Reproductive biology of four large riverine fishes (Cyprinidae) in a man-made lake, Orange River, South Africa

The reproductive biology of Barbus holubi, B. kimberleyensis, Labeo capensis and L. umbratus was examined in a large reservoir on the Orange River, South Africa. The findings are integrated into the existing knowledge on large Barbus and Labeo species, which coexist in most river systems in Africa and Asia. Large Barbus spawn on gravel beds within the river channel during floods in spring or summer. In continuously flowing regulated rivers, time of spawning is governed by water temperatures. They have moderate fecundity, large eggs, incubation time of several days and the larvae are initially immobile with large yolk sacs. In contrast, Labeo species generally spawn on newly flooded ground, usually leaving the main river channel. Spawning may or may not be preceded by a longitudinal migration. Labeos are relatively fecund with small (30% Barbus size) eggs which hatch quickly and the larvae swim in bursts up into the water column before sinking down again. Early dependence on external feeding and undependable occurrence of conditions for spawning and juvenile feeding makes for variable reproductive success.