Posted on 22/03/2022 by Phillip Island Nature Parks
Latest seal pup census reveals worrying trend
New census findings reveal that Australian fur seal numbers have continued to decline, with concerned researchers working to understand why – and turn it around.
The number of seal pups recorded at breeding sites in Victoria and Tasmania decreased by around 22 per cent between 2007 and the most recent count in 2017.
It takes years of research after the census takes place before the study can be released, as scientists need to be sure of their findings, which are then peer reviewed and published.
Phillip Island Nature Parks marine scientist Rebecca McIntosh, who led this census, said the continued decline was worrying and likely due to a combination of many factors.
“The fur seals are wonderful to study and an important part of the ecosystem, both bottom-up - adding nutrients and top-down - helping to keep the fish populations healthy. People love going to see them on seal tour cruises because they are so entertaining. People may think there are a lot of seals out there, but only about half the original population exists today,” Dr McIntosh said.
“There may be several contributing factors including disease and pollutants affecting pup birth rates and survival, as well as seals dying in fishing nets and marine plastic entanglements.
“Then there are climate change impacts such as storm inundation of breeding areas and changes in the food chain of southeast Australia – a hot spot of ocean warming – which may also be affecting the seals.”
The five-yearly census of Australian fur seals began 20 years ago to better understand their populations after over-harvesting in the 1800s almost drove them to extinction. Fur seals are not endangered and are classified as being of ‘least concern’.
The highest count of around 21,600 pups was recorded in 2007, but numbers had dropped to 17,500 by the next census in 2013.
Researchers hoped it was an anomaly. But the recently released 2017 census reported a further decline to just 16,900 pups.
The census will be used to inform future planning, including being provided to fisheries managers for ecosystem management of fisheries and to government for planning responses to emergencies such as oil spills.
And of course, it is already being used by researchers as they furiously work to turn the declining numbers around.
Phillip Island Nature Parks is using drones to monitor Seal Rocks and The Skerries to gain a deeper understanding of the population decline. For example, is it the pups that aren’t surviving? Or is it because there are fewer breeding females?
Nature Parks researchers are also studying different impacts to the seal population, including disturbance by boats and jet skis at Seal Rocks, ecotoxicity and pollutants, and marine plastics.
“The Nature Parks team is committed to a variety of research projects at home and internationally. We hope to conserve the fur seals and the penguins, with flow on benefits to the other species and the people that share the ocean with them.”
“As top predators, fur seals are excellent ecosystem sentinels – if they are healthy, then in a general sense, the ecosystem underneath them can be assumed to be doing well. So all of this work is not just vital to our seals, but to our entire ecosystem.”
The next fur seal census will take place at the beginning of next year.
The full 2017 census paper Sustained reduction in numbers of Australian fur seal pups: implications for future population monitoring is available at: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0265610
It is co-authored by Karina Sorrell, Monash University; Sam Thalmann, Tasmanian Department of Natural Resources and Environment; Anthony Mitchell, DELWP Victoria; Rachael Gray, The University of Sydney; Harley Schinagl and Peter Dann, Phillip Island Nature Parks; John Arnould, Deakin University; and Roger Kirkwood, South Australian Research and Development Institute.
This research was funded by the Telematics Trust and the Princess Melikoff Trust Marine Mammal Conservation Program.