Abstract
The translation of survey data into estimates of absolute abundance hinges on the availability of an accurate estimate of gear efficiency. In many fisheries, however, a wide range of estimates exists and research directed at quantifying this critical parameter has focused on relatively small, fishery-independent data sets. In the present study, a technique was developed to utilize the copious amounts of data available from an open-ocean fishery for sea scallops Placopecten magellanicus in a spatially explicit depletion model. In June 1999, Georges Bank Closed Area II was opened to the commercial scallop fleet after a 5-year multispecies fishing ban. During the 5-month opening, the spatial distribution and magnitude of fishing effort was tracked through vessel monitoring systems, and a relatively small but still substantial number of catch observations were made aboard vessels from the commercial fleet. A spatial analysis of both catch and effort data was utilized to select areas consistent with the assumptions of a DeLury analysis. Maximum likelihood estimation was then used to generate a single estimate of the catchability coefficient (and thus efficiency), while simultaneously estimating the initial abundance in each area. The gear efficiency of the New England-style scallop dredge used during the fishing season was estimated to be 42.7%. A sensitivity analysis of model results shows a potential range of 35.5–52.5%, depending on model assumptions.