Food and feeding of Ehirava fluviatilis (Osteichthyes, Clupeidae) in Rajanganaya Reservoir, Sri Lanka

Abstract

Ehirava fluviatilis is of marine origin and has colonized some freshwater reservoirs of Sri Lanka. A small scale fishery of E. fluviatilis exists at the outflow LB canal of Rajanganaya reservoir. This study was carried out to investigate food and feeding habits of E. fluviatilis collected from this location. Sampling was done fortnightly from the landings. From the length-weight relationship, an allometric growth is evident. The theoretical weight of 50 mm E. fluviatilis calculated from length weight relationship was 928 mg, a comparable value to that of the estuarine population in Bolgoda Lake, Sri Lanka but a higher value than that of reservoir population in Parakrama Samudra, Sri Lanka, indicating that the population in Rajanganaya is as healthy as estuarine population. The highest index of relative importance in the stomach contents was recorded for diatoms. In addition, two genera of copepods, two genera of cladocerans, and two genera of rotifer, one genus each of insect larvae and crustaceans other than copepods and cladocerans were also present. Diatoms were also an important food item. As colonization success of E. fluviatilis in inland reservoirs seems to be due to the presence of their preferred food, micro-crustaceans, findings of the present analysis will be useful for investigating physiological advantages of being a stenophagous fish species.