Gill net catch composition and catch per unit effort in Flag Boshielo Dam, Limpopo Province, South Africa

Abstract

Gill net surveys were conducted in 2013 to determine species composition and fisheries potential of Flag Boshielo Dam. Species contributing the most towards total biomass were Labeo rosae (40%), Oreochromis mossambicus (15%), Schilbe intermedius (10%) and Labeobarbus marequensis (9.8%). Catch per unit effort for gill nets set at night (4.4 ± 0.6 kg·100 m-net⁻¹·hr⁻¹) was significantly higher (P < 0.05) than for those set during the day (0.9 ± 0.1 kg·100 m-net⁻¹·hr⁻¹). Total fish biomass captured in 30, 50, 70, 90 and 110 mm mesh sized nets was 3.1, 31.5, 43.5, 23.5 and 16.1 kg, respectively. Catch in gillnets with mesh sizes ≥ 70 mm was dominated by L. rosae comprising 60% of the catch in the 70 mm mesh; L. rosae (40%) and O. mossambicus (36%) in the 90 mm mesh; and O. mossambicus (40%) and Clarias gariepinus (40%) in the 110 mm mesh. If a small-scale fishery were to be initiated, it is recommended that mesh sizes should exceed 70 mm and that further research on the biology and ecology of the main target species and of the current utilisation of the fishery be conducted to guide sustainable utilisation.