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Saws and the city: smalltooth sawfish (Pristis pectinata) encounters, recovery potential and research priorities in urbanized coastal waters off Miami, Florida


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As coastal urbanization increases globally, the subsequent effects on marine animals, especially endangered species, inhabiting nearshore waters have become a research priority. The smalltooth sawfish Pristis pectinata , once abundant in US waters, now only persists in a few parts of its former range, including South Florida. Many areas utilized by smalltooth sawfish are estuarine systems or other shallow coastal habitats, making this species particularly vulnerable to threats associated with coastal development. To date, P. pectinata has been understudied in the waters in and around Biscayne Bay, Florida, a coastal waterway subjected to the urbanization of adjacent Miami-Dade County. Here, we summarize data from reported smalltooth sawfish encounters dating as far back as 1895 (N = 90) and detail opportune recordings (incidental catches, acoustic detections, and baited remote underwater videos) of sub-adults and adults (N = 14 individuals) in Biscayne Bay and the adjacent reef tract. These data demonstrate historical and increased contemporary use of the study area by this imperiled species, suggesting potential local and regional recovery. Most documented sawfish occurrences were near the urban center, indicating a need to understand the effects of coastal urbanization on sawfish and on the species' recovery potential. We suggest priorities for future research on P. pectinata in the study area that will assist in addressing regional management goals and contribute to understanding the ecology of smalltooth sawfish under environmental change.
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Endang Species Res
Vol. 43: 543– 553, 2020 Published December 17
Animals living in urban landscapes face different
threats and stressors than those inhabiting pristine
and relatively intact environments. Threats associated
with urbanization include noise, chemical, and light
pollution, habitat degradation, and disturbances such
as harassment and exploitation. Despite imminent
threats from fishing, boat traffic and noise, coastal
run-off, and sea-level rise, the effects of urbanization
©L. McDonnell, G. Burgess, L. Phenix, A. Gallagher, N. Hammerschlag,
and outside the USA the US Government 2020. Open Access under Cre-
ative Commons by Attribution Licence. Use, distribution and reproduc-
tion are un restricted. Authors and original publication must be credited.
Publisher: Inter-Research ·
*Corresponding author:
Saws and the city: smalltooth sawfish
Pristis pectinata encounters, recovery potential,
and research priorities in urbanized coastal waters
off Miami, Florida, USA
Laura H. McDonnell1,2, Thomas L. Jackson3, George H. Burgess4, Lindsay Phenix5, 6,
Austin J. Gallagher5,7, Helen Albertson3, Neil Hammerschlag1, 2, Joan A. Browder3,*
1Leonard and Jayne Abess Center for Ecosystem Science and Policy, University of Miami, Coral Gables, Florida 33146, USA
2Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, Miami, Florida 33149, USA
3National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Southeast Fisheries Science Center,
Miami, Florida 33149, USA
4University of Florida, Gainesville, Florida 32611, USA
5Beneath the Waves, Inc., PO Box 126, Herndon, Virginia 20172, USA
6Three Seas Program, Northeastern University, 430 Nahant Road Nahant, Massachusetts 01908, USA
7Department of Marine Science, Northeastern University, 430 Nahant Road Nahant, Massachusetts 01908, USA
ABSTRACT: As coastal urbanization increases globally, the subsequent effects on marine animals,
especially endangered species, inhabiting nearshore waters have become a research priority. The
smalltooth sawfish Pristis pectinata, once abundant in US waters, now only persists in a few parts
of its former range, including South Florida. Many areas utilized by smalltooth sawfish are estuar-
ine systems or other shallow coastal habitats, making this species particularly vulnerable to
threats associated with coastal development. To date, P. pectinata has been understudied in the
waters in and around Biscayne Bay, Florida, a coastal waterway subjected to the urbanization of
adjacent Miami-Dade County. Here, we summarize data from reported smalltooth sawfish en -
counters dating as far back as 1895 (N = 90) and detail opportune recordings (incidental catches,
acoustic detections, and baited remote underwater videos) of sub-adults and adults (N = 14 individ-
uals) in Biscayne Bay and the adjacent reef tract. These data demonstrate historical and increased
contemporary use of the study area by this imperiled species, suggesting potential local and
regional recovery. Most documented sawfish occurrences were near the urban center, indicating
a need to understand the effects of coastal urbanization on sawfish and on the species' recovery
potential. We suggest priorities for future research on P. pectinata in the study area that will assist
in addressing regional management goals and contribute to understanding the ecology of small-
tooth sawfish under environmental change.
KEY WORDS: Conservation · Southeast Florida · Acoustic array · Endangered species ·
Urban ecology · Biscayne Bay Habitat Focus Area
Endang Species Res 43: 543– 553, 2020
on marine species have not been well studied (Todd
et al. 2019). The coastline of Florida (USA) is among
the most populous in the world and is regarded as a
hotspot for ‘coastal syndromes’: habitat fragmenta-
tion, eutrophication, species loss, and coastal runoff.
However, the same waters are in habited by ecologi-
cally and economically important species, including
those that are threatened and en dangered, such as
the smalltooth sawfish Pristis pectinata.
Various regulatory actions have been taken to pro-
tect and promote recovery of the US population of P.
pectinata, which now only persists in a few parts of
its former range, including South Florida (NMFS
2009). This species was first provided protection in
Florida in 1992 by the Florida Fish and Wildlife Con-
servation Commission and was further protected by
the banning of gillnets in 1994. Due to continued
threats to the remaining US population of P. pecti-
nata (Seitz & Poulakis 2006), the species was formally
listed as ‘endangered’ under the US Endangered
Species Act (ESA) in 2003. Along with these regula-
tory actions there has been a pointed effort to protect
specific areas to support the conservation and recov-
ery of the remaining US population. The ESA recov-
ery plan for P. pectinata identified key research and
conservation needs revolving around habitat desig-
nation, restoration, and conservation, including iden-
tification of historic migration corridors and nursery
areas (Carlson et al. 2013).
Many areas utilized by smalltooth sawfish are estu-
arine systems or other shallow coastal habitats in
close proximity to shorelines (Poulakis & Seitz 2004,
Carlson et al. 2014), where they are particularly vul-
nerable to threats associated with coastal develop-
ment and urbanization. Nursery areas harboring
young of the year and small juveniles have been rel-
atively well studied, and movement patterns within
them have been examined (Poulakis et al. 2011,
2013, Norton et al. 2012, Scharer et al. 2017). How-
ever, considerably less is known about movements of
sub-adult and adult smalltooth sawfish. An enhanced
understanding of smalltooth sawfish occurrence, dis-
tribution, and habitat use in relation to coastal urban-
ization is needed to understand the vulnerability of
this species to increasing urbanization and related
threats (Brame et al. 2019, Poulakis & Grubbs 2019).
The Biscayne Bay watershed encompasses the city
of Miami, one of the largest coastal metropolises in
the USA. Located along the southeast Florida coast,
Biscayne Bay is a productive estuarine ecosystem;
however, the northern part of the bay is a degraded
environment. The US National Oceanic and Atmos-
pheric Administration (NOAA) designated Biscayne
Bay and its associated reef tract as a Habitat Focus
Area (HFA) in 2015 with the goal of focusing re sources
and increasing habitat science and conservation
efforts in this area. The Biscayne Bay HFA initiative
included a stated objective to support and enhance
the recovery of smalltooth sawfish (NOAA 2019).
However, relatively little is known about the occur-
rence of this species on Florida’s lower east coast.
Moreover, P. pectinata has previously been consid-
ered near-absent from Biscayne Bay (Lewis 2008,
Brame et al. 2019). To date, there have been no
directed or published studies related to the use of
Biscayne Bay and its adjacent reef tract by smalltooth
sawfish. Information on the use of the Biscayne Bay
HFA by P. pectinata is particularly important given
that these waters are partially bordered by the
Miami metropolitan area and are highly impacted by
anthropogenic effects associated with coastal urban-
ization, including fishing, boating, and pollution
(sound, chemical, and light) (Browder et al. 2005).
The lack of scientific coverage of the species in this
area has increased the importance of combining local
knowledge and data from a public reporting system
with recent local scientific efforts to document the
presence of endangered species. Citizen-based re -
ported sawfish encounter data have been very useful
in providing evidence of habitat use in US waters
(Poulakis & Grubbs 2019), and such data can provide
additional support to conservation efforts (Norton et
al. 2012). The International Sawfish Encounter Data-
base (ISED) maintains citizen reports from 1782 to
present (
map/). Reports sent to ISED can include details such
as location, method of observation, and estimated
capture metrics (if obtained pre-release) and consist
of encounters by both the public (boaters, recre-
ational fishers, etc.) and researchers.
The present study summarizes patterns of encoun-
ters of this species from ISED reports and an inde-
pendent historical search and provides details on
recent opportunistic recordings from a suite of re -
search methods on both sub-adult and adult small-
tooth sawfish within the Biscayne Bay HFA. We rec-
ommend research priorities for P. pectinata in this
urbanized coastal waterway based on our findings.
2.1. Study area
The study region is subject to a humid sub-tropical
climate, characterized by a hot and rainy ‘wet sea-
McDonnell et al.: Smalltooth sawfish in urbanized coastal waters
son’ (May−October) and a relatively colder and more
arid ‘dry season’ (November−April). During the wet
season, coastal waters exhibit relatively higher tem-
peratures and lower salinities, whereas during the dry
season, they exhibit relatively lower temperatures and
higher salinities.
The Biscayne Bay HFA, as designated by NOAA in
2015, extends nearly 80 km from northern Dum-
foundling Bay to southern Barnes Sound and Mana-
tee Bay, encompassing the entirety of Biscayne Bay
and its connected reef tracts (Fig. 1). Biscayne Bay is
a shallow, clearwater lagoon with a predominantly
Fig. 1. All smalltooth sawfish encounter locations (N = 112). These 112 locations include 90 from historical and recent sightings
(S), baited underwater remote videos (BRUVs), and incidental catches (IC) in addition to 22 receiver locations with acoustic
detections (AD), labeled with letters (as in Fig. 4). Locations of Turkey Point nuclear plant, Shoal Point, and Deering Estate are
also shown (purple dots)
Endang Species Res 43: 543– 553, 2020
benthic-based ecosystem (Browder et al. 2005) that
supports a wide array of marine species, including
seagrasses and hard and soft corals. The northern
half of the Biscayne Bay HFA borders the Miami met-
ropolitan area; therefore, its waters are affected by
urbanization and anthropogenic activities, including
boating and recreational fishing (Browder et al. 2005).
A natural coastline with a mangrove fringe and slight
shoreline indentations borders Biscayne Bay.
Since it was hydrologically connected to the Ever-
glades, Biscayne Bay has had its watershed drastically
altered over the past century for both agricultural
and urban purposes, changing the quantity and tim-
ing of freshwater flow to the bay and replacing natu-
ral flow paths with canals (Browder et al. 2005). This
has increased salinity, converting the bay from estu-
arine conditions to more oceanic conditions. How-
ever, new water management policies encapsulated
in the Com prehensive Everglades Restoration Plan
(CERP) have sought to restore historical flow pat-
terns to Biscayne Bay to convert it to a more natural
estuarine system (USACE 2019). Water pumping sta-
tions to distribute canal flows into sheet flows have
already been established at certain locations in the
southcentral bay, redistributing freshwater input
along the shoreline in a phased approach (NOAA
2019, 2020). These restoration efforts are relevant to
the smalltooth sawfish, whose juveniles prefer estuar-
ine conditions (Simpfen dorfer et al. 2011).
2.2. Data collection
Several independent data sources were used to
compile historic and current records of smalltooth
saw fish within the Biscayne Bay HFA. These were:
(1) literature searches, including public news sources,
(2) encounter records reported to the ISED, and (3)
recent opportune encounters with smalltooth saw-
fish by our research team during unrelated re search
surveys. Details on each approach are de scribed
A literature search was completed in 2020 with the
aim of finding historical records of smalltooth sawfish
within the area that became designated the Biscayne
Bay HFA, as well as compiling more recent sightings
reported to public news outlets. This search was con-
ducted using standard electronic resources, i.e. Web
of Science (ISI) and Aquatic Sciences and Fisheries
Abstracts (ASFA; ProQuest) with ‘Sawfish in Bis-
cayne Bay’ and ‘Sawfish in Miami’ as qualifiers. In
addition, local news sources and their archives, in -
cluding the Palm Beach Post (1904−present) and
Miami Herald (1911−present), were searched using
the same qualifiers.
Smalltooth sawfish records in Miami-Dade were
also collected from ISED with data download re -
quests in 2019 and 2020. All records obtained from
ISED and the bibliographic search were compiled
and compared. Any duplicate observations (reports
of the same sawfish at the same location and time but
from different people) were combined. While we
summarize and report all records from these sources,
only those with adequate time (month/year) and
location data (GPS coordinates provided by the
reporter or assigned by ISED) were included in spa-
tial analyses.
Between 2017 and 2020, our research team inci-
dentally encountered smalltooth sawfish during sev-
eral different research surveys in the Biscayne Bay
HFA to monitor the habitat use and relative abun-
dance of coastal sharks and fish. These included (1)
incidental catches of smalltooth sawfish on drum-
lines, (2) recordings on baited-remote underwater
video (BRUV) stations, and (3) detections of acousti-
cally tagged sawfish on underwater receivers (hydro -
phones). Since 2009, we have been conducting
standardized circle-hook drumline shark surveys (de -
scribed by Gallagher et al. 2014) to monitor shark
spatiotemporal patterns in the area. Between 2017
and 2018, we deployed BRUVs within Biscayne Bay
to compare the abundance, richness, and behavior of
fish species in different habitats and management
regions (Fig. S1 in the Supplement at
com/ articles/suppl/n043p543_supp.pdf; BRUV set-up
and procedures described by Phenix et al. 2019 and
Enchelmaier et al. 2020). To record the presence of
sharks, we have acoustically tagged sawfish with
69 kHz Vemco transmitters, and we maintain an
array of 40 single-frequency omnidirectional VR2W
Vemco acoustic receivers (installed in stages begin-
ning in 2016), positioned mainly in the urban en -
vironment of the bay, but also in other parts of the
Biscayne Bay HFA (Figs. 1 & S2), These hydro phones
can detect the presence of any acoustically tagged
animal carrying a compatible 69 kHz Vemco trans-
mitter that enters their detection range (~500− 1000 m;
see de scription in Hammerschlag et al. 2017).
Based on information available from all smalltooth
sawfish records, we extracted the date and location
of the encounter as well as the identity code and
size and sex of the sawfish, if available. Total length
(TL: length from rostrum to caudal fin) of sawfish
caught on drumlines was estimated using the boat-
based 3.6 m wide platform as a reference during
release. For individuals detected on BRUVs, TLs
McDonnell et al.: Smalltooth sawfish in urbanized coastal waters 547
were estimated relative to the dimensions of the
attached bait crate (17.8 × 12.7 × 8.9 cm [7 × 5 ×
3.5 inches]; length × width × height), as approached
by the sawfish. The TL of all acoustically detected
individuals was measured on the tagging date. Infor-
mation from all mentioned sources was screened
for temporal, spatial, or seasonal patterns in the
occurrence of smalltooth sawfish in the Biscayne
Bay HFA. Encounters with associated GPS data
(latitude and longitude) were mapped using Arc -
GIS Pro software (ESRI), and spatial spread was
3.1. Records, literature, and news source search
A total of 90 historical and recent smalltooth sawfish
encounter records in Miami-Dade County were ob-
tained from a combination of the literature search, news
reports, and available ISED reports (Fig. 2, Table S1).
We found that sawfish sightings in the study area date
back to at least 1895. The search of literature, archives,
and other sources yielded several accounts from 1905
to 1929 (N = 18), including 1 reference to a location
called ‘the sawfish hole’ that was posted in the Mi-
ami Daily Metropolis on 20 May 1909.
Among the total 90 records collected
from our searches, we noted that 8
sightings from the Biscayne Bay HFA
with sufficient details required for in-
clusion in ISED were not yet posted in
the database; we have since submitted
our records of these to ISED. Of these, 4
were from historical archives while the
other 4 were very recent sightings (2019,
2020) detailed in public news sources.
The search for records from this area
also resulted in several images of saw-
fish captured in Miami-Dade waters,
photographed during the early decades
of the 20th century (Fig. 3A).
Of all 90 reported encounters, 51 %
(N = 46) oc curred within the last de -
cade (Figs. 1 & 3B). Over three- quarters
(77%, N = 69) of all encounters had
precise location data assigned to them
and, of these, 96% (N = 66) were within
the Biscayne Bay HFA (Fig. 1). Over
half (N = 49) of the encounter records
included estimated TL, which ranged
from 122 to 549 cm (mean = 294.75 cm).
Sixteen of estimated TLs were within
the juvenile size range, i.e. <220 cm
(Brame et al. 2019). Season of encounter
was determined for records with suf -
ficient date information (69 records):
48 were encountered during the wet
season and 21 during the dry season.
3.2. Recent incidental encounters
We deployed 12215 drumlines in the
area of the Biscayne Bay HFA over 10 yr
(2009−2018), catching and releasing
Total no. of STS encounters to date
1900 1950 2000
2005 2010 2015 2020
Fig. 2. (A) All historical and recent sightings (cumulative, N = 90) of smalltooth
sawfish in Miami-Dade County from 1890 to 2020 from the International Saw-
fish Encounter Database and historical literature data sources. (B) More recent
encounters are enlarged to provide more resolution and to highlight important
dates. Vertical green lines mark the date of listing of smalltooth sawfish on the
US Endangered Species List (April 2003, ESA), implementation of the Bis-
cayne Bay Coastal Wetlands (BBCW) Project of the Comprehensive Everglades
Restoration Plan (CERP) at Deering Estate (Fig. 1) (December 2012, CERP 1),
and incrementation of pumping from 12 h on 12 h off flows to continuous flows
(September 2018, CERP 2)
Endang Species Res 43: 543– 553, 2020
1808 sharks. We deployed 221 BRUV stations through-
out the Biscayne Bay HFA between 2016 and 2018
(Table 1, Fig. S1). We established an array of 40
acoustic recorders in the Biscayne Bay HFA between
2015 and 2017, and the maintenance and collection of
data from these is ongoing (Table 1, Fig. S2). Acoustic
data collected from January 2017 to April 2020 are re-
ported here.
Three activities targeting sharks in the area of the
Biscayne Bay HFA within the past 4 yr (2017−2020) in-
cidentally en countered 14 individual smalltooth saw-
fish: drumlines incidentally captured 4 individuals in
2018, all were re leased immediately in good condition
(Fig. 1); BRUVs recorded 2 individuals in 2017 and
2018; and 8 individuals were detected on the acoustic
array between 2017 and 2020 (Table 1). The small-
tooth sawfish incidentally encountered on drumlines
and on BRUVs were immediately reported to ISED
and are therefore included in the 90 records de -
scribed in the previous section (Table S1). The size
differences of the drumline captures and those ob-
served on the BRUVs indicate that they were not the
same individuals, and the lack of any external tags
indicates that none of these were the same individuals
detected on the acoustic arrays. Their relatively small
size indicated that the 2 smalltooth sawfish on BRUV-
camera captures were sub-adults.
Acoustic records of smalltooth sawfish in the Bis-
cayne Bay HFA are worth noting further. The 8
smalltooth sawfish individuals were detected on 22
different acoustic receivers within the Biscayne Bay
HFA between 2017 and 2020, for a total of 487 indi-
vidual detections (Figs. 1 & S2). All individuals were
tagged by authorized investigators who were not part
of this study (Table 1). Six of the detected sawfish
had been tagged in the Florida Keys and were de -
tected 447 times in the Biscayne Bay HFA (Table 1).
In addition, 2 individuals originally tagged in Port St.
Lucie were detected 40 times in the Biscayne Bay HFA
(Table 1). Individuals remaining within the array for
prolonged periods often moved between receivers
(Table 1, Fig. 4). Six of the 8 individuals were de tected
on more than 1 receiver within the array, while 5 in -
dividuals were detected in more than 1 year (Table 1,
Fig. 4). Wet seasons accounted for 58% of detections.
Approximately 49% of detections were logged on 1
receiver located off South Beach (Fig. 1, receiver E),
with 7 out of 8 individuals detected at this location,
while 25% of total detections occurred near Fisher
Island (Fig. 1, receivers M and N).
While the use of Biscayne Bay and surrounding
waters by smalltooth sawfish has previously been
unstudied, our investigation uncovered 90 individual
smalltooth sawfish encounters (not counting re -
peated encounters with the same individuals from
the acoustic array) in the Biscayne Bay HFA, with
sightings dating as far back as 1895. These data sug-
gest both historical and contemporary use of the area
by this imperiled species. Occurrences were mainly
in waters bordered by highly urbanized areas near
Fig. 3. (A) Photograph taken by W. A. Fishbaugh in the 1920s, recorded as taken in Miami (courtesy of State Library & Archives
of Florida, Florida: (B) Photograph taken by 2 national park rangers in
Biscayne Bay National Park near Elliott Key on 23 November 2018, showing a smalltooth sawfish entangled in fishing gear
(courtesy of Biscayne National Park:
McDonnell et al.: Smalltooth sawfish in urbanized coastal waters 549
ID Date Geographic coordinates Discrete detections (AD) Data source Sex Life stage Estimated TL (cm)
1 01/13/2017 25° 45’ 23” N, 80° 8’ 32” W 1 AD (NOAA) F Adult 438
05/17/2017 25° 40’ 11” N, 80° 9’ 40” W 4
05/18/2017 25° 45’ 43” N, 80° 11’ 27” W 1
09/21/2017 25° 46’ 20” N, 80° 7’ 28” W 50
09/24/2017 25° 45’ 23” N, 80° 8’ 32” W 69
09/24/2017 25° 46’ 20” N, 80° 7’ 28” W 20
09/25/2017 25° 45’ 43” N, 80° 8’ 58” W 4
09/26/2017 25° 40’ 11” N, 80° 9’ 40” W 2
09/26/2017 25° 46’ 20” N, 80° 7’ 28” W 50
09/30/2017 25° 46’ 20” N, 80° 7’ 28” W 29
10/24/2017 25° 40’ 11” N, 80° 9’ 40” W 2
09/05/2019 25° 45’ 43” N, 80° 7’ 54” W 1
09/06/2019 25° 45’ 23” N, 80° 8’ 32” W 3
09/06/2019 25° 45’ 43” N, 80° 8’ 58” W 2
09/09/2019 25° 19’ 19” N, 80° 10’ 30” W 2
03/11/2020 25° 43’ 52” N, 80° 9’ 52” W 1
03/12/2020 25° 21’ 12” N, 80° 15’ 40” W 9
03/13/2020 25° 45’ 43” N, 80° 7’ 54” W 6
03/14/2020 25° 45’ 43” N, 80° 8’ 58” W 16
03/18/2020 25° 45’ 43” N, 80° 11’ 27” W 1
03/20/2020 25° 46’ 10” N, 80° 11’ 17” W 1
03/21/2020 25° 45’ 42” N, 80° 11’ 3” W 6
03/21/2020 25° 45’ 43” N, 80° 11’ 27” W 3
03/21/2020 25° 44’ 26” N, 80° 12’ 36” W 7
03/21/2020 25° 43’ 22” N, 80° 13’ 13” W 3
03/21/2020 25° 42’ 8” N, 80° 14’ 42” W 2
03/22/2020 25° 43’ 52” N, 80° 9’ 52” W 2
03/23/2020 25° 45’ 43” N, 80° 7’ 54” W 1
04/03/2020 25° 47’ 9” N, 80° 11’ 3” W 4
04/03/2020 25° 46’ 10” N, 80° 11’ 17” W 2
04/03/2020 25° 45’ 42” N, 80° 11’ 3” W 2
04/03/2020 25° 45’ 43” N, 80° 11’ 27” W 6
04/04/2020 25° 21’ 12” N, 80° 15’ 40” W 1
2 04/20/2017 25° 20’ 37” N, 80° 15’ 5” W 2 AD (NOAA) F Sub-adult 355
04/24/2017 25° 21’ 12” N, 80° 15’ 40” W 18
3 7/28/2017 25° 26’ 11” N, 80° 9’ 30” W NA BRUV (BTW) ND Sub-adult 300
4 9/28/2017 25° 46’ 20” N, 80° 7’ 28” W 29 AD (FWC) M Adult 349.5
5 03/08/2018 25° 45’ 23” N, 80° 8’ 32” W 3 AD (NOAA) F Adult 426
03/08/2018 25° 45’ 43” N, 80° 8’ 58” W 1
03/08/2018 25° 45’ 43” N, 80° 7’ 54” W 1
03/09/2018 25° 46’ 20” N, 80° 7’ 28” W 29
03/12/2018 25° 45’ 23” N, 80° 8’ 32” W 11
03/12/2018 25° 45’ 43” N, 80° 7’ 54” W 1
03/14/2018 25° 43’ 35” N, 80° 9’ 35” W 1
03/20/2018 25° 40’ 11” N, 80° 9’ 40” W 9
03/24/2018 25° 43’ 35” N, 80° 9’ 35” W 6
04/03/2018 25° 40’ 11” N, 80° 9’ 40” W 5
03/01/2020 25° 40’ 11” N, 80° 9’ 40” W 1
03/07/2020 25° 21’ 12” N, 80° 15’ 40” W 1
03/12/2020 25° 46’ 20” N, 80° 7’ 28” W 3
03/12/2020 25° 45’ 23” N, 80° 8’ 32” W 3
03/12/2020 25° 39’ 10” N, 80° 12’ 51” W 4
03/17/2020 25° 36’ 39” N, 80° 18’ 12” W 2
03/18/2020 25° 43’ 22” N, 80° 13’ 13” W 1
03/18/2020 25° 46’ 10” N, 80° 11’ 17” W 2
03/18/2020 25° 47’ 9” N, 80° 11’ 3” W 5
Table 1. Recent smalltooth sawfish Pristis pectinata encounters in the Biscayne Bay Habitat Focus Area, recorded from incidental
captures (IC), baited remote underwater video (BRUV) sightings, and acoustic detections (AD) of tagged individuals in chronolog-
ical order of first recording. TL: total length. Tagging details are included for the first detection; subsequent detection details of the
same individual are provided. Data sources are SRC: University of Miami Shark Research & Conservation Program; BTW: Beneath
the Waves; FWC: Florida Fish and Wildlife Conservation Commission (ESA Permit No. 21043); NOAA: National Oceanic and At-
mospheric Association (ESA Permit No. 17787-01). Dates are given as mo/d/yr; NA: not applicable; ND: not determined
Endang Species Res 43: 543– 553, 2020
ID Date Geographic coordinates Discrete detections (AD) Data source Sex Life stage Estimated TL (cm)
6 04/11/2018 25° 39’ 57” N, 80° 15’ 30” W NA IC (SRC) F Sub-adult 340
7 06/11/2018 25° 47’ 33“ N, 80° 5’ 10” W NA BRUV (SRC) F Sub-adult 364
8 06/11/2018 25° 47’ 34” N, 80° 5’ 10” W NA IC (SRC) ND Adult 430
9 06/29/2018 25° 46’ 20” N, 80° 7’ 28” W 3 AD (FWC) F Sub-adult 371.6
03/20/2019 25° 45’ 23” N, 80° 8’ 32” W 2
03/20/2019 25° 45’ 43” N, 80° 8’ 58” W 6
10 07/03/2018 25° 42’ 32” N, 80° 5’ 9” W NA IC (SRC) F Sub-adult 360
11 10/18/2018 25° 46’ 20” N, 80° 7’ 28” W 5 AD (NOAA) F Sub-adult 349
01/28/2019 25° 24’ 39” N, 80° 8’ 10” W 6
03/23/2019 25° 35’ 28” N, 80° 9’ 47” W 3
12 10/22/2018 25° 46’ 20” N, 80° 7’ 28” W 5 AD (NOAA) F Sub-adult 364
13 10/26/2018 25° 39’ 13” N, 80° 9’ 33” W NA IC (SRC) M Adult 375
14 10/30/2018 25° 46’ 20” N, 80° 7’ 28” W 4 AD (NOAA) M Sub-adult 293
10/30/2018 25° 45’ 43” N, 80° 7’ 54” W 1
03/12/2019 25° 30’ 37” N, 80° 6’ 47” W 1
Table 1. (continued)
01/2017 01/2018 01/2019
Detection date
07/2017 07/2018 07/2019
Fig. 4. Smalltooth sawfish (STS) acoustic detections in the Biscayne Bay Habitat Focus Area from January 2017 to April 2020.
Detection dates are listed as month/year. Individual smalltooth sawfish (N = 8) detected (denoted by the same ID number as
in Table 1) are plotted as a different color, and each discrete detection is represented as a circle at a given receiver station
(denoted by same letter as in Fig. 1)
McDonnell et al.: Smalltooth sawfish in urbanized coastal waters
the city of Miami, but this was where detection
opportunities by most methods, including the report-
ing public, were concentrated.
The exponential rate of smalltooth sawfish sight-
ings in the Biscayne Bay HFA in the last decade is
likely due in part to the increased marketing and
educational efforts of the Sawfish Recovery Team to
report public sightings (Brame et al. 2019). However,
taken together with opportunistic encounters of 14
individuals during our research surveys in only the
last 4 yr, this increase could point towards a re-emer-
gence of smalltooth sawfish in the Biscayne Bay
HFA. Some degree of regional recovery could be due
to the success of the ESA listing, NOAA goals, and
HFA efforts. Furthermore, recovery has likely been
driven synergistically by various added state prohibi-
tions, gillnet bans in critical habitat for juveniles,
increased boater awareness, and live release by fish-
ers arising from outreach efforts (Brame et al. 2019).
The increasingly frequent encounters of adult and
sub-adult smalltooth sawfish in the Biscayne Bay HFA
provide a unique opportunity to further investigate
these relatively understudied life stages.
Acoustic monitoring with long-lasting tags com-
bined with other local data sources has been recog-
nized as one of the most informative ways to monitor
large- and small-scale movements of smalltooth saw-
fish (Poulakis & Grubbs 2019). Results from the
acoustic receivers within Biscayne Bay HFA are par-
ticularly interesting, as they demonstrate use of this
area by a considerable proportion of total smalltooth
sawfish individuals tagged from adjacent regions.
Based on acoustic tagging data provided by J. Carl-
son (pers. comm.), the 6 NOAA-tagged individuals
that were detected by acoustic receivers in the Bis-
cayne Bay HFA represented almost one-third of the
21 adult and/or sub-adult smalltooth sawfish that
were acoustically tagged by NOAA researchers be-
tween May 2016 and October 2019. Some tagged in-
dividuals were repeatedly detected over several days
or remained within the Biscayne Bay HFA for over a
month, demonstrating a certain level of site fidelity
(Table 1, Fig. 4). Most acoustic detections oc curred
with some regularity, usually during late spring or
early fall. Patterns observed from these initial data
suggest that smalltooth sawfish may be migrating
through the Biscayne Bay HFA along a longer corri-
dor on an annual or semi-annual basis, stopping
within the Biscayne Bay HFA for short (~days) or
more prolonged (~1−2 mo) stays. We cannot deter-
mine movement paths of the tagged sawfish from our
acoustic receivers in Biscayne Bay, as they only indi-
cate presence and absence. The seasonality observed
in the detections suggests that their presence may be
part of a seasonal migration, but our limited array
placement does not give us directionality of move-
ments, nor does it tell us where the individuals are ulti-
mately going. Increased monitoring effort in this and
ad joining areas would be required to enhance our
understanding of the role that the Biscayne Bay HFA
serves within a migration route or as a stopover point.
Interestingly, smalltooth sawfish reports and en -
counters were more numerous in the northern part of
the Biscayne Bay HFA, which is more heavily im -
pacted by urbanization and anthropogenic stressors,
including high levels of boat traffic and recreational
fishing, compared to the remaining relatively pris-
tine, mangrove-lined coastline in the southern por-
tion. However, both passive and active observation
methods were more concentrated in the north; both
acoustic recorder and BRUV efforts indicate this bias
(Figs. S1 & S2), which may prevent these data from
being useful for adequately assessing smalltooth
sawfish presence along the western shoreline of
southern Biscayne Bay. It is still noteworthy that the
majority of acoustic detections occurred at receiver
sites that are subject to a high level of urbanization,
such as those deployed near downtown Miami, a
busy shipping channel, and popular tourist beaches
(Fig. 1, receivers T, K, and E, respectively). In addition,
8 receivers that had been deployed at least 3 yr prior
(Fig. S2), 7 of which are located in urban-influenced
areas in the northern part of Biscayne Bay HFA, only
detected their first smalltooth sawfish during the
spring of 2020. These were detections of 2 individu-
als that had returned to the array at several points
during the previous 3 yr (Table 1: ID 1 and 5). There-
fore, their most recent detections at previously unvis-
ited receivers sites may indicate use of expanded space
within the Biscayne Bay HFA by these individuals.
To date, research aimed at better understanding
and mitigating the effects of biodiversity loss has
focused on preserving large and pristine natural
habitats, often overlooking altered urban ecosystems
where less natural habitat remains (McKinney 2002).
Little is currently known about smalltooth sawfish
movement within urban areas. Previous research
comparing estuarine nursery habitats has shown that
juvenile smalltooth sawfish occupying an urbanized
estuary had higher metabolic stress levels than those
within a comparatively pristine estuary (Prohaska et
al. 2018). Urban development leading to loss of natu-
ral coastline is thought to be a primary cause of pop-
ulation declines in smalltooth sawfish (Seitz & Pou -
lakis 2006). However, smalltooth sawfish are among
many other species that continue to utilize the highly
Endang Species Res 43: 543– 553, 2020
urbanized areas of Biscayne Bay HFA and surround-
ing waters, despite being subject to several synergis-
tic stressors, including boat traffic and fishing. In
addition to a more concentrated weekday and week-
end boat traffic (Rider 2020), the City of Miami hosts
a variety of boating shows and fishing events through-
out the year. Nevertheless, the ecological shoreline
of the Biscayne Bay HFA provides valuable hunting
and foraging grounds for marine predators (Ham-
merschlag et al. 2010), and recent research has doc-
umented the use of this area by several shark species
despite high levels of boat activity and vessel noise
(Rider 2020). The considerable number of smalltooth
sawfish detections recorded at receiver stations in
urban areas is intriguing and leads to future ques-
tions about urbanization effects on habitat use by this
Some encounters occurred on the mainland side of
south-central Biscayne Bay, downstream from an
implemented component of the freshwater flow res-
toration efforts occurring in Biscayne Bay as part of
CERP. It is plausible that the slight reduction in salin-
ity associated with these restoration efforts has made
the area more suitable for sawfish, leading to their
increased occurrence there. Thus far, operations com-
pleted or in construction are located from Shoal Point
(25.6282° N, 80.2808° W) to Turkey Point (25.4353° N,
80.3313° W); however, multi-phased restoration efforts
likely will span a larger length of the mainland
shoreline of the bay. The extent to which these oper-
ations will affect sawfish are unknown but should be
considered in future studies. Subsequent research
could examine whether activities of smalltooth saw-
fish in the Biscayne Bay HFA could lend support to
the project’s ecological objectives and contribute
benefits to the evaluation of planned restoration
actions in the area, which could have implications for
future local restoration planning.
As with any data voluntarily reported by the pub-
lic, caution should be taken in interpreting ISED
data. As noted earlier, increased reported encounters
of smalltooth sawfish since 2000 are likely partly
attributable to increased public awareness of the
species, the advent of smartphones and camera tech-
nology, and the substantial efforts by ISED and
NOAA to stimulate reporting via public outreach that
explains the need to report sightings. However, the
magnitude of increased sightings reported in recent
years could also suggest a rise in the occurrence of P.
pectinata in the Biscayne Bay HFA and be indicative
of early stages of recovery, as documented in other
South Florida waters (Poulakis & Grubbs 2019). These
findings are especially relevant given their previ-
ously purported near-absence from the area (Lewis
2008). Citizen-based reporting systems could signal
geographic expansion by sawfish or other rare spe-
cies into otherwise unmonitored areas.
The present findings advocate a closer examina-
tion of the use of the Biscayne Bay HFA by smalltooth
sawfish and the role this area may play in its life his-
tory, migration, and recovery. We propose the follow-
ing future research priorities for this species within
the Biscayne Bay HFA, with emphasis on long- and
short-range movement patterns, effects of anthro-
pogenic stressors, and population ecology:
(1) Document short-range movement patterns and
habitat use of adult sawfish with augmented cover-
age within southwestern Biscayne Bay.
(2) Determine whether suitable nursery habitat for
this species within the Biscayne Bay HFA might exist
at present or with further planned freshwater inflow
(3) Determine how existing or potential smalltooth
sawfish habitat will be affected by changes in fresh-
water distribution to Biscayne Bay expected from
future restoration efforts.
(4) Evaluate the effects of coastal development and
other anthropogenic activities on sawfish behavior
and physiological function and their relevance to
population ecology.
(5) Determine large-scale movement patterns (e.g.
via satellite tracking) to address whether the Bis-
cayne Bay HFA is a significant part of a smalltooth
sawfish migratory pathway.
(6) Describe the biological and ecological charac-
teristics of the potential resident/migratory popula-
tion of smalltooth sawfish in the Biscayne Bay HFA.
Acknowledgements. We thank S. Cain, M. Rider, and A.
Tinari of the University of Miami (UM) Shark Research and
Conservation Program for their assistance in data compila-
tion, as well as the UM scuba divers who assisted in acoustic
receiver deployment and maintenance. We recognize the
individuals who reported and provided details on their
smalltooth sawfish encounters in the Biscayne Bay HFA, as
well as E. Quintero and M. Riera for field assistance. The
FACT network supported collaboration and data sharing for
this work. We thank D. Grubbs, J. Carlson, M. Ajemian, and
G. Poulakis, who were responsible for the acoustic tagging
of sawfish that were detected on the Biscayne Bay receivers.
Thanks to D. Grubbs and G. Poulakis, who supplied meta-
data for these individuals to be used in this study; D. Grubbs
also provided feedback on an earlier version of this manu-
script. We also thank D. Bouck for early information acquisi-
tion and NOAA Corps officers J. Europe and J. Boeck for
their assistance, as well as J. Castro for his early help and
guidance. Four anonymous reviewers and 3 NOAA techni-
cal reviewers provided comments that helped to strengthen
earlier versions of this manuscript. Funding for acoustic
receivers was provided through grants to N.H. from the
McDonnell et al.: Smalltooth sawfish in urbanized coastal waters 553
Save Our Seas Foundation, the Ocean Tracking Network,
and the Disney Conservation Fund; the NOAA Cooperative
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Editorial responsibility: Eduardo Martins,
Vancouver, British Columbia, Canada
Submitted: February 10, 2020; Accepted: October 15, 2020
Proofs received from author(s): December 15, 2020
... While a limited number of published studies have specifically examined the occurrence (Werry et al. 2012, Curtis et al. 2013, McDonnell et al. 2020) and nutrition (Rangel et al. 2021a,b) of marine predators in coastal urban areas, no studies have explicitly investigated space use and movement patterns of marine predators in relation to spatial variation in urbanization. While previous studies found regional population abundances to be lower in proximity to areas of high human activity, these observations were largely attributed to the exploitation of fisheries (Valdivia et al. 2017, MacNeil et al. 2020, Clementi et al. 2021, with no examination of how movement patterns relate to proximity to urban centers. ...
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... How this will impact the shark assemblages are unknown, but would be expected to negatively impact species for which either occurrences or CPUE were positively influenced by salinity, which included G. cirratum, C. acronotus, N. brevirostris and R. terraenovae. Interestingly, just downstream from a CERP-implemented freshwater pumping station has been a site of recently detected higher occurrences of the smalltooth sawfish (Pristis pectinata; McDonnell et al., 2020), an elasmobranch species, for which juveniles have been found to prefer estuarine conditions. Habitat type and depth emerged as the most influential parameters affecting abundance patterns for the greatest number of species. ...
Given population declines of many shark species, coupled with increasing conservation efforts and recoveries, there is a need for baseline assessments and continued monitoring of shark populations to support management. The waters of South Florida, USA, are used by a diverse array of sharks that occur among a mosaic of habitats and management zones. Here we conducted standardized drumline surveys from Miami through the middle Florida Keys to examine spatial, seasonal and environmental patterns in shark occurrence, catch per unit effort, composition, and demographic structure. Between 2009 and 2021, a total of 21,755 drumlines were deployed, capturing 3398 sharks, comprising fifteen species. Ginglymostoma cirratum, (n = 1335), Carcharhinus limbatus, (n = 650), Negaprion brevirostris, (n = 314), C. leucas, (n = 253), and Sphyrna mokarran, (n = 238) were the most common species encountered. Overall, the largest shark surveyed was a 450 cm S. mokarran and the smallest shark was a 50 cm Rhizoprionodon terraenovae. At the assemblage level, relative abundance among regions and seasons were generally similar; however clear species-specific patterns of abundance, size structure, and sex-composition were detected by season, region, habitat, and management zones. Of the physical conditions evaluated, habitat type and depth emerged as the most influential parameters affecting abundances and sizes of species captured. While few species exhibited significant differences in catches by management zone, areas with the most restrictive fisheries regulations generally supported higher abundances for which differences were detected. These data serve as a baseline for future monitoring of shark populations in South Florida and assessing their response to environmental change.
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The indirect effect of predators on prey behavior, recruitment, and spatial relationships continues to attract considerable attention. However, top predators like sharks or large, mobile teleosts, which can have substantial top–down effects in ecosystems, are often difficult to study due to their large size and mobility. This has created a knowledge gap in understanding how they affect their prey through nonconsumptive effects. Here, we investigated how different functional groups of predators affected potential prey fish populations across various habitats within Biscayne Bay, FL. Using baited remote underwater videos (BRUVs), we quantified predator abundance and activity as a rough proxy for predation risk and analyzed key prey behaviors across coral reef, sea fan, seagrass, and sandy habitats. Both predator abundance and prey arrival times to the bait were strongly influenced by habitat type, with open homogenous habitats receiving faster arrival times by prey. Other prey behaviors, such as residency and risk‐associated behaviors, were potentially driven by predator interaction. Our data suggest that small predators across functional groups do not have large controlling effects on prey behavior or stress responses over short temporal scales; however, habitats where predators are more unpredictable in their occurrence (i.e., open areas) may trigger risk‐associated behaviors such as avoidance and vigilance. Our data shed new light on the importance of habitat and context for understanding how marine predators may influence prey behaviors in marine ecosystems. Assessing behavioral risk effects of marine predators on mobile prey species across varying habitats in Biscayne Bay, FL. Providing new insights into the role marine predators play in influencing prey behavior in a variety of contexts.
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Human population density within 100 km of the sea is approximately three times higher than the global average. People in this zone are concentrated in coastal cities that are hubs for transport and trade – which transform the marine environment. Here, we review the impacts of three interacting drivers of marine urbanization (resource exploitation, pollution pathways and ocean sprawl) and discuss key characteristics that are symptomatic of urban marine ecosystems. Current evidence suggests these systems comprise spatially heterogeneous mosaics with respect to artificial structures, pollutants and community composition, while also undergoing biotic homogenization over time. Urban marine ecosystem dynamics are often influenced by several commonly observed patterns and processes, including the loss of foundation species, changes in biodiversity and productivity, and the establishment of novel assemblages, ruderal species and synanthropes. Further, we discuss potential urban acclimatization and adaptation among marine taxa, interactive effects of climate change and marine urbanization, and ecological engineering strategies for enhancing urban marine ecosystems. By assimilating research findings across disparate disciplines, we aim to build the groundwork for urban marine ecology – a nascent field; we also discuss research challenges and future directions for this new field as it advances and matures. Ultimately, all sides of coastal city design: architecture, urban planning, and civil and municipal engineering, will need to prioritize the marine environment if negative effects of urbanization are to be minimized. In particular, planning strategies that account for the interactive effects of urban drivers and accommodate complex system dynamics could enhance the ecological and human functions of future urban marine ecosystems. This article is protected by copyright. All rights reserved.
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Globally, sawfishes are threatened with extinction because they occur in coastal habitats, which are disproportionally affected by human activities. In particular, sawfishes are susceptible to myriad fisheries that operate in the same regions. Unfortunately, these well-documented threats can be only partly mitigated because of ongoing human resource needs. However, the outlook for sawfishes is optimistic if we build on 5 successful research and conservation approaches developed over the past 2 decades: (1) local ecological knowledge, (2) identification of nurseries, (3) state-of-the-art techniques, (4) tagging studies, and (5) threat mitigation. If appreciation of healthy ecosystems that contain top predators like sawfishes can be fostered by healthy human populations where sawfishes occur (e.g. ecosystem management, promotion of sustainable livelihoods), and if local knowledge can be used to influence scientific studies that inform customized management decisions, this group of iconic species will have a chance to recover. In addition, promoting sample collection, sample archiving, and collaboration, especially in instances of sawfish mortality, will maximize the knowledge gained, despite often limited funding and limited samples. The first 2 decades of the 21st century have seen the first steps taken toward sawfish recovery, but there is more to do. Ultimately, translation of research results into conservation actions that include enforcement and fisher behavior change will be the key to sustained recovery. This Overview provides a context for the papers in the Theme Section ‘Biology and ecology of sawfishes’, and we incorporate them as part of a mini-review of research on this threatened group to provide a future outlook.
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The smalltooth sawfish Pristis pectinata is threatened with extinction throughout its range and has been designated as Critically Endangered by the IUCN. In the USA, the species historically ranged from Texas to North Carolina, but mortality in fisheries and habitat loss have reduced the range to primarily southwest Florida. The US population was listed as endangered under the US Endangered Species Act in 2003. At that time, data on the biology and ecology of the species were limited. Research and outreach efforts have since expanded, and the quality and quantity of information has increased such that the US population is now one of the most well-studied sawfish populations worldwide. Smalltooth sawfish are born in litters of 7-14 individuals at lengths of 64-81 cm stretched total length (STL), reach maturity in 7-11 yr at approximately 340 cm STL for males and 370 cm STL for females, grow to a maximum size of about 500 cm STL, and live an estimated 30 yr in the wild. Smalltooth sawfish are piscivorous and shift from shallow estuarine waters as small juveniles to a broader array of coastal habitats as large juveniles and adults. The species is physiologically resilient to anthropogenic stressors, but preserving habitat and reducing fishing effects remain priorities. Data synthesized in this review have advanced our understanding of smalltooth sawfish life history and habitat needs, as well as the threats that continue to affect the population. Cumulatively, these data support optimism for recovery of the smalltooth sawfish in the USA and potentially beyond, though recovery will still require decades.
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Similar to other elasmobranchs, the smalltooth sawfish Pristis pectinata is slow growing, matures late in life, and produces relatively few young, all factors that have contributed to its sensitivity to dramatic population declines from overfishing and habitat loss. Currently, the physiological stress response of these fish to capture or to other physiological challenges such as habitat loss, climatic changes, or pollution is unknown. In the absence of these data, conservation plans may be less effective, making populations susceptible to further declines. We examined basic stress physiology over ontogeny and as a function of capture using different fishing gears. We also examined stress parameters to test whether degraded habitat and water quality from altered habitats may have resulted in chronic stress in juveniles. Results suggested that the stress response to capture by all methods was low, particularly for blood lactate, compared to other elasmobranchs examined to date. Metabolic stress was found to change over ontogeny, with young of the year (YOY) eliciting the highest responses. Glucose, pCO2, bicarbonate, potassium, and hematocrit indicated that gillnet capture induced greater stress responses than longline capture. Significantly higher metabolic stress was observed in YOY and juveniles captured in the 2 nurseries most influenced by anthropogenic activities, the Peace and Caloosahatchee rivers, than in the 2 relatively pristine nurseries in Everglades National Park. Overall, the low physiological stress responses to all capture methods investigated in this study suggest that this species is resilient, which should promote optimism for recovery of the population. © The authors and, outside the USA, the US Government 2018.
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Smalltooth sawfish Pristis pectinata use southwest Florida nurseries during at least their first 2 to 3 yr, and understanding region-specific habitat use patterns is important for effective management. Research occurred in 2 nurseries within the Charlotte Harbor estuarine system: the Caloosahatchee River, a highly human-altered nursery, and a more natural nursery, the Peace River. Between 2010 and 2013, a total of 148 juveniles ranging from 70.8 to 218.7 cm stretch total length were caught in gill nets, and 133 were acoustically tagged. The probability of encountering a sawfish during sampling was most influenced by season in both nurseries (highest during spring and summer), followed by dissolved oxygen in the Caloosahatchee River, and salinity and temperature in the Peace River. Temperature had lasting, atypical effects on movements when severe cold events occurred during the study. Outside of these disturbances, sawfish used all habitats available to them in both nurseries, but tended to reside in perennial high-use areas called nursery hotspots. Acoustic monitoring showed that juveniles gradually moved between 4 hotspots along a 20 river kilometer stretch of the Caloosahatchee River with seasonal changes in freshwater inflows or sometimes suddenly in response to large flow events. In contrast, sawfish in the Peace River remained associated with one nursery hotspot year-round. Reasons for these inter-nursery variations are attributed to differences in geomorphology and freshwater inflow regimes. This study illustrates that a full understanding of the life history of a species and the development of a conceptual model requires investigation of the species on a broad spatial scale. This consideration is important to avoid overgeneralization of habitat use patterns between nurseries.
The effects of boat activity on various aspects of fish biology and ecology have been widely studied in the past few decades. However, these studies primarily focused on teleost fish species and not elasmobranchs. The goal of this study was to determine if there was a negative relationship between boat activity and the habitat use of three coastal shark species (bull (Carcharhinus leucas), nurse (Ginglymostoma cirratum), and great hammerhead (Sphyrna mokarran)) in Biscayne Bay, Florida - an area subject to intense boat activity (both commercial and recreational). According to past studies on marine mammals and teleost fish species, we expected sharks to present patterns of avoidance (reduced residency and activity space) during times and in areas of intense boat activity. Using aerial surveys and underwater recording stations, patterns of boat activity were quantified both spatially and temporally, while shark activity space and residency were determined using acoustic telemetry. Our results indicated that boat activity was more intense both on the weekends/holidays and closer to Miami Proper. However, there was no relationship between boat activity patterns and the activity space or residency of each species. These results may be explained by each species' hearing ability and how their detectable frequency range does not overlap with that produced by boat engines. Additionally, it is possible that the shark species in this area have habituated to the human activity and associated sound as demonstrated by a population of bottlenose dolphins (Tursiops truncates) in the same area. This study lays a foundation that future research can use to explore the relationship between boat activity and other vulnerable species as well as expand our current understanding of the relationship between sharks and urbanization.
Mangroves provide essential habitat for juvenile fish species. Restoration and monitoring are important conservation tools to ensure the recovery and maintenance of coastal mangrove habitats impacted by humans. In this study, Baited Remote Underwater Video Stations (BRVUS) were used to non-invasively examine the relative abundance and richness of fishes within restored mangrove pools in Biscayne Bay, Florida, 15 years after replanting. The potential influence of several environmental factors on fish abundance and richness within the restored mangrove pools was also evaluated. Limited seine sampling was also conducted to provide a comparison of the current fish assemblage with that of two prior surveys using seine nets. Twenty fish taxa were observed in the current study, consisting of five families, two genera, and thirteen species. Several environmental factors emerged as significant influences on the presence and abundance of different fish taxa, especially individual pools. A comparison of CPUE between current and prior seine studies found an increase in forage fish taxa and a shift from taxa that prefer a range of habitats to mangrove specific taxa, indicating an increased ecological function of these mangroves as fish habitat.
Knowledge of the diel spatial ecology of wild animals is of great interest to ecologists and relevant to resource management and conservation. Sharks are generally considered to be more active during nocturnal periods than during the day; however, few studies have empirically evaluated diel variation in shark habitat use and how anthropogenic disturbances may influence these patterns. In the western central Atlantic Ocean, tiger sharks (Galeocerdo cuvier) are highly abundant in the shallow waters of the Little Bahama Bank, Bahamas. Within the northwest edge of the Bank, there is an area nicknamed “Tiger Beach,” where tiger sharks are provisioned year-round at spatially discrete ecotourism dive sites spanning ~ 1.5 km². In this study, we used an array of acoustic receivers encircling an area of 102.4 km² to evaluate for potential differences in diel spatial habitat use patterns for 42 tagged tiger sharks at Tiger Beach and the surrounding area. Using tracking data from 24 June 2014 to 13 May 2015, we evaluated spatial and diel patterns of shark activity space, centers of activity, residency and the daily proportion of sharks detected within the array. Sharks were detected during both day and night with no significant diel differences in habitat use metrics across the array, although spatial differences in residency existed. Four sharks accounted for 53.8% of residency data throughout the tracking period, with the majority of sharks primarily entering and exiting the array, except during summer months when the most of the tagged tiger sharks were absent from the array. We also found limited empirical support for hypothesized effects of provisioning tourism on tiger shark habitat use. However, additional research at finer, individual scales, may be needed to better resolve the potential influence of provisioning on tiger sharks at Tiger Beach.
Research on rare and threatened species is often limited by access to sufficient individuals to acquire information needed to design appropriate conservation measures.Using a combination of data from pop-up archival transmitting (PAT) tags across multiple institutional programmes, movements and habitat use of endangered smalltooth sawfish, Pristis pectinata were determined for animals from southern Florida and the Bahamas.All P. pectinata (n = 12) generally remained in coastal waters within the region where they were initially tagged, travelling an average of 80.2 km from deployment to pop-up location. The shortest distance moved was 4.6 km and the greatest 279.1 km, averaging 1.4 km day-1. Seasonal movement rates for females were significantly different with the greatest movements in autumn and winter.Pristis pectinata spent the majority of their time at shallow depths (96% of their time at depths