Usefulness of Meristic and Morphometric Characters in Discriminating Populations of American Shad (Alosa sapidissima) (Ostreichthyes:Clupeidae) Inhabiting a Marine Environment

American shad (Alosa sapidissima) concentrate each summer in the basins of the inner Bay of Fundy during their coastal migration. Tag returns from 6124 marked shad indicated that these fish return to every important shad spawning stream on the Atlantic coast. Ten meristic and 16 morphometric characters of shad collected from 14 rivers (range: Florida to Quebec) were used to develop linear discriminant functions (LDF). Variables which differed significantly (p < 0.05) between the sexes, year of sampling, and the time of collection during the spawning run were removed prior to LDF classification. The highest mean percent correct classification was achieved by the allocation of fish into regional groups, after classification into individual rivers, using pooled meristic and morphometric variables: 87.2% for males and 82.4% for females. The functions were then used to assign shad from a mixed populations (Cumberland Basin) to individual rivers and regions. Of these, 10.9% were assigned to rivers south of Cape Lookout, North Carolina, 38.1% to rivers between Cape Lookout and Cape Cod, 32.5% into rivers of the Bay of Fundy, and 18.5% into rivers in the Gulf of St. Lawrence. In-river tag returns were compared with LDF classification and were found to be similar.