calls. In addition, various sources of natural and man-made noise
were also recorded including: outboard boats, barges, jet-skies, dock noises, fishing noises, depth-
finders, and gas release from sediments. Based on the occurrence of vocal choruses, we found sun-
set spawning aggregations of the striped cusk-eels at eight of 12 locations sampled across the
length of Cape Cod, including two sites (Barnstable Harbor and Provincetown Harbor) on the north
shore. Cusk-eels were recorded from the first sampling date (June 11) through the end of August,
but abruptly stopped by early September. Oyster toadfish were also already calling at the start of
the field season, but sunset choruses had ceased by mid-July. Striped searobin calls were not associ-
ated with sunset, but occurred throughout the night. Searobin calls were most frequent in August
and September but were still present in October. The cusk-eel sounds recorded in MA are nearly
identical to striped cusk-eel sounds recorded by the first author under laboratory conditions in New
Jersey (Mann et al. 1997), and more recent sounds recorded in the field and attributed to stripe cusk-
eels in Narragansett Bay (Perkins 2002) and North Carolina (Sprague and Luczkovich 2001). Our
attribution of these sounds to the striped cusk-eel is further validated by the capture of a 170 mm
TL specimen while recording sounds in Cotuit, MA in July 2001, and by subsequent sightings of a
larger individual later that same month. Cusk-eels can sometimes be observed in the shallows at
night with the aid of a spot light (Rountree, pers. Observ.). In Figure 1, chatters vary in relative ampli-
tude and range form 8 to 16 pulses and call times of 275 msec to 730 msec. The dominant frequen-
cy was 1098-1866 Hz (compared to the toadfish call at the beginning of the sequence at 171-585
Hz). A sample call recorded from Provincetown, MA on August 23, 2001 is shown in Figure 2. This
call is considerably longer (31 pulses, 1,715 msec) than those in Figure 1, but is still well within the
range characteristic of the species (Mann et al. 1997, Sprague and Luczkovich 2001). A single repre-
sentative pulse has most energy between 914 and 1524 Hz (Fig. 2).
Striped cusk-eel calls can be heard sporadically throughout the day, but calls clearly become more
frequent at sunset (Fig. 3). Peak number of calls occurred between 20 to 60 minutes after sunset,
and declined to near zero within two hours. In contrast, the oyster toadfish calls more frequently
during the day, but also exhibits a strong increase in activity associated with sunset (Figure 4).
Although data are more limited, peak activity occur 1-2 hours after sunset, with more gradual
declines through the night compared to the striped cusk-eel.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Discussion
It is significant that the striped cusk-eel was the most frequently heard and widely distributed
species encountered during this study as it has previously been thought to occur from Block Island
south to Florida, with only rare stragglers occurring as far north as Cape Cod (Collette and Klein-
MacPhee 2002), despite extensive faunal surveys in the region over several decades.This finding
nicely demonstrates the usefulness of passive acoustics as a supplement to traditional survey meth-
ods, particularly for species difficult to sample in other ways. The seasonal and daily pattern of
striped cusk-eel vocal activity agrees with published laboratory findings (Mann et al. 1997, Sprague
and Luczkovich 2001). Striped cusk-eels were already chorusing by mid-June when sampling
began, but had stopped by mid-September in good agreement with previous studies. Call frequen-
cy increases rapidly at sunset developing into a loud chorus that lasts from 1 to 2 hours (Fig. 3).
Captive cusk-eels have been observed to chorus after sunset as part of courtship and spawning
behavior (Mann et al. 1997, Rountree and Bowers-Altman 2002). We believe that our observations
suggest widespread spawning of striped cusk-eels within estuaries of both the north and south
shores of Cape Cod. The species’ cryptic nocturnal behavior, and habit of remaining burrowed dur-
ing the day likely account for the failure of previous researchers using conventional sampling gears
(i.e., trawls and seine sampling mostly limited to daylight hours) to recognize its importance to the
region. At this time the northern range of the striped cusk-eel must be reconsidered. How much
farther up the cost the species extends is unknown. It is notable that Geoghegan et al. (1998)
recorded a single adult striped cusk-eel at Seabrook, New Hampshire and argued that it might rep-
resent a small local population. Therefore, we suspect that reproducing populations of this species
may occur at least to New Hampshire waters. However, the scarcity of ophidiid eggs in ichthyoplank-
ton surveys of the region is puzzling (e.g., Fahay 1992) and future studies on the distribution and
ecology of this cryptic species are needed. Boat sounds were problematic during the day, some-
times occurring during 50-99% of the sound sample clips. During these times, sounds of fishes
could not be heard above the boat’s noise. Boat noise was rare during the evening hours. The
impact of boat-associated noise on the behavior of fishes is poorly known, but it had a strong
impact on our ability to record day-time fish sounds. It is hoped that the newly available archive of
fish sounds originally published by Fish and Mowbray (1970) and recently repackaged by the
University of Rhode Island (Rountree et al. 2002) will aid in the identification of the unknown calls
recorded on Cape Cod. In summary this study has demonstrated the usefulness of even low-cost
passive acoustics technology as a tool to survey estuarine and marine fishes. Information on the
temporal and spatial patterns of fish vocal behavior can be used to gain insight into temporal and
spatial patterns in habitat use patterns by vocal species. In particular, identification of spawning
habitats through passive acoustics surveys is promising.
Acknowledgements
Megan Hendry-Brogan and Katie Anderson are thanked for diligent work in both the field and labo-
ratory to collect and process fish sound data. This project received major funding from the
Northeast and Great Lakes National Undersea Research Center, which also provided extensive logis-
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
tical support. The Woods Hole Sea Grant College Program also provided supporting funds.
The Sounds Conservancy, Quebec-Labrador Foundation/Atlantic Center for the Environment provid-
ed a stipend for Megan’s fieldwork.
Literature Cited
Collette, B.B., and G. Klein-MacPhee. (eds.). 2002. Bigelow and Schroeder’s Fishes of the Gulf of Maine.
3rd Edition. Smithsonian Institution Press, Washington, D.C. 748 p.
Fahay, M.P. 1992. Development and distribution of cusk eel eggs and larvae in the middle Atlantic
Bight with a description of Ophidion robinsi n.sp. (Teleostei: Ophidiidae). Copeia 1992(3):799-819.
Fish, M.P., A.S. Kelsey, Jr., and W.H. Mowbray. 1952. Studies on the production of underwater sound by
North Atlantic coastal fishes. J. Mar. Res. 11:180-193.
Fish, M.P., and W.H. Mowbray. 1970. Sounds of Western North Atlantic fishes. Johns Hopkins Press,
Baltimore, MD. 205 p.
Geoghegan, P., J.N. Strube, and R. A. Sher. 1998. The first occurrence of the striped cusk eel, Ophidion
marginatum (Dekay), in the Gulf of Mexico. Northeastern Naturalist 5(4):363-366.
Hawkins, A.D. 1986. Underwater sound and fish behaviour. pp. 114-151. In: The Behaviour of Teleost
Fishes. (ed.T.J. Pitcher). Groom-Hellm. London.
Hawkins, A.D., and K.J. Rasmussen. 1978.The calls of gadoid fish. J. Mar. Biol. Ass. U.K. 58:891-911.
Mann, D.A., J. Bowers-Altman, and R.A. Rountree. 1997. Sounds produced by the striped cusk-eel
Ophidion marginatum (Ophidiidae) during courtship and spawning. Copeia 1997(3):610-612.
Perkins, P.J. 2002. Drumming and chattering sounds recorded underwater in Rhode Island.
Northeastern Naturalist 8(3):359-370.
Rountree, R.A. and J. Bowers-Altman. 2002. Soniferous behavior of the striped cusk-eel, Ophidion
marginatum.Bioacoustics 12(2/3):240-242.
Rountree, R.A., P.J. Perkins, R.D. Kenney, and K.R. Hinga. 2002. Sounds of Western North Atlantic Fishes:
Data rescue. Bioacoustics 12(2/3):242-244.
Sprague, M.W. and J. J. Luczkovich. 2001. Do striped cusk eels, Ophidion marginatum (Ophidiidae) pro-
duce the ‘chatter’ sound attributed to weakfish, Cynoscion regalis (Sciaenidae)? Copeia 2001 (3): 854-859.
Tavolga, W.N. 1980. Hearing and sound production in fishes in relation to fisheries management.
P.102-123, In: Bardach, J.E., J.J. Magnuson, R.C. May, and J.M. Reinhart (eds.). Fish Behavior and its use
in the capture and culture of fishes. ICLARM Conference Proceedings 5, 512 p. International Center
for Living Aquatic Resources Management, Manila, Philippines.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Illustrations and Diagrams
Ca l
Toadfish
Ca ll 1
Call 2
Ca ll 3
Call 4
Ca ll 5
Call 6
Cusk eel
Figure 1. Representative sample of cusk-eel calls recorded in Cotuit, MA on June 20th 2001.The lower panel shows a
string of six separate cusk-eel calls, likely from six different individuals. The first call overlaps with that of a toadfish.
The upper left figures show the waveform and spectrogram for call 3. The power spectrum of call 3 is shown in the
upper right panel.
Figure 2. Single chatter attributed to the striped cusk-eel, Ophidion marginatum, recorded from Provincetown, MA on
23 August 2001. The lower panel shows the energy spectrum for the entire call, while the upper panels show the
waveform, energy spectrum and power spectrum of a single pulse.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Daily Pattern of C usk-ee l C alls
0
25
50
75
100
125
150
175
200
12:00 PM 2:24 PM 4: 48 PM 7:1 2 PM 9:3 6 P M 12:0 0 AM 2 :24 AM 4: 48 AM 7:1 2 AM 9 :3 6 A M
Ti me
Calls (Number/2min)
June July Sunset
Dai ly Pattern o f Oyster Toadfi sh Calls
0
10
20
30
40
50
12:00 PM 2: 24 PM 4:4 8 PM 7 :12 PM 9 :36 PM 12 :00 AM 2:2 4 AM 4:4 8 A M 7: 12 AM
Ti me
Calls (Number/2min)
Sunset Toadfish
Figure 3. Daily pattern of striped cusk-eel, Ophidion marginatum, calls collected on two dates (20-21 June and 2-3 July, 2001).
All calls heard within 2 minutes sound clips were counted. Sample clips were taken randomly from within 10-minute sample
bins. The vertical arrow marks the time of sunset as obtained from a hand-held GPS.
Figure 4. Daily pattern of oyster toadfish, Opsanus tau, call on June 20-21, 2001.
The mating behaviour of Atlantic cod (Gadus morhua).
Sherrylynn Rowe and Jeffrey A. Hutchings
Department of Biology, Dalhousie University, Halifax, Nova Scotia, B3H 4J1, Canada.
rowes@is2.dal.ca
Introduction
Atlantic cod (Gadus morhua) is a marine demersal fish that inhabits cool-temperate to subarctic
waters from inshore regions to the edge of the continental shelf on both sides of the North Atlantic
(Scott and Scott 1988). Atlantic cod has been harvested throughout its range for hundreds of years
and yet despite being of theoretical interest and practical importance, very little has been learned
about its reproductive behaviour during this period.
Throughout the Atlantic, there are many recognized cod stocks, each of which has its own set of
characteristics. Age at maturity varies between 2 and 7 years (Myers et al. 1997) and Atlantic cod
typically spawn over a period of less than 3 months (Brander 1994; Chambers and Waiwood 1996;
Kjesbu et al. 1996) in water depth ranging from tens (Smedbol and Wroblewski 1997) to hundreds of
metres (Brander 1994; Morgan et al. 1997). Individuals are assumed to breed annually and Atlantic
cod are considered to be batch spawners as only 5-25% of a female’s egg complement is released at
any time during her 3- to 6-week spawning period (Chambers and Waiwood 1996; Kjesbu et al.
1996). Individual females release hundreds of thousands, often millions, of tiny eggs (1.2-1.6 mm in
diameter), for which no parental care is provided, directly into oceanic waters (Scott and Scott 1988).
The limited information available on Atlantic cod spawning behaviour suggests complex mating
patterns, the occurrence of behavioural and acoustic displays by males, mate choice by females, and
alternative reproductive strategies among males (Brawn 1961a; Hutchings et al. 1999). However,
there is no information on the selective causes and consequences of these behaviours, nor the
structure of the mating system (Nordeide and Folstad 2000).
Our research employs a quantitative approach to understand causes and consequences of variation
in the mating system of Atlantic cod at the individual and population levels. We are incorporating
both detailed experimental studies in the laboratory and observations of cod in the wild. Our
research involves several components including the following: (i) mating system structure and iden-
tification of behavioural and phenotypic correlates of reproductive success, (ii) intra- and inter-pop-
ulation variation in sound production during spawning, and (iii) patterns of variation in drumming
muscle mass.
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Proceedings from the International Workshop on the Applications of Passive Acoustics to Fisheries
Laboratory observations of spawning Atlantic cod
The laboratory component of our research involves cod from two spatially distinct areas in the
Northwest Atlantic: Southwest Scotian Shelf and Southern Gulf of St. Lawrence, identified by the
Northwest Atlantic Fishery Organization (NAFO) Divisions as 4X and 4T, respectively. Mature adults
from each stock were collected and taken to a 680 m
3
aquarium at Dalhousie where spawning
occurred. Groups of fish representing each stock were examined separately during their temporally
distinct spawning periods. Cod were maintained at densities similar to those in nature (approxi-
mately 0.1 fish per m
3
;Rose 1993; Morgan et al. 1997) and spawning behaviour of individually
tagged fish was recorded by videotape and visual observation. A hydrophone was placed in the
centre of the tank and sounds were recorded continuously during the spawning season. A random
sample of fertilized eggs was collected daily and pedigree analysis is being undertaken using
microsatellite DNA. In addition to providing information on individual male and female reproduc-
tive success, the DNA analyses, coupled with behavioural observations, will allow us to determine
phenotypic and behavioural correlates of reproductive success.
Observations t