Spatial Variations in the Shape and Chemistry of Sagittal Otoliths in Channa punctatus (Channidae) Populations of Ganga Basin, India.

Variations in the shape and elemental microchemistry of sagittal otoliths in Channapunctatus (Bloch, 1793) populations of three different rivers (Gomti, Ganga and Ken) of Gangetic basin sampled at three geographically distant locations (Lucknow, Kanpur and Banda) were analyzed. In this study, otolith shape was analyzed using shape indices, geometric morphometrics and Fourier analysis and tested through univariate and multivariate statistical procedures. 3 shape indices namely circularity, roundness and rectangularity out of 6 were significantly different in ANOVA (p < 0.05) between the three population groups. Principal component analysis of shape variables in geometric morphometrics and normalized elliptical Fourier descriptors (NEFDs) accounted for 82.25% and 80.10% of total variance respectively. Visualization of shape variation explained by principal components was depicted in the form of shape deformation grids (relative warps) and otolith contour reconstruction. The elemental concentrations in the otoliths of the three rivers also differed, and elements Sr and Ba, Mn and Pb, and Fe were significantly higher (ANOVA, p < 0.05) in the otoliths of river Ken, Gomti and Ganga respectively. Discriminant function analysis (DFA) of the shape variables, NEFDs and otolith elemental concentration clearly differentiated the otoliths of different rivers in scatter plots with isolated distant population groups and 100% classification of all the specimens into their respective river population. The study indicated regional variations in the shape and otolith microchemistry and also that fish from different rivers lived in different environmental conditions. These variations in the present study might be due to geographical isolation and river fragmentation due to the change in the habitat that limits fish movements. Thus, C. punctatus of river Gomti, Ganga and Ken sampled at Lucknow, Kanpur and Banda districts respectively existed as three different phenotypic stocks. This study is useful for the development of effective plans for sustainable fisheries management with the aim of conservation of this economically exploited fish in the Ganga basin. [ABSTRACT FROM AUTHOR]