R-08-02 The benefits and risks of increased spatial resolution in management of New England groundfish stocks

Daniel Holland
Research Scientist, Resource Economics
Gulf of Maine Research Institute
350 Commercial St.
Portland, ME 04101
207.228.1643
dholland@gmri.org

The New England groundfish industry continues to struggle despite tightened restrictions on harvest. Stock assessments and harvest guidelines are typically based on the concept of a “fish stock,” which may encompass a very large area. For example, cod is managed as two stocks, the Gulf of Maine and Georges Bank/Southern New England. Evidence is building, however, that cod are not one or even two big stocks, but groups of smaller or isolated subpopulations. Managers use area closures to reduce catches of certain species and to protect concentrations of juveniles, spawning aggregations and habitat, and interest in more localized management, smaller harvest areas, and ecosystem-based management is growing, despite continuted uncertainty about fish stock structure and the effectiveness of these management measures. 

Daniel Holland and his team used a simple but flexible spatial simulation model of a fishery to test hypotheses on the optimal scale of management under uncertainty. This initial model divides the fishery into two areas with fish populations in each area, and compares the relative average profitability and biological risk associated with managing with separate total allowable catch quotas (TACs) for the two areas or a combined TAC for both areas. The results suggest that the optimal management strategy in terms of both profitability and risk minimization will depend on levels of uncertainty in combination with characteristics of the fishery, particularly exploitation rates, mixing and migration, and harvest cost. The second stage of the research is using more realistic models representative of Gulf of Maine cod and other groundfish stocks.

2-year project, 2008-2010
Total Sea Grant funds: $99,835