Food niche segregation among co-occurring endemic fish species in Sri Lanka
R.R.A.R. SHIRANTHA, M.J.S. WIJEYARATNE AND U.S. AMARASINGHE
The food and feeding habits of six endemic freshwater fish species namely, Belontia signata, Rasbora vaterifloris, Puntius cumingii, Puntius nigrofasciatus, Puntius titteya and Garra ceylonensis inhabiting the streams of the Kalu and Kelani river basins in Sri Lanka were studied from October 1998 to September 2000 with the objective of quantifying the food niche overlap and evaluating the degree of competition for food resources among them. All fish species studied except R. vaterifloris were found to be omnivorous, feeding on different varieties of food items. R. vaterifloris was found to be strictly carnivorous. P. titteya and B. signata were highly selective for diatoms, aquatic insects and rotifers while P. cumingii, although highly selective for diatoms, was non-selective for aquatic insects and filamentous algae. P. nigrofasciatus was selective for diatoms, aquatic macrophytes and non-selective for green algae. R. vateriflons and G. ceylonensis were selective for aquatic insects and crustaceans and nonselective for diatoms, rotifers and detritus.
P. nigrofasciatus showed a moderate dietary overlap with P. cumingii and a low dietary overlap with other co-occurring species. R. vaterifloris showed moderate dietary overlap with G. ceylonensis and a low dietary overlap with other co-occurring species. A moderate dietary overlap was observed among B. signata, P. cumingii, P. titteya and G. ceylonensis. The results indicated that there is very little or no interspecific competition among these species due to low or moderate dietary overlap and different degree of selectivity for different food items, which has enabled them to co-exist.