Age and growth of sharptooth catfish, Clarias gariepinus (Burchell, 1822) (Clariidae), in the Lower Okavango Delta, Botswana

Abstract

Managing any inland fishery requires reliable age data and accurate estimates of growth rate. Clarias gariepinus, the largest catfish species in most tropical African floodplain river systems, is an important constituent of subsistence fishery catches. We used otolith-derived age estimates to describe patterns of age and growth for C. gariepinus from the Lower Okavango Delta in northern Botswana. Edge analysis of sectioned sagittal otoliths showed that growth zone deposition occurred during the annual flood peak between July and September. The maximum recorded age was 8 years. Growth was best described by the von Bertalanffy Growth Model of the form E[L|age] = 528.70(1–e–0.72(age+1.35)). A comparison of growth parameters from this study with those from previous studies suggests two distinct populations of C. gariepinus between the Upper and Lower Okavango Delta, emphasising the importance of regional stock assessment for key fishery species. The fairly short life span and high variability in growth of C. gariepinus are important indicators that it is imperative to maintain natural habitat and flow regime for sustainable management of fishery resources in the Lower Okavango Delta.