Application of otolith shape analysis in identifying different ecotypes of Coilia ectenes in the Yangtze Basin, China

Abstract

The variability in otolith shape of the tapertail anchovy Coilia ectenes was investigated as a tool for identifying its different ecotypes. The outlines of 350 sagittal otoliths of known ecotypes collected from seven sampling areas, covering most of the distributional range of the species in the Yangtze Basin, were digitized and analyzed. Canonical Discriminant Analysis (CDA) of the shape indices and Fourier descriptors pooled together showed three distinct clusters of individuals representing anadromous, land-locked, and freshwater-resident ecotypes. A test of the classification success of CDA indicated that individuals of the freshwater-resident ecotype could be efficiently discriminated from either the anadromous or the landlocked ecotypes. A high rate of misclassification of the anadromous ecotype as the land-locked ecotype indicated some weakness when distinguishing individuals of these two ecotypes from each other. Average otolith shapes of the anadromous and the land-locked ecotypes shared similarities in the form of the rostrum and antirostrum, while the freshwater-resident ecotype showed marked dissimilarity from them. The information generated in this study is useful in ecotype-adapted resource assessment and management of C. ectenes in the Yangtze Basin.