The present study was undertaken with the objective to investigate the intraspecific variation of Channa punctatus on the basis of morphometric characters using the truss network system that was constructed from the fish body. Fish samples were collected from the Narora (n = 62) and Kanpur sites (n = 46) of the Ganga River, the Firozabad site in the Yamuna River (n = 66) and at the Lucknow site of the Gomti River (n = 60). Data were subjected to principal component analysis, discriminant function analysis and univariate analysis of variance. The first principal component (PC I) analysis explained 47.75% of total variation while PC II and PC III explained 8.18 and 7.48%, respectively. The step-wise discriminant function analysis retained seven variables that significantly discriminated the populations. Using these variables 81.85% of the original groups were classified into their correct samples. Misclassification was higher for the samples from Ganga River (19.6% at the Kanpur site and 19.4% for the Narora site). Of the total 27 transformed morphometric measurements, 23 exhibited significant differences among the populations. These findings indicate the presence of different stocks of fish from the three rivers. U.S.

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Otoliths, vertebrae, and pectoral fin spine sections were compared to ascertain the best ageing structure in Clarias gariepinus. Standard procedures were followed to prepare and study the age structures. All ageing structures showed alternating opaque and translucent bands that were interpreted as annuli. Age estimates were evaluated for comparison between readers and among structures. Among all structures otoliths showed highest (95.6%) agreement between readers, followed by vertebrae (91.2%) and pectoral spine sections (79.7%). Due to the highest values of percent agreement and lowest average percent error and coefficient of variation values between two readers, otoliths were considered to be the most suitable structure for ageing C. gariepinus. When otoliths' ages were compared with other bony structures, viz. vertebrae and pectoral spine sections, the highest percent agreement and lowest average percent error and coefficient of variation values were found between otoliths and vertebrae age estimates (90.7%). Mean age estimates from otoliths were comparable (P > 0.05) to the values obtained from vertebrae but significantly (P < 0.05) different to those from pectoral fin spine sections.

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The present study describes the length-weight relationship of two commercially important freshwater fish species of India viz., Channa marulius and Heteropneustes fossilis collected from the Ganga