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Information on the diet and foraging patterns of white sharks in Australia
is limited, especially for Eastern Australia and New South Wales (NSW).
Apex predators, such as white sharks often pose significant management challenges which
arise due to a combination of factors including; 1) their populations are often
under pressure from human activities, 2) they have a propensity for
involvement in conflicts with humans, necessitating strategies to manage these
conflicts, and 3) there is often a scarcity of data on aspects of their ecology that
are relevant for their management.
White sharks are listed as vulnerable by the
International Union for Conservation of Nature and are protected across much of
their range, including Australia. Concurrently, white sharks are also the primary
species of shark responsible for bites on humans in Australian waters. Despite
this, information on the diet and foraging patterns of white sharks in Australia
is limited, especially for Eastern Australia and New South Wales (NSW). Understanding
more about diet, prey selection and the foraging patterns of white sharks is
critical if we are to gain insights into broader aspects of their ecology, such
as potential drivers behind their movement patterns (Huveneers et al., 2018), and subsequently their
interactions with humans.
Therefore, the goal of this project is to investigate the
foraging ecology of white sharks in NSW and examine the role of nutrition in
prey selection by this apex marine predator. To do this, a range of complementary
techniques are being used to address the following aims:
In addition to nutritional analyses, the stable isotope
signatures of prey items are also being investigated and combined with isotopic
measurements of shark tissues. Stable isotopes are advantageous because they provide
a time-averaged dietary signal and, when applied to tissues that are formed
sequentially throughout the life of the shark (e.g. calcified tissues), can be
used to examine foraging profiles at the individual level. Here, an isotopic
approach is being employed to investigate potential variation in dietary inputs
and foraging habitat use among individual white sharks (i.e. individual-level
specialisation in foraging patterns).
Shark-Management-Alert-In-Real-Time (SMART) drumlines are a promising
new, non-lethal technology for shark bite mitigation which are used to catch,
tag, relocate and release sharks. This technology is currently being trialled
as part of the NSW Government’s Shark Management Strategy, however there is a
need to better quantify what sharks do immediately following release. Custom-built
animal-borne “SharkCams”, comprising a video camera and other integrated data
loggers, are being deployed on white sharks released from SMART drumlines to investigate
their post-release behavioural responses, including potential foraging
activities. This information will be highly valuable for better understanding
the utility of SMART drumlines for non-lethal shark bite mitigation.
The new information on the diet, foraging patterns and
behaviours of white sharks provided by this project is intended to help inform
future decisions for the management of this species in NSW, including
strategies for bather protection.
This study is led by Richard Grainger from the University of
Sydney, with supervision from Prof. David Raubenheimer (USYD), Dr. Gabriel
Machovsky-Capuska (USYD) and Dr. Vic Peddemors (NSW DPI Fisheries). The project
is being run in collaboration with the NSW Department of Primary Industries
Fisheries, with funding support from the NSW Shark Management Strategy.