Diet components, dietary habits, resource and its use in the coexisting catfish species

Abstract

In over last six decades fisheries of the Ganga river System in general and the Ganga R. in particular have witnessed a radical change in dominance from the carp to catfish and now to invasive exotic species. Has this happened due modified river environment (natural flows, pollution) or have the species modified the food-web of the river is an issue that should be addressed in deep earnest intent. Among many facets that need to be answered, we should know the food resources base available in the river environment, preferences of fish species, if it is selective and the extent of overlap among the sympatric and co-existing species. The present investigation precisely examines this for the co-existing catfish species, Rita rita and Bagarius bagarius. R. rita feeds with greater intensity than B. bagarius. In R. rita intensity was high in pre-monsoon (January to May) compared to B. bagarius where intensity was higher in post monsoon (October to December). R. rita showed +ve preference for chironomid-Diptera and variety of Trichoptera among insects.Others include crustaceans and gastropod molluscs. In contrast B. bagarius shows preferences for a consortium of Diptera (Simuliidae), Trichoptera (Glossosomatidae), Ephemeroptera (Heptageniidae), Coleoptera and Odonata among insect food. It has high preference for fish elements. Both species select these items. There is a biologically significant diet overlap but these species avoid competition not only by selecting different items from the common food resource base but also by seasonal variation in feeding intensity. Such studies need to be extended to fish within and among feeding guilds. Keywords Catfish, diet composition, co-existance