Stock Definition in Atlantic Herring (Clupea harengus harengus): Genetic Evidence for Discrete Fall and Spring Spawning Populations

Abstract

Ripe Atlantic herring (Clupea harengus harengus) were sampled from seven discrete spawning grounds in the Gulf of Maine and Gulf of St. Lawrence over a period of 3 yr. Genetic polymorphisms were observed at 13 enzyme loci by starch gel electrophoresis. Five highly polymorphic loci were used to assess population structure of herring stocks by contingency analysis of log-likelihood differences in gene frequencies. Significant temporal variation was observed at several localities. Within both spring spawning and fall spawning populations, significant spatial heterogeneity was noted for particular years, but was not temporally stable. By contrast, overall heterogeneity between spring and fall spawning populations was highly significant indicating genetic isolation of spring spawning populations in the Gulf of St. Lawrence from fall spawning aggregates in the Gulf of St. Lawrence and Gulf of Maine. The low levels of genetic heterogeneity and absence of both temporal stability within fall spawning samples and spatial stability among samples is not consistent with the existence of more than a single genetic population of fall spawning herring in the northwest Atlantic.Key words: Clupea harengus harengus, population genetics, biochemical genetic variation, stock differentiation