Population structure and biology of alewives (Alosa pseudoharengus) and blueback herring (A. aestivalis) in the Saint John River,New Brunswick

Synopsis Examination of more than 2,000 alewives (Alosa pseudoharengus) and blueback herring (A. aestivalis) from various areas in the Saint John River, N.B., showed differences in their morphometric and meristic characters. They differed also in length and age, compositions, spawning time, length and age at maturity, back-calculated lengths, and growth parameters. Within each species, between-area comparisons showed significant differences in some of their meristic characteristics.To test a homing hypothesis for alewives, a multivariate analysis was performed on eight meristic characters. Two discriminant function programs, discriminant analysis for two groups and a multiple group stepwise discriminant analyses were used. Values of the generalized Mahalanobis D² and percent overlap in frequency distributions of meristic characters suggest that considerable straying of fish, especially between adjacent areas occurs during upstream spawning migration.This article is one of several papers presented at the Second European Ichthyological Congress, Paris, 8–15 September 1976, to be published in Environmental Biology of Fishes.