Pelagic fishes and sharks occupy surface waters from the coast to the open ocean.
There are ~260 pelagic species around Australia. While some of the most well known
are the large offshore apex predators such as tunas, billfish and sharks, the midtrophic level small pelagic species, such as sardines, anchovies, and squids, are
critical to ecosystem function.
In Australia, both small and large pelagic species have
high ecological, economic and social value. Observed impacts of climate change are
restricted to changes in local abundance and distribution, particularly southward range
extensions.
Little is known regarding changes in phenology, physiology or
community structure. In future, general ocean warming around Australia and in
particular on the east coast, in combination with predicted strengthening of the East
Australian Current, is likely to see the distribution of a range of pelagic species extend
southwards from present limits.
Recent years have seen a number of reports of fish
detected south of their typical range limits on the east coast. On the west coast,
changes in the strength of the Leeuwin Current are likely to have major implications
for the distribution and abundance of some species, including western Australian
salmon and Australian herring in waters off South Australia.
Recent extreme events
on the west coast have also seen pelagic species reported far to the south of their
normal distribution.
Changes in productivity, for example due to increased coastal
upwelling, may lead to increases in abundance of some species, particularly of small
coastal pelagic fishes, such as sardines and anchovy, in the upwelling system between
Cape Otway and the central Great Australian Bight. Confidence in observed impacts
is generally low to medium as observed changes are limited. Similarly, confidence in
future impacts is also generally low to medium, as lack of data on observed impacts
makes prediction difficult.
Impacts on sharks are poorly known compared to teleost
fishes.
Overall, impacts in southern Australia are more commonly reported than in
northern Australia. Knowledge gaps include an absence of information on species
habitat tolerances and methods to detect changes. Recent efforts to develop empirical
models for future prediction of species ranges and potential abundance changes are in
agreement with earlier projections (Report Card 2009).
The adaptation potential is
high for many species because of significant opportunity for large-scale movements of
most pelagic species, and thus the main impacts are likely to be localized changes in
the composition of pelagic fish community. The impact of such changes in Pelagic Fishes and Sharks
community composition is unknown.
To address knowledge gaps, focused regional
studies on the relationship between climate variables and the distribution and
abundance of species of high interest are one way to improve understanding of the
potential impacts of climate change. Predictive modelling at appropriate scales is also
reliant on downscaled climate models, which can generate a range of environmental
variables at the scale of individual fish movements.
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Further ReadingYou can view the full report by clicking here. |
