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Sound is a potentially important navigational cue for organisms in aquatic environments. Most reef fishes produce pelagic larvae that must locate suitable settlement habitat for the completion of their life-cycle. We used light traps and underwater loudspeakers to determine whether reef fish larvae are attracted to sounds produced on a reef. 'Sound traps' caught more triplefin (a benthic reef fish) larvae than did 'silent traps', demonstrating that the larvae of some reef fishes may use sound as a navigational cue in the field. Catches of pilchard larvae, a pelagic fish, did not vary between treatments. These results are the first demonstration, of which we are aware, of sound as a potential navigational cue in the aquatic environment.
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MARINE ECOLOGY PROGRESS SERIES
Mar Ecol Prog Ser
Vol. 207: 219–224, 2000 Published November 22
Animals are capable of amazing feats of migration
and navigation. Directed long-distance migrations
occur in animals as diverse as sea turtles (Bowen et al.
1989), monarch butterflies (Hobson 1998), birds (Ber-
hold 1991), marine snails (Hamilton & Russell 1982),
spiny lobsters (Herrnkind & Kanciruk 1978), whales
(Swartz et al. 1987) and salmon (McKeown 1984). The
mechanisms of animal migration include the use of
magnetic, celestial, and olfactory cues. Despite its po-
tential importance, the use of ambient sound as a navi-
gational cue has, to our knowledge, rarely been investi-
gated and has never previously been clearly isolated as
an orientation mechanism (Popper & Carlson 1998).
Many reef fishes produce pelagic larvae that deve-
lop in the open water from days to weeks prior to
returning to the benthos (Sale 1980, Leis 1991), a com-
plex life-cycle common in the marine environment
(Thorson 1950, Roughgarden et al. 1988). Settlement
by these free-swimming larvae onto the reef habitat is
a critical step in the life-cycle of reef fishes. During this
step, fish larvae do not appear to be passive particles.
They are excellent swimmers, capable of swimming
from 10s of km up to 90+ km non-stop at speeds great
enough to overcome currents (Leis & Carson-Ewart
1997, Stobutzki & Bellwood 1997). Work on the Great
Barrier Reef has shown that larvae can detect reefs
from distances of at least 1 km (Leis et al. 1996). They
move off-shore during the day (Leis et al. 1996), prob-
ably to avoid reef-based predation from visual pre-
dators. When they are developmentally ready, they
actively move on-shore at night to settle to the reef
habitat (Stobutzki & Bellwood 1998). Recent evidence
shows that they can settle to their natal reef to some
extent (Jones et al. 1999, Swearer et al. 1999). The cues
that these larvae use to locate and move toward reefs
remain unknown.
Underwater sound is one cue that reef fish larvae
may use to orient to reefs. Compared to other potential
cues, such as visual and olfactory cues, sound is trans-
mitted long distances through water with little attenu-
ation and is highly directional (Rogers & Cox 1988,
Richardson et al. 1995). Reefs can be especially noisy,
with much of the sound being biological in origin (Tait
1962, Cato 1980). Nocturnal activity by snapping
shrimp, fish and urchins creates an ‘evening chorus’ on
both rocky and coral reefs (Tait 1962, Cato 1980, Myr-
berg et al. 1986, Lobel 1992, McCauley 1994, 1995),
including those in New Zealand (Tait 1962). Here we
report the results of a field experiment testing the
response of fish larvae to reef-generated noise.
© Inter-Research 2000
*E-mail: n.tolimieri@auckland.ac.nz
NOTE
Ambient sound as a cue for navigation by the
pelagic larvae of reef fishes
Nick Tolimieri1, 2,*, Andrew Jeffs3, John C. Montgomery1
1Experimental Biology Research Group, School of Biological Sciences, University of Auckland, Private Bag 92019,
Auckland, New Zealand
2Leigh Marine Laboratory, PO Box 349, Warkworth, New Zealand
3National Institute of Water and Atmospheric Research, PO Box 109695, Auckland, New Zealand
ABSTRACT: Sound is a potentially important navigational
cue for organisms in aquatic environments. Most reef fishes
produce pelagic larvae that must locate suitable settlement
habitat for the completion of their life-cycle. We used light
traps and underwater loudspeakers to determine whether
reef fish larvae are attracted to sounds produced on a reef.
‘Sound traps’ caught more triplefin (a benthic reef fish) larvae
than did ‘silent traps’, demonstrating that the larvae of some
reef fishes may use sound as a navigational cue in the field.
Catches of pilchard larvae, a pelagic fish, did not vary
between treatments. These results are the first demonstration,
of which we are aware, of sound as a potential navigational
cue in the aquatic environment.
KEY WORDS: Reef fish · Larvae · Sound · Orientation ·
Navigation · Light traps
Resale or republication not permitted
without written consent of the publisher
Mar Ecol Prog Ser 207: 219–224, 2000
Methods. We used light traps (Doherty 1987) and
underwater loudspeakers to determine whether fish
larvae were attracted to sound emanating from a reef.
Many fish larvae are attracted to light and generally
settle at night (but see Leis & Carson-Ewart 1999),
making light traps excellent (but selective) tools for
their collection. Our light trap design follows that of
Sponaugle & Cowen (1994) (Fig. 1). A separate water-
tight barrel housed a 12 V marine battery, amplifier
and portable cassette player. An underwater loud-
speaker (Lubell Labs Inc., LL964, 200 to 20 kHz, 180 dB
at 1 m, reference sound pressure 1 µPa) was sus-
pended under the barrel. Traps and the loudspeaker
were suspended ~2 m below the surface.
We recorded ambient reef sound at night when reef
fish larvae generally settle. Ambient underwater sound
recordings were taken approximately 200 m offshore of
the southern side of Ti Point Reef (36° 19’ S, 174° 48’ E)
in 14 m water depth (Fig. 2). We made calibrated digital
sound recordings with a Sonatech 8178 hydrophone
lowered to a depth of 8 m from the surface. The fre-
quency spectra of the digital recordings were analysed
using Canary software (Charif et al. 1995). A 3 min seg-
ment of the digital recording of Ti Point Reef was trans-
ferred directly to a 3 min TDK endless cassette (EC-3M)
ready for play back.
Light traps were deployed overnight in 2 pairs
(Fig. 2). One trap in each pair played back the
recorded reef sound, while the other was a silent con-
trol. We established 4 permanent moorings in Omaha
Bay, New Zealand (36°20’ S, 174° 48’ E) in ~10 m of
water. The moorings were arranged in pairs, with 1
pair placed further back in the bay. Paired traps were
~500 m apart and at least 500 m from shore or the
nearest reef and over a sand bottom. On each deploy-
ment, we randomly assigned a treatment (sound/
silent) to the first mooring. We then alternated treat-
ments between moorings such that there was always
1 sound treatment in the front and back, and 1 sound
treatment on either side of the bay. We deployed all
the experimental apparatus about 1 h before sunset
and collected the equipment and cleared the traps the
following morning. Sampling was repeated on 14
nights from 19 August to 2 November 1999 when
weather permitted.
We could not use parametric statistics to analyse the
data because of high variance and non-normal distrib-
utions. Instead, we used 2 alternate approaches. First,
we paired traps within nights and used a Wilcoxon
220
Fig. 1. Experimental apparatus showing configuration of the
light trap and underwater sound playback equipment. The
‘silent’ control traps included a ‘dummy’ surface barrel but no
loudspeaker. Drawing not to scale
Fig. 2. Location of study site. Sound recordings were made at
Ti Point (36° 19’ S, 174° 48’ E) approximately 50 m from shore
and 1 m above a rocky reef
Tolimieri et al.: Ambient sound as a navigation cue
signed-ranks test. This approach maintains some
information about the amount of difference in catch
between pairs but analyses only rankings of the differ-
ences in size not the absolute size of the difference
(Sokal & Rohlf 1995). However, because larvae may
travel in patches, we also wanted to analyse the data in
a way that would not be potentially biased by large
patches of larvae passing one trap but not another. We
used G-tests to compare the number of times a sound
trap caught more larvae than its silent partner. Here,
the null hypothesis is that sound traps should catch
more larvae than silent traps only 50 % of the time (at
random). For triplefin larvae, we used a Kolmogorov-
Smirnov test to compare size distributions of larvae
between treatments for data pooled across nights. We
also compared median size between treatments and
among nights using the Scheirer-Ray-Hare extension
of the Kruskal-Wallis test (Sokal & Rohlf 1995). We
chose this test instead of analysis of variance because
data were non-normal. Data from Night 11 could not
be used due to loss of silent samples after counting but
prior to measurement.
Results. The sound from Ti Point Reef was typical of
evening chorus recordings from elsewhere in northern
New Zealand and other locations (Tait 1962, Cato
1980) (Fig. 3). The peak of sound around 2 kHz is
thought to be due to sea urchin feeding, while the
higher frequency pulses are probably snapping shrimp
(Tait 1962, Cato 1980).
We caught fish larvae of primarily 2 taxa. Triplefins
(Tripterygiidae) are benthic reef fishes that one would
expect to be attracted to reefs. These triplefins were
primarily Fosterygion spp. Only a few specimens (8,
<2%) were positively identified as either Ruanoho
(Gilloblenius?) spp. or Notoclinus spp., which is consis-
tent with previous results for this area and time of year
(Tricklebank et al. 1992). With counts this low, the data
are not meaningful at the genus level given the varia-
tion in the catches. Instead, we chose to examine the
triplefins as a group.
Pilchard (Clupeidae, Sardinops neopilchardus) are
pelagic fishes that one would not expect to be attracted
to reefs or to the sound emanating from a reef. Other
species were caught in numbers too low for meaning-
ful analysis: Kathetostoma giganteum (Uranoscopidae)
(1), Acanthoclinus spp. (Plesiopidae) (5), Parika scaber
(Monocanthidae) (7), Notolabrus celidotus (Labridae)
(4) and Trachurus spp. (Carangidae) (11).
The response of triplefin and pilchard larvae differed
markedly. Sound traps caught 86% (560) of all triplefin
larvae, while only 14% (90) were caught in the silent
traps (Fig. 4). When we paired traps within nights,
sound traps caught more triplefin larvae than did silent
traps (Fig. 5a, Wilcoxon signed-ranks test, Z= 2.08, p <
0.05). Examined slightly differently, a sound trap
221
Fig. 3. Ambient underwater sound recorded at Ti Point
approximately 200 m from shore. Recordings were made at
21:45 h, 20 February 1999. (a) Spectra; (b) spectrogram;
(c) waveform. The data show a band of sounds around 2 kHz
probably arising from sea urchin feeding, while the higher
frequency pulses are probably snapping shrimp
Fig. 4. Median number of fish larvae caught per trap per night
for sound and silent treatments over 14 nights (n = 27).
Numbers over bars = range (and maximum, as minimum
number was 0 for all treatments); #p < 0.05; horizontal line
indicates treatments that could not be distinguished statisti-
cally (Wilcoxon signed-ranks test)
Mar Ecol Prog Ser 207: 219–224, 2000
caught more larvae than its paired silent trap on 14 of
19 occasions (ties of 0 excluded), which was more often
than would be expected at random (G-test, df = 1, G=
4.39, p < 0.05). There was high variation in the abun-
dance of triplefin larvae among nights, with catches
ranging from 0 to 350 larvae in the sound traps and 0 to
24 larvae in the silent traps.
Overall, the median size of triplefin larvae in sound
traps (20.01 mm standard length, SL, range = 18.38)
was greater than that of larvae in silent traps
(19.34 mm SL, range 14.02) when data were pooled
across nights (Mann-Whitney U-test, H= 11 161, df = 1,
χ2= 6.574, p < 0.05). However, there was no difference
in the shape of the size (SL) distributions (Kolmogorov-
Smirnov test, p > 0.05, Fig. 6a,b). The slightly larger
size of triplefin larvae in sound traps appears to have
been due to the large catches on Night 2 (Fig 5a).
When examined by night, there was no effect of treat-
ment on median size (Scheirer-Ray-Hare test, df = 1,
SS = 17926, H= 0.99, p > 0.05, Fig 6c). However,
median size did differ among nights (Scheirer-Ray-
Hare test, df = 5, SS = 727403, H= 40.27, p < 0.001).
There was no interaction between nights and treat-
ment (Scheirer-Ray-Hare test, df = 4, SS = 31800, H=
1.76, p > 0.05). The mode for both treatments was
20 mm SL (Fig. 6a,b), approximately the size at settle-
ment for triplefins (Willis 1994).
Pilchard larvae did not show a response to reef
sound (Fig. 4). Sound traps caught 8847 (57%) pilchard
larvae, while silent ones caught 6801 (43%). When we
compared pairs of traps within nights, there was no
significant difference between the sound and silent
treatments (Fig. 5b, Wilcoxon signed-ranks test, Z=
0.59, p > 0.05). Likewise, a sound trap caught more
pilchard larvae than its paired silent trap on only 14
222
Fig. 5. Number of (a) triplefin and (b) pilchard larvae caught
from sound and silent light-traps per night. Data are arranged
in pairs. Pairs (1 sound/1 silent) to the left of an x-axis tick re-
present traps at the back of the bay; pairs to the right of a tick
represent traps at the front of the bay. The experimental
nights were not consecutive, but consisted of nights when
weather permitted deployment of the experimental appara-
tus. Trials 1 to 3 and 11 to 13 occurred on or within several
nights of the first quarter moon
Fig. 6. Size distributions for triplefin larvae from (a) sound
traps and (b) silent traps pooled across nights, and (c) median
standard length in sound and silent traps for 6 nights
Tolimieri et al.: Ambient sound as a navigation cue
of 25 comparisons, which did not differ from random
(G-test, df = 1, G= 1.10, p > 0.05). Catches of pilchard
were highly variable both among and within nights,
with catches ranging from 0 to 7908 larvae per trap for
sound traps and 0 to 5888 larvae for silent traps.
Discussion. The results of this field experiment pro-
vide the first evidence that sound may be an important
navigational cue in aquatic environments. Triplefin
larvae were attracted to reef sound while the larvae of
pilchards were not. Conducting the experiment in the
field demonstrates that the attraction of triplefin larvae
functions in the natural environment and at spatial
scales relevant to the settlement of reef fishes.
Our data also indicate that the lunar cycle may be
important in determining the level of response by lar-
val fish to reef sound. Sampling Nights 1 to 3 and 11 to
13 occurred on or within several nights of the first
quarter moon. These nights had the largest differences
between sound and silent traps, as well as the highest
catches of triplefin larvae. Notably, sound traps almost
always caught more triplefin larvae than silent traps
during this phase of the moon (8 of 9 comparisons).
If data are pooled within nights, sound traps always
caught more triplefin larvae during these nights
(6 nights). The stronger patterns around the first quar-
ter moon observed in our study may have been the
result of greater availability of larvae (and therefore
better resolution) or a change in larval behaviour
(attraction to reef sound only when attempting to set-
tle). However, Thorrold (1992) found that tidal currents
may affect catches by moored light traps. Therefore,
larvae may have been better able to swim to traps dur-
ing neap tides when tidal currents are lower.
Aside from the triplefins and pilchard, the traps in
this study caught few other species. The low numbers
and small range of other species are due partly to the
timing of larval supply and partly to the placement of
light traps. In New Zealand, most taxa are more abun-
dant in the summer (January to March) (Tricklebank et
al. 1992, Hickford & Schiel 1999). However, some trip-
lefins (Fosterygion spp.) and pilchard larvae are most
abundant in June and July, with reduced numbers
through October (Tricklebank et al. 1992). Traps from
other locations nearer reefs that were fished simulta-
neous with those in this study caught a greater number
of the other species, especially Trachurus spp. and
Parika scaber (Tolimieri unpubl. data), in addition to
triplefins and pilchard. The placement of light traps in
a sandy bay may, therefore, have reduced the actual
larval supply to these traps.
The data on size differences of triplefin larvae
between treatments are ambiguous. While there was
an overall (pooled) difference in median size, this
difference was due to the large sample in 1 sound trap
on Night 2, which may have been coincidental. When
analysed by night, the difference was not consistent,
but sample sizes on other nights were much smaller.
Ontogenetic differences in larval distribution (Leis
1991, Leis & Reader 1991, Smith 2000) and habitat
selection at settlement (Danilowicz 1997) have been
noted before, so the subject merits future study.
At present, we do not know which component of the
reef sound attracted the triplefin larvae. Much of the
sound from our recording of a reef is biological in
origin, probably produced by snapping shrimp and sea
urchins (Tait 1962, Cato 1980). Fish larvae may be
attracted to sound of biological origin because it indi-
cates a suitable ‘healthy’ reef environment. If fish lar-
vae are attracted to biological sound generated on the
reef, this may have implications for conservation and
management of ‘noisy’ reef species such as urchins.
Furthermore, in many coastal areas human activities,
such as shipping, have come to dominate the under-
water acoustic spectra, which may also have biological
consequences. Researchers, especially in the aquatic
environment, have largely overlooked the potential of
ambient sound as a source of orientation information
for animals. While this study points to the importance
of ambient sound to reef fish larvae, further research is
required to elucidate the role of this cue among reef
fishes in general as well as for other taxa.
Acknowledgements. We thank M. Birch, T. Wustenburg, B.
Doak, B. Dudley, J. Schimanski, T. Langlois, F. Giambartolomei,
N. Managh, D. Snell, V. Stamp, B. Dylan, M. Morganfield and
A. Cozens for logistic support. S. Dawson kindly loaned the
hydrophone. B Danilowicz, P. Levin, P. Sale, T. Willis and 4
anonymous reviewers provided useful discussion and com-
ments. This work was supported by the Foundation for Re-
search, Science and Technology, a University of Auckland post-
doctoral fellowship (to N.T.), and the Marsden Committee.
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Editorial responsibility: Otto Kinne (Editor),
Oldendorf/Luhe, Germany
Submitted: February 28, 2000; Accepted: June 22, 2000
Proofs received from author(s): October 25, 2000
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... Countless marine animals rely on sound to survive, e.g. to detect predators, echolocation, navigation and communication with conspecifics (Leis et al., 2011;Montgomery et al., 2006;Slabbekoorn, 2010;Staaterman et al., 2010;Tolimieri et al., 2000). In recent decades, however, anthropogenic low-frequency noise has invaded natural soundscapes, pervading oceanic ambient sounds and potentially disrupting the biotic interactions. ...
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Sounds from human activities such as shipping and seismic surveys have been progressively invading natural soundscapes and pervading oceanic ambient sounds for decades. Benthic invertebrates are important ecosystem engineers that continually rework the sediment they live in. Here, we tested how low-frequency noise (LFN), a significant component of noise pollution, affects the sediment reworking activities of selected macrobenthic invertebrates. In a controlled laboratory setup, the effects of acute LFN exposure on the behavior of three abundant bioturbators on the North Atlantic coasts were explored for the first time by tracking their sediment reworking and bioirrigation activities in noisy and control environments via luminophore and sodium bromide (NaBr) tracers, respectively. The amphipod crustacean Corophium volutator was negatively affected by LFN, exhibiting lower bioturbation rates and shallower luminophore burial depths compared to controls. The effect of LFN on the polychaete Arenicola marina and the bivalve Limecola balthica remained inconclusive, although A. marina displayed greater variability in bioirrigation rates when exposed to LFN. Furthermore, a potential stress response was observed in L. balthica that could reduce bioturbation potential. Benthic macroinvertebrates may be in jeopardy along with the crucial ecosystem-maintaining services they provide. More research is urgently needed to understand, predict, and manage the impacts of anthropogenic noise pollution on marine fauna and their associated ecosystems.
... Underwater sound is critical to fish, as it helps them communication, detect predators and prey, navigate habitats (Tavolga 1971;Tolimieri et al. 2000;Simpson et al. 2005Simpson et al. 2010Ladich and Winkler 2017) and detect other long-range acoustic field information (Montgomery et al. 2006;Atema et al. 2015). Due to the low visibility of the marine environment, the auditory organs in fishes are considered to be more important than visual organs (Popper and Hawkins 2018). ...
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The inner ears of fish contain three pairs of otoliths-lapilli, asterisci and sagittae-which play important roles in hearing and balance. However, acoustic properties and dynamic responses of fish otoliths are poorly understood. The large yellow croaker (Larimichthys crocea), like many species in the family Sciaenidae, is extremely sensitive to sound. The present study used L. crocea sagittae as the research subject and examined the variation in shear stress on sagittae under different acoustic stimuli. For the first time, the sound speed of the sagitta was measured using ultrasonic pulse-echo techniques, and the acoustic impedance and natural frequency of the sagitta were calculated. Larimichthys crocea adults (20-22 cm standard length, n = 10) had a sagitta density of 2781.5 ± 28.06 kg/m3, sound speed of 4828-6000 m/s and acoustic impedance range of 13.4-16.7 MPa·s/m, approximately 9-11 times that of seawater (1.48 MPa·s/m). The natural frequency of the sagitta was 76.4-95.5 kHz. The shape and structural details of sagittae were reconstructed by 3D scanner and the shear stress responses of sagittae under different acoustic stimulus were investigated based on a finite element model. The simulation results showed that the shear stress responses tended to increase and then decrease in the range of sciaenid hearing frequency from 200 to 1300 Hz, peaking at 800 Hz. The shear stress responses varied with the direction of acoustic stimulus and peaked when the incident direction was perpendicular to the inner surface of the otolith. These results provide important parameters that may be used to protect L. crocea from possible underwater noise damage, particularly during their spawning aggregations and over-wintering aggregations.
... Biotic -biologicalsources include the sounds produced by conspecifics (other members of the same species), other fish species, marine mammals and invertebrates. Snapping shrimp are possibly the most ubiquitous source of background biotic noise in some parts of the ocean (Lagardère et al., 1994;Tolimieri et al., 2000;Popper andHastings, 2009a, 2009b). Sound is an ideal means of communication in the aquatic environment for distances over several metres because, at a given frequency, the absorption of sound by water is far less than the absorption of light (Leighton, 2007). ...
Thesis
The effects of noise on aquatic life is a topic of growing international concern. Underwater noise can impact both the physiology and behaviour of fish species on a wide-ranging scale, from minor changes and adaptations to major injury and death. Future mitigation of anthropogenic noise in the ocean is dependent on greater awareness of the effects of noise, the amount of risk, and degree of harm, likely to affect fish populations. Currently, there is a lack of incentive for mitigation measures to be put in place. Knowledge and evidence of the impacts of anthropogenic noise on fish is rapidly increasing (Figure 1.2) but with over 32,000 species of fish of differing conservation and commercial importance, it is extremely difficult to decide where to focus research for maximum benefit (Hawkins et al., 2015). Predictions and assumptions about potential impacts lack accuracy as variations in experimental equipment and techniques, lack of agreed standards, different algorithms for analysis, ambiguous and interchangeable terminology, and different quantities, units and metrics, all lead to incongruities (ISVR Consulting, 2004; Barlow et al., 2014; Rogers et al., 2016). Often it is not possible to compare studies or make generalisations (OSPAR, 2009; Wilcock et al., 2014). Here the aim is to aid the mitigation process by directing research priorities toward the most vulnerable fish species, and developing models and tools that allow for informed and cost-effective mitigation methods in a bid to reduce the effects of anthropogenic noise from marine traffic.
... There is an increasing number of studies revealing that there are more soniferous fish species than previously thought (Carriço et al. 2019). Fish use sounds to communicate (Ladich 2019), in courtship and during spawning (Rowe & Hutchings 2006;Erisman & Rowell 2017), to orientate towards preferred ecosystems like reefs (Tolimieri et al. 2000) and to startle predators (Vester et al. 2004). ...
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The mechanisms that link reef soundscapes to larval fish settlement behaviors are poorly understood, yet the management of threatened reef communities requires we maintain the recruitment processes that recover and sustain populations. Using a field-calibrated sound propagation model, we predicted the transmission loss in the relevant frequency band as a function of range, depth, and azimuth to estimate the spatial heterogeneity in the acoustic cuescape. The model highlighted the frequency- and depth-dependence of the sound fields fishes may encounter, and we predict these complex spatial patterns influence how sounds function as settlement cues. Both modeling and field measurements supported a non-monotonic decline in amplitude with distance from the reef. We modeled acoustic fields created by sounds at frequencies from 2 common soniferous reef-based animals (snapping shrimps and toadfish) and estimated detection spaces of these sounds for larvae of 2 reef fish species. Results demonstrated that larval depth will influence cue availability and amplitude, and these spatial patterns of detection depend on cue frequency and the larval receiver’s auditory sensitivity. Estimated spatial scales of detection coupled with field measurements suggest cue amplitudes might allow some larvae to detect reef-based sounds at a range exposing them to the predicted spatial variation in the acoustic cuescape. In an individual-based model, cues available to even the shortest modeled distances improved settlement success. Our results emphasize the need to consider the frequency- and depth-dependence of the acoustic cues larval fishes encounter to increase understanding of the role of soundscapes in larval settlement.
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Science is an ecosystem, and its evolution is driven by the legacy of what has gone before. I have been privileged to be part of this, finding a niche in which to work and live, in the biome of marine science. Entering science through curiosity and connection to the sea, I was lucky to encounter mentors who lit up potential career paths and facilitated connections to community. My career is an ongoing part of their legacy. Like evolution itself, the journey of science practice is not pre-ordained, with no itinerary. Various paths are tried, and some become established through the selection pressure of success. Opportunities arise, and collaborations are formed with a commonality of interest and purpose, and a diversity of ideas and expertise. Supervision of postgraduates also provides an expanding legacy out in to the wider world. What will our individual and collective legacy look like? My hope is that our understanding of complex systems, such as ocean ecosystems, is captured and challenged by computational models capable of predicting future states. Being able to see what different futures look like, with and without positive interventions, should help us make better choices and create a sustainable Anthropocene future by active design.
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Spatial cognitive abilities allow individuals to remember the location of food patches, predator hide-outs, or shelters. Animals typically incorporate learnt spatial information or use external environmental cues to navigate their surroundings. A spectacular example of how some fishes move is through aerial jumping. For instance, fish that are trapped within isolated pools, cut off from the main body of water during dry periods, may jump over obstacles and direct their jumps to return to safe locations. However, what information such re-orientation behaviour during jumping is based on remains enigmatic. Here we combine a lab and field experiment to test if guppies (Poecilia reticulata) incorporate learnt spatial information and external environmental cues (visual and auditory) to determine where to jump. In a spatial memory assay we found that guppies were more likely to jump towards deeper areas, hence incorporating past spatial information to jump to safety. In a matched vs. mismatched spatial cue experiment in the field, we found that animals only showed directed jumping when visual and auditory cues matched. We show that in unfamiliar entrapments guppies direct their jumps by combining visual and auditory cues, while in familiar entrapments they use a cognitive map. We hence conclude that jumping behaviour is a goal-directed behaviour, guided by different sources of information and involving important spatial cognitive skills.
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For close to a century, recruitment of larvae to a local population has been widely accepted as a primary determinant of marine population dynamics. However, progress in elucidating the causes of recruitment variability has been greatly impeded by our ignorance of the sources of recruits. Although it is often assumed that recruitment is independent of local reproduction, there is increasing circumstantial evidence that physical and behavioural mechanisms could facilitate larval retention near source populations. To develop a direct method for reconstructing the dispersal history of recruiting larvae, we put forward the hypothesis that differences in nutrient and trace-element concentrations between coastal and open oceans could result in quantifiable differences in growth rate and elemental composition between larvae developing in coastal waters (locally retained) and larvae developing in open ocean waters (produced in distant locations). Using this method, we show that recruitment to an island population of a widely distributed coral-reef fish may often result from local retention on leeward reefs. This result has implications for fisheries management and marine reserve design, because rates of dispersal between marine populations-and thus recruitment to exploited populations-could be much lower than currently assumed.
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Swimming speeds of the late-stage, pelagic larvae of coral-reef fishes were measured in situ near Lizard Island on Australia's Great Barrier Reef, and Rangiroa Atoll, Tuamotu Islands, French Polynesia during 1995-96. Larvae were captured with light traps End crest nets, and released individually in open water. They were then followed by SCUBA divers, normally for 10 min, and their speed was measured with a modified plankton-net flow meter and a stop watch. Swimming speeds of 260 larvae of 50 species in 15 families of mostly perciform reef fishes are presented. Most measurements were for pomacentrids (8 genera, 16 species, 127 individuals), apogonids (1 genus, similar to 5 species, 18 individuals), chaetodontids (3 genera, 8 species, 49 individuals), lethrinids (1 genus, similar to 4 species, 11 individuals), nemipterids (1 genus, 2 species, 10 individuals), serranids (2 genera, 2 species, 14 individuals) and acanthurids (2 genera, similar to 4 species, 13 individuals). Numbers of individuals per species ranged from 1 to 25. Speeds were remarkably high for such small fishes (0.7 to 5.5 cm). Average speed was 20.6 cm s(-1) (range 2 to 65), or 13.7 body lengths s(-1) (range 2 to 34). SE for species with n > 4 ranged from 0.8 to 5.3 cm s(-1) (4.1 to 25.0% of mean speed), but speed of the fastest individual of each species averaged 144% of mean speed. A taxonomic component was evident, with apogonids the slowest (2 to 13 cm s(-1)), followed by nemipterids (10 cm s(-1)). Speed of pomacentrids and chaetodontids varied widely among species (7 to 35 cm s(-1)), whereas acanthurids, lethrinids and serranids were fast (19 to 55 cm s(-1)). Except for apogonids and nemipterids, nearly all species had mean swimming speeds greater than average ambient current speeds in the Lizard island area. Mean speed was positively correlated with size (slope 8.2, r(2) = 0.43) when all taxa were included, but was not correlated with size for the Pomacentridae and Chaetodontidae when each were considered alone. The speeds reported here combined with data on swimming endurance recently reported by Stobutzki & Bellwood (1997; Mar Ecol Prog Ser 149:35-41) reveal remarkable swimming abilities for late-stage pelagic larvae of coral-reef fishes which could either greatly enhance dispersal or eliminate it.
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This paper reviews the application of several sensory signals for their possible use in the control and modification of fish behavior but emphasizes the use of sound. Basic principles of underwater acoustics are introduced, followed by an overview of the structures and function of the fish ear and lateral line. Sounds in the sonic, infrasonic, and ultrasonic ranges are potentially useful for controlling fish behavior. However, most experiments testing the usefulness of such sounds have given ambiguous results except when ultrasound has been used to control some clupeid species. Very little is known about the potential usefulness of chemical and electric signals (other than electric shocks) for behavioral control. A substantial literature on the use of light to attract or repel fish offers encouraging possibilities for this control medium in some circumstances. We conclude that too little is actually known about the suitability of various signals for control of fish behavior. Many variables, such as time of day and age of the fish, affect the effectiveness even of signals that seem to “work.” These variables can influence the success or failure of a technique and need to be considered in the evaluation of any stimulus considered for the control fish behavior. Moreover, it is increasingly apparent that flow field has a powerful effect on the local success of one stimulus or another. We suggest that sound and light be further explored for control of fish behavior, particularly in combination. This work cannot be done with only field studies or only laboratory studies or by only applied biologists or only basic scientists; all methods and expertise are needed. Finally, no behavioral control method will work unless the behavior of the subject species is thoroughly understood in each place of application.
Chapter
During autumnal mass migrations of spiny lobster in the northern Bahamas, large numbers move from the shallows to the areas fringing oceanic waters (e.g., the Gulf Stream). The phenomenon involves nocturnal immigration of lobsters over several weeks into the fringe. Concurrent with the first severe autumnal squall, the population moves synchronously in queue formations often both day and night. Thermal declines caused by the storms correlate statistically with onset of hyperactivity and queuing in captive lobsters. Lobsters becoming active facilitate others to queue up; queuing behavior serves migration by reducing hydrodynamic drag on each individual. Hydrodynamic stimuli, water currents and wave surge oscillations, serve as orientational guideposts under certain conditions.
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Light traps were used to sample small fish and squid from open waters in the central Great Barrier Reef lagoon. A total of 7203 fish, representing some 38 families, and 706 lologinid squid were caught during sampling periods October to January, 1988 to 1990. The fish catch was dominated by the family Pomacentridae (63 % of fish collected), with lower numbers of lethrinids (6.7 %), clupeids (6.3 %), mullids (3.8 %), and scombrids (2.7 %). Size-frequencies of the fish collected indicated that the light traps sampled late-stage larvae and pelagic juveniles exclusively. No effect of time of night on catch rate was detected. Light traps that were allowed to drift with prevailing water currents caught more fish than anchored traps; this unexpected result may be a function of the effect of current velocity on trap efficiency. Analysis of standard error/sample size curves suggested that optimum replication was achieved with 5 to 6 traps, but that reasonable precision could be obtained with 2 to 3 traps. Coefficients of variation among replicate traps were taxon-specific, ranging from 0.9 (for clupeids) to 0.2-0.1 (for pomacentrids). These values compare favourably with those obtained from trawl nets. Light traps have considerable potential for sampling nekton that are capable of avoiding conventional towed nets.
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Groups of Aplysia brasiliana Rang were released during the day in shallow water at various locations to study their offshore-oriented swimming response. The effect of ambient current was subtracted from each animal's path vector to obtain a thrust vector, and distributions of the mean path vectors and mean thrust vectors of each animal were analyzed. Intact Aplysia swam offshore in relatively straight paths at three release sites having markedly different shoreline directions. Eyeless animals started out in the offshore direction, but their paths soon became contorted. In contrast rhinophoreless animals were randomly oriented, but followed relatively straight paths. Sham-operated animals and animals lacking oral tentacles both behaved like normal animals. Correlational analyses suggest that wave direction is the primary orientational guidepost used when larger waves are present, but that some other cue(s) is involved when waves are small or absent. Collectively these data suggest that when larger waves are present, offshore-oriented swimming results from rhinophore-mediated detection of wave surge and that some other cue, possibly visual, is involved in maintenance of the original direction once an Aplysia is in the water column.
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The sustained swimming abilities of the late pelagic stages of 9 families of reef fishes were measured at 13.5 cm s(-1). There was a 25-fold difference in abilities among the families. Acanthurid juveniles swam on average for 194.3 h, covering the equivalent of 94.4 km. In comparison nemipterids swam for only 7.4 h, the equivalent of 3.6 km. The distances covered by other taxa ranged from 8.3 to 62.2 km. Among the families swimming ability was related to size and age but this relationship explained little of the variation present (R-2 = 0.403). Our results demonstrate that the pelagic stages of reef fishes are competent swimmers and capable of actively modifying their dispersal. This has direct implications on the replenishment of reef fish populations, especially with respect to mechanisms for self-seeding and maintenance of regional biogeographical patterns.
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Distributions of small and large larvae of Centroberyx affinis (Berycidae) and Gonorynchus greyi (Gonorynchidae) were examined along a shore-normal transect across the Sydney continental shelf, south-eastern Australia during January and April 1994. Both species were abundant, and 3016 individuals of C. affinis and 3184 individuals of G. greyi were taken. Distributions of small and large C. affinis reflected hydrographic variability and suggested passive dispersal. Previous observations of high year-class variability for this species may therefore reflect oceanographic variability during the larval stage. In contrast, the distributions of G. greyi only partially reflected hydrography and appeared to be influenced by larval behaviour at both sizes. Size distributions during each month indicated protracted spawning periods for both species. Spawning by C. affinis may have occurred over the inner shelf although the location was unclear because of the complexity of nearshore currents. Spawning by G. greyi probably occurred over the outer shelf. An increasing influence of larval behaviour with larval size on the distribution of G. greyi restricted larger individuals to the shelf break; this may have been a response to higher productivity in this region.
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Late pelagic stages of coral reef fishes captured with light-traps were individually released during daylight by SCUBA divers in open water, 20-35 m deep, in the Great Barrier Reef Lagoon at three sites > 1 km from the reefs of Lizard Island. Observations in situ on 111 individuals of 11 families, but primarily Apogonidae, Chaetodontidae and Pomacentridae, constitute the first data of their kind. Most fish showed no overt reaction to the divers. Some individuals of some taxa of three families settled quickly to the bottom. Acceptable observations on swimming were made on 66 larvae. Individuals selected a wide range of depths, but when grouped by family, mean depths chosen by individuals were: apogonids, 6.5 (± 1.5, 95% CI) m; pomacentrids, 7.7 (± 1.5) m; and chaetodontids, 9.3 (± 1.3) m. Rough estimates of speed of up to 30 cm s-1 varied among taxa. Swimming directions of 59 of the 66 larvae were non-random. Mean directions differed among sites and were offshore at all of them. Most larvae swam offshore regardless of the side of the island where they were released. The late pelagic stages of coral reef fishes are strong swimmers capable of active horizontal and vertical movement. They swim directionally, can apparently detect reefs >1 km away, and orientate relative to those reefs. A taxonomic component is evident in many of these behaviours.