MORPHOMETRIC, MERISTIC AND TRUSS NETWORKING DISTANCES AMONG THREE SPECIES OF CROAKER (Johnius borneensis, Johnius argentatus and Johnius belangerii) FROM THE BAY OF BENGAL, BANGLADESH

Abstract

Morphometric features are efficiently used for the improved differentiation and long term management of fish populations. Truss analysis is a frequently used taxonomic method to dissimilitude the morphologically similar species as well as a stock identification tool. It's a geometric morphometric method that uses landmarks in a fish body to acquire information about the shapes of fish. Using landmark-based truss networking techniques following 18 morphometric lengths, 10 meristic counts, and 23 truss network distance, the morphological variation of three croaker species (Johnius borneensis, Johnius argentatus, and Johnius belangerii) were analyzed from the northern Bay of Bengal. Data were analyzed and visualized through univariate ANOVA, canonical discriminate function analysis (DFA), and principal component analysis (PCA). Results found that the first DFA was responsible for 80.6% and 81.1%, whereas the second DFA was responsible for 19.4% and 18.9% variations among three species for the morphometric and truss distances respectively. In addition, 14 out of 18 morphometric measurements and 12 out of 23 truss-network measurements were significantly different (p < 0.05) among means of three different species. 1st PCA found 70.76% and 64.49% explained variations and 2nd PCA displayed 12.8% and 11.5% explained variations respectively for morphometric and truss distances among the three species. The high degree of morphological variations among the three species of croaker demonstrates Johnius borneensis and Johnius belangerii are morphologically highly similar and Johnius argentatus is completely distinct which may be due to their physiological and genetic variations among the studied species. The findings of the present study may be helpful in identifying species differences and for the management action in the Bay of Bengal. Further studies regarding the molecular characterization of the cytochrome c oxidase subunit I (COI) gene could finally determine the genetic variations among these three species from other croakers in the Bay of Bengal.