Background. Rivers in India harbouring a rich diversity of fish are at present subjected to intense anthropogenic stress leading to degradation of the habitat. An understanding of the complex ecological variables determining species richness in these rivers is lacking. The relation between the ecological parameters (climate, hydrology, and morphometry) and the fish species richness were assessed in fourteen major rivers of India. Materials and methods. The data of seven ecological variables of fourteen major rivers of India for the years 1994–2009 were quantitatively analysed for determining their influence on fish species richness. Principal factor analysis (PFA) was carried out for dimension reduction and eliminating collinearity. Subsequently, fish richness was regressed on the retained factors under generalised linear model (GLM) for determining contribution of factors towards species richness in rivers. Results. The most influential determinants of species richness were the factors such as: surface area of the river basin (0.439) followed by fish habitat availability potential (0.326) a synthesis of the variables rainfall, discharge and sediment load. The predicted loss of fish species is evident at a 10% alteration in the ecological variables of the rivers. Conclusion. The predicted loss of fish species richness is indicated at a10% alteration of the habitat factors in most of the rivers and can be useful for river planners and conservationists.

fish species richness, tropical Indian rivers, ecological factors