A contribution to the ecology of the fish fauna of the Parakrama Samudra Reservoir.

Abstract

Some 23 species were encountered. Numerically abundant species can be grouped in 1) littoral 'Aufwuchs' feeders (eg. Puntius sarana, P. filamentosus, Labeo dussumieri, Etroplus suratensis, Rasbora daniconius); 2) zoobenthivorous species (eg. Puntius dorsalis, P. chola); and 3) limnetic species feeding on phytoplankton (Sarotherodon mossambicus, Amblypharyngodon melettinus and zooplankton (Ehirava fluviatilis). High food-overlap values were encountered in the species pairs P. sarana - R. daniconius and P. filamentosus - E. suratensis in the littoral zone, and in P. dorsalis - P. chola in the offshore zone. An analysis of the diel feeding pattern of the latter 2 species indicates the mechanisms by which food competition between them is relaxed. Puntius chola feeds throughout the 24-h cycle, predominantly in the offshore areas. Puntius dorsalis feeds mainly during the night and its nocturnal feeding activity is connected with inshore migrations. Seasonal changes in species composition and population structure of the fish fauna are discussed with regard to a) discontinuous breeding activity and spawning migrations of species, b) predation effects by fish and fish-eating birds.-from Authors