The scallop fisheries in the Central Bass Strait and in Tasmanian waters are both moving to area based management schemes in which only part of the available fishing grounds will be opened to fishing each year. The proportion of available beds opened in Tasmania is likely to be smaller than in the Central Bass Strait. The Victorian fishery, at the time of writing, will retain its current management regime, which involves an extended open season every year across all grounds. The effectiveness of area based management and how it is best implemented will be determined by how the open scallop beds respond to differences in relative fishing intensity (as defined and determined by VMS data) and how quickly they can recover from the losses due to fishing. In a manner equivalent to the effect of the single small bed that remained in Central Bass Strait, the hope is that the un-fished bed(s) will aid in the reseeding of the fished beds. In the process of attempting to assess the effectiveness of area-based management for Bass Strait scallops, the project will assess the effectiveness and importance of another major management rule/guide, the juvenile trashing rate. If all juvenile scallops on a scallop bed are destroyed when fishing occurs then the bed will take longer to recover than if the very smallest scallops survive the fishing. An understanding of the relative vulnerability of different sized scallops to the effects of fishing will enable the current guess of 20% being undersized leading to a management response of no fishing, to be modified into a workable and justifiable target reference point in the management of scallops. Finally, the impact of scallop dredging on benthic communities is assumed to be profound and destructive. This project will permit an examination of the relationship between the benthic communities found in areas that experience different levels of fishing intensity and thereby determine whether the impacts on bycatch are the same at all levels of dredging intensity. In summary, the three major needs are to determine whether area based management will succeed in permitting a sustainable scallop fishery to operate, to formalize and refine the management rule relating to the assumed destruction of juvenile scallops when a bed is fished, and to examine the actual extent of fishing and its impact on benthic communities.
Project number: 2003-017
Budget expenditure: $400,531.00
Principal Investigator: Malcolm Haddon
Organisation: University of Tasmania (UTAS)
Project start/end date: 29 Jun 2003 - 30 Jul 2006
1. Determine, using VMS, the relative fishing intensity and extent of scallop dredging in both the Bass Strait Central scallop fishery and the Tasmanian scallop fishery, in the areas opened to fishing in 2003 and 2004.
2. Determine the relative impact of fishing on different size classes of scallops on those beds open to fishing, especially the rate of survival of undersized scallops.
3. Determine whether a relationship exists between juvenile settlement success in different areas and the relative fishing intensity, as defined by VMS data, experienced by those different areas.
4. Determine the major bycatch species taken with commercial scallop dredging gear on the main scallop beds fished in Bass Strait (including Tasmanian, Central Bass Strait and, if possible, Victorian scallop beds).
5. Initial study of the effects of scallop dredging on benthic fauna by comparing closed areas and areas open to fishing in a before and after sampling design.
6. Generate management options aimed at optimizing the use of area based management strategies for scallop fisheries.