Abstract

The possible population structure of the Chilean herring Strangomera bentincki (Norman, 1936) was studied, using a network of 21 morphometric characters and an aditional 6 meristic characters. Samples were obtained between October (1993) and December (1994) from the purse-seiner fishery landings at San Antonio, Talcahuano and Puerto Montt. Data analysis, quarterly grouped, was carried out using multivariate methods based on variance-covariance matrices. As such, Principal Component Analysis was used as an exploratory approximation for the identification of discrete groups and Multigroup Discriminant Function Analysis was used to compare groups and individuals in a discriminant space. The latter method assigns each individual to the group it most closely resembles. The characters that best explained differences between the three fishing areas were identified and their variability was analyzed on a temporal scale and by age-class. Results show the existence of at least two population (stock) of Chilean herring along its latitudinal distribution. Puerto Montt has a distinctive morphological identity, while Talcahuano appears to be a transition zone, with a high degree of morphological overlapping with San Antonio. Morphological variation among localities was more clearly discernible for age-class 1 fishes than for age-class 2 and 3, this might mean that characteristic regional patterns become less pronounced as the fish grow old. Meristic characters produced similar results, with gill rakers and vertebral numbers as the most discriminant variables and, again, with Puerto Montt as the most clearly defined independent locality.