Evidence is mounting that Australia's native sea lion population has levelled off and may be declining, prompting a leading CSIRO scientist to call for more intensive research into the species.
The call, by Dr. Peter Shaughnessy, principal research scientist with the Division of Wildlife and Ecology, follows a joint study between CSIRO and National Parks and Wildlife South Australia.
Found only in Australia, the Australian sea lion has its principal breeding colonies at Kangaroo Island and Dangerous Reef, near Port Lincoln, in South Australia. Smaller colonies exist on the west coast of SA and in Western Australia.
"Data collected suggests to us that too many pups are dying and
we don't really know why," says Shaughnessy. "For example in
1996 at two colonies we found mortality rates of 30 per cent and 50 per
cent respectively."
The following year mortality decreased to only four per cent among Dangerous
Reef sea lions but the worry is that we have no idea what's causing these
dramatic fluctuations in pup mortality, says Dr Shaughnessy.
Possible causes of death include parasites, such as hookworm, environmental perturbation causing food shortage for lactating female sea lions, high rates of aggression by adult males, direct human harassment or by interacting with fishing gear.
Another possibility, says Dr Shaughnessy, is that sea lions may be facing stronger competition for food from their cousin, the New Zealand fur seal, whose numbers are increasing on Kangaroo Island at an annual rate of around 10%.
"The Australian sea lion is an endemic species which we need to
take care of. It's a tourist icon, up there with the koala, which attracts
tens of thousands of visitors to the sea lions' colonies every year. If
we don't find out why their numbers are not increasing, we may face more
serious problems later on," he says.
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Contact: Mr David Salt
david.salt@dwe.csiro.au
61-2-6242-1645
CSIRO Australia
18-Mar-1998