Stock identification of tiger tooth croaker Otolithes ruber (Schneider, 1801) along the Indian coast using truss network analysis

Abstract

The tiger toothed croaker Otolithes ruber (Schneider, 1801) of the family Sciaenidae is a demersal fish that contributes significantly to the marine landings of India. To identify stock units of O. ruber based on body shape morphometry, truss network analysis was carried out based on specimens collected from four selected  locations, two each from  east coast (Digha and Chennai along Bay of Bengal) and the west coast (Cochin and Ratnagiri along Arabian Sea) of India. A total of 20 truss distances along the fish surface, including head, mid body and posterior region were measured and transformed measurements were subjected to factor analysis and discriminant function analysis. The bivariate plot score of factor analysis indicating two distinct stocks on both the coasts may be the consequence of geographical isolation and different environmental conditions along the Bay of Bengal (east coast) and Arabian Sea (west coast). The Ratnagiri and Cochin population showed considerable mixing which indicated the presence of a unit stock along the west coast. However, existence of strong morphometric differentiation between Digha and Chennai populations indicated two separate spawning populations in the Bay of Bengal. In the cross-validation of Discriminant function analysis, the most well classified group was Digha population (97.85%). The present study suggests the possible existence of three stocks of O. ruber, one in west coast (Cochin and Ratnagiri) and two in east coast (Digha and Chennai) which can be considered while formulating effective management strategies for the species.

 Keywords: Discriminant analysis, Factor analysis, Otolithes ruber, Stock identification, Truss network system