Researchers have made some significant breakthroughs in understanding the early growth and survival of Australia’s most valuable single-species fishery, the western rock lobster.
Led by Professor Anya Waite, from UWA’s School of Environmental Systems Engineering, the research project is an international collaboration between UWA, Murdoch University, the University of Auckland and the CSIRO.
Professor Waite said the study involved researchers capturing hundreds of phyllosoma – the first larval stage of western rock lobster – in surface nets off the coast north of Perth, Western Australia.
It was the first time live phyllosoma – transparent 10-legged organisms up to 2cm long – had been brought on board for research purposes.
“The impetus for the study was the increasingly low numbers of second stage larvae called puerulus – in 2008 puerulus numbers were at their lowest for 40 years,” Professor Waite said.
“Although phyllosoma may be small, their impact is large. They are the first larval stage in Australia’s most valuable single-species fishery, representing 20 per cent of the total value of all Australia fisheries.”
Professor Waite said the way phyllosoma captured their prey in the wild was critically linked to their survival.
“They spend between nine and 11 months floating in a planktonic prey field within the Leeuwin current, up to 1500km offshore,” she said. “If they can’t source enough dietary fat from their prey they won’t metamorphose into puerulus and begin the journey across the current to settle in seagrasses along the coast.”
Professor Waite said the study, due to be completed by mid-year, had already produced several key outcomes.
“Firstly we have a better understanding of the feeding process of western rock lobster phyllosoma,” she said. “By identifying key prey we’ve opened up new research potential in fisheries and aquaculture.
“We’ve assessed productivity of the Leeuwin Current and evaluated the capacity of plankton to provide a food source for phyllosoma. And we’ve also identified an oceanographic feature – the Abrolhos front – which appears to bring together two contrasting water masses, providing a shoreward flow pattern favourable to successful development to the puerulus stage.”
The next step involved using an underwater video technique to map three dimensional aspects of phyllosoma behaviour in real time, providing a clearer picture of the relationship between phyllosoma and their prey field, Professor Waite said.