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Ichthyofaunal survey was conducted in the Ib River (21°44’ to 22°50’ N; 83°56’ to 83°54’ E), an important tributary of Mahanadi, to evaluate the diversity and distribution of freshwater fishes along six sites on seasonal basis between February, 2016 and January, 2017. A total of 55 species belonging to 42 genera, 21 families and 9 orders were recorded from the study area. Maximum number of species belonged to the Order Cypriniformes (41.8%) followed by Siluriformes (21.8%) and Perciformes (21.8%). Maximum value of species richness was observed in downstream areas; Sundargarh and Barghat and least in upper stretches of Pamsala. Shannon–Weiner diversity index ranged between 2.47 to 3.68 at the six sites of Ib River indicating healthy state of the river. Bray-Curtis similarity cluster analysis suggests that similarities between sites decrease with increasing distance, with highest similarity found between Sundargarh and Barghat sites. Baseline data on fish biodiversity has been generated in this study which can now be periodically monitored and form basis for future conservation plans.

Length-weight relationship and condition factor in 57 freshwater fish species of 19 families and 38 genera from various rivers, and lakes of different climatic zones in India were studied. The estimates (total 67) for the parameter b of the length-weight relationship ranged between 1.422 and 3.917, with a mean value of 2.994. Correlation coefficient was found to be highly significant (r 2 >0.90) in all except for Crossocheilus latius latius, Acanthocobitis botia and Garra lamta. Growth was found to be isometric (b = 3) in 32 species, positively allometric (b>3) in 21 species and negatively allometric (b<3) in 14 species. It was also found that some species exhibited variations in their growth pattern in different habitats, which showed the influence of preference and availability of suitable habitat conditions.

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