Reef Sharks at Risk from Climate Change
Reef-Living Sharks May Suffer From Changes Caused By Global Warming
Apr 1, 2009
Researchers from Charles Darwin University, the Australian Institute of Marine Science, the University of Adelaide and CSIRO, have been tagging sharks with electronic sensors to track their movements off the Western Australian coast.
The reef sharks are being tracked by the Australian Acoustic Tagging and Monitoring System (AATAMS) which have set up permanent acoustic receivers at strategic points on the 280 kilometre-long reef. The receivers collect acoustic data from transmitters either implanted in the sharks or attached as tags.
Acoustic monitoring is a powerful tool for observing tagged marine animals using networks or arrays of receivers.
A series of acoustic receivers can be left on the sea floor for up to seven years with the ability to upload data as often as needed.
Patterns of Shark Habitat Use Studied
Conrad Speed, a Charles Darwin University PhD candidate attached to the Arafura Timor Research Facility has been studying groups of sharks, using the AATAMS equipment.
Speed is investigating the movement patterns and feeding ecology of black tip (Carcharhinus melanopterus), white tip (Triaenodon obesus), grey reef (Carcharhinus amblyrhynchos), as well as monitoring juvenile lemon sharks (Negaprion acutidens) and nervous sharks (Carcharhinus cautus).
He said variations in oceanographic conditions will result from climate change, and this could affect the sharks’ ability to hunt and feed.
“Shifting current patterns, rising sea levels and increasing temperatures could all affect the availability of prey and suitable habitat for shark populations.”
Tracking the sharks will provide a basis for predicting their adaptability over longer time scales.
“Long term patterns of habitat use and dispersal will help manage the populations in areas where sharks are vulnerable to habitat degradation due to climate change.”
Juvenile Reef Sharks Behave Differently from Adults
As well as overall acoustic scanning of the sharks, Speed actively tracked a number of tagged black tip reef sharks.
This was to help answer the question of why reef sharks aggregate in inshore areas and how these sharks move and use their habitat.
He found that juvenile and adult black tip sharks visit the same inshore areas, where the reef is close to the WA coastline, but they travelled there at different times.
Sharks have also been found to travel great distances, crossing the borders of marine parks.
“The distances the sharks travel have implications for management and protection of the reef sharks at Ningaloo,” he said.
At least one tagged shark has caught by a recreational fisher outside the park border.
Speed presented the initial results of the reef shark tagging program at GREENHOUSE 2009 environmental conference in Perth during March.
The next stage of his project will look at the feeding habits of sharks at Ningaloo Reef.
“I will use fatty acid profiles and stable isotope ratios to examine the diet of reef sharks to establish the trophic role of these sharks within the reef community,” he said.
Not Only Sharks Vulnerable To Climate Change
As well as many species of sharks, including the whale shark, Ningaloo reef supports 500 species of fish, 300 species of corals, 600 species of molluscs and many other marine invertebrates.
The beaches are important breeding grounds for loggerhead, green and hawksbill turtles, and in winter, the reef is part of the migratory routes for dolphins, dugongs, manta rays and humpback whales.
This abundance of life will be affected by rising sea temperatures and changes in sea levels and currents, but researchers do not yet know what the effects will be or how much animals’ life cycles will be disrupted.
See Also: 100 New Sharks and Rays Named
Carbon Dioxide (CO2) Increase Killing Corals
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