Small isolated populations pose a threat to new dolphin species

Victoria’s iconic new dolphin species, the Burrunan dolphin, is at risk due to its small and isolated populations, according to the first study investigating the dolphin’s population using DNA and requires special conservation action.

Researchers from the Marine Mammal Foundation (MMF) and Monash University have been investigating the population genetic structure of the Burrunan from the two only known resident populations, Port Phillip Bay and the Gippsland Lakes, and from across coastal Victoria and Tasmania.

Dr Kate Charlton-Robb, the papers lead author, said the new research published in Conservation Genetics found the Port Phillip Bay and Gippsland Lakes population were genetically very distinct and showed little genetic mixing.

“We had hypothesised that the Port Phillip and Gippsland Lakes populations would be more similar than the Tasmanian population, given the potential barrier of Bass Strait, but what we found was quite unexpected” Dr Charlton-Robb said.

“The results suggested the Gippsland Lakes population showed more genetic similarity to those in Tasmania, whilst the Port Phillip population was more isolated.”

Dr Charlton-Robb said based on the dolphin’s DNA the effective population size – the number of individuals that are contributing genes into the next generation - is estimated to be less than 100 dolphins in each region.

“This is concerning, and conservation action is required to protect the species – the very small population size, lack of genetic diversity, the isolation of these populations and the effects that could have on the future of not only these resident populations, but on the entire species.”

Dr Charlton-Robb identified these dolphins as a separate species and named them in 2011, her efforts have already seen the dolphin be listed as threatened under Victoria Flora and Fauna Guarantee Act.

“For a species that lives so close to a major capital city like Melbourne, we still know very little about them.”

MMF’s ongoing research into their behaviours, population structure, levels of migration and DNA diversity is aimed at using the results to further protect and conserve these unique dolphins.

“It is crucial we understand more about these unique population and about the species as a whole. Applied research with real conservation and protection outcomes is our mission.”

Charlton-Robb, K., Taylor, A.C., McKechnie, S.W. (2014) Population genetic structure of the Burrunan dolphin (Tursiops australis) in coastal waters of south-eastern Australia: conservation implications. Conservation Genetics. DOI 10.1007/S10592-014-0652-6