Research to underpin better understanding and management of western Gemfish stocks in the Great Australian Bight

Research Project

Full description Gemfish (Rexea solandri) is a benthopelagic snake mackerel of the Family Gempylidae. Gemfish inhabits the continental shelf and slope waters off southern, southwestern and southeastern Australia as well in waters of New Zealand. It is found at depths ranging from 100 to 800 metres, but commonly at 300 to 450 metres. A trawl fishery was established in southeastern Australia in the late 1960s when fishers discovered winter aggregations extending from Newcastle (33°S) and Sydney (34°S) on the coast of New South Wales to eastern Bass Strait (39°S). Fisheries for Gemfish have also operated off western Tasmania, southwestern Victoria and south eastern South Australia. These fisheries are managed as a separate stock to the east coast and have a substantially different fishing history and level of exploitation. The most recent stock assessment suggested biomass is at 74 per cent of virgin biomass levels. However, the Great Australian Bight Resources Assessment Group (GABRAG) had sufficient concerns regarding the population structure of the western stock and its impact on the stock assessment, (whether western gemfish constituted a single population and where the boundary between east and west arises) to reject the assessment. This project was initiated to address these stock structure issues. The objectives of this project were to: 1) improve understanding of stock structure for Western Gemfish west of Bass Strait, 2) improve understanding of spawning locations for western gemfish west of Bass Strait; and 3) provide the Australian Fisheries Management Authority with recommendations on stock structure and boundaries on the basis of this evidence.