Gilnet selectivity of two indigenous fish species, Ompok bimaculatu.- and Puntius dorsalis was determined in a small-scale fishery at Uruwal Oya, i: the Gampaha district. The optimal lengths (L^) of the two species for difieren mesh sizes were determined by the Baranov-Holt method. The relationship between L^and mesh size (M) of gillnet for the two species are described by th> following equations:
■ O. bimaculatus: = 4.076 + 3.694 M (r = 0.992; p < 0.01) P. dorsalis: = 2.445 + 3.410 M (r = 0.994; p < 0.001)
The mean sizes of maturity of O. bimaculatus (21.6 cm for males and 2C cm for females) and P. dorsalis (13.4 cm for males and 14.8 cm for femali approximately correspond to Lopt in stretched gillnet mesh sizes of 5.8 cm and .' cm respectively according to the above relationships. Therefore there seems be a need for regulating mesh size of gillnets in this fishery in order to prevt immature O. bimaculatus and P. dorsalis being caught.
Keywords: Baranov-Holt method, Biodiversity, Cyprinidae, Fisheries mans ment, Freshwater fish, Gillnet selectivity, Ompok bimaculatus, Puntius dorse. Riverine fish, Siluridae, Uruwal Oya.