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According to ABC News, pygmy blue whale sightings in western Victorian waters have fallen by 50 per cent over the past 20 years, raising concern about changes in the Bonney Upwelling system. The current brings cold, nutrient-rich deep water to the surface near the Victorian and South Australian border, creating a summer feeding ground for marine wildlife from November to May.

Pete Gill, who has monitored pygmy blue whales near Portland for 28 years, said aerial surveys once recorded an average of 12 to 18 whales per survey in the early 2000s, compared with five or six now. His comparison of surveys from 2000-2004 and 2020-2024 found sightings had dropped by 51 per cent. Scientists do not yet know whether the population has declined or whether the whales have changed their migration habits.

The endangered whales migrate between Cape Otway in Victoria and Robe in South Australia to feed on krill. Dr Gill said surface krill swarms have decreased by 65 per cent since the early 2000s. He said fewer swarms near the surface can force wildlife to travel farther and use more energy to find food. An Australian fur seal colony that feeds on fish in the Bonney Upwelling system has also been found to be suffering malnourishment and population decline.

Marine ecologist and Deakin University PhD candidate Alex Shute said the upwelling’s strength had become more variable during the past five years. The Bonney Upwelling was the strongest on record in 2024, but Mr Shute said a stronger current did not necessarily produce more nutrients and krill, as extreme conditions could affect zooplankton and the wider food chain.

The current supports fishing and tourism in Portland, including tuna fishing and whale watching. Portland’s annual Bonney Upwelling Festival begins this weekend, with a parade, market stalls, live music and marine-science talks. Glenelg Shire Mayor Karen Stephens said protecting the environment was important to the local economy and tourism.