Where have all Australia's freshwater sharks and sawfish gone?

A survey of the northern river systems is expected to confirm that while some of the largest freshwater fish species on the planet may have disappeared from many areas, the Australian systems may contain surviving populations of speartooth sharks and freshwater sawfishes.

Once prominent in tropical river systems, fishing pressure, pollution and habitat destruction through overdevelopment have decimated their natural populations, according to shark biologist Dr John Stevens.

"Australia may contain the last healthy populations of speartooth sharks and freshwater sawfish and there is an urgent need to establish how many remain, where they occur and how those should be managed," says Dr Stevens, from CSIRO Marine Research.

"Sharks and rays are more vulnerable to human exploitation than bony fishes because of their different life-history strategy. Freshwater sharks and rays are even more at risk because they combine these biological characteristics with all the problems associated with a reduced habitat and inland development", he says.

Currently, there is international concern over the population status of freshwater sharks and rays around the globe and this has been expressed through the World Conservation Union (IUCN) Shark Specialist Group and the Food and Agriculture Organisation International Plan of Action for Sharks.

In Australia, the Freshwater Speartooth Shark, the Northern River Shark and the Freshwater Sawfish are listed as threatened under the Commonwealth Environment Protection and Biodiversity Conservation Act.

Speartooth sharks are currently known from only about 25 specimens from Queensland and the NT. Concern for sawfishes extends to the marine species; this group are large, long-lived predators with inshore distributions, which are particularly susceptible to fishing due to entanglement of their saws in nets.

Dr Peter Last, who heads up the National Fish Collection at CSIRO, was a member of the last significant freshwater shark and ray survey funded by the Japanese Research Council in 1989.

"This is an important opportunity in which research and conservation management agencies in northern Australia can establish what sort of numbers we have to work with in future," says Dr Last.

The new survey is now underway, and the region to be covered extends from the Fitzroy River in Western Australia to the Burdekin River in North Queensland.

Scientists will be consulting landowners, aboriginal associations and park and coastal authorities, cattle station operators and recreational and commercial fisher organisations.

Dr Stevens said it has been during this process that scientists often received news of sightings of freshwater sharks and sawfishes from river systems.

Funded under the Commonwealth Government's Natural Heritage Trust, and with support from Conservation Volunteers Australia, the $400,000 survey and population assessment will be conducted by CSIRO, the Museum and Art Gallery of the Northern Territory (MAGNT), the Northern Territory Fisheries Division, the University of Western Australia, Murdoch University, the Queensland Department of Primary Industries and the Queensland Parks and Wildlife Service.

More information about the project visit : http://www.marine.csiro.au/LeafletsFolder/52river/52.html.

Dr John Stevens, CSIRO Marine Research, 03-6232 5353

Dr Helen Larson, MAGNT, 08-8999 8201

Dr Barry Russell, MAGNT, 08-8999 8201

Media contact:

Leane Regan, CSIRO Media, 02 6276 6478, Mobile: 0419 236 519

Craig Macaulay, CSIRO Marine, 03 62325219.