Establishing fine-scale industry based spatial management and harvest strategies for the commercial scallop fishery in South East Australia
University of Tasmania (UTAS)
The spatial management of scallop fisheries elsewhere in the world has demonstrated the ability of this method to reduce recruitment variation, while increasing production. The implementation of detailed, spatially explicit management regimes in Tasmania offers a greater prospect for sustainability and continuity of the scallop fishery, but as yet there is insufficient information on the ability of the method to ensure adequate recruitment. The long-term continuity and sustainability of the commercial scallop resource is dependant on refining spatial management strategies, such that they are buffered against the impacts of recruitment variation. Spatial harvest strategies applied within one jurisdiction may be influencing recruitment and harvesting ability within other jurisdictions. Such cross-jurisdictional effects are more probable if the scallop resource constitutes one stock. At finer spatial scales, there have been observations of localised recruitment, which implies regional/bed level self-recruitment. Therefore, detailed spatial management harvest strategies applied to a scallop bed/region may influence scallop recruitment processes. Additionally, research has identified the importance of maintaining high densities of spawner biomass for promoting recruitment over all spatial scales. Broad- and fine-scale scallop stock structure, spawner biomass density/recruitment relationships, and an understanding of impacts of intensive fishing on scallop communities are needed to refine detailed spatial management/industry fine-scale management harvest strategies, such that they promote recruitment and minimise impacts on the broader environment. This will allow a move towards uniformity of sustainable spatial harvest strategies across the fishery, and simplification of the jurisdictional arrangements between Victoria, Tasmania and the Commonwealth (OCS).
1. Determine the broad- and fine-scale population linkages and stock status of commercial scallops (P. fumatus) in SE Australia.
2. Evaluate the effects of intensive rotational dredge fishing on scallop beds and scallop recruitment events.
3. Examine the importance of scallop density (spawner biomass) on synchronisation of spawning and recruitment success
Principal Investigator: Jayson Semmens
Keywords: Commercial scallop; Pecten fumatus; fisheries management; spatial management; rotational harvest; microsatellites; fisheries stocks; population linkages; spawner biomass; recruitment; effects of fishing
Summary: Spatial management of the scallop fishery requires adequate information on the stock to ensure the implementation of appropriate management decisions. In addition to abundance and population data used for management decisions, more information is needed to improve management of the commercial scallop (Pecten fumatus) resource.
This project focused on genetic stock structure as a tool to determine a demographically cohesive unit because genetic differences between regions imply a limitation to dispersal. Findings showed the south east Australian commercial scallop population has a genetically homogeneous single population. This largely allows for a uniform harvest strategy to be adopted across all three jurisdictions of the commercial scallop fishery. There was however some evidence of population structure within Bass Strait, which has implications for management of apparently genetically-linked populations in separate management jurisdictions.
With a view to ensuring the ecological sustainability of the scallop fishery this study explored the effect of dredging activities on the benthic community within the fishing grounds of the Bass Strait Central Zone Scallop Fishery (BSCZSF). Abundance of all species (commercial scallop and all by catch) comprising the communities did not differ significantly between fished and non-fished areas in the regions examined. The total number of species and species richness did not differ significantly either. This suggests that scallop dredging has a relatively low short-to medium-term impact on the benthic communities within the fishing grounds of the BSCZSF.
The density of adult spawners does have an impact on the level of synchronicity between spawning adults. This study showed a difference in spawning intensity and synchronisation between sites of high and low densities, and suggests that maintaining dense areas of adult scallops may increase the chances of recruitment, through increased spawning intensity.