A team of national and international marine researchers has identified the key prey of western rock lobster larvae, a finding that has important implications for the future of the country's most valuable fishery.
The research team is led by Professor Anya Waite from The University of Western Australia's Oceans Institute and the University's School of Environmental Systems Engineering.
Professor Waite said the research gave a new insight into the feeding habits, nutritional needs and survival of the early larval stage - phyllosoma - of rock lobster. This work will help us understand why numbers of rock lobster larvae that survive can vary considerably from year to year.
Identifying the preferred food of the lobster larvae could also assist attempts to establish a viable western rock lobster aquaculture industry.
The findings were announced at the conference of the Australian Marine Sciences Association (AMSA) in Fremantle today.
"In experiments designed by Dr Megan Saunders and Nik Sachlikidis, our team has shown for the first time that the rock lobster larvae are healthier when they feast on their preferred prey - and we have identified that prey," said Professor Waite.
The western rock lobster is the most valuable, single-species fishery in Australia, representing up to 20 per cent of the total value of Australia's fisheries.
Rock lobster larvae (puerulus) numbers have been below average for the past five years, including the two lowest recorded years on record, prompting significant management changes to ensure the sustainability of the rock lobster industry.
"Dr Peter Thompson (CSIRO) has shown evidence that the phyllosoma have a preference for key prey with specific nutritional attributes," she said.
"This suggests that this is directly related to the need to accumulate substantial nutritional reserves before they can metamorphose into the puerulus stage, cross the continental shelf, and settle to form the next generation of fishable adult lobsters.
"We propose that the autumn phytoplankton bloom off the WA coast is a key food resource driving production of healthy phyllosoma, and thus more abundant numbers."
The research team includes scientists from The University of Western Australia, Murdoch University, Auckland University, CSIRO and the WA Department of Fisheries, as well as rock lobster aquaculture specialists from WA and Queensland. It is funded by the Fisheries Research and Development Corporation (FRDC).
Members of the research team spent most of last July at sea, chasing the elusive rock lobster larvae between Fremantle and the Abrolhos Islands, sometimes up to 300 kilometres offshore.
Because rock lobster larvae drift in the open ocean for almost a year before returning to the coast, they are vulnerable to fluctuations of the Leeuwin Current and changing food supplies.
The research team conducted shipboard experiments examining the diet and food preferences of larval rock lobster with a wide menu of naturally occurring food sources.
They also used satellite remote sensing of ocean features and computer-generated models to gain a greater understanding of this vital stage in the rock lobster's life cycle.
"We will be going to sea again this spring to target later stage larvae closer to their adult phase," Professor Waite said. "This is extremely challenging work, demanding long hours and exacting work, on a research vessel moving through often very demanding conditions.
"We are lucky to have in our team, expert colleagues from Murdoch University (Professor Lynnath Beckley) as well as the WA Department of Fisheries, Queensland Department of Primary Industries (Nik Sachlikidis), and the University of Auckland, whose experience and skill will support further ground-breaking outcomes for this project."
Professor Waite presented the findings of the initial research at the AMSA conference at the Esplanade Hotel in Fremantle.
Her paper is called "The Biological Oceanography of Western Rock Lobster Larvae".