Flinders and Macquarie University reveal scale of threat to our dolphins

A landmark study of dolphin numbers in South Australian gulf waters shows the creatures are facing unprecedented challenges.

Dolphins encountered on the Baird Bay Ocean Eco Experience at Baird Bay, Eyre Peninsula. Picture: Robert Lang, Robert Lang Photography.

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The first large scale audit of bottlenose dolphins in South Australian gulf waters shows thousands of dolphins are under a growing threat from climate change and human activity.

Flinders and Macquarie University marine biologists estimate at least 3200 bottlenose dolphins populate the sheltered waters of Spencer Gulf and Gulf of St Vincent following aerial surveys covering 42,400 sq/kms of sea.

Most of the dolphins occupy the upper reaches of the gulfs feeding on cuttlefish, octopus, squid and sardines in the shallow shelf waters, reveals the study.

Dr Kerstin Bilgmann. Picture: Supplied

The findings were published in the nature science journal Scientific Reports.

“Both gulfs are inverse estuaries with no freshwater inflow and limited water exchange, especially in the northern sections, where the dolphin densities are highest,” lead author Dr Kerstin Bilgmann, pictured, an honorary research fellow at Flinders and Macquarie.

“These are the areas of the gulf most likely to be impacted by future climate change,” she said.

“Loss of prey … due to climate change will lead to poor dolphin health and the spread of disease like morbillivirus that is linked to warmer waters.”

A morbillivirus outbreak in the Gulf of St Vincent in 2013 led to the deaths of 41 dolphins.

Dr Bilgmann said the dolphins were also at higher risk of human impact in gulf waters, including boating strikes, coastal development and pollution.

She said the research highlighted the importance of SA’s gulf waters to bottlenose dolphins as well as exposing their vulnerability.

Dr Bilgmann said the study would be used for marine park planning, fisheries and boating management and environmental impact assessments for marine based activity, like Norwegian oil company Equinor’s plan to drill for oil in the Great Australian Bight.

Dolphin diagram for web channel - 650px x 920px

Concerns over Equinor’s operations were heightened in the past few days ago when a supply vessel collided with the company’s Statfjord A platform in the North Sea. Workers were evacuated from the platform, which was not producing oil at the time and had been shut since the end of May for maintenance.

Dr Bilgmann and her study co-authors from Flinders University, associate professors Luciana Möller and Guido J. Parra, felt compelled to better understand local populations of bottlenose dolphins in SA waters when they first embarked on the research in 2011.

She said smaller scale boat surveys had been conducted along the Adelaide coast, but there was little data on dolphin densities and habitat preferences over more expansive areas.

The study’s finding couldn’t be more timely with World Oceans Day yesterday, promoting conservation and protection of the “blue” planet.