Download Report Here

Expedition Report - Flag #212
Expedition #22: The Migration and Movement Behavior of Tiger
Sharks in Western Australia
Tiger sharks are apex predators throughout many tropical and warm-temperate marine
ecosystems. However, we still lack the essential information on the ecology of these
sharks needed to understand and manage the consequences of human impacts on their
populations. Globally, fisheries are thought to provide the largest threat to populations of
tiger sharks. Some commercial fisheries target tiger sharks, but they are also caught as
by-catch and in illegal, unreported and unregulated (IUU) fishing. Due to the important
role these large sharks play as apex predators in the structuring of marine ecosystems and
in the connectivity between distinct habitats, the removal of tiger sharks might generate
widespread impacts at different locations throughout their range. For this reason, the
description of migration and residency patterns of these animals has direct implications
for understanding their ecological roles in coastal and open ocean food webs. The
development of an understanding of the drivers of these movements is also essential for
identifying critical habitats for the species and for defining the appropriate spatial scale at
which management plans should be implemented. An understanding of spatial ecology and how it relates to the size, sex, maturity and
feeding behavior of individuals throughout home range of tiger sharks provides
information that can be directly applied to strategies to minimize the risk of shark bites
on humans. For example, the Shark Monitoring Program in Brazil used tracking data to
describe and understand tiger shark movements off the northeastern coast. This work
identified areas of highest risk and educated swimmers both about appropriate behaviors
to minimize the chances of shark bite and the importance of these animals to marine
ecosystems.
Such science-based mitigation programs require detailed information on the movement
and residency patterns, habitat use and foraging behavior of sharks. By combining a
large-scale study of movement patterns and diet analysis of tiger sharks, we will be able
to provide essential information that can be incorporated into the Western Australia
mitigation program to reduce the risk of shark bites with minimum impact to the
environment.
A 15-year study at Shark Bay represents the only long term monitoring of tiger sharks in
Western Australia. That work has reported high, though seasonally variable, abundances
of tiger sharks in that area when compared to other locations on the coast. The same
study has also shown that tiger sharks regularly use the shallower habitats and are a major
force driving the behavior and influencing the structure of the prey community of the sea
grass environment of Shark Bay. This study supports the importance of the Shark Bay
Marine Reserve for the species and how the conservation of that habitat must receive
special attention in management plans for the species.
Our goal is to take a multi-disciplinary approach to describe movement behavior,
migration pathways and the drivers of movement and residency patterns of tiger sharks
across the north and western coasts of Australia. This information can inform and
prioritize policy for the management and conservation of tiger sharks in Australia.
Building on existing work, gaps and needs, the key objective of this expedition is to
generate data that can be used to understand what these sharks are doing in each stage of
their life cycle and in different locations. Stable isotopes will indicate diet through time
and space and tagging will help us define the role tiger sharks play in the connectivity of
different habitats throughout their range. The combination of both methods will help
describe foraging and migrating behaviors and their implications for residency and the
determination of important habitats for conservation. As we will target animals varying in
size and sex for sampling, this information will be obtained for the species at varying life
history stages. Combined, these data will help us understand the impact of human
activities on the population of an iconic and threatened top predator, and provide insights
into the consequences of their removal to health of marine ecosystems. Specifically,
describing the size and sex-specific movement, diet patterns, reproductive state and
genetic structure of tiger sharks tagged in different areas of the Western Australian coast
will allow us to:
-
Effectively assess the degree of protection offered by marine reserves to tiger
sharks on the west coast of Australia.
-
Define migration pathways and connectivity between different habitats across
their range.
-
Identify areas of high use that may be granted special attention for the
management and conservation of tiger shark populations.
We had planned to tag tiger sharks along the Western Australian coast in key locations
which included: Jurien Bay Marine Park, the Abrolhos Islands, Shark Bay Marine Park,
Ningaloo Marine Park and Rowley Shoals Marine Park (Figure 1). We began the
expedition at Ningaloo Marine Park. Due to the number of tiger sharks we encountered,
we exhausted the number of tags we had ready, causing us to only tag at Ningaloo
Marine Park.
Figure 1) Key research sites include Jurien Bay, Abrolhos Islands, Shark Bay, Ningaloo Park and Rowkey Shoals
OCEARCH assembled a large team of scientists/researchers and fishermen to catch and
tag sharks and release them safely. In addition to the 6 OCEARCH crew, a team of
scientists, led by Dr. Mark Meekan conducted 15-min research studies on each of the
sharks caught.
Dr. Mark Meekan is a Principal Research Scientist with the Australian Institute of Marine
Science and is based in Perth, Western Australia. He is a tropical fish ecologist and a
major part of his research portfolio examines the ecosystem role and ecology of
elasmobranchs, with a specialist focus on whale sharks. In Australia, he is a committee
member of the Australian Animal Tagging and Monitoring System (AATAMS), a project
that funds and maintains networks of sensors for tracking of marine animals around the
Australian coastline. He currently supervises post-doctoral fellows and PhD students on
working shark and reef fish projects throughout the Indian and Pacific Oceans.
Jessica Meeuwig is the Director of the Centre for Marine Futures and a Professor in the
School of Animal Biology, University of Western Australia. Her main expertise is marine
and fisheries conservation and quantitative modeling. As a modeler, her focus is on
quantifying how species respond to their environment and to human pressures. Recent
work relevant to this application focuses on modeling habitat use by sharks and
humpback whales as well as quantifying the impacts of fishing on sharks. Jessica has
conducted research in the Caribbean, North Atlantic, Baltic Sea, Philippines, Vietnam,
Western Pacific, British Indian Ocean and Australia over nearly 25 years. She has an
interdisciplinary Master’s degree in environmental policy from Dalhousie University,
Halifax, Canada (which helps her translate science into policy outcomes), and a PhD with
Distinction from McGill University, Montreal, Canada. Jessica is also a Conservation
Fellow of the Zoological Society of London.
Dr. Randall Davis is Regents Professor in the Department of Marine Biology and of
Wildlife and Fisheries Science at Texas A&M University at Galveston. He has studied
the behavior, physiology and energetics of marine mammals and birds since 1976,
including numerous field studies on six continents in polar, temperate and tropical marine
ecosystems. He pioneered the development and use of animal-borne instruments (video
and data recorders) that combine video with multiple channels of data (three-dimensional
movement, locomotory performance and oceanographic) to improve our understanding of
the behavior and ecology of marine mammals (pinnipeds and cetaceans), birds (penguins)
and large fishes (whale shark) and their habitat at sea.
Luciana Ferreira is a marine biology PhD candidate at the University of Western
Australia, under the supervision of Professor Jessica Meeuwig and Dr. Mark Meekan
from the Australian Institute of Marine Science. Her research is based on tiger shark
tracking data to determine movement patterns for the species on cross-shelf and ocean
basin scales, the influence of biological and environmental drivers on their spatial
ecology, migratory pathways and connectivity among different locations. She also
worked for Professor Fabio Hazin in Recife, Brazil, contributing to several studies on
shark ecology and marine biology in Brazil, such as the Shark Monitoring Program off
Recife.
Robert Nowicki is a biology PhD candidate at Florida International University in Miami,
working with shark ecologist Dr. Mike Heithaus. Rob's research interests revolve around
the "ecology of fear"- how apex predators like tiger sharks shape ecosystems through
generating risk and changing the behavior of their prey. For the past several years Rob
has been doing fieldwork in Shark Bay, Western Australia to determine how tiger sharks
structure sea grass ecosystems that have been degraded. This research involves figuring
out where tiger sharks go, what they eat, how they interact with their prey, and how these
interactions have changed as the sea grass has been lost. This research may help inform
what functions tiger sharks play in ecosystems degraded by humans, and what will
happen if large sharks continue to be over-exploited.
Kristen McGovern is a Doctoral student at Texas A&M University where she studies the
behavioral ecology of marine animals using animal-borne video and data recorders
(VDRs) that monitor three-dimensional movements, performance and habitat
associations.
Charlotte Birkmanis is a marine biologist with a special interest in shark behavior and
conservation. She is currently a marine ecology PhD candidate at the University of
Western Australia working with Professor Jessica Meeuwig of the School of Animal
Biology and Dr. Mark Meekan of the Australian Institute of Marine Science. Charlotte’s
research in shark ecology, behavior and genetics focuses on the role of sharks as
regulators of coral reef ecosystems across the Indian Ocean. This research involves
studying a variety of shark species and their prey to discover the implications of reduced
shark populations in our oceans, and to determine the relative health of coral reef
communities in the Indian Ocean. Charlotte attained a Bachelor of Science with
distinction in ecology and a Bachelor of Arts in mandarin from Queensland University of
Technology. Following on from this her research on shark and ray biomechanics earned
her a Bachelor of Science (Honors I) degree from the University of Queensland.
Charlotte’s research will combine her passion for sharks and previous research as a
consultant marine ecologist in Australia, the Pacific Region and Asia to highlight the
importance of sharks in our oceans.
Clark Morgan graduated from Florida State University in 2014 after spending 3 years
working in shark biologist Dr. Dean Grubbs' laboratory as an undergraduate research
assistant, primarily studying shark population demographics in the Gulf of Mexico and
physiological stress responses to long line capture in the Bahamas. Shortly after
graduation, Clark traveled to Australia in the name of shark science and adventure,
starting in Shark Bay. Clark has spent 5 months total working as a research assistant for
Florida International University's Dr. Mike Heithaus' Shark Bay Ecosystem Research
Project focusing on understanding how tiger sharks impact the recovery of degraded
ecosystems. He has spent 6 weeks studying social aggregations and movement patterns of
Port Jackson sharks in Jervis Bay, NSW and is currently assisting with great white
research as a dive master with Rodney Fox Shark Expeditions in Port Lincoln, SA. Upon
his return to the states in August, Clark will begin pursuing his Masters of Science in
Biology under OCEARCH collaborator Dr. Jim Gelsleichter at the University of North
Florida
Christopher Thompson is a marine biologist based in Perth, Western Australia who
currently works deploying and analyzing footage from baited remote underwater video
systems (BRUVS). This involves deploying both mid-water and benthic rigs in the field,
as well as reviewing the footage to provide fish identifications, counts and measurements.
This allows a range of facets of the fish populations present to be investigated. Most
recently he was involved in a pelagic expedition to the Chagos Archipelago collecting
data on mid-water fish communities. He completed his Bachelors majoring in Marine
Biology and Zoology at the University of Western Australia in 2012, including a sixmonth exchange with the University of Vermont. He then completed an Honors project
investigating the behavior of a number of shark species in the Chagos Archipelago using
footage from BRUVS collected on an expedition in 2012. Throughout these studies and
in voluntary positions Chris has been involved in a number of other projects around
Western Australia including tagging juvenile sharks in Exmouth; investigating coral,
butterfly fish, rock lobster and intertidal invertebrate populations at Rottnest Island and
monitoring intertidal mollusk communities in Princess Royal Harbour, Albany.
Frazer McGregor is a postgraduate student at Murdoch University under the supervision
of Dr. Mike van Keulen. His doctoral research on the trophic ecology of manta rays at
Ningaloo Reef aims at defining their population status, foraging ecology, movements and
behaviors.
We tagged tiger sharks and collected tissue samples for analyses of diet, genetics and
reproductive state (hormones) in different locations throughout the coast of Western
Australia. This sampling will allow us to characterize movement and feeding ecology
patterns and population structure of tiger sharks and define areas of high use for feeding
and reproduction, as well as to define the relationship between diet, movement and the
environment in which these sharks move. The combination of movement and biological
data represents a significant opportunity to address the following scientific objectives:
1. Describe the large-scale movement patterns and the influence of biological and
environmental drivers on the spatial ecology of tiger sharks using high-resolution
satellite telemetry.
2. Define residency and site fidelity of tiger sharks in coastal waters of Western
Australia.
3. Identify patterns of dietary specialization of tiger shark across ecosystems in
Western Australia.
4. Determine reproductive state of females through hormonal analysis to identify
important habitats for the reproductive cycle of tiger sharks
5. Assess the implications of spatial variation in diet and movement patterns for the
management and conservation of the species in Western Australia.
6. Define population structure and connectivity of tiger sharks in Australia.
Tiger sharks were tagged with both satellite and acoustic transmitters and samples of
muscle, blood and fin clips were taken for dietary, hormonal and genetics studies. Sharks
were caught from tenders by the OCEARCH team using handlines with baited circle
hooks (size 12/0, 14/0 and 18/0). The size specification of hooks is consistent with the
methodology used in long-standing tiger shark tagging programs in Australia, Brazil and
USA. Circle hooks will be used as they also reduce harm to animals when captured by
minimizing the risk of internal injury. After capture, sharks will be brought to the
submerged platform of the M/V OCEARCH vessel and the platform will be raised.
Once the sharks were restrained, they were measured, satellite and acoustic tags were
attached and tissues (blood and muscle sample and fin clip) were collected. Fin clips
were removed with a pair of scissors. They will be used for genetic analysis and are being
kept in 95% ethanol. A small sample (0.5 cm2 or 3g) of white dorsal muscle was
collected using a 8mm biopsy punch, about 5 cm lateral to the first dorsal fin.
Blood was collected with an 18-cauge needle from the caudal vein. Muscle samples for
stable isotope and fatty acids analysis will be stored in liquid nitrogen after collection.
Blood was placed into collection vials with no additives or interior coating and separated
into components (red cells and plasma) using a portable centrifuge. Both blood
components were then frozen for isotope and hormonal analysis.
At sites that are too shallow for the main vessel (inside reef lagoons) and/or when
weather conditions do not allow use of the main vessel, all procedures were completed
from a tender. In these cases, sharks were kept in water by restraining them alongside the
tender using a hook line and a tail rope.
SPOT tags were mounted on the shark’s dorsal fin using screws made of corrodible
material that allow the tag to fall off after battery exhaustion (maximum 2 years). This
procedure is standard but is also mandatory, as the tag’s antenna must remain out of the
water when the shark is on the surface to transmit data. These tags are unlikely to cause
long term damage on the shark’s dorsal if attached for 24 months or less (Jewell et al.
2011). V16 (Vemco) acoustic tags were used for the long term acoustic monitoring of
tiger sharks (~10 years). Acoustic tags were implanted internally on sharks though an
incision made approximately 3 cm in front of the cloaca along the centerline of the
abdomen. The tag was inserted and the incision was closed with surgical sutures
(approximately 3 stitches). This procedure follows established practice in acoustic
telemetry studies of sharks.
The team was able to tag 20 tiger sharks in only 11 days – a record for OCEARCH. We
are currently following the patterns of these sharks so we can learn more about their
migratory behaviors.
Whenever possible, other sharks and mesopredators were fished, sampled and released, in
addition to tiger sharks. Fin clips and muscle samples of reef sharks caught as bycatch
(grey reef Carcharhinus amblyrhynchos, silver tip C. albimarginatus, black tip C.
limbatus, and lemon shark Negaprion acutidens) and mesopredator fish species (Lutjanus
bohar, L. decussatus, L. gibbus, L. kasmira) were collected in order to be analyzed for
genetics and stable isotopes.
Reports are currently being written by scientists and researchers involved with the
expedition. These outcomes will be publicized in a series of scientific publications in the
peer-reviewed literature as well as popular articles and other media for the general public.