Hatchery scallops successfully deployed off Rottnest in stock replenishment trial

Hatchery-reared juvenile scallops have been successfully deployed for the first time off the coast of Rottnest in a crucial step towards developing a more productive and sustainable saucer scallop fishery for Western Australia.

The WA Department of Primary Industries and Regional Development (DPIRD) recently deployed about 5,000 scallop spat, testing the transport and deployment process for the scallop fishery stock enhancement.

The $2.7 million project includes support and investment by DPIRD, industry partner One Sea, and the Fisheries Research and Development Corporation on behalf of the Australian Government.

DPIRD’s shellfish aquaculture research manager Roger Barnard said the scallop larvae and spat were successfully cultured in the Hillarys shellfish hatchery after induced spawning of broodstock collected from the Rottnest fishery.

Spat were cultured in the hatchery for over four months to 5mm to 15mm size on a mixed microalgae diet before being deployed.

Mr Barnard said the two-year research project aimed to boost wild scallop stocks and develop a more productive and sustainable fishery, increasing resilience and mitigating the effects of harsh conditions such as marine heat waves.

Mr Barnard added that the team has been testing a number of key variables to develop successful hatchery protocols, including algae feed rates and species, water exchange rates, temperature and settlement media. Moving forward, the focus will be on propagating larger numbers of scallops.

DPIRD marine shellfish research scientist Dr Lotus Hassan said the successful deployment trial was a team effort with DPIRD’s Aquatic Science and Assessment (Ecosystem and Invertebrate Trawl), Aquatic Research Management and Shark Research providing the boat.

Dr Hassan said that, as part of the research, the team is also testing the feasibility of an ocean-based nursery, using a Floating Upweller System (FLUPSY) and lantern nets to grow out scallop spat to a larger size prior to release, with the aim to increase survival post-deployment.

For the trial deployment, the team recorded the movement of scallops deployed near the seafloor.

The team also tested the survival of the deployed spat by bringing back a sub-set of spat to Hillarys. The majority of spat survived and thrived on feeds naturally available, growing up to 20 mm in size.

Dr Hassan said the results indicated that the transport and deployment process was effective and can be upscaled when required.

WA’s wild scallop fisheries are located off the coast of Shark Bay and the Abrolhos Islands on the sandy sea floor. There is also a South Coast scallop fishery and the Rottnest Island Boutique scallop fishery located off the coast of Fremantle.