Population of Australia’s only unique seal has fallen by 60 per cent: Study
The Khaled bin Sultan Living Oceans Foundation published Global Reef Expedition: The Republic of Palau Final Report, which summarizes the Foundation's research on the status of coral reefs and reef fish in Palau and provides conservation recommendations that can help preserve these outstanding coral reefs for generations to come. Credit: ©Keith Ellenbogen/iLCP. Sketched by the Pan Pacific Agency.
CANBERRA, May 4, 2021, The Guardian. The population of Australia’s only unique seal has fallen by more than 60% in just four decades, with experts worried about the fate of the species, according to a study of the number pups born at breeding sites, The Guardian reported.
The number of Australian sea lion pups is now at just 2,739 across 80 known breeding sites off the coasts of South Australia and Western Australia, according to the research.
The Australian sea lion is Australia’s only endemic seal and one of four marine mammals listed as endangered, but the only one with declining numbers.
“I think we should be really concerned,” said Prof Simon Goldsworthy, a scientist at the South Australian Research and Development Institute who led the research, published in Endangered Species Research.
“I have seen some colonies halve in pup production in a decade. Seeing these declines has been really worrying.”
In late 2020 the federal environment minister, Sussan Ley, raised the status of the Australian sea lion from vulnerable to endangered after recommendations from the threatened species scientific committee.
The Australian sea lion, together with two species of fur seals, were commercially hunted from the late 18th century to the early 20th century. Fur seal numbers are recovering but Australia sea lion numbers are not.
The sea lions are known to get caught in fishing nets and lobster pots, in particular gillnets set on the ocean floor in the same places where the seals forage for food.
Some restrictions have been introduced on fisheries in South Australia and Western Australia to prevent seals drowning or being injured in nets and pots, the threatened species scientific committee’s advice said. The advice said it was too early to know if the measures had helped.
Goldsworthy said there were now only four breeding sites producing more than 100 pups and less than 15 pups are being born at half of the 80 sites.
“When you see these declines at this level at tiny colonies, they are incredibly vulnerable. You are dealing with only tens of animals. It is probable we will lose some of these breeding sites in the near future if we don’t arrest the declines.”
He said the Australian sea lion was one of four marine mammals listed as endangered nationally, but the only one that was in decline. The numbers of blue whales, southern right whales and subantarctic fur seals were increasing.
Goldsworthy said the mammals are notoriously hard to monitor. They have a breeding cycle of about 18 months, but unlike other seals, the timing of the breeding season can be unique to each colony, even those that are only a few kilometres apart.
Dr Rachael Gray, a veterinarian at the University of Sydney, has been studying and treating Australian sea lions since 2006 at one of the larger colonies at Seal Bay on South Australia’s Kangaroo Island.
“It scares me that the population is declining at the rate we have seen,” said Gray, who was not involved in the study.
Gray has been part of a program to test, treat and microchip pups at Seal Bay to allow detailed research into each newborn’s progress. She has seen the number of pups falling.
Her research had found the Australian sea lion had higher levels of mercury and toxic chemicals known as PFAS in their tissue than other seal species.
She said it was possible the chemicals were causing developmental and immune system problems that made it harder for them to survive the parasitic hookworm, but much more research was needed.
Rising sea levels caused by global heating inundating some breeding sites was also an emerging threat, she said.
Alexia Wellbelove, of conservation group Humane Society International, which nominated the species for endangered status, said sea lions should now be prioritised for government funding. “This is an alarm bell. There is no time to waste.”
In a statement, the South Australian Department for Environment and Water said the ongoing decline was a concern and the state government had spent $680,000 in the past five years on research.
Clinton Syers, a fisheries manager at WA’s Department of Primary Industries and Regional Development, said in a statement that a 17,390 sq km network of gillnet exclusion zones had been in place around all Australian sea lion colonies in the temperate demersal gillnet and demersal longline fishery since 2018.
“Importantly, no interactions with [Australian sea lions] have been reported since the zones were introduced,” Syers said.
A statement from the federal Department of Agriculture, Water and the Environment said the government had supported conservation for the species for more than 10 years, “providing over $1.6m on conservation research grants over that time”. A recovery plan had been in place since 2013.
The funding had supported population research in South Australia that had contributed to the change in threatened species status to endangered, which the statement was as a result of of new information “rather than a genuine deterioration in status”.
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