Dorsal Coloration as an Indicator of Different Life History Patterns for Striped Bass within a Single Watershed of Atlantic Canada

Abstract

Abstract The striped bass Morone saxatilis spawning within a single river system are generally considered to be members of a single population unit. For some rivers in Canada, however, fishers have reported different-colored groups of striped bass in the watershed during the prespawning and spawning seasons, which suggests the existence of population subgroups. We examined this “colormorph” phenomenon for a striped bass population in the Shubenacadie watershed of Nova Scotia, Canada. Spawning fish had three dorsal coloration patterns: green, which was indicative of fish from the ocean; black, which was indicative of fish that overwinter in a freshwater headwater lake; and mottled, which were fish of unknown origin. Body morphology appeared to be similar among the three groups. Although the age structures of the spawning populations revealed a wider range of age-classes among greenbacked fish, the growth aspects (e.g., length, weight, and length at age) were similar. We estimated that during the prespawnin...