Influence of the annual flood-pulse on catch per unit effort, condition and reproduction of Clarias gariepinus from the upper Okavango Delta, Botswana

T Bokhutlo, OLF Weyl, K Mosepele & GG Wilson

The flood-pulse is a major force shaping the population dynamics of fishes in tropical floodplain river systems
(Junk et al. 1989; Merron et al. 1990; Bayley 1995). In the Okavango Delta, Botswana, waters in the permanent swamps are poor in nutrients (Cronberg et al. 1996) and the arrival of the annual flood leads to immediate increases in nutrient levels, particularly in lagoons and off-channel areas (Mosepele et al. 2009). This results in increased primary production, and consequently zooplankton abundance, during the early stages of the flood (Mosepele et al. 2009). Increased habitat and zooplankton availability provide suitable conditions for the early development of fishes, and the annual flood-pulse is considered to be one of the major drivers of fish reproduction in the Okavango Delta (Merron et al. 1990; Mosepele et al. 2009). There is, however, a paucity of published literature on the effects of the floodpulse on fishes in this system and there is a need to provide quantitative evidence to support existing conceptual models.

Link to this article: http://dx.doi.org/10.2989/16085914.2016.1138279