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

Abstract

The chapter provides a survey on the fish fauna of the Parakrama Samudra reservoir; 23 species were encountered during two research visits, using different sampling techniques. According to their habitat preferences and feeding biology, the numerically abundant species can be grouped in

• a) Littoral ‘Aufwuchs’ feeders (e.g. Puntius sarana, P. filament osus, Labeo dussumieri, Etroplus suratensis, Rasbora daniconius),

• b) zoobenthivorous species (e.g. Puntius dorsalis and P. chola), and

• c) limnetic species feeding on phytoplankton (Sarotherodon mossambicus, Amblypharyngodon melettinus) and zooplankton (Ehirava fluviatilis)

High food-overlap values have been encountered in the species pairs P. sarana - R. daniconius and P. filament osus - 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 two 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.

Observed seasonal changes in the species composition and population structure of the fish fauna are discussed with regard to (a) discontinuous breeding activity and spawning migrations of species, (b) seasonal changes in habitat and resource availability and (c) predation effects by fish and fish-eating birds.