Identification of morphologic traits for a rapid differentiation of Fuegian sardine and Chilean herring.

The artisanal purse seiner multiespecies fishery which operates in the interior waters of Chiloe Island captures Chilean herring ( Strangomera bentincki ) and Fuegian sardine ( Sprattus fuegensis ) at the same time in the same area. These species have very similar external morphology making difficult the species identification in the field, even for an experience scientific observer. Therefore, the aim of this work is to propose which external morphologic trait(s) should be considered for a rapid identification of these species in the field. During April 2008, 60 individuals of Chilean herring and 79 of Fuegian sardine were collected in landing ports of the X region of Chile. Once in the laboratory, individuals collected were identified at the level of specie and the following measurements were recorded: total length, head length, snout, eye orbital and post-orbital. Before the analysis, all measurements were standardized. Using multivariate statistics including principal component analysis, MANOVA, ANOVA and linear discriminant analysis we found that the post-orbital measurement is the morphological trait which shows the largest differentiation between species. We conclude that post-orbital measurement is the single external morphological traits which enable 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.