Food habits of Pterygoplichthys disjunctivus (Vermiculated sailfin cat fish) and coexisting fish species in Victoria and Kalawewa reservoirs, Sri Lanka

Pterygoplichthys disjunctivus is now recognized as an invasive alien species (IAS) in Sri Lanka. This species has established populations in local water bodies including Victoria and Kalawewa reservoirs. Current study aims to find out food habits of P. disjunctivus. Fish samples of P. disjunctivus and coexisting fish species were collected from Victoria and Kalawewa reservoirs in the months of August and September in 2018, respectively, with prior permission and their total length, standard length and weight were recorded to the nearest 0.1 cm and 0.1 g, respectively. Relative importance of food items, Pianka’s food niche overlapping index values were analyzed in the study. Relative importance of food items of P. disjunctivus, Oreochromis niloticus and Etroplus suratensis show similar values for both reservoirs illustrating similar food preferences and omnivorous feeding habit. Diets of Rasbora daniconius, Glossogobius guiris, Mystus vittatus and Heteropneustes fossilis consisted of more insects and fish particles in both reservoirs indicating a carnivorous feeding habit including Mastecembelus armatus. Diets of Puntius filamentosus (Dawkinsia filamentosa) and Puntius chola consisted mainly with plant particles showing that these species are macrophyte feeders which were caught from Victoria and Kalawewa reservoirs. Pianka’s food niche overlapping index values for the diets of O. niloticus, E. suratensis, with P. disjunctivus in both reservoirs showed high overlapping values indicating high dietary overlap but G. guiris, M. vittatus, H. fossilis, P. filamentosus, R. daniconius, P. dorsalis and P. chola with P. disjunctivus in Victoria reservoir showed low overlapping values indicating relaxed dietary overlap. Pianka’s food niche overlapping index values for the diets of G. guiris, M. vittatus, H. fossilis, P. filamentosus, R. daniconius, and P. chola with P. disjunctivus showed low overlapping values indicating low dietary overlap in Kalawewa reservoir. Pianka’s food niche overlapping index values revealed P. disjunctivus is in competition with food habits with O. niloticus and E. suratensis. Therefore, suitable fishing gear or trap should be identified for effective controlling of P. disjunctivus in Sri Lankan water bodies.