June 2005
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Future of shy dolphins in human hands
A CRC Reef research project has provided new insight into the ecology of the elusive Irrawaddy and Indo-Pacific humpback dolphins. These two species of dolphins are known to frequent coastal waters throughout the Indo- Pacific and often occur in areas of high human population densities. Due to their coastal distribution, these marine mammals are particularly vulnerable to the effects of human activities such as boating, fishing, pollution, and other environmental impacts associated with coastal zone development. Both the Irrawaddy dolphin and the humpback dolphin are listed as endangered species by the World Conservation Union. Despite living close to people, they are rarely sighted by ocean-goers and little is known about their ecology. “These dolphins tend to be very shy and have a low profile when they come out of the water, so if you aren’t looking for them, you probably won’t see them,” says CRC Reef researcher Mr Guido Parra. Guido found that Irrawaddy and humpback dolphins in the Townsville region occur in surprisingly small populations. Fewer than 100 individuals of each species were found in Cleveland Bay. The dolphins tend to congregate around river mouths to feed. River deltas harbour an abundance of life and are a favourite spot for local fishers as well as hungry dolphins: one of the big threats facing the dolphins is entanglement in gill nets. Human activities are not a new threat to the survival of the dolphins. The Irrawaddy or ‘river’ dolphins, which look similar to beluga whales, were traditionally hunted for their oil. In southeast Asia, pollution from the gold industry also poses a risk to the Irrawaddy dolphins. Parasites entering the ocean from terrestrial sources also represent a threat to the local dolphins. In the past four years, there have been four strandings of humpback dolphins infected with Toxoplasma gondii. This parasite can be lethal to marine mammals (as well as other mammals including the human foetus) and enters the marine ecosystem via cat faeces. “Given the small numbers of dolphins in Cleveland Bay, human activities can have strong negative impacts on local populations,” warns Guido. People can help protect these rare dolphins by using smart and safe practices when enjoying the marine environment. Tips for dolphin-safe oceangoing: do not approach dolphins, report any suspicious fishing or boating activities to the appropriate authorities, make sure your boat motor doesn’t leak oil or fuel, and never throw cigarette butts or other materials into rivers or oceans. For more information on how you can help conserve and protect marine mammals, visit the Great Barrier Reef Marine Park Authority website: www.gbrmpa.gov.au/corp_site/key_issues/conservation/threatened_species For more information, contact Mr Guido Parra, James Cook University, guido.parravergara@jcu.edu.au |
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PO Box 772 Townsville
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