Research Sampling and Survey Design for Sea Scallops ( Placopecten magellanicus ) on Georges Bank

Abstract

A comparison of stratification schemes developed by Canada and the United States for sea scallop surveys on Georges Bank did not provide a clear indication of a superior approach. The United States employs depth and latitude asthe basis for stratification, while Canada uses strata defined from commercial catch and effort. Analysis of variance of research catch data and comparisons of the mean squares and of the reductions in variance were the criteria for comparison. Based on the standard error of abundance, at least 20 tows per stratum are advocated, but little improvement would be expected with more than 40 stations per stratum. Neither approach uses an optimal allocation of stations to strata. The highly non-proportional allocation of stations in the Canadian scheme is due to an emphasis on management and assessment of the stock on the commercially-important grounds.