Dynamics Of The Floodplain Fisheries Of The Zambezi And Chobe Floodplain, Zambezi Region, Namibia

ABSTRACT

Floodplain fisheries are typically multi-species and in most cases harvested with a variety of gears. In the upper- Zambezi, artisanal gillnet fishers mainly target three cichlids: Oreochromis andersonii, Oreochromis macrochir and Coptodon rendalli. However, their abundance is declining because of increased fishing pressure and their stocks are becoming vulnerable to overfishing. The principal aim of this PhD thesis was to assess the fish population dynamics in a highly variable system and the implications of these dynamics to fisheries management by investigating the response of floodplain fisheries to water flow and to determine fish harvesting patterns and catch rates on the Zambezi/Chobe floodplain. The specific objectives of this study were: (1) to link littoral fish colonization rates with water quality and water level in floodplain littoral habitats; (2) to determine the feeding ecology of Hydrocynus vittatus (Tigerfish) in the Zambezi/Chobe floodplain (3) to assess the fishing patterns and harvesting rates of the gillnet fishery on the Zambezi/Chobe floodplain; (4) determine the volume and turnover of fish exports from the Zambezi/Chobe floodplain and finally (5) to assess the significance of fish protected areas in protecting the fish stocks of the Zambezi/Chobe floodplains. Seine net surveys showed that the marginal zone of the Zambezi/Chobe floodplain were dominated by fishes of the fish families Cichlidae, Cyprinidae and Characidae. Individual fish densities of small fishes showed spatiotemporal variations among the different stages of flooding with a marked increase in juvenile cichlids during the peak flooding phase while cyprinids were most abundant during the receding (fall) phase. Among other environmental filters, dissolved oxygen and water level had a marked influence on the distribution and abundance of the littoral fish species.

The feeding ecology of Hydrocynus vittatus (Tigerfish) (Characidae), in the Zambezi River was investigated between February - December 2016. The findings indicated that large size classes of H. vittatus (>176mm) were largely piscivorous, and showed a diet shift with change in size. The small size classes (