Studying archived data has helped researchers determine the homing instincts of rock lobsters in Australia, a result that will help inform lobster fishery management.
The new study by South Australian Research and Development Institute (SARDI) researchers has found that southern rock lobsters (Jasus edwardsii) orientate using a magnetic compass sense to navigate considerable distances in particular directions from unfamiliar surroundings.
Project leader, Dr Adrian Linnane, said the findings stemmed from a translocation study undertaken in 2007 within the Southern Zone rock lobster fishery in South Australia.
More than 5000 lobsters were physically moved from offshore grounds over 100 metres deep into an inshore shallow water site of less than 20 metres.
“While the primary aim was to see if lobsters changed colour from the pale white to the red colour preferred by export markets, we were also interested in the movement patterns of individual lobsters after the translocation event,” Linnane said.
He added that previous lobster studies were based on lobsters tagged and released at their point of capture. This study however, was unique in that it allowed researchers to monitor movement patterns in lobsters displaced from their normal environment.
“This study was successful in that the light coloured deep water lobsters did indeed change to the preferred red coloration within 12 months of being translocated. In addition, 60% of all recaptures decided to remain within their new inshore environment, with no evidence to suggest that any significant mortalities occurred.” said Linnane. “While most lobsters remained resident, some lobsters were observed to move considerable distances in a highly directional nature away from the release site.
“We found that 40% of the lobsters that were recaptured had travelled in a consistent south-west bearing back out into deeper waters. This supports the theory that lobsters have some kind of true navigational sense.
Linnane said females travelled significantly further than males, with one female lobster recaptured 48 kilometres from the translocation site after a period of 735 days.
“That’s quite a distance considering the only way adult lobsters can move is by crawling across the sea floor,” he said.
Why some individuals would want to move to specific areas offshore is speculative but some scientists believe that females prefer to release their larvae in offshore currents to improve survival.
Dr Linnane added that the information also helped inform lobster fishery management.
“Given that we now know that lobsters move between different regions in the fishery, this supports the view that the resource may need to be managed as a single fishery, rather than discrete spatial units.”
The Residency and movement dynamics of southern rock lobster (Jasus edwardsii) after a translocation event study was funded by the Fisheries Research and Development Corporation (FRDC).