Understanding recruitment variation (including the collapse) of Saucer Scallop stocks in Western Australia and assessing the feasibility of assisted recovery measures for improved management in a changing environment
Department of Primary Industries and Regional Development (DPIRD) WA
The perception that fisheries collapse or recruitment failure is the result of overfishing reflects badly on industry, researchers and managers. It is important therefore to understand the cause of recruitment variation (and failures) and to clearly explain these to stakeholders. In light of recent stock surveys, indicating extremely low levels of recruits and adults, it is likely that natural recovery is now impeded due to insufficient spawning stock to produce successful recruitment even under ideal environmental conditions. Closure of these fisheries has had a major financial impact on the industry. This led to a workshop of scallop experts, industry and managers to discuss the cause of the collapses; whether these conditions are likely to remain and if they will improve to permit some recovery. Due to very low stock abundance it could be that the breeding stock is too low or the survival of larvae/juveniles has been reduced to compromise a significant stock recovery. An urgent need was identified to understand recruitment variation including the initial stock collapse, investigate the potential of assisted recovery measures (such as restocking) to re-establish founder populations in these extremely depleted stocks, and provide management/industry with a cost-benefit evaluation of these measures to aid recovery. Fishery restoration through assisted recovery has shown some success with Roe’s Abalone in WA and may lend itself as a management tool in a changing marine environment.
1. Understanding factors influencing recruitment variations in existing scallop WA stocks, particularly the collapse of the stocks in 2011
2. Determining feasibility of re-establishing founder population of scallops in the Abrolhos Islands and Shark Bay through seeding of hatchery produced juveniles
3. Determining feasibility of re-establishing founder population of scallops in the Abrolhos Islands through translocations