Spatial aspects of the reproductive and feeding biology of the striped robber, Brycinus laterolis (Pisces : Characidae), in the Okavango Delta, Botswana

The Okavango Delta is a vast inland wetland system situated in northern Bot swana. High rainfall is received in early summer in the southern Angolan hi ghlands and throughout the Delta with the flood waters reaching the upper r iverine floodplain between March and May where it percolates through to the lower drainage rivers between July and September. Aspects of the reproduct ive and feeding biology of two allopatric populations of the striped robber , Brycinus lateralis, a small characin species inhabiting the northern rive rine floodplain and southern drainage rivers, were investigated. Both popul ations were similar in the biological aspects studied, with the flood cycle having little influence on the timing of reproduction, sexual maturity and dietary composition. Female fish from both populations matured sexually at 57 mm SL, breeding over a protracted period during the warm, summer months . In both populations, the sex ratio was female-dominated at 4.8:1 (riverin e floodplain) and 2.2:1 (drainage rivers). The striped robber is an opportu nistic micro-carnivore with immature fish feeding predominantly on Daphnia spp. and adults being largely insectivorous.