Age estimation, growth rate and size at sexual maturity of tigerfish Hydrocynus vittatus from the Okavango Delta, Botswana

The aims of this study were to determine relative age, growth rate and size at maturity of tigerfish in the Okavango Delta as a basis for the development of a fisheries management plan. A total of 206 tigerfish Hydrocynus vittatus, collected by angling in August 2005, 2006 and 2007, was assessed for sexual maturity and relative ages were estimated from 135 of these, using scales and whole and sectioned otoliths. Sectioned otoliths were the most appropriate method for ageing H. vittatus of up to 20 years old. Males were present in all relative age classes, proving that they do not disappear from the population at a young age, as previously thought. Males matured at 451 mm TL and females at 522 mm TL, corresponding to an approximate relative age of four years for both sexes. Males lived for up to 20 years, females for up to 16 years.