Mixed-stock analysis of striped bass in two rivers of the Bay of Fundy as revealed by mitochondrial DMA

Abstract

Mark–recapture studies have shown that striped bass from the Hudson River and Chesapeake Bay migrate to the Bay of Fundy and its tributaries during spring and summer. The objective of this study was to determine the relative contributions of U.S. stocks and the endemic Shubenacadie River population to the adult striped bass aggregations that occurred during 1992 and 1993 in two rivers of the Bay of Fundy: the Saint John River, New Brunswick (where striped bass spawning may not presently occur), and the Shubenacadie River, Nova Scotia (where striped bass spawning occurs). Mitochondrial DNA genotype frequency data were used in a mixture model. Up to 97% of adults from the Saint John River were determined to be of U.S. origin, whereas less than 10% of adult striped bass collected in the Shubenacadie River were migrants from U.S. stocks. Consequently, we suggest that efforts to maintain or restore the Saint John River population with native broodstock may be unsuccessful owing to possible extinction of the native stock; however, protection of the Shubenacadie River spawning stock should be enhanced.