The fishery, growth rates and notes on reproduction of the snakehead Channa striata (Bloch) (Perciformes: Channidae) in some irrigation reservoirs of Sri Lanka

Abstract

The fishery for snakehead ( Channa striata) in Sri Lanka was studied by monitoring the monthly catch from a large reservoir of 972 ha surface area and that of five closely situated smaller reservoirs of surface areas ranging from 37 to 265 ha for 18 months. The annual snakehead yield in the large reservoir was 1.76 kg ha −1 while that of smaller reservoirs was 7.08 kg ha −1. In all reservoirs, snakehead was only a by-catch of the tilapia fishery. The total annual C. striata yield in Sri Lanka is estimated to be over 317 t which is only about 0.8% of the total reservoir fish production. The growth parameters asymptotic length ( L ∞) and growth constant ( K) of the snakehead populations, as determined by monthly size-frequency data, were respectively 60 cm total length and 0.40 for the large reservoir and 53 cm total length and 0.35 for the smaller reservoirs. The mean length of the ten largest individuals ( L max), the mean length of the ten smallest individuals ( L min), mean length at recruitment to the fishery ( L′) and mean size at first capture ( L c) of the two populations were respectively 51.6 cm, 26.6 cm, 37.5 cm, 42.5 cm for the large reservoir and 46.4 cm, 2.2 cm, 36.0 cm and 35.4 cm for the smaller reservoirs. The respective total, natural and fishing mortalities of the populations were 1.53, 0.84 and 0.69 in the large reservoir and 1.19, 0.77 and 0.42 in the smaller reservoirs. In all reservoirs, over 90% of the catch consisted of third and fourth year fish. Spawning was observed in all months, but it was much more enhanced during and immediately following the major rainy season.