DISCRIMINATION AMONG ATLANTIC COAST POPULATIONS OF AMERICAN SHAD (ALOSA-SAPIDISSIMA) USING MITOCHONDRIAL-DNA

We used restriction endonuclease analysis of mitochondrial DNA (mtDNA) to differentiate among spawning stocks of American shad (Alosa sapidissima). Highly purified mtDNA was isolated from shad from four major spawning rivers: the St. John's (Florida), the Delaware, and the Hudson in the United States and the Miramichi in New Brunswick, Canada. Primarily four-and-five-base-cutting restriction enzymes were used to prepare both individual enzyme profiles and composite genotypes. Three separate spawning stocks, St. John's, Delaware-Hudson, and Miramichi, could be distinguished based on frequency differences in mtDNA genotypes generated by single restriction enzyme digests. We could not distinguish Delaware from Hudson River shad. Only a single definitive restriction site polymorphism was observed among all samples, but polyacrylamide gel electrophoretic mobility variants were common. Eco RI, Dde I, and Rsa I revealed stock-specific mtDNA genotypes. The frequencies of some genotypes occurred in latitudinal clines. Fifty-seven of 81 fish showed individual-specific composite genotypes. Geographic partitioning of genotypes suggests that mtDNA analysis may be useful for the identification of some American shad stocks and their relative contributions to mixed coastal fisheries.