Terms of Reference

Assessment Framework for Georges Bank Scallop
Maritimes Region Science Advisory Process

18-20 February 2009
Bedford Institute of Oceanography (BIO)
Dartmouth, Nova Scotia

Context

Georges Bank is one of the main sea scallop stocks fished by the offshore scallop fleet. Since 1986, the offshore scallop fleet has fished Georges Bank year round under an Enterprise Allocation management regime. The long-term objectives of the offshore scallop fishery are biological sustainability and economic viability. The following three management objectives, which were contained in the Enterprise Allocation document approved by DFO in 1989 and carried forward in subsequent Integrated Fishery Management Plans, are applicable for the Georges Bank scallop fishery:

• to ensure the conservation and restoration of the resource;
• to the degree possible, stabilize landings over time; and,
• to provide increased economic benefits for crews, vessel owners, shore workers and the people of Canada.

To this end, the scallop fishery is managed through limited entry, gear restrictions, the establishment of fishing areas and seasons, and meat count limits. Catches are monitored through an industry-funded dockside-monitoring program and vessels are required to carry vessel monitoring systems. The industry also participates in and funds the research vessel surveys, collects data through a port sampling program and conducts sea-bed mapping.

The research vessel survey uses a commercial catch rate-stratified sampling design with allocation proportional to the areas of five catch rate strata. The original strata boundaries were not recorded and, therefore, need to be reconstructed. This reconstruction will allow a full assessment of the efficiency of the catch rate-stratified design with a view to developing improved survey designs in the future.

Stock assessments have been conducted since 1986 using a Sequential Population Analysis (SPA) to estimate population abundance and biomass based on research vessel survey indices, commercial CPUE's and age composition in the stock. The SPA is an age-based model but no aging data exists for the Georges Bank stock; implementation of the SPA has relied on old growth rates for Georges Bank published in 1972 (Brown et al. 1972). The 2008 Georges Bank assessment (DFO 2008) concluded that the SPA was inadequate for assessing resource status due to a poor fit to the data in recent years and due to projections that were not consistent with our understanding of the resource. Due to the absence of aging data and the inadequacy of the SPA to model rapid changes often observed in scallop stock age structure and growth, there is an immediate need to develop more appropriate (size-based) assessment methodology.

Objectives

Review survey index of abundance

• Reconstruct original catch-rate strata boundaries to facilitate an evaluation of the efficiency of the survey design
• Propose and evaluate alternate survey stratification design(s)

Review of Model(s) to Assess Status and Productivity

• Determine the methodology to estimate the current state of the stock, including methods for estimating stock size and fishing mortality.
• Determine the methodology to characterize stock productivity including reference points.
• Determine forecasting methodology for providing advice on harvest levels.
• Provide guidance on next steps, including research recommendations.

Outputs

CSAS Science Advisory Report outlining the assessment framework

CSAS Proceedings of the discussion of meetings

CSAS Research Documents

Participation

External experts
DFO Maritimes Science
DFO Maritimes FAM
Fishing industry
Aboriginal communities / organizations
Nova Scotia Provincial representatives

References

Brown, B.E., M. Parrack, and D.D. Flescher. 1972. Review of the current status of the scallop fishery in ICNAF division 5Z. Int. Comm. Northw. Atl. Fish. (ICNAF) Res. Doc. 72/113: 1-13

DFO. 2008. Assessment of Georges Bank Scallops (Placopecten magellanicus). DFO Can. Sci. Advis. Sec. Sci. Advis. Rep. 2008/045.