STUDY: Ms Bolin and her supervisor, senior lecturer in animal ecology Dr Kylie Scales.
STUDY: Ms Bolin and her supervisor, senior lecturer in animal ecology Dr Kylie Scales. Contributed

REVEALED: Why whales get caught in shark nets

A UNIVERSITY of the Sunshine Coast researcher has found a connection between the likelihood of humpback whales getting stuck in shark nets and a major ocean current.

Animal ecology graduate Jessica Bolin undertook research for her honours degree in collaboration with supervisors Dr Kylie Scales, Professor David Schoeman and PhD student Carme Piza-Roca.

The findings revealed the likelihood of entanglements was higher when the East Australian Current was closer to shore.

The findings will be presented to the Australian Marine Science Association conference in Fremantle from July 7-11, and could be used to guide shark net monitoring.

Ms Bolin and the team used satellite data, an ocean model and a mathematical algorithm to plot the changing flow of the current off southeast Queensland everyday from 2001-2017.

The 23-year-old from Nambour and the team then compared the data to whale entanglement incidents between Fraser Island the Queensland-New South Wales border.

"We found a higher likelihood of humpback entanglement in shark-control nets when the inner edge of the East Australian Current meandered closer to shore, and when the inner edge was mixed and messy on the ocean surface," Ms Bolin said.

"This indicates that whales may be using this inner edge as a navigation aid during their annual migrations along the Australian eastern seaboard."

 

STUDY: Jessica Bolin hard at work.
STUDY: Jessica Bolin hard at work. Contributed

Dr Scales said the likelihood of accidental whale entanglement in shark nets in southeast Queensland was very low, with 58 incidents recorded in the research period.

"It's lower than one per cent chance, per shark net, per day, and the Queensland Shark Control Program strives to make sure this chance remains as low as possible," she said.

"If the whales are using the East Australian Current as part of their navigation 'roadmap', as the findings suggest, this could be useful in helping to guide monitoring of the shark nets.

"One example might be to increase monitoring when the current is closer to shore, which can be seen on freely available satellite data that shows sea surface temperatures."