Pacific sardine (Sardinops sagax) stock discrimination off the west coast of Baja California and southern California using otolith morphometry

The hypothesis that there are three Pacific sardine (Sardinops sagax) stocks along the west coasts of Baja California and southern California was evaluated using multivariate discriminant analysis of otolith morphometric variables. Four synoptic data sets were analyzed to test the three-stock hypothesis: warm Magdalena Bay (Warm MB), temperate Magdalena Bay (Temp MB), temperate Ensenada (Temp EN), and cold Ensenada (Cold EN). A gradual increase in the overlap index (Wilks' Lambda values) reflected the relative degree of similarity among the groups when all comparisons were considered. The Warm MB was the most differentiated group from the others, particularly the Cold EN. The highest degree of similarity was found among the two temperate groups (Temp MB and Temp EN), and they could not be significantly separated in 68% of the repeated tests. Our results support the existence of the three Pacific sardine stocks in the study area and are consistent with previous findings obtained using different methodologies, e.g. temperature-at-catch data.