Health the top priority

A dolphin leaps out of the river in Freshwater Bay during research last week. Picture: Delphine Chabanne
A dolphin leaps out of the river in Freshwater Bay during research last week. Picture: Delphine Chabanne

With funding provided by the Swan River Trust, Murdoch University researchers are using remote biopsy equipment to assess the potential impact of contaminants on dolphin health after the death of six dolphins in the riverpark in 2009.

The technique, similar to that used by wildlife and zoo veterinarians when delivering sedative or anaesthetic darts, measures biomarkers to reveal cellular or biochemical changes caused by exposure to foreign chemicals.

Veterinary pathologist and researcher Nahiid Stephens said it remained unclear whether contaminants contributed to the deaths but they highlighted the vulnerability of the Canning River dolphins.

Post-mortem testing of tissue from the deceased dolphins identified certain industrial and agricultural substances and that cetacean morbillivirus – not previously documented in the Indian Ocean – played a major role in some of the deaths, as it suppressed the immune system of whales and dolphins.

But Dr Stephens said tests on deceased dolphins weren’t necessarily a good indicator of the health of the live population.

‘For example, exposure to a pathogen like cetacean morbillivirus can lead to changes in feeding habits, metabolism and weight,’ she said.

‘These factors can alter the levels of contaminants in different tissues, making it impossible to identify the particular contribution, if any, of the contaminants present.’

The dart heads in current use contain a biopsy tip that takes a small sample of skin and blubber. ‘The process is similar to what happens when people get skin biopsies done to check suspicious moles,’ Dr Stephens said.

‘After taking the sample, the biopsy dart floats in the water and we collect it immediately to preserve it for testing. The equipment has been specially designed and used globally for a range of studies of dolphins and other species.’