Food and feeding biology of the endemic carplets Barbus cumingi and B.nigrofasciatus (Oateichthyes, Cyprinidae) of Sri Lanka

Abstract

The food and feeding biology of B. cumingi and B. nigrofasciatus were studied in a small stream of the upper reaches of the river Mahaweli. Both species are herbivorous substratus feeders and their diets consist mainly of diatoms and detritus. Diatoms were the most abundant food item (50.1perc.) in the diet of B. nigrofasciatus but both diatoms (36.8perc.) and detritus (38.4perc.) were common in the diet of B. cumingi. Both species appear to avoid blue-green algea. The relative abundance of detritus and diatoms in the diet of both species varied from month to month and the importance of diatoms generally increase and that of detritus decreased with the increase of body size. The "intestinal" contents of B. cumingi contained a larger amount of diatoms in comparison to that of "stomach" contents, whereas in B. nigrofasciatus the amount of diatoms was low in the intestine. The relative gut length(RGL) of B. cumingi varied from 0.96 to 2.64 while that of B. nigrofasciatus varied from 0.89 to 2.54. These ranges agree well with reported RGL ranges for other herbivorous cyprinids. The RGL increased with increase in body size in both species as has been observed in other cyprinids.