Gill net selectivity in relation to important life history parameters of eight fish species from Hardap dam, Namibia

Abstract

Abstract by author:

Gill net selectivity of eight fish species from Hardap dam was studied to investigate the selectivity of the different gill net mesh sizes. The main purpose was to find out whether the fish being caught is undersized and what implications might have to [there might be for] sustainable production at Hardap dam. Samples for this research project were collected in 2003-2004 with gill nets of various mesh sizes. Using gill nets of different mesh sizes, a total of 1080 fishes were caught while a combined total 1332 fishes were obtained for all the gears including drag netting. Analysis revealed that the minimum length at first maturity was larger in all the species except for Labeo umbratus. Furthermore, the number of fish caught varied with mesh size of the nets. The length frequency of eight fish species indicated also that the number of fish caught per species varies with mesh size of nets. This was attributed to the distribution of different fish species in various habitats. Statistically analysis [shows that] there was no support of hypothesis that states that all the fish have the same probability of being caught. Results indicated that the survey method was efficient research purposes catching most species and size groups of the fish in the areas studied but could be destructive if used for normal exploitation, as it would lead to "recruitment overfishing"