Identification of morphologic traits for a rapid differentiation of Patagonian sprat (Sprattus fuegensis) and Chilean herring (Strangomera bentincki)

The artisanal purse seiner multispecies fishery operating in the interior waters of Chiloe Island captures Chilean herring (Strangomera bentincki) and Patagonian sprat (Sprattus fuegensis) at the same time in the same area. These species have very similar external morphology, difficulting the species identification in the field, even for an experience scientific observer. Therefore, the aim of this work is to propose the external morphologic traits to be considered for a rapid identification of these species in the field. 60 specimens of Chilean herring and 79 Patagonian sprat were analyzed. Individuals collected were identified at the level of species and the following measurements were recorded: total length, head length, snout, eye orbital and postorbital. Before the analysis, all measurements were standardized to avoid collinearity. Using multivariate statistics including principal component analysis, analysis of variance and covariance (ANOVA and ANCOVA), multivariate analysis of covariance (MANOVA) and linear discriminant analysis, we found that the post-orbital measurement is the morphological trait which shows the largest differentiation between species. We concluded that the post-orbital measurement is the single external morphological trait which enables a rapid identification of these species in the field. The results of this research can be taken as a baseline analysis upon the generation of field guides, and thus, supporting the species identification by scientific observers.