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Knowledge of the habitat use and migration patterns of large sharks is important for assessing the effectiveness of large predator Marine Protected Areas (MPAs), vulnerability to fisheries and environmental influences, and management of shark-human interactions. Here we compare movement, reef-fidelity, and ocean migration for tiger sharks, Galeocerdo cuvier, across the Coral Sea, with an emphasis on New Caledonia. Thirty-three tiger sharks (1.54 to 3.9 m total length) were tagged with passive acoustic transmitters and their localised movements monitored on receiver arrays in New Caledonia, the Chesterfield and Lord Howe Islands in the Coral Sea, and the east coast of Queensland, Australia. Satellite tags were also used to determine habitat use and movements among habitats across the Coral Sea. Sub-adults and one male adult tiger shark displayed year-round residency in the Chesterfields with two females tagged in the Chesterfields and detected on the Great Barrier Reef, Australia, after 591 and 842 days respectively. In coastal barrier reefs, tiger sharks were transient at acoustic arrays and each individual demonstrated a unique pattern of occurrence. From 2009 to 2013, fourteen sharks with satellite and acoustic tags undertook wide-ranging movements up to 1114 km across the Coral Sea with eight detected back on acoustic arrays up to 405 days after being tagged. Tiger sharks dove 1136 m and utilised three-dimensional activity spaces averaged at 2360 km(3). The Chesterfield Islands appear to be important habitat for sub-adults and adult male tiger sharks. Management strategies need to consider the wide-ranging movements of large (sub-adult and adult) male and female tiger sharks at the individual level, whereas fidelity to specific coastal reefs may be consistent across groups of individuals. Coastal barrier reef MPAs, however, only afford brief protection for large tiger sharks, therefore determining the importance of other oceanic Coral Sea reefs should be a priority for future research.
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Reef-Fidelity and Migration of Tiger Sharks,
Galeocerdo
cuvier,
across the Coral Sea
Jonathan M. Werry
1,2
*, Serge Planes
3
, Michael L. Berumen
4,5
, Kate A. Lee
6
, Camrin D. Braun
4
, Eric Clua
7,8
1 Australian Rivers Institute and School of Environment, Griffith University, Gold Coast, Queensland, Australia, 2 Ocean and Coast Research, Gold Coast, Queensland,
Australia, 3 Centre de recherches insulaires et observatoire de l’environnement (CRIOBE), Moorea, French Polynesia, 4 Red Sea Research Center, King Abdullah University
of Science and Technology, Thuwal, Saudi Arabia, 5 Biology Department, Woods Hole Oceanographic Department, Woods Hole, Massachusetts, United States of America,
6 Marine Mammal Research Group, Graduate School of Environment, Macquarie University, New South Wales, Australia, 7 Secretariat of the Pacific Community, CRISP
Programme, Noumea, New Caledonia, 8 French ministry of Agriculture and Fisheries, Paris, France
Abstract
Knowledge of the habitat use and migration patterns of large sharks is important for assessing the effectiveness of large
predator Marine Protected Areas (MPAs), vulnerability to fisheries and environmental influences, and management of shark–
human interactions. Here we compare movement, reef-fidelity, and ocean migration for tiger sharks, Galeocerdo cuvier,
across the Coral Sea, with an emphasis on New Caledonia. Thirty-three tiger sharks (1.54 to 3.9 m total length) were tagged
with passive acoustic transmitters and their localised movements monitored on receiver arrays in New Caledonia, the
Chesterfield and Lord Howe Islands in the Coral Sea, and the east coast of Queensland, Australia. Satellite tags were also
used to determine habitat use and movements among habitats across the Coral Sea. Sub-adults and one male adult tiger
shark displayed year-round residency in the Chesterfields with two females tagged in the Chesterfields and detected on the
Great Barrier Reef, Australia, after 591 and 842 days respectively. In coastal barrier reefs, tiger sharks were transient at
acoustic arrays and each individual demonstrated a unique pattern of occurrence. From 2009 to 2013, fourteen sharks with
satellite and acoustic tags undertook wide-ranging movements up to 1114 km across the Coral Sea with eight detected
back on acoustic arrays up to 405 days after being tagged. Tiger sharks dove 1136 m and utilised three-dimensional activity
spaces averaged at 2360 km
3
. The Chesterfield Islands appear to be important habitat for sub-adults and adult male tiger
sharks. Management strategies need to consider the wide-ranging movements of large (sub-adult and adult) male and
female tiger sharks at the individual level, whereas fidelity to specific coastal reefs may be consistent across groups of
individuals. Coastal barrier reef MPAs, however, only afford brief protection for large tiger sharks, therefore determining the
importance of other oceanic Coral Sea reefs should be a priority for future research.
Citation: Werry JM, Planes S, Berumen ML, Lee KA, Braun CD, et al. (2014) Reef-Fidelity and Migration of Tiger Sharks, Galeocerdo cuvier, across the Coral Sea. PLoS
ONE 9(1): e83249. doi:10.1371/journal.pone.0083249
Editor: A. Peter Klimley, University of California Davis, United States of America
Received June 13, 2013; Accepted October 25, 2013; Published January 8, 2014
Copyright: ß 2014 Werry et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reprod uction in any medium, provided the original author and source are credited.
Funding: Funding was provided by the the Agence Francaise de De
´
veloppement (http://www.afd.fr), French Pacific Fund, the CRISP program (www.crisponline.
info) and QLD Fisheries. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing Interests: Dr. E. Clua is employed by CRISP. The authors’ affiliation with CRISP does not alter their adherence to all the PLOS ONE policies on sharing
data and materials.
* E-mail: jwerry@oc-research.com
Introduction
Recent studies have highlighted the critical role that sharks play
in regulating food chain diversity through top-down control [1],
[2], [3]. In coral reef ecosystems, models suggest reduced reef
resilience with shifts in coral to fleshy algal-dominated habitats
possibly due to the absence of sharks and other predatory fish from
coral reef systems [4], [5]. More recently, Sandin et al. [6] used
underwater visual censuses at reef sites with different densities of
top predators to show that fish species targeted by sharks tended to
allocate more energy to reproduction than to somatic storage. This
phenomenon led to increased biomass because of more individuals
in spite of their smaller size compared to sites without sharks.
Unfortunately shark populations are declining on a global scale,
largely due to illegal and uncontrolled fishing practises [7], [1].
This has led to concerns about shark populations in the Oceania
region [8]. Overfishing and poaching are driven by an increasing
demand for fins in the booming Asian economies [9]. Conse-
quently, there is a critical need to support shark conservation
through a better understanding of their ecology to insure the
balance and long-term resilience of marine ecosystems [10]. This
global conservation goal may be achieved using tools such as
Marine Protected Areas (MPAs) at several spatial scales [11]. The
declaration of MPAs can slow shark population declines [12], but
the spatial scale must encompass the home range of the relevant
species [13]. The extent of movement within and among high
value coral reef habitats can vary with shark species, as some
species are relatively sedentary (e.g. the blacktip, Carcharhinus
melanopterus) [14] and others migratory (e.g. the tiger shark,
Galeocerdo cuvier) [15]. These potentially complex movements can
determine the role sharks play as trophic links between distant
coral reef habitats, the potential interaction with fishing activities
and the vulnerability of sharks to these pressures [16], [17], [18].
Therefore, identifying the movement patterns and habitat-use of
key tropical shark species is essential for their conservation.
Many sharks undertake migrations and utilise resources in
different habitats with site-fidelity varying at different spatial and
temporal scales. This can influence the trophic role of larger
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predators in connecting distant habitats and reduce the risk of
regional extinctions [19]. Furthermore, adults of species previously
considered to exhibit strong reef fidelity (e.g. Grey reef whaler,
Carcharhinus amblyrhynchos) have been shown to range further than
previously thought, reducing the effectiveness of protected areas
for these species [18]. As a first step, MPAs for top-level predators
require an understanding of the spatial movements of individual
sharks, the determination of centres of shark activity, the
proportion of time spent in potential management areas and their
migration pathways to and from these areas. In addition,
ontogenetic differences need to be considered as many large
sharks display increasing home ranges with size and maturity [13],
[18], [20]. Heightened public concern about the occurrence of
large and dangerous sharks in New Caledonian waters has arisen
as a result of several human deaths since 2007 [21]. This makes it
increasingly important to understand the localised and migratory
movements of large sharks and how often they utilize regions with
high human activity. A better understanding of the movement
patterns of these migratory top predators is therefore essential, and
the absence of ecological data is often a limiting factor for the
efficacy of marine managed areas [22].
Despite the ecological importance of large species of shark and
their direct and indirect influence on the distribution of prey and
other species, information on the movements of large sharks has
largely been confined to USA, Europe, South Africa and Australia
[23]. In contrast, little is known about the movement of large
sharks in New Caledonia and the Coral Sea. This is due to their
wide-ranging, elusive behaviour and the challenges associated with
their capture [12], [24]. Moreover, the development of better
capture techniques and satellite and acoustic tagging technology
has led to substantial advances in documenting the movements of
these animals than was previously possible with traditional tagging
techniques (e.g. [25]).
The tiger shark is one of the top-level predators in coral reef
ecosystems and is listed as ‘near-threatened’ by the IUCN [26],
[27]. It has a cosmopolitan distribution and occurs throughout the
South Pacific, including the Coral Sea [28], [29]. Tiger sharks are
often considered to be a reef-associated ‘coastal’ species that
exhibits seasonal and diel visits to coral reef lagoons when
traversing between coral shoals and atolls [30] and visits to areas
with large prey items, such as green turtle, Chelonia mydas, rookeries
(e.g. Raine Island, northern Great Barrier Reef, GBR), are
independent of the prey’s nesting aggregations [31]. Tiger sharks
provide important trophic links between distant habitats [32] and
exhibit movements up to 6747 km, identified by conventional
tagging [25], [33]. Directional movements occur across ocean
basins [34], [35], during which dives to depths of 335 and 680 m
have been documented via acoustic and satellite telemetry,
respectively [34], [36]. Acoustic telemetry studies in Hawaii
suggest tiger sharks occupy home ranges of at least 109 km of
contiguous coastline with detections on acoustic receivers typically
brief (mean = 3.3 mins) and interspersed by weeks, months and
years [36]. In contrast, home ranges were considered to be larger
but undefined by a study in Shark Bay, Western Australia, because
satellite tracked tiger sharks displayed relatively low displacement
rates relative to sharks tracked over shorter time periods [35].
Furthermore, in the Atlantic, satellite telemetry revealed that large
female tiger sharks spent substantially more time in the open ocean
rather than coastal areas, with long-range migrations confirming
that this species is oceanic. These authors suggest, however, that
patterns of reef residency and migration may vary for different
sites, locations and regions around the world [37]. Recent work by
Papastamatiou et al. [15] suggests the complexity of tiger shark
movements could be due to triennial migrations of adult female
tiger sharks triggered by their reproductive cycle. In addition to
these observations, Driggers et al. [38] suggest it is probable that
parturition occurs in shelf areas of less than 100 m deep where
neonates remain until their first large-scale migration, as they
found no areas of increased juvenile abundance associated with
oceanic areas of high productivity. Importantly, the movements
and habitat-use of tiger sharks, remain largely unknown in the
Southwest Pacific.
The Coral Sea is a vast tropical/sub-tropical region in the
Southwest Pacific comprising both significant coral reef systems
around its boundary and open oceanic habitat with sea mounts
and reef aggregations across its basin [39], [40]. Connectivity of
reefs across the Coral Sea relies on sparse seamounts and reef
aggregations, both in the Australian and French Exclusive
Economic Zones (EEZ) [41]. Recent work suggest that these
isolated seamounts, such as the Osprey and Shark reefs in the
Australian EEZ, require urgent protection in order to conserve
reef-associated shark populations [42]. Moreover, demonstrated
interactions between large sharks and commercial long-lining and
illegal shark-fining occur across the Coral Sea [41]. Despite this,
information on the movement of large sharks in coastal coral reefs
and open oceanic and seamount habitats in the Coral Sea is scant
and as such the protection of large sharks in this region is of
concern, particularly for wide ranging species that undertake large
scale movements. Furthermore, recent work suggests the economic
value of an individual shark is substantially greater when it is kept
alive and available for various ecotourism activities [37], [43].
In March 2010 and affirmed in January 2012, a ‘‘declaration of
intention between France and Australia for the Coral Sea
sustainable management’’ was signed by the Minister for Foreign
and European Affairs of the French Republic and the Minister for
Foreign Affairs of the Commonwealth of Australia [44]. This
document identified strategies for cooperative management of
Coral Sea coastal and high seas ecosystems. Given the critical role
of large sharks in this region, the future co-management process
requires reliable ecological information for tiger sharks. The study
we present herein sought to provide the type of information
needed for effective management in the region. In the present
study we used multiple tagging techniques to quantify the spatial
dynamics of tiger sharks in the Coral Sea, with a particular
emphasis on New Caledonia. The aims of this study were to (1)
determine the level of site-fidelity to specific coral reef habitats and
temporal connectivity (days to years) among habitats, (2) quantify
the range of variation in movement patterns among individual
tiger sharks and, (3) determine the extent to which these
movement patterns represent migratory behaviours. In so doing
we test the hypothesis that tiger sharks undertake regular or
predictable migrations across the Coral Sea between New
Caledonia and Australia with no difference in the habitat-use
and site-fidelity at coastal barrier reefs of New Caledonia and
Australia compared to oceanic reefs in the Coral Sea.
Materials and Methods
Ethics Statement
This research was done in accordance with permit No. 6024-
4916/DENV/SMer (New Caledonia), permit No. G10 33187.2
(Great Barrier Reef Marine Park Authority), permit No. 143005
(Queensland Fisheries), permit No. QS2010 GS065 (Great Sandy
Marine Park) and permit No. LHIMP/R/2012/009 (Lord Howe
Island). This study was specifically approved by Griffith University
ethics ENV/16/08/AEC. Sharks were also satellite tagged in
Queensland (QLD) under Ocean and Coast Research animal
ethics approval CA 2010/11/482.
Coral Sea Tiger Shark Movement
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Study Area
The Coral Sea lies off the northeast coast of Australia (QLD)
and is bounded in the east by New Caledonia, in the north by the
southern extremity of the Solomon Islands and the south coast of
eastern New Guinea (Fig. 1). On the western seaboard of this
region and at similar latitudes along the tropic of Capricorn, the
largest barrier reef system in the world (the Great Barrier Reef -
GBR) extends along the east coast of Australia. Approximately
1000 km to the east, New Caledonia boasts the world’s second
largest lagoonal reef system.
Our study area included six key locations widely separated
(.500 km each apart) to enable sampling and detection of shark
movements across the spatial extent of New Caledonia, the Coral
Sea and the east coast of Australia (Fig. 1): (1) Prony Bay in the
south of New Caledonia, (2) Reef barrier off Belep archipelago in
the north of New Caledonia, (3) the Chesterfield Islands in the
centre of the Coral Sea, (4) Lord Howe Island in the central south
of the Coral Sea, (5) Noosa to Rockhampton in Australia and (6)
Mackay and Cairns in the central and far north of the GBR. New
Caledonia has a large coral reef lagoon with interspersed island
and barrier reefs separated by channels typically 30–40 m deep.
The main island is surrounded by deep drop-offs to .1200 m with
ocean basins separating the Loyalty Islands to the east and the
Chesterfield Islands in the centre of the Coral Sea (Fig. 1). In the
north of New Caledonia, Belep is lightly populated by local
indigenous communities and is approximately 500 km to the north
of Noumea, the capital of New Caledonia. Prony Bay in the south
is approximately 100 km south of Noumea. A substantial nickel
mine is situated near the bay and supports a working population of
up to 10,000 people. From the west coast of New Caledonia a
deep oceanic ridge runs south to the Lord Howe rise. To the west,
Lord Howe basin (average 1500 m deep) separates the Chester-
fields from the east coast of Australia. The Chesterfield Islands
were used for commercial whaling in the early 1960s, but have
been uninhabited by humans for over 40 years. This seamount
sustains vast seabird populations and nesting green turtles. Isolated
from Australia to the west and New Caledonian to the east by 500
nautical miles in either direction, the Chesterfield Islands lie at the
northern end of a series of seamounts that run south in the centre
of the Coral Sea to Lord Howe Island. On the east coast of
Australia, the GBR extends from the north of Fraser Island to the
northern tip of Queensland. Beyond the barrier reef the Australian
continental plate extends out into the Coral Sea basin. We divided
our capture, tagging and tracking efforts among these study
locations (Fig. 1).
Acoustic Tags
All but one of the captured sharks were tagged with acoustic
transmitters via surgical implantation (see below). Acoustic
transmitters, Vemco V16 R-coded 69 kHz acoustic tags (Amirix
Systems Inc., Nova Scotia, Canada), were used to provide high-
resolution movement information in key study areas and long-term
Figure 1. Seamounts and surrounding bathymetry across the Coral Sea between New Caledonia and Australia. Acoustic receiver array
locations are shown along the east coast of Queensland, Australia and the southern Great Barrier Reef and inserts. Different shades of blue in the
legend indicate different water depths.
doi:10.1371/journal.pone.0083249.g001
Coral Sea Tiger Shark Movement
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measurements of site fidelity. Acoustic tag battery lives were
estimated to be 696, 835, or 1448 days according to manufacturer
specifications/estimates and differences in battery size, given a
delay period of 50 to 130, 40 to 80, 30 to 90 s, respectively. Given
average coastal sea-conditions, wind-strengths of 11–16 knots (20–
29 km/hr), and high (H) or low (L) tag power output at 69 kHz,
we assumed acoustic detection ranges of 400–800 m (www.vemco.
com/education/range.php).
VR2W Acoustic Receiver Arrays
Transmissions from these tags were detected by acoustic
receivers moored underwater when a tagged shark came within
acoustic range. Thirty Vemco VR2W acoustic receivers (Amirix
Systems Inc., Nova Scotia, Canada) were deployed to passively
track movements of tiger sharks from January 2009 to February
2013 (Fig. 1). Receivers were deployed in six separate arrays in (1)
Prony Bay in the southern lagoon of New Caledonia 2009 (n = 8;
Fig. 1A), (2) the barrier reef off Belep in the northern lagoon of
New Caledonia in January 2010 (n = 3; Fig. 1B), (3) the
Chesterfield Islands in the centre of the Coral Sea in August
2010 (n = 7; Fig. 1C), (4) Lord Howe Island in June 2012 (n = 4;
Fig. 1D) and (5) receivers were also deployed in coastal areas along
the east coast of Queensland, Australia, as part of the QLD Large
Shark Tagging Program (QLSTP) (http://www.oc-research.com/
pages/tagging-program.php) in March 2010 on the Sunshine
coast (n = 4) and coastal area of Bundaberg to Rockhampton
(n = 2), and (6) Mackay and Cairns (n = 2) in the GBR. Receivers
on Lady Elliot Island, GBR, deployed by independent researchers
studying Manta rays, Heron and One Tree Island, GBR, by the
Australian Acoustic Tagging and Monitoring System (AATAMS)
and Bourail, New Caledonia, by the Aquarium des Lagons and
Universite´ de la Nouvelle-Cale´donie were also used to detect shark
movements. One receiver deployed at Estree Pass in Belep in
March 2010 received no detections and was subsequently
relocated to Yande Passe, Belep, in August 2010. However, this
receiver was unable to be retrieved in 2012 and was presumed
missing. Receivers were moored on concrete filled tyres (as per
Otway and Ellis [45]) in depths of 5–25 m or attached to anchored
float lines approximately 5 m above the sea floor. Data were
downloaded periodically throughout the study.
Satellite Tags
We used two types of satellite tags: (1) Pop-up Satellite Archival
Tags (PSATs) (models: MK10-PAT, miniPAT and Fastloc MK10-
AF, Wildlife Computers, Redmond, WA, USA) to quantify
swimming depths and migration pathways, and (2) dorsal fin-
mounted, position-only satellite tags (SPOT5, Wildlife Computers,
Redmond, WA, USA) to provide information on shark movements
outside the detection range of our acoustic receivers.
Geolocation of Satellite Tags
PSAT tags were pre-programmed to detach from the tiger shark
100–290 days after deployment. PSAT tags archived temperature,
depth and light intensity data during deployment and transmitted
to the Argos satellite array after the tags released from the shark.
Light-based geolocations were approximated using proprietary
software provided by the tag manufacturer (WC-GPE: Global
Position Estimator Program suite, Wildlife Computers, Redmond,
WA, USA) that employs threshold light-level geolocation methods
[46]. Most probable tracks were constructed from these estimates
using a state space unscented Kalman filter and blended sea
surface temperature in the UKFSST library [47] for the R
Statistical Environment [48]. Secondary bathymetric correction
was performed using maximum daily depth of each individual in
Figure 2. Restraint of 3.8 m tiger shark in harness.
doi:10.1371/journal.pone.0083249.g002
Coral Sea Tiger Shark Movement
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the analyzepsat library for R [49], [50] and 95% confidence
interval envelopes were included in plots to illustrate the
equivalent error bubble around most probable tracks. Due to
lack of approximated locations from WC-GPE, the most probable
track for one individual (TS 25) was constructed using raw light
levels in a state space model performed in the TrackIt library for R
[51] followed by bathymetric correction.
SPOT tags transmit a signal to the Argos satellite array
whenever the dorsal fin breaks the surface for long enough (i.e. 15
to 30 seconds). This provides a near real-time estimate of the
shark’s position. The accuracy of the position estimate however,
depends on the number and time between transmissions received
during a satellite pass and are classified as either 3 (,250 m), 2,
(250–500 m), 1 (500–1,500 m) and 0, A or B (1,500 to 3000 km)
[52]. Z positions provide no estimates of the shark’s position. We
used all class 3, 2 and 1 positions to plot tracks and included class
0, A or B positions if these were within a realistic swimming
distance at a maximum speed of 3.5 km hr
21
[34], [53] from a
Table 1. Tiger sharks monitored at New Caledonia (Southern Province, Northern Province), the east coast of Australia (Southern
Queensland and the Great Barrier Reef) and the Chesterfields in the Coral Sea with acoustic tags.
Tiger
Shark
Tagging
Location
Date of
Capture Sex
TL
(cm)
days bw
tagging and
first detection
No. of
days
monitored
No of
days
detected
No. of
detections
Av minutes
at each
station
Max linear
distance bw
detections (km)
1 SP 30/01/2009 F 154 192 1273 14 39 4.5 5.5
2 SP 7/07/2009 F 164 10 1141 6 55 5.7 3.5
3 SP 1/02/2010 F 192 na 906 0 0 0
4 SP 9/07/2009 F 270 21 1143 9 35 6.75 6.75
5+ SP 1/10/2008 F 300 495 1442
6 SP 26/01/2009 F 300 0 1277 1 1 1 0.9
7 SP 13/07/2009 M# 312 0 1139 1 2 4 0.9
8 SP 13/07/2009 M* 340 0 1139 3 8 2.5 2
9 SP 24/08/2010 F 370 225 702 31 91 3.14 5.5
10 SP 28/01/2009 M* 380 62 1275 30 103 4.35 10.9
11 SP 15/07/2009 M* 390 405 875 2 20 1.3 4.7
12 NP 4/03/2010 F 286 200 875 1 2 1 1
13 NP 4/03/2010 F 290 110 875 5 31 4 1
14 NP 11/03/2010 M
#
294 267 868 1 3 3 244
15 NP 3/03/2010 F 338 28 876 7 11 2.85 1
16 CI 12/08/2010 F 260 6 432 155 872 4.13 22
17 CI 13/08/2010 F 270 2 432 36 438 12.2 0
18 CI 12/08/2010 F 310 4 595 255(4) 2948(68) 5.5 22(742)
19 CI 16/08/2010 M* 310 8 432 183 1292 3.93 22
20 CI 18/11/2011 M* 323 YBR
21 CI 25/11/2011 M* 323 YBR
22 CI 20/11/2011 M* 328 YBR
23 CI 22/11/2011 F 329 YBR
24 CI 12/08/2010 F 330 13 432 2 10 6 14.4
25 CI 15/08/2010 F 332 14 858 3(1) 9(9) 2.5 9.5(761)
26 C GBR 20/04/2011 F 232 YBR
27 C GBR 20/04/2011 F 260 YBR
28 C GBR 20/04/2011 F 276 YBR
29 C GBR 31/10/2012 M* 346 YBR
30 C GBR 30/10/2012 F 367 YBR
31 C GBR 31/10/2012 F 370 YBR
32 SQ 1/03/2011 F 210 YBR
33 SQ 21/09/2011 F 270 YBR
34 SQ 19/09/2011 F 300 98 98 1 2 2 117
Individual sharks bolded and underlined were also tagged with various satellite tags (see Table 2).
+refers to shark identified with photo-ID.
*refers to mature males.
#
refers to male sharks with semi-calcified claspers. TL refers to total length. Tagging locations include, SP (Southern Province, New Caledonia), NP (Northern Province,
New Caledonia), CI (Chesterfields), SQ (Southern Queensland, Australia), C GBR (Cairns, Great Barrier Reef).
–indicates no data available. na refers to not applicable. YBR refers to yet to be recorded. Brackets for TS18, TS 25 refer to detections on the GBR.
doi:10.1371/journal.pone.0083249.t001
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previous class 1–3 position, capture location or acoustic receiver
detection.
Shark Capt ure and Tagging Procedures
At each location large sharks were captured using barbless hook
and line (baited with tuna pieces) and restrained in a specially
designed harness developed by Werry et al. [54] (Fig. 2). Captured
sharks were guided into the harness, which was placed parallel to
the vessel. The restrained shark was maintained with its head
directed into the current to ensure constant flow of water over the
gills. Sharks were then tail-roped and inverted to initiate tonic
immobility. Sharks remained docile in this position while
morphometrics of total length (TL) (cm) and gender were
recorded. Dorsal fins and distinguishing body features of all
captured sharks and tiger sharks that broke away from baited lines
before tagging were photographed as per Clua et al. [55]. The
harness also enabled the opportunistic identification of stomach
contents for sharks that regurgitated their contents after capture
and restraint in the harness. For individual comparisons, tiger
sharks were assigned ontogenetic categories of mature, sub-adult
or juvenile. Size-at-maturity estimates of 330 cm TL and 292 cm
TL for females and males respectively were determined based on
tiger sharks from Hawaii [56]. The presence of semi-calcified
claspers were used to define sub-adult males and sharks .259 cm
TL for sub-adult females. Juveniles were defined as ,259 cm TL
for females and the presence of non-calcified claspers for males. A
Vemco R-code V16 transmitter was then surgically implanted into
the body cavity through a small incision in the abdominal wall (as
per Holland et al. [34]). PSAT tags were attached to selected tiger
sharks by creating a small incision in the shark’s skin at the base of
the dorsal fin and inserting a titanium dart under the skin. The
titanium dart was then locked in place with a small stitch. SPOT
tags were attached on selected sharks by creating 4 small holes
near the top of the shark’s dorsal fin and using threaded nylon with
washers and lock nuts to secure the tag. After tagging, sharks were
maintained in the harness while the research vessel slowly moved
forward to push oxygenated water over the gills of the shark.
Tagging and capture stress was monitored as per Werry et al. [54].
Sharks swam away vigorously on release (Video S1), although one
tiger shark in the Chesterfields was also released via underwater
assistance on scuba.
Behavioural Patterns
Localised behavioural patterns of tiger sharks with acoustic tags
were defined into four categories. (1) Passer-by, for individuals
never detected on acoustic arrays after the first month of release
after acoustic tagging. (2) Transient, for individuals that were re-
detected on individual acoustic arrays after temporal periods
greater than one month. (3) Pseudo-Resident, for individuals
detected on the same acoustic array for more than five days within
each month for three or more months of the year and for ,30% of
their potential detection period, and (4) Residents, for individuals
detected within ten or more months in each year within individual
acoustic arrays and for .30% of their entire potential detection
period.
Table 2. Tiger sharks monitored at New Caledonia (Southern Province, Northern Province), the Chesterfields in the Coral Sea and
Cairns (GBR) with satellite tags.
Tiger
Shark
Tagging
Location Sex
TL
(cm)
Satellite
tag type
and id
MK10
Pop-off date,
SPOT 5 last
transmission
Duration of
deployment
(days)
Max distance
from release
point (km)
Max depth
during
deployment
(m)
Modal
depth
(m)
Mean
depth
(m)
Max
temp
(
6
C)
Min
temp
(
6
C)
Modal
temp
(
6
C)
Mean
temp
(
6
C)
3 SP F 192 SPOT 5 11/03/2010 38 240
6 SP F 300 MK10 2/02/2009 4 208 80 64.0 48.5 26.2 25.1 26.1 25.7
8 SP M* 340 MK10 1/08/2009 19 150 368 40.0 53.0 24.4 14.4 23.8 23.2
9 SP F 370 MK10 22/02/2011 181 1141 1136 16.0 11.2 26.2 5.6 22.0
11 SP M* 390 MK10 11/02/2010 210 154 640 40.0 61.0 28.8 8.2 23.7 23.5
13 NP F 290 SPOT 5 17/03/2010 13 60
14 NP M
#
294 SPOT 5 17/03/2010 7 23
16 CI F 260 mini
MK10
27/08/2010 15 124 312 62.5 55.0 24.4 17.8 23.6 23.0
17 CI F 270 Fast-loc
MK10
17/08/2010 4 19 12.0 13.9 27.8 22.8 23.6 23.7
18 CI F 310 mini
MK10
13/12/2010 93 207 536 39.5 91.0 27.4 9.4 24.0 20.7
25 CI F 332 Fast-loc
MK10
22/08/2010 7 101 66 40.5 28.0 32.2 23.4 23.6 23.8
29 C GBR M* 346 MK10 31/10/2012 78 240
30 C GBR F 367 Fast-loc
MK10
30/10/2012 DNR
31 C GBR F 370 Fast-loc
MK10
31/10/2012 DNR
Tiger shark numbers correspond to sharks with acoustic tags in Table 1.
*refers to mature males.
#
refers to male sharks with semi-calcified claspers. TL refers to total length. DNR refers to did not report.
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Statistical Analysis
Data from receivers were processed to define the length of time
an individual was monitored (calculated as release date till date of
last detection), the number of days an individual was present
during the monitoring period, the average number of days
between subsequent detections, the movements within and
between acoustic arrays and the difference in diel detection
frequency. Significant differences in proportion of detections
between night (18:00 to 5:59, sunset to sunrise) and day (6:00 to
17:59, sunrise to sunset) detected between individuals were
determined using Chi-square. A standardized Residency Index
(RI) was calculated for all sharks as the total number of days a tiger
shark was detected within an acoustic receiver array divided by the
number of days the shark could possibly have been detected
assuming its transmitter worked for the period of estimated battery
life [57].
To determine if there were differences in the space use of each
of the satellite tagged sharks three-dimensional 50% and 95%
kernel utilisation distributions were calculated using methods
described in Simpfendorfer et al. [58] using the ‘ks’ package in R
[59]. This method incorporates both horizontal and vertical
movements together to provide a more accurate representation of
the shark’s movement [58]. The plug-in bandwidth was used to
calculate smoothing factor for the kernel estimation as it has been
shown to be the most appropriate for bandwidth for home-range
studies (see [60]). No further statistical analysis was conducted on
the 3D kernels due to the high variability in the number of days
that each shark was tracked.
Results
Characteristics of Acoustic and Satellite Tagged Sharks
Thirty-four tiger sharks 154–390 cm TL were captured across
five study locations between October 2008 and October 2012
(Table 1). Thirty-three sharks were tagged with acoustic transmit-
ters: four males and six females in the Southern Province of New
Caledonia, one male and three females in Belep, Northern New
Caledonia, four male and six females in Chesterfield and eight
females and one male on the east coast of Australia. Tiger sharks
on the east coast of Australia were tagged with acoustic tags as part
of the QLSTP. Female tiger sharks were primarily sub-adult
(n = 10). Fewer adult females were captured (n = 4), of which only
one was captured and tagged within New Caledonia. Juvenile
sharks (n = 4) were captured only in the Southern Province while
both sub-adult (n = 2) and mature (n = 4) males were captured in
the north and south of New Caledonia and at the Chesterfield
Islands in the centre of the Coral Sea. Only a single male was
tagged within the Australian study locations.
Of these sharks, fourteen were also tagged with satellite tags
(Table 2), three with SPOT tags and 11 with PSATs. Sharks with
acoustic tags were detected over total days (d) ranging from one to
255 (less than the battery length of the acoustic tags)(median 4.5 d)
with two to 858 days between acoustic tagging and first detection
on either an array closest to location of tagging or another array in
Figure 3. Temporal occurrence of tiger sharks tagged at New Caledonia (Southern Province, Belep), the southern GBR and the
Chesterfield Islands in the Coral Sea with acoustic tags. Individual sharks are numbered with sex (M = male; F = female) (see Table 1) and
arranged by increasing body size from top to bottom within each study location. Numbers are bolded for mature sharks. Note shark 34 F was tagged
at Fraser Island (Australia) and 14 M was detected at Bourail (New Caledonia) after being tagged at Yande Pass (Table 1). x refers to tagging date. Blue
dots indicate detections in the respective acoustic arrays. D refers to end of available reception period for an acoustic array or tag.
doi:10.1371/journal.pone.0083249.g003
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the study location (median 28 d)(Table 1). This compared to
detection periods of four to 210 days (median 19 d) for PSATs and
seven to 38 days (median 13 d) for SPOT tags (Table 2). With the
exception of TS9, TS11 and TS29, premature release occurred for
all PSATs, and no data was received from two PSAT tags
deployed in Australia on mature females (Table 2).
Acoustic Monitoring
Patterns of acoustic detections differed between acoustic arrays
and individuals. Individual temporal patterns of occurrence were
highly variable in coastal arrays and displayed little evidence of
residency (Fig. 3, 4), however sharks tagged in 2010 and monitored
until November 2011 in the Chesterfield Islands, with the
exception of mature females, displayed consistent patterns of
movement and strong residency (Fig. 3, 4). These individuals
undertook extensive excursions between receivers within the array
area in the Chesterfields with continual movement patterns back
and forward across the lagoon that varied with each individual
(Fig. 5). Days detected for these sharks ranged from 36 to 255
across all months of the year (Fig. 5). In contrast, the number of
days tiger sharks were detected on acoustic receivers in the
Southern Province varied from 0 to 31 with one mature 370 cm
TL female (TS9) and a mature 380 cm TL male (TS10) displaying
pseudo-residency behaviour (Fig. 6). Days detected for tiger sharks
varied between one to seven in Belep and zero to one in Australia.
Mature females (TS24 and TS25) in the Chesterfield Islands,
however, were detected for only two and three days respectively
and exhibited similar patterns of transitory and asynchronous
occurrence to those of tiger sharks detected in coastal acoustic
arrays (Fig. 3, 4 and 5). More than half of the sharks detected on
acoustic arrays displayed transitory or a combination of pseudo-
residency and transitory behaviour, with the remaining eight
sharks detected in coastal arrays displaying passer-by behaviour
(Table. 1, Fig. 4 and 6). For example, TS34 was briefly detected
once, 117 km from her tagging location off Fraser Island,
Australia, by an acoustic receiver at Lady Elliot Island (Fig. 7).
Likewise, TS14 tagged at Yande Pass, Belep, was detected at
Bourail, New Caledonia, on an acoustic receiver array deployed
by another research team over 240 km from the shark’s tagging
location (Table 1; Fig. 7). In addition TS25 was detected at One
Tree Island, adjacent to Heron Island on the GBR 842 days after
being tagged in the Chesterfields in August 2010. Furthermore,
TS18 was detected at Lady Elliot Island, GBR, 591 days after
being tagged in the Chesterfields in August 2010 and at Heron
Island, GBR, 595 days after being tagged. This shark displayed
strong residency to the Chesterfields for her first year of tracking
before detection on the GBR. Both TS 18 and TS 25 displayed
migrations of over 600 linear km providing direct evidence of
temporal connectivity between oceanic reefs of the Coral Sea in
New Caledonia and the GBR. All tiger sharks were detected only
on acoustic receivers closest to their respective capture locations
except TS14, TS18, TS25 and TS34. Tiger sharks were detected
across all months in the south of New Caledonia irrespective of
ontogeny or sex (Fig. 3, 6). Movements between acoustic receiver
stations in the Southern Province occurred primarily in the
Woodin Channel and the coral bommie in the greater lagoon.
One 380 cm TL mature male (TS10) was detected well within
Prony Bay at the Carenage River on several occasions. Visits at
individual stations were typically brief as sharks were typically
detected only once within a three minute period on individual
stations. No tiger sharks were captured, tagged or detected at Lord
Howe Island during the period of acoustic receiver deployment.
Overall 55% of the 33 tiger sharks with acoustic tags were
detected after release. 30% were yet to be recorded (detected)
(YBR) and one shark was resighted although this shark was not
tagged (Table 1). Diel patterns of detection showed individual
Figure 4. Residency Index (RI) of tiger sharks tagged at New Caledonia, the southern GBR and the Chesterfield Islands in the Coral
Sea with acoustic tags. Individual sharks are numbered (see Table 1) and arranged by increasing body size from top to bottom for those tagged in
the Coral Sea (top section) and those in New Caledonia/GBR (bottom section). Numbers are bolded and sex (M = male; F = female) shown for mature
sharks.
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differences between day and night for sharks detected for sufficient
temporal periods (Table 3).
SPOT Tracks
Three tiger sharks fitted with SPOT tags produced 43 positional
fixes between February and March 2010. Most of these positions
(n = 34) were from TS3, a 192 cm TL juvenile tagged in the
Southern Province. Interestingly, TS3 was not detected on any of
the acoustic receivers in the vicinity of her tag and release location,
however SPOT positions showed she moved throughout the
Southern Province, remaining within the lagoon and adjacent to
the barrier reef for the period of her tracking (Fig. 7). Alternatively,
TS13 (n = 7) and TS14 (n = 2) had few positional fixes, although
TS13 was periodically redetected on acoustic receiver stations at
her original tagging location after 200 days. TS14 was also
detected on another acoustic array after 294 days (Table 1).
PSAT Tracks and Ocean Migration
Eight tiger sharks fitted with PSATs revealed long distance,
open-ocean and inter-island migrations with seven of these sharks
detected on acoustic arrays at the site of capture after four to 405
days (Fig. 7). Tiger sharks tagged in the Southern Province showed
migrations out of the main lagoon into open-ocean. TS6 moved
south and was one of two satellite tagged sharks in New Caledonia
not to be detected on an acoustic receiver. TS8 migrated east
towards the Loyalty Islands, whereas TS11 migrated into the
Coral Sea south of New Caledonia before returning to the
Southern lagoon after 210 days. During this journey, TS11
underwent dives of up to 640 m. TS9 underwent a significant
migration south and appeared to be oriented to the oceanic
Norfolk ridge. TS9 spent most of her time near the surface, but
underwent a deep dive of 1136 m to waters of 5.6uC (Fig. 8C).
This shark then moved south past Norfolk Island before turning
north back along the Norfolk ridge. TS9 was then detected back
on the southern New Caledonia acoustic array after 225 days
(Fig. 7).
Tiger sharks satellite tagged in the Chesterfield Islands showed
movements out into open-ocean before returning to the lagoon
and were then detected on the acoustic array. TS16 and TS17
appeared to be resident or pseudo-resident, whereas TS24 and
TS25 were detected back on the Chesterfield array after 326 and
86 days, respectively. TS18 was tracked for 93 days. Interestingly,
this shark showed numerous deep dives between periods of
remaining at depths of no more than 40 m (Fig. 8A). Only one
satellite tagged shark in the Great Barrier Reef (TS 29) provided a
track for 78 days out into the Coral Sea off Cairns before the
satellite tag popped-off west of Lizard Island. Satellite tags from
two female tiger sharks 367 and 370 cm TL (Table 2) tagged in
Cairns did not report (Table 2). Photo-ID of the dorsal fin of TS5
revealed the movement of this shark across the Coral Sea between
Woodin Channel, Southern New Caledonia, in 2008 to Noosa
Heads, Australia, in 2010 (Fig. 9). The combination of satellite and
acoustic telemetry revealed the ocean migration and periodic
return of TS11 to Woodin Channel 405 days after tagging.
Dive Profiles and Three-dimensional Habitat-use
Dive profiles showed extraordinary levels of vertical movement
with the deepest depth on record for a tiger shark at 1136 m
(Fig. 8). Three-dimensional 95% kernel estimates demonstrated
tiger sharks utilised deep open ocean relatively close to the GBR,
off Cairns (Fig. 10), whereas kernels suggest utilisation of the
shallow lagoon with interspersed diving/movement down into
deep water (possibly foraging) before returning to the lagoon. This
pattern ties in nicely with the acoustic data (Fig. 3 and 8). The
kernel estimates for the south of New Caledonia reflected the
migration of sharks away from the southern New Caledonia
lagoon, but indicated that the sharks also utilise the lagoon itself,
which is a vast area with depths up to 80 m (Fig. 7F). Three-
dimensional activity spaces (95%) averaged at 2.36610
3
km
3
and
varied from 0.16 to 4.48610
3
km
3
. Kernel estimates 50% varied
from 37.7 to 9.49610
2
km
3
.
Patterns of Coral Reef Site-fidelity
Our study demonstrates extraordinary reef fidelity among tiger
sharks in New Caledonia and the Chesterfield reefs. In New
Caledonia, dorsal fin photo-ID of TS5 confirmed this shark was
present in Prony Bay, New Caledonia, in 2002 on a whale carcass
[55] and in 2008. As far as we are aware, this is the longest
confirmed record of site-fidelity for a large tiger shark. This shark
was later captured on shark control equipment at Noosa on the
east coast of Queensland, Australia, in 2010 before being tagged
and released by another research team (Fig. 9). In addition, TS 11
was captured and tagged with satellite and acoustic tags in New
Caledonia in 2009 before returning to the site of capture in 2010.
Eight sharks with satellite and acoustic tags were detected back on
acoustic arrays at sites of release two to 405 days after tagging
(median 24.5 d).
Discussion
Tiger sharks monitored by a combination of acoustic and
satellite telemetry across the Coral Sea utilised a remarkable range
of habitat both horizontally among shallow coastal and island reefs
and open ocean as well as vertically through the epi-, meso- and
bathypelagic layers. This range of habitat-use is entirely consistent
with results from previous studies conducted in other geographic
regions (e.g. [34], [35], [36], [37]). The novelty in our findings is
the remarkable year round residency of the sub-adult females and
an adult male tiger shark in the isolated oceanic Chesterfield
Island reef(s). Our study, however, did not support the hypothesis
that tiger sharks undertake regular or predictable migrations
between New Caledonia and Australia across the Coral Sea.
Unlike other large apex predators and top level consumers, such as
the white shark (Carcharodon carcharias) and humpback whale
(Megaptera novaeangliae) which do appear to undertake consistent
seasonal migrations within the Coral Sea (e.g. [61], [62], [63]),
tiger sharks in our study displayed complex individual variability in
both their wide-ranging migrations and localised movement
patterns. Our results suggest discrete groups of tiger sharks across
the Coral Sea utilise specific coral reefs incorporating nearby deep
water oceanic environments 98 to 249 km from the location of
tagging with three-dimensional (combined horizontal and vertical)
Figure 5. Spatial occurrence of tiger sharks tagged at the Chesterfield Islands in the Coral Sea with acoustic tags. Individual tiger shark
numbers correspond to Table 1. Arrows indicate direction of movement between receivers; double headed arrows indicate repeated movements
between receivers. Coloured bubbles indicate the proportion of detections at numbered acoustic receivers. Shades of blue in the legend are labelled
to indicate different water depths. Inset bar graphs indicate the number of days detected in each month and localised behaviours; PB (Passer-by), T
(Transient), PR (Pseudo-Resident), R (Resident). Blue arrows indicate the month of capture.
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activity spaces typically ranging from 0.16 to 4.48610
3
km
3
.In
addition, our data suggest that selected individuals then undertake
more wide-ranging migrations that provide temporal (but unpre-
dictable and irregular) connectivity between reefs of New
Caledonia and Australia. Recent work by Papastamatiou et al.
[15] suggests this may be due to a phenomenon known as ‘partial
migrations’ based on analysis of tiger shark movements in the
Hawaiian island chain where only a proportion of the shark
population migrate in a given period. In light of our data we
propose two provisional and interlinked hypotheses related to
mating/pupping and coastal vs oceanic reef-use to explain the
observed migratory patterns.
Mating/Pupping as a Driver for Adult Movement
Mature females were captured at all sites other than Lord Howe
Island (LHI), although a small juvenile was filmed in 30 m of water
on the LHI plateau during Baited Remote Underwater Video
(BRUV) surveys undertaken by I. Kerr (LHI marine parks)
providing evidence of pupping and the presence of mature females
at this oceanic Coral Sea island (see Video S2). Mature females
also displayed the longest migrations (e.g. TS9) and least frequent
occurrence on acoustic receiver arrays suggesting they may be the
main participants in wide-ranging movements that provide
important temporal connections between ‘local’ groups of spatially
separated (i.e. 500 km ) tiger sharks.
Mature females have triennial reproductive cycles [56] that
probably drive unpredictable and seemingly inconsistent, yet
extremely important, long-range migrations between mating and
foraging grounds and suitable pupping habitats. Mating and
pupping requirements may partially explain adult tiger shark
migration patterns in the Coral Sea. Using random walk models
from male and female tiger sharks recoded via passive acoustic
telemetry in the Hawaiian Islands, Papastamatiou et al. [15]
proposed that inter-island movements by tiger sharks were a result
of a combination of partial reproductive migrations and individual
decisions related to water temperature and primary productivity.
This was also based on the limited inter-island movement of large
males compared to that of mature females. Our data seemingly fit
the proposed model of Papastamatiou et al. [15] and suggest that
mature females may be of primary concern for conservation of
tiger shark populations in the Coral Sea. For example, the
transient nature of mature females in the Chesterfields compared
to sub-adult and mature male sharks supports the notion that large
females may move in three year cycles between pupping and
foraging grounds on the east coast of Australia and the west coast
of New Caledonia with mating taking place in the oceanic reefs in
the Coral Sea. This strategy provides a largely unpredictable
means of utilising sparse foraging and pupping habitats, but
increased and varied mating opportunities with males that may be
more restricted in their movements. Isotope analysis of tiger shark
tissues from different regions in the Coral Sea will be a useful
means to compare the signatures of males and females to further
quantify these patterns [64]. In addition, blood analysis of adult
females in coastal and oceanic areas will help to elucidate
movements in response to parturition. This method was also
proposed by Hammerschlag et al. [37] for tiger sharks in the
Atlantic and Papastamatiou et al. [15] for tiger sharks in the
Hawaiian Islands.
Our longest satellite track was undertaken by a 3.7 m female
(TS 9) who undertook a directional migration of 1141 km from the
coastal areas of the southern province of New Caledonia to close
to Norfolk Island before being detected back at her coastal site of
tagging after 225 days. During our survey efforts and repeat
tagging trip in the Chesterfield Islands, we did not capture or
observe small juvenile or new born tiger sharks; however, small
juveniles were caught in the coastal areas (,60 m of water) of New
Caledonia and have been recorded in Australia [65]. In addition,
pregnant females have been recorded on the east coast of
Australia, suggesting parturition occurs in these coastal areas.
Overall, general migration patterns of tiger sharks in the Coral
Sea may be masked by highly variable individual movement
patterns. In our study mature males showed high levels of site
fidelity at oceanic reefs (e.g. TS 19) and repeated occurrence in
only one of our defined tiger shark ‘group’ areas of the south of
New Caledonia (e.g. TS 10), consistent with the model proposed
by Papastamatiou et al. [15]. However, one male made a long
range movement 294 km south along the west coast of New
Caledonia, whereas TS 5 (a 3 m sub-adult female) showed
extensive movement from southern New Caledonia to Noosa
Heads, Australia, over a period of 495 days. TS 5 occurred in
southern New Caledonia in 2002 and 2008 prior to its occurrence
in Australia in 2010 (Fig. 9). In the future, new and advanced
satellite tags (e.g. satellite-linked radio-telemetry (SLRT) tag with a
multi-year battery capacity), such as those used over a two-year
period by Domeier and Nasby-Lucas [66] on white sharks, may
better reveal these movement patterns for large female tiger
sharks.
Localised Habitat-use
Our data lead us to reject our hypothesis of no difference in
localised habitat-use of reefs across the Coral Sea by tiger sharks.
In fact, we found an obvious difference in the shark behaviour
between coastal (New Caledonia and GBR) and isolated oceanic
reefs (Chesterfields). While we acknowledge differences in the
number of receivers providing coverage in acoustic arrays, the
novelty in our findings is the remarkable year round residency of
the sub-adult females and an adult male tiger shark in the isolated
oceanic Chesterfield reef(s). Satellite telemetry revealed members
of this group of sharks made frequent deep dives, but acoustic data
revealed frequent returns to the lagoon area with ongoing
‘‘patrolling’’ movements between cays across the lagoon. While
Meyer et al. [36] and Lowe et al. [30] demonstrate that isolated
lagoons are important to Hawaiian tiger sharks and some
individuals occur year round, we are not aware of any studies
that have demonstrated year round, continual residency for large
tiger sharks to the extent of those in our study.
Mature male and female tiger sharks utilise coastal and oceanic
reef habitats in different ways most likely driven by a combination
of female parturition requirements, suitable pupping grounds for
offspring [56], [67] and utilisation of productive prey patches.
Differences in female and male occurrence and habitat-use
patterns have been recorded for other shark species, e.g. the
Figure 6. Spatial Occurrence of tiger sharks within the Southern Province (A to H) and Northern Province (I) monitoring arrays in
New Caledonia (see Fig. 1). Individual tiger shark numbers correspond to Table 1. Arrows indicate direction of movement between receivers;
double headed arrows indicate repeated movements between receivers. Coloured bubbles indicate the proportion of detections at numbered
acoustic receivers. Different shades of blue in the legend indicate different water depths. Inset bar graphs indicate the number of days detected in
each month and localised behaviours; PB (Passer-by), T (Transient), PR (Pseudo-Resident), R (Resident). Bar graph arrows indicate the month of
capture. Numbers alongside the bubbles correspond to receiver number.
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Figure 7. Spatial patterns of tiger shark movements across the Coral Sea between 2008 and 2013. Bubble plots show 95% confidence
interval envelope for PSAT tracks. (A) Satellite tracks of PSAT tiger sharks tagged in the Southern lagoon of New Caledonia; (B) SPOT satellite tagged
tiger sharks in the north of New Caledonia; (C) PSAT tiger sharks in the Chesterfield Islands, and (D) off Cairns in the GBR. (E) Includes the straight
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oceanic short-fin mako, Isurus oxyrinchus, and blue shark, Prionace
glauca [68] and coastal species such as the blacktip, Carcharhinus
melanopterus [69] and scalloped hammerhead, Sphyrna lewini [70],
[71] and were attributed to female avoidance of males as a strategy
to increase fitness and reduce competition, different dietary
requirements, and the locating of suitable pupping grounds for
offspring [68], [70]. In our study area, data based on capture of
328 mature tigers in the QLD Shark Control Program between
2002 and 2012 along the QLD coast confirm the regular
occurrence of both mature male and female tiger sharks (at a
ratio of 1:1.5). While adult male and female tiger sharks occur at
sites across the Coral Sea, different life history requirements for
males and females are likely driving individual differences in shark
behaviour and habitat-use on both local and basin-wide scales in
the Coral Sea.
Coastal vs Oceanic Reef Foraging Hypothesis
Different reefs have varying prey and habitat characteristics that
influence shark behaviour. The abundance and diversity of
suitable prey available in the Chesterfields lagoon, in contrast to
the sparsely distributed resources found on coastal reefs, may
explain tiger shark residency. The Chesterfield reefs sustain large
turtle populations including seasonal aggregations of breeding
green turtles, populations of numerous sea snake species and
breeding colonies of different species of sea bird (.200,000
individuals) in addition to teleost populations [41], [72]. For
example, the stomach contents of one tiger shark (TS 19) tagged in
the Chesterfield Islands contained hawksbill turtle (Eretmochelys
imbricata), seabird and sea snake remains; prey items consistent
with prey availability in the Chesterfields. Individual prey species
do not necessarily explain residency as tiger sharks in the remote
northern GBR do not necessarily occur in conjunction with the
seasonal aggregations of the world’s largest breeding colony of
green turtles at Raine Island [31]. However, Hawaiian tiger sharks
undertake pelagic migrations between islands to coincide with
seasonal prey accessibility such as the availability of fledging black-
footed albatross, Phoebastria nigripes [32]. These anomalies around
the Pacific Ocean add to the confusing and seemingly unpredict-
able patterns of tiger shark movement. However, the diversity of
food resources and temporal variability in prey in the Chesterfields
could explain the abnormally long residency (and absence of
seasonality) of one adult male tiger in our study (TS 19) and
indicates the Chesterfields may be a very important feeding
ground for tiger sharks. In turn these favourable conditions may
facilitate this area as a fertile mating ground. In contrast, adult
female tiger sharks appeared to simultaneously leave the Chester-
fields and were only briefly re-detected approximately one year
after initial tagging, suggesting transitory behaviour among the
isolated oceanic coral reefs probably due to the aforementioned
mating/pupping hypotheses. Tiger sharks are true generalists and
able to utilise wide and varied food sources and probably adapt
their behaviour accordingly and with opportunity [73]. Tiger
sharks likely seek out and exploit productive and predictable
resource patches that exhibit abundant food. Tiger sharks visiting
turtle rookeries or bird fledging sites are therefore no more
anomalous than white sharks visiting seal rookeries. Sharks move
on when the resources are depleted as some of these resources
(birds, turtles) are highly seasonal. Other locations may perhaps
encourage more resident behaviour, especially for pre-reproduc-
tive animals (e.g. Chesterfields/oceanic reefs), as these locations
have permanent high resource abundance. Maturity/breeding
may provide a powerful incentive to leave these highly productive
sites.
Reef Fidelity
Individual differences in movement patterns are not uncommon
in reef-associated sharks (e.g. C. amblyrhynchos, [18]). Juveniles often
show high site fidelity to a small region, whereas larger and older
individuals are likely to move beyond a single reef or display wider
ranging movements [20], [74]. To some extent, this trend remains
true for the tiger shark, which, unlike smaller reef-associated shark
species, shows no evidence for long-term residency in previous
studies, instead exhibiting movements through large home ranges
of at least 109 km [32], [35]. In our study, a SPOT track of a
juvenile tiger shark in southern New Caledonia showed that this
shark remained within the lagoon and close to the barrier reef (an
distance between the first photo-ID spotting of TS5 in New Caledonia and the second on the east coast of Australia. (F) The movement of a juvenile
TS in the south of New Caledonia. Red arrows indicate movements from point of release to detection on spatially separated array for tiger sharks with
acoustic tags. Orange arrows indicate generalised patterns/directions of major currents within the region of tiger shark migration. EAC refers to the
East Australian Current.
doi:10.1371/journal.pone.0083249.g007
Table 3. Diel patterns of tiger shark occurrence at acoustic receiver stations.
Tiger
Shark
Tagging
Location
Date of
Capture Sex TL (cm)
day time
detections
night time
detections X
2
P
1 SP 30/01/2009 F 154 30 9 19.4 ,0.001
2 SP 7/07/2009 F 164 5 50 34.2 ,0.001
4 SP 9/07/2009 F 270 20 15 7.7 0.398
9 SP 24/08/2010 F 370 56 35 24.3 0.028
10 SP 28/01/2009 M* 380 44 58 14.6 0.166
16 CI 12/08/2010 F 260 474 389 173.4 0.004
17 CI 13/08/2010 F 270 62 374 203.2 ,0.001
18 CI 12/08/2010 F 310 1081 1868 443.7 ,0.001
19 CI 16/08/2010 M* 310 526 522 175.8 0.902
Chi-square analysis and P values refer to day and night time detections.
doi:10.1371/journal.pone.0083249.t003
Coral Sea Tiger Shark Movement
PLOS ONE | www.plosone.org 14 January 2014 | Volume 9 | Issue 1 | e83249
area of approximately 3145 km
2
) (Fig. 7F), whereas four PSAT
tagged sub-adult and adult tiger sharks (both male and female)
migrated out of the same area and undertook wide-ranging ocean
migrations. This is consistent with other studies that suggest
restricted movement of young of the year (YOY) and small
Figure 8. Depth-temperature profiles of selected PSAT tagged
tiger sharks. (A) TS25 Chesterfield Islands, (B) TS11 South lagoon of
New Caledonia, and (C) TS9 South Lagoon of New Caledonia. Black bars
above A refer to periods of acoustic detection in the Chesterfield array.
Note differing spatial and temporal scales.
doi:10.1371/journal.pone.0083249.g008
Coral Sea Tiger Shark Movement
PLOS ONE | www.plosone.org 15 January 2014 | Volume 9 | Issue 1 | e83249
juvenile tiger sharks out to a depth of 100 m from the coast based
on long-term catch records on the east coast of the USA [38], [75],
as opposed to adults which occupy shelf and oceanic waters across
the western Atlantic [1], [37]. Furthermore, the literature suggests
that tiger shark movement becomes more localised over short
periods (weeks) at hotspots of resource availability, such as
seamounts [76], rather than in coastal areas [35], [37].
A recent review comparing horizontal and vertical movements
of coastal sharks suggests fidelity is common in species that use
nursery areas, but fidelity to mating, pupping, feeding and natal
sites has rarely been observed [67]. Our data presents extensive
fidelity to sites of tagging in the south of New Caledonia and the
Chesterfields, with eight double-tagged (i.e., both satellite and
internal acoustic tags) sharks detected back on our acoustic array
at the site of tagging after two to 405 days (median 62 d) (Table 1).
These data illustrate the potentially long-term site fidelity of large
tiger sharks to specific coastal areas. Conservation of tiger sharks
may be facilitated by the recently established MPAs in southern
New Caledonia, especially as the southern New Caledonian
coastal site may operate as a feeding area with obvious multi-year
sporadic use by large tiger sharks. However, the wide ranging
movements of TS 11 and other large tiger sharks also suggest a
better understanding of the use of ocean habitats is necessary for
effective conservation.
Three-dimensional Habitat Use
Three-dimensional (3D) space use was estimated when the
horizontal and vertical coordinates were determined simulta-
neously, however few studies consider 3D when describing the
habitat-use of large sharks. Our study provides the first estimate of
long-term 3D habitat-use by tiger sharks. Caution should be
applied however, as light-based geolocation position estimates may
contain considerable spatial errors compared to real time SPOT
tag locations; nonetheless this method enables informed MPA
design by providing an estimate of 95% of the (3D) activity space
of individual tiger sharks. Clearly tiger sharks are utilising deep
water habitats, which appear to be particularly important in the
sub-adult and adult life history stages. MPA design for large sharks
can be greatly improved if the 3D habitat use is known,
particularly if incorporating open ocean areas. Our estimates of
95% home range showed large variability between individuals;
however sharks frequented the epipelagic layer (0–100 m). In the
vertical plane, movements are often attributed to foraging or
navigation, but are less well understood than horizontal move-
ments for almost all shark species. Hammerschlag et al. [37] noted
that pelagic migrations by tiger sharks in the Atlantic coincide with
areas of the Gulf Stream and its associated eddies that are highly
productive and known for aggregations of prey including tuna and
billfish. Use of deep water habitat by tiger sharks probably varies
with ocean productivity, upwelling and proximity to highly
productive prey patches (e.g. oceanic reefs such as the Chester-
fields). Dive patterns by tiger sharks tagged in coastal areas could
also be a means to utilise bathymetric cues to navigate/migrate
between islands in addition to foraging [33], [61].
Implications for Conservation and Management
The migratory movements of large tiger sharks from New
Caledonia out into the Coral Sea toward Australia reflects the
potential conservation implications for managing these widely
separated habitats lying on a migration ‘highway’ for marine
megafauna. Few fish species utilize such a remarkable range of
habitat in such a short amount of time, thus tiger sharks provide
novel trophic links horizontally among the shallow coastal and
island reefs and open ocean as well as vertically through the epi-,
meso-, and bathypelagic layers. Across the Coral Sea, tiger sharks
demonstrate bi-partite habitat use (between ocean and coral reef)
with high individual variability. Our data has shown direct
evidence of reef site fidelity in the Chesterfield Islands, suggesting
oceanic Coral Sea reefs may be particularly important for this
species, both as potential mating grounds and feeding grounds for
large individuals. Based on our data trends we suggest that mature
females may be the primary individuals migrating between
Australia and New Caledonia across the Coral Sea driven by
reproductive cycles. Females may also be returning to suitable
coastal areas for parturition after utilising productive ‘stop-over’
prey patches (e.g. seamounts such as the Chesterfields), hence
providing important trophic links between distant reef habitats in
the Coral Sea. Protection of oceanic reefs in the Coral Sea may be
a critical means to conserve future stocks of this species and will
Figure 9. Resightings of individual tiger shark based on dorsal
fins. Arrows highlight the distinguishing features of the individual
sharks fin. Note A1 was identified by Clua et al. [55]. The photo taken in
A3 is after a tissue sample was taken from the second notch in the
shark’s dorsal fin.
doi:10.1371/journal.pone.0083249.g009
Figure 10. Individual 3D (95%) activity space of satellite tagged tiger sharks in the Coral Sea. (A) South New Caledonia: Green TS 6,
Orange TS 8, Grey TS 11, (B) Chesterfields: Blue TS 16, Green TS 18, (C) Cairns: Purple TS 29.
doi:10.1371/journal.pone.0083249.g010
Coral Sea Tiger Shark Movement
PLOS ONE | www.plosone.org 16 January 2014 | Volume 9 | Issue 1 | e83249
require international cooperation. The conservation of tiger sharks
can be facilitated in some cases by the use of coastal barrier reef
marine protected areas, especially for specific sites that demon-
strate continual fidelity over multiple years across individuals (such
as southern New Caledonia). However these areas only provide
brief protection for large life-history stages of tiger sharks which
frequent pelagic waters. Oceanic migration of adults, especially
females, is of particular concern. Our findings further emphasize
the need to address marine conservation issues at an international
scale, as top predators such as the tiger shark traverse country
EEZ’s and leave the protection afforded by coastal barrier reef
managed areas [11], [77]. A joint-managed (Australia and France)
connectivity corridor across the Coral Sea may be one method to
address this. Successful international management initiatives will,
however, require more long-term research on habitat-use and
migration by large tiger sharks [67]. Future research should
therefore focus on comprehensive satellite tracking of mature tiger
shark (both male and female) along the chain of seamounts and
oceanic reefs in the centre of the Coral Sea, from the Chesterfield
Islands south to LHI. Determining the role of other oceanic coral
reefs should be a priority for the conservation of tiger sharks in the
Coral Sea.
Supporting Information
Video S1 Tiger shark release.
(MP4)
Video S2 Juvenile tiger shark on Baited Remote Under-
water Video at Lord Howe Island.
(MP4)
Acknowledgments
We thank the following for assistance in the field: Celine Barre, Mael
Imirizaldu, Thomas Vignaud, Thomas Robertson, Claude Chauvet,
Tyffen Read, James Hook, Juergen Zier, the Southern and, Northern
Province councils, Barry Bruce, Andrew Chin and numerous other
volunteers. We thank Sophie Olivier for helping initiate contact amongst
the French and Australian authors and Paddy Dimond for a dorsal fin
photo of TS 5 captured off Noosa. Ciaran Morris, Joanna Burston, Jordyn
De Boer and Gerard Bourke kindly provided assistance with production of
some of the maps. We thank Lydie Couturier and Kathy Townsend for
forwarding detections of our sharks on their acoustic array at Lady Elliot
Island (GBR), AATAMS for the detections at Heron Island, GBR, and
Aquarium des Lagons and Universite´ de la Nouvelle-Cale´donie for
detections of one of the male tiger sharks on their acoustic array in Bourail,
New Caledonia, and the QLD Boating and Fisheries patrol for assistance
with the QLSTP acoustic array and shark tagging off Fraser Island.
Logisitcs and ethical support was provided by Griffith University. We
thank ACREM with the loan of diving equipment and seven VR2W units
and acoustic and satellite tags from CRIOBE. We thank Greg Skomal for
assistance in processing some of the satellite data and Ian Kerr and Jimmy
Maher for assistance with VR2W deployment and retrieval at Lord Howe
Island. VR2W units at LHI and helpful comments throughout the work
were provided by Dr. Nicholas M. Otway. We thank the comments of two
reviewers who helped to improve the manuscript.
Author Contributions
Conceived and designed the experiments: EC JMW SP. Performed the
experiments: JMW EC. Analyzed the data: JMW KL CB. Contributed
reagents/materials/analysis tools: SP EC JMW MB. Wrote the paper:
JMW MB EC CB KL.
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Coral Sea Tiger Shark Movement
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... Tiger sharks in Australia are thought to be part of a large Indo-Pacific population 28 , and satellite-tag tracking studies have revealed extensive movements up to several thousand kilometres in the region 40,41 with some individuals seen moving as far as New Caledonia (maximum reported distances: of 1141 and 1800 km) 42,43 . In this context, we hypothesised that tiger sharks in eastern Australia, form a single panmictic population, from tropical Queensland to temperate Victoria 42,44 . ...
... Consequently, we hypothesize tiger sharks in east Australian waters consisted of at least two populations in the past, but likely comprise a single population now. This may sound counterintuitive in the light of satellite tag-tracking studies that have shown evidence of individuals migrating over 1000 km 23,43,61 . However, large migrations and local populations at fine geographical scales are not mutually exclusive since dispersal events may be related to foraging and not reproductive purpose hence contributing differently to a population genetic make-up. ...
Article
Full-text available
Over the last century, many shark populations have declined, primarily due to overexploitation in commercial, artisanal and recreational fisheries. In addition, in some locations the use of shark control programs also has had an impact on shark numbers. Still, there is a general perception that populations of large ocean predators cover wide areas and therefore their diversity is less susceptible to local anthropogenic disturbance. Here we report on temporal genomic analyses of tiger shark (Galeocerdo cuvier) DNA samples that were collected from eastern Australia over the past century. Using Single Nucleotide Polymorphism (SNP) loci, we documented a significant change in genetic composition of tiger sharks born between ~1939 and 2015. The change was most likely due to a shift over time in the relative contribution of two well-differentiated, but hitherto cryptic populations. Our data strongly indicate a dramatic shift in the relative contribution of these two populations to the overall tiger shark abundance on the east coast of Australia, possibly associated with differences in direct or indirect exploitation rates.
... However, population structure of tiger sharks at a local scale remains largely unknown. On the Australian east coast they are found from tropical Queensland to temperate Victoria 23,24 with some satellite-tagged individuals seen to move as far as New Caledonia and Papua New Guinea 24,25 . ...
... Consequently we hypothesize tiger sharks in east Australian waters consisted of at least two populations in the past, but likely comprises a single population now. This may sound counterintuitive in the light of satellite tagtracking studies that have shown evidence of individuals migrating over 1,000 km 25,30,43 . However, large migrations and local populations at ner geographical scales are not mutually exclusive, but could be caused by basic "triangle migrations" 15,44 of sh between parturition sites and juvenile and adult habitats 45 . ...
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Over the last century, many populations of sharks have been reduced in numbers by overexploitation or attempts to mitigate human-shark interactions. Still, there is a general perception that populations of large ocean predators cover wide areas and therefore their diversity is less susceptible to local anthropogenic disturbance. Here we report retrospective genomic analyses of DNA using archived and contemporary samples of tiger shark ( Galeocerdo cuvier ) from eastern Australia. Using SNP loci, we documented a significant overall change in genetic composition of tiger sharks born over the last century. The change was most likely due to a shift over time in the relative contribution of two well differentiated, but hitherto cryptic populations. Our data strongly indicate a dramatic shift in relative contribution of the two populations to the overall tiger shark abundance of the east coast of Australia, possibly associated with differences in direct or indirect exploitation rates.
... Por su parte, la captura y liberación de los peces consiste en utilizar diferentes artes de pesca con el fin de reconocer el complejo de especies en un sitio (Talwar et al., 2020). Su principal ventaja destaca en minimizar errores en la identificación taxonómica, además de que permite llevar a cabo una colecta de datos mucho más fina, pues permite llevar a cabo mediciones precisas del tamaño de los peces y colectar muestras para otros tipos de estudios (Bethea et al., 2014;Werry et al., 2014). Desafortunadamente se trata de un método invasivo, que ocasiona altos niveles de estrés en los individuos capturados, la posible muerte de algunos individuos, sin mencionar el enorme esfuerzo de muestreo que se necesita para tener una muestra representativa. ...
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Realizar un seguimiento continuo de las comunidades marinas es importante para su manejo y conservación. Desafortunadamente, debido a las dificultades metodológicas, los esfuerzos de monitoreo en el ambiente pelágico han sido pocos en comparación con los del ambiente bentónico. Es por ello que se han implementado nuevas tecnologías para facilitar el monitoreo en estos hábitats, tal y como son las cámaras remotas cebadas (BRUVS por sus siglas en inglés). El presente estudio tiene como objetivo utilizar esta herramienta para comparar las comunidades de peces pelágicos en dos regiones y sus localidades: el Suroeste del Golfo de California (SGC) y el Archipiélago de Revillagigedo (AR); haciendo énfasis en el nivel trófico promedio y el efecto de la profundidad de fondo. Para cada sitio se identificaron las especies y sus abundancias con base al número máximo de individuos en un data frame por hora (MaxNhr). Para cada localidad se calcularon los índices de diversidad (H, D, J, Δ+) y se realizaron análisis de ordenación. Para conocer si existían diferencias en la composición de especies se realizó un análisis PERMANOVA, y un análisis SIMPER para conocer las especies responsables de dichas diferencias. Para comprobar si existían diferencias significativas en el Nivel Trófico por región y localidades, se realizó una prueba de Kruskall-Wallis utilizando el valor trófico de cada especie, obtenido de FishBase, en función de su abundancia relativa y gremio trófico. En cuanto a la profundidad de fondo, las cámaras fueron clasificadas en someras (≤30 metros) o profundas (>30 metros). Finalmente se aplicó un análisis PERMANOVA para comprobar las diferencias estadísticas, y se distinguió la aportación de cada gremio trófico y preferencia de hábitat en función de la abundancia relativa. Se lograron colocar y analizar correctamente 140 cámaras (SGC = 29, AR =111), lo que corresponde a 244.1 horas efectivas de grabación. Se identificaron un total de 60 especies (SGC = 41; AR = 30) y se contabilizaron 8,507 individuos. Las curvas de acumulación y estimadores de diversidad indicaron un buen esfuerzo de muestreo para el AR, pero pobre para el SGC. Con excepción del índice J a nivel localidad, y el índice D a nivel región, no se encontraron diferencias significativas entre los índices de diversidad. En contraste, los análisis de ordenación y PERMANOVA si encontraron diferencias entre regiones y localidades. De manera similar el Nivel Trófico fue mayor en el AR debido a una mayor cantidad de carnívoros superiores. Con respecto a la profundidad, el análisis PERMANOVA encontró diferencias significativas entre los ensambles. Mientras que los ambientes someros tuvieron más abundancia de peces arrecifales y carnívoros inferiores, los ensambles profundos presentaron una proporción similar de carnívoros superiores e inferiores, dominados por especies pelágicas. Los resultados anteriores indican que la diversidad de peces pelágicos es similar entre ambas regiones, pero difieren en cuanto a uniformidad y composición, lo que deja en evidencia la importancia de las áreas naturales protegidas para la conservación de los depredadores tope.
... Oceanographic influences affect the movement patterns of larger migratory individuals, but these influences are less apparent for smaller, more resident sharks (Lea et al. 2018). In the Pacific Ocean, along the east coast of Australia, tiger sharks are found year-round at locations such as Raine Island on the northern Great Barrier Reef (Fitzpatrick et al. 2012), and the Chesterfield Islands in the Coral Sea region (Werry et al. 2014), but also make large-scale oceanic movements across the greater western Pacific region (Lipscombe et al. 2020). An optimal thermal regime centred around 22 °C has been proposed (Payne et al. 2018), and suggests that tiger shark dispersion and residency will change with ocean warming, as has been observed for other large coastal predators such as black marlin (Istiompax indica) and bull sharks (Carcharhinus leucas) in this region (Hill et al. 2016;Niella et al. 2020). ...
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Globally, marine animal distributions are shifting in response to a changing climate. These shifts are usually considered at the species level, but individuals are likely to differ in how they respond to the changing conditions. Here, we investigate how movement behaviour and, therefore, redistribution, would differ by sex and maturation class in a wide-ranging marine predator. We tracked 115 tiger sharks (Galeocerdo cuvier) from 2002 to 2020 and forecast class-specific distributions through to 2030, including environmental factors and predicted occurrence of potential prey. Generalised Linear and Additive Models revealed that water temperature change, particularly at higher latitudes, was the factor most associated with shark movements. Females dispersed southwards during periods of warming temperatures, and while juvenile females preferred a narrow thermal range between 22 and 23 °C, adult female and juvenile male presence was correlated with either lower (< 22 °C) or higher (> 23 °C) temperatures. During La Niña, sharks moved towards higher latitudes and used shallower isobaths. Inclusion of predicted distribution of their putative prey significantly improved projections of suitable habitats for all shark classes, compared to simpler models using temperature alone. Tiger shark range off the east coast of Australia is predicted to extend ~ 3.5° south towards the east coast of Tasmania, particularly for juvenile males. Our framework highlights the importance of combining long-term movement data with multi-factor habitat projections to identify heterogeneity within species when predicting consequences of climate change. Recognising intraspecific variability will improve conservation and management strategies and help anticipate broader ecosystem consequences of species redistribution due to ocean warming.
... Our analytical approach demonstrated that tiger sharks consistently followed a Brownian (near-random) search strategy with widespread, highly mobile movements throughout the coastal and pelagic waters of Florida's continental shelf and into the Gulf Stream. This is in agreement with various global studies describing tiger sharks as nomadic and highly migratory, although they are also known to have periods of resident behaviour in localized regions with high resource availability (Meyer et al. 2009, Werry et al. 2014, Acuña-Marrero et al. 2017. Considering the tiger shark trajectories analyzed in the present study demonstrated Brownian motion, this suggests these animals are moving in resource-rich habitats with abundant prey (Humphries et al. 2010, Sims et al. 2012). ...
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Animals follow specific movement patterns and search strategies to maximize encounters with essential resources (e.g. prey, favourable habitat) while minimizing exposures to suboptimal conditions (e.g. competitors, predators). While describing spatiotemporal patterns in animal movement from tracking data is common, understanding the associated search strategies employed continues to be a key challenge in ecology. Moreover, studies in marine ecology commonly focus on singular aspects of species' movements, however using multiple analytical approaches can further enable researchers to identify ecological phenomena and resolve fundamental ecological questions relating to movement. Here, we used a set of statistical physics-based methods to analyze satellite tracking data from three co-occurring apex predators (tiger, great hammerhead and bull sharks) that predominantly inhabit productive coastal regions of the northwest Atlantic Ocean and Gulf of Mexico. We analyzed data from 96 sharks and calculated a range of metrics, including each species' displacements, turning angles, dispersion, space-use and community-wide movement patterns to characterize each species' movements and identify potential search strategies. Our comprehensive approach revealed high interspecific variability in shark movement patterns and search strategies. Tiger sharks displayed near-random movements consistent with a Brownian strategy commonly associated with movements through resource-rich habitats. Great hammerheads showed a mixed-movement strategy including Brownian and resident-type movements, suggesting adaptation to widespread and localized high resource availability. Bull sharks followed a resident movement strategy with restricted movements indicating localized high resource availability. We hypothesize that the species-specific search strategies identified here may help foster the co-existence of these sympatric apex predators. Following this comprehensive approach provided novel insights into spatial ecology and assisted with identifying unique movement and search strategies. Similar future studies of animal movement will help characterize movement patterns and also enable the identification of search strategies to help elucidate the ecological drivers of movement and to understand species' responses to environmental change.
... Herein, our findings of 3 highly related tiger shark pairs (half-siblings or higher) from within the waters off Honolulu and Kaneohe Bay, are consistent with previous work indicating local reproduction within the Hawaiian archipelago (Whitney and Crow 2007;Papastamatiou et al. 2013;Meyer et al. 2018) and suggest some degree of site fidelity by these animals. These observations, along with the overall fairly high spatial residency displayed by these sharks around Hawaii suggest that tiger sharks inhabiting waters surrounding one of the earth's most remote archipelagos have the potential for demographic independence, despite some individuals in the Pacific demonstrating clear capacity for long-distance, offshore excursions (Holmes et al. 2014;Werry et al. 2014;Ferreira et al. 2015;Meyer et al. 2018). We also note that even though several studies have investigated tiger shark movements in Hawaii (e.g., Holland et al. 1999;Papastamatiou et al. 2013;Meyer et al. 2009Meyer et al. , 2010Meyer et al. , 2014Meyer et al. , 2018, to date, no tiger shark movements linking the Hawaiian archipelago to Australian or other coastal western Pacific waters have been observed. ...
Article
Understanding the population dynamics of highly mobile, widely distributed, oceanic sharks, many of which are overexploited, is necessary to aid their conservation management. We investigated the global population genomics of tiger sharks (Galeocerdo cuvier), a circumglobally distributed, apex predator displaying remarkable behavioral versatility in its diet, habitat use (near coastal, coral reef, pelagic), and individual movement patterns (spatially resident to long-distance migrations). We genotyped 242 tiger sharks from 10 globally distributed locations at more than 2000 single nucleotide polymorphisms. Although this species often conducts massive distance migrations, the data show strong genetic differentiation at both neutral (FST=0.125-0.144) and candidate outlier loci (FST=0.570-0.761) between western Atlantic and Indo-Pacific sharks, suggesting the potential for adaptation to the environments specific to these oceanic regions. Within these regions, there was mixed support for population differentiation between northern and southern hemispheres in the western Atlantic, and none for structure within the Indian Ocean. Notably, the results demonstrate a low level of population differentiation of tiger sharks from the remote Hawaiian archipelago compared to sharks from the Indian Ocean (FST=0.003-0.005, P<0.01). Given concerns about biodiversity loss and marine ecosystem impacts caused by overfishing of oceanic sharks in the midst of rapid environmental change, our results suggest it imperative that international fishery management prioritize conservation of the evolutionary potential of the highly genetically differentiated Atlantic and Indo-Pacific populations of this unique apex predator. Furthermore, we suggest targeted management attention to tiger sharks in the Hawaiian archipelago based on a precautionary biodiversity conservation perspective.
... In contrast, many cartilaginous fishes appear to have evolved an obligate multiennial reproductive cycle, which presumably maximizes their lifetime reproductive success. In highly migratory species with triennial reproductive cycles, such as the tiger shark G. cuvier (Whitney & Crow, 2006), future long-term tracking studies are likely to uncover robust triennial cycles of migration and philopatry in mature females, which have been postulated for tiger sharks off the Hawaiian Islands (Papastamatiou et al. 2013) and in the Coral Sea (Werry et al., 2014). In other threatened species, whose reproductive cycles have been described as biennial or triennial, such as the grey nurse shark Carcharias taurus (Bansemer & Bennett, 2009), sandbar shark Carcharhinus plumbeus (Baremore & Hale, 2012) and several species of mobulid rays Mobula spp. ...
Article
Globally, one quarter of shark and ray species are threatened with extinction due to overfishing. Effective conservation and management can facilitate population recoveries. However, these efforts depend on robust data on movement patterns and stock structure, which are lacking for many threatened species, including the Critically Endangered soupfin shark Galeorhinus galeus, a circumglobal coastal‐pelagic species. Using passive acoustic telemetry, we continuously tracked 34 mature female soupfin sharks, surgically implanted with coded acoustic transmitters, for 7 years via 337 underwater acoustic receivers stationed along the west coast of North America. These sharks and an additional six were also externally fitted with spaghetti identification tags. Our tagging site was a shallow rocky reef off La Jolla (San Diego County), California, USA, where adult females were observed to aggregate every summer. Tagged soupfin sharks were highly migratory along the west coast of North America, between Washington, USA and Baja California Sur, Mexico. However, every 3 years, they returned to waters off La Jolla, California, where they underwent gestation. This is the first conclusive evidence of triennial migration and philopatry (‘home‐loving’) in any animal, which is apparently driven by this species’ unusual triennial reproductive cycle. Females of other shark and ray species with triennial reproductive cycles are also likely to exhibit triennial cycles of migration and philopatry. At least six (15%) of our tagged soupfin sharks were killed in commercial gillnets in Mexico. Policy implications. Identifying multiennial migratory cycles in mature female sharks can reveal hidden stock structure in the form of discrete breeding cohorts, which are spatially and temporally segregated as they cycle through different reproductive phases. Accounting for this complexity may improve the performance of spatially structured stock assessment models, particularly when fishery removals are spatially heterogeneous, as well as inform the spatiotemporal design of fishery‐independent surveys. In the United States, the soupfin shark is neither actively managed nor recognized as a Highly Migratory Species; however, given the highly migratory behaviour we report, this designation should be revisited by the US Pacific Fishery Management Council. Finally, given the extensive fishery removals in Mexico, any future management must be internationally cooperative. Identifying multiennial migratory cycles in mature female sharks can reveal hidden stock structure in the form of discrete breeding cohorts, which are spatially and temporally segregated as they cycle through different reproductive phases. Accounting for this complexity may improve the performance of spatially structured stock assessment models, particularly when fishery removals are spatially heterogeneous, as well as inform the spatiotemporal design of fishery‐independent surveys. In the United States, the soupfin shark is neither actively managed nor recognized as a Highly Migratory Species; however, given the highly migratory behaviour we report, this designation should be revisited by the US Pacific Fishery Management Council. Finally, given the extensive fishery removals in Mexico, any future management must be internationally cooperative. Photo credit: T. Snodgrass.
... P. glauca is an abundant species, with a wide distribution in all temperate and tropical oceans (Megalofonou et al. 2005;Ebert et al. 2013). The blue shark's distribution is influenced by seasonal variations in water temperature, reproductive cycle, and availability of food resources (Kohler et al. 2002;Werry et al. 2014). Recently, its distribution range was determined to be between 62°N and 54°S (Coelho et al. 2017), expanding the previous distribution (60°N, and 50°S) (Last and Stevens 2009;Mejuto et al. 2014). ...
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The blue shark (Prionace glauca) is a large predator in marine ecosystems, figuring as the most common and abundant species in oceanic fisheries. For this reason, many studies on this species were conducted throughout its entire distribution range. However, no comparison has been made regarding the variability of the aspects addressed herein. Thus, the present study aims at analyzing the available information on P. glauca. This species constitutes between 85 and 90% of the total elasmobranchs caught by oceanic fisheries with pelagic longlines. Growth parameters reveal that individuals in the Atlantic Ocean show the highest asymptotic lengths when compared to those found in other oceans. Females present an average uterine fecundity of 30 embryos. Although it shows a diverse diet, it is mainly composed of teleost fish and cephalopods. Currently, the main threat to the species is commercial fishing, being listed in Brazil and worldwide, according to IUCN as Near Threatened. Regardless, information on crucial aspects, such as its population dynamics, are still scarce or unreliable for many areas. Despite the number of studies regarding its distribution, abundance, and biology, data for new stock assessments of P. glauca are still needed to improve the species' management.
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Background. The tiger shark ( Galeocerdo cuvier ) is a large iconic marine predator inhabiting worldwide tropical and subtropical waters. So far, only mitochondrial markers and microsatellites studies have investigated its worldwide historical demography with inconclusive outcomes. Here, we assessed for the first time the genomic variability of tiger shark by Rad-sequencing 50 individuals from five sampling sites in the Indo-Pacific (IP) and one in the Atlantic Ocean (AO) to decipher the extent of the global connectivity and its demographic history. Results. Clustering algorithm, F ST and an approximate Bayesian computation framework revealed the presence of two clusters corresponding to the two oceanic basins. By modelling the two-dimensional site frequency spectrum, we tested alternative isolation/migration scenarios between these two populations. We found the highest support for a divergence time of ~193,000 years before present (B.P) and an ongoing but limited asymmetric migration ~176 times larger from the IP to the AO ( Nm ~3.9) than vice versa ( Nm ~0.02). Conclusions. The two oceanic regions are isolated by a strong barrier to dispersal more permeable from the IP to the AO through the Agulhas leakage. We finally emphasized contrasting recent demographic histories for the two regions, with the IP characterized by a recent bottleneck around 2,000 years B.P. and the AO by an expansion starting 6,000 years B.P. The large differentiation between the two oceanic regions and the absence of population structure within highlight the existence of two large management units and call for future conservation programs at the oceanic rather than local scale, particularly in the Indo-Pacific where the population is declining.
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Ongoing declines in production of the world's fisheries may have serious ecological and socioeconomic consequences. As a result, a number of international efforts have sought to improve management and prevent overexploitation, while helping to maintain biodiversity and a sustainable food supply. Although these initiatives have received broad acceptance, the extent to which corrective measures have been implemented and are effective remains largely unknown. We used a survey approach, validated with empirical data, and enquiries to over 13,000 fisheries experts (of which 1,188 responded) to assess the current effectiveness of fisheries management regimes worldwide; for each of those regimes, we also calculated the probable sustainability of reported catches to determine how management affects fisheries sustainability. Our survey shows that 7% of all coastal states undergo rigorous scientific assessment for the generation of management policies, 1.4% also have a participatory and transparent processes to convert scientific recommendations into policy, and 0.95% also provide for robust mechanisms to ensure the compliance with regulations; none is also free of the effects of excess fishing capacity, subsidies, or access to foreign fishing. A comparison of fisheries management attributes with the sustainability of reported fisheries catches indicated that the conversion of scientific advice into policy, through a participatory and transparent process, is at the core of achieving fisheries sustainability, regardless of other attributes of the fisheries. Our results illustrate the great vulnerability of the world's fisheries and the urgent need to meet well-identified guidelines for sustainable management; they also provide a baseline against which future changes can be quantified.
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The Northwestern Hawaiian Islands (NWHI) host a variety of large vertebrate animals including seabirds, green sea turtles (Chelonia mydas), Hawaiian monk seals (Monanchus schauislandi), and large teleost fish such as trevally (Family Carangidae) and several species of sharks. The air-breathing vertebrates have been the subjects of relatively continuous and well-funded research programs over the past several decades, and many aspects of their biology in the NWHI have been documented fairly well. However, studies directed at understanding the biology and ecology of large teleost fishes and sharks in the NWHI have lagged substantially behind research conducted on birds, turtles and seals. In the summer of 2000, an array of autonomous acoustic receivers was deployed at French Frigate Shoals (FFS) in the NWHI as part of a project investigating the movement patterns of tiger sharks (Galeocerdo cuvier) within the atoll, particularly in relation to the high seasonal abundance of potential prey (birds, turtles, seals). Shortly after the establishment of the initial array of monitors in 2000, additional monitors were deployed in an effort to monitor the movements of Galapagos sharks (Carcharhinus galapagensis) at FFS, particularly at locations where monk seal pups had been preyed upon by these sharks. The scope of the monitoring study was further expanded to Midway Atoll during summer of 2001 to monitor movements of Galapagos sharks near seal haul-out beaches and to examine survivorship and behavior of giant trevally (Caranx ignobilis) captured and released in a commercial sport fishing operation conducted within the Midway National Wildlife Refuge. For each study, experimental animals were captured and surgically fitted with long-life, individually-coded acoustic transmitters. During nearly 4 years of acoustic monitoring at FFS and 2 years of monitoring at Midway, a total of over 45,000 detections of sharks and fish with transmitters were recorded on acoustic monitors. These data enable an assessment of long-term movement patterns of these large predators within the NWHI. Each species investigated demonstrated somewhat repeated and predictable behavioral patterns that provide a basis for improved understanding of determinants of behavior and for enhanced management of these animals and prey (birds, seals, turtles) with which they may interact.
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The presence of numerous seamounts in the world's oceans, especially in the Pacific, has only become known to the scientific community in the last 50 years. This chapter deals with the current knowledge on the effects of seamounts on pelagic ecosystems, factors that influence the structure of seamount communities, the establishment, maintenance and genetic isolation of populations on seamounts and on the effects of commercial exploitation on seamounts organisms. The reviews, addresses in the chapter, cover aspects of the biology of seamounts especially those in Keating et al., but this literature has had limited circulation amongst biologists. Moreover, this chapter also throws attention on seamounts especially in respect to the current topography interactions, the biology of the soft benthos on seamounts and on the biology of commercially valuable species of fish associated with seamounts. Finally, the combination of this new data with that obtained in previous studies provides a complete picture of the current knowledge of the biology of seamounts, which can be of use to marine biologists, fisheries biologists and oceanographers.
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Many pelagic fishes exhibit 'yo-yo' diving behavior, which may serve several possible functions, including energy conservation, prey searching and navigation. We deployed accelerometers and digital still cameras on 4 free-ranging tiger sharks Galeocerdo cuvier, to test whether their vertical movements are most consistent with energy conservation or prey searching. All sharks swam continuously, with frequent vertical movements through the water column at mean swimming speeds of 0.5 to 0.9 m s(-1). Tail-beating was continuous except for sporadic, powerless gliding during descents (from 0 to 18% of total descent time). At a given tailbeat frequency, swimming speeds were lower during ascent than descent (consistent with negative buoyancy). Burst swimming events, which might represent prey pursuits, were observed during all phases of vertical movements. Camera images showed a variety of potential prey and the possible capture of a unicornfish. Collectively, results suggest that yo-yo diving by tiger sharks is not primarily for energy conservation, but probably represents an effective search strategy for locating prey throughout the water column.
Article
The E Australian Megaptera novaeangliae stock severely depleted by 1962, is now recovering at 9.7% per annum. The stock disperses in the sheltered waters of the Great Barrier Reef to breed although some calving occurs at higher latitudes. -from Author
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Methods to calculate an animal’s position from light-level data collected by archival tags (geolocation by light levels) have been employed by wildlife researchers and the engineers who design the tags for over a decade. The problem of estimating longitude proved easy to solve, but accurate latitude estimates remain elusive. This paper addresses the absolute accuracy in estimating latitude (as defined by physical constraints) that is achievable using the astronomical equations and offers a new approach to minimize the variability of latitude estimations.
Article
Growth parameter estimates were calculated for the tiger shark (Galeocerdo cuvier) by using tag and recapture data. Results were compared to published estimates based on bands in vertebrae. The von Bertalanffy parameters (sexes combined) based on tag and recapture growth data were as follows: L(∞) = 337 cm fork length, k = 0.178, and t0 = -1.12. Monthly length-frequency data for six year classes from birth to two years old for tiger sharks were used to verify the tag-recapture growth curve for this age range. The predicted age at maturity is 7 years for both sexes. Data from an ongoing in situ study with oxytetracycline were used in conjunction with length data to determine the effect of tagging and oxytetracycline injection on growth. The data suggest that tagging alone or tagging combined with oxytetracycline injection has little or no effect on the growth rate of tiger sharks up to two years of age.
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The humpback whale stock that migrates along the east Australian coast comprises part of the Area V (130°E-170°W) stock and was monitored by shore-based observations from Point Lookout (27°26'S, 153°33'E) during 1978-1999. Devastated by whaling which ceased in 1962, the stock is estimated to be recovering at a rate of 10.9% per annum (99% CI ± 1%) and to number 3,600 ± 440 in 1999. Advantages and limitations of the Point Lookout observation methods are discussed.
Article
Knowledge of migratory movements and depth/temperature-related use of coastal waters by sharks can lead to more sustainable fisheries and assist in managing the long-term conservation of those species now considered threatened. Pop-up archival satellite tags (PATs) provide an alternative to conventional tagging for documenting migratory movements. This study focussed on the migratory movements of Carcharias taurus, a critically endangered shark found along the east coast of Australia. From October 2003 to July 2008, 15 C. taurus individuals were tagged with PATs with varying deployments (60-150 days) and acoustic tags linked to an acoustic monitoring system providing accurate geo-location. Distances moved by C. taurus individuals ranged from 5 to 1550 km and varied according to sex and season. Migrations north and south were punctuated en route by occupation of sites for varying periods of time. The deepest depth recorded was 232 m off South West Rocks on the New South Wales mid-north coast. On average, C. taurus males and females spent at least 71% of their time in waters <40 m and 95% of their time in waters 17-248 degrees C. By mainly occupying inshore waters, C. taurus is exposed to potentially adverse fishing-related interactions that may be difficult to mitigate.