PROBLEMS OF STOCK DEFINITION IN ESTIMATING RELATIVE CONTRIBUTIONS OF ATLANTIC STRIPED BASS TO THE COASTAL FISHERY

Stock contribution studies of mixed-stock fisheries rely on the applic ation of classification algorithms to samples of unknown origin. Altho ugh the performance of these algorithms can be assessed, there are no guidelines regarding decisions about including minor stocks, pooling s tocks into regional groups, or sampling discrete substocks to adequate ly characterize a stock. We examined these questions for striped bass Morone saxatilis of the U.S. Atlantic coast by applying linear discrim inant functions to meristic and morphometric data from fish collected from spawning areas. Some of our samples were from the Hudson and Roan oke rivers and four tributaries of the Chesapeake Bay. We also collect ed fish of mixed-stock origin from the Atlantic Ocean near Montauk, Ne w York. Inclusion of the minor stock from the Roanoke River in the cla ssification algorithm decreased the correct-classification rate, where as grouping of the Roanoke River and Chesapeake Bay stock into a regio nal (''southern'') group increased the overall resolution. The increas ed resolution was offset by our inability to obtain separate contribut ion estimates of the groups that were pooled. Although multivariate an alysis of variance indicated significant differences among Chesapeake Bay substocks, increasing the number of substocks in the discriminant analysis decreased the overall correct-classification rate. Although t he inclusion of one, two, three, or four substocks in the classificati on algorithm did not greatly affect the overall correct-classification rates, the specific combination of substocks significantly affected t he relative contribution estimates derived from the mixed-stock sample . Future studies of this kind must balance the costs and benefits of i ncluding minor stocks and would profit from examination of the variati on in discriminant characters among all Chesapeake Bay substocks.