Assessing The Current Status Of Local Floodplain Fisheries In The Okavango River, Kavango East Region, Namibia

ABSTRACT

Globally, floodplains are acknowledged as hydrologically important, environmentally sensitive, and ecologically productive ecosystems that perform several natural functions. They provide both cultural and natural services that are of great value to society (Peel, 2012). Flooding occurs naturally along river’s and is an integral part of a healthy watercourse. It is believed that flooding may nurture life in and around rivers as the waters transport nutrient-rich sediments that contribute to a fertile environment for growth of plants that maintain and support biota. Particularly, these nutrient rich areas may perhaps play an important role for many fish species that utilize the floodplain (Hay et al., 2002). It has been suggested that floodplain areas could be used for spawning, nursery, breeding and feeding grounds for many freshwater fish species. A fish survey in the floodplain at Kamutjonga Inland Fisheries Institute (KIFI) was conducted from February to April 2017. Fish sampling was carried out once a week using a seine net. Whereas data from fishermen catches were recorded daily for the flood period. The total area covered was 261 753m² for all sampling events. From the fishermen catches, a total of 12 353 individuals were collected representing 24 species along the floodplain at KIFI. From this, the Cyprinidae and Cichilidae families dominated the fishermen catches with 45.8% and 37.50% respectively according to percentage number (%N). The less common families included the Schilbedae and Cyprinodontidae families which combined made up less than 17% of the caches for the group. The species were ranked based on percentage index of relative importance (%IRI). The five most important fish species accounted for 96% (total IRI) when combined with Oreochromis andersonii (57.8%), Hydrocynus vittatus (10.7%), Serranochromis altus (10.2%), Tilapia sparrmanii (5.1%), and Pseudocrenilabrus philander (5.9%). In comparison, the seine net survey resulted in a total of 2915 fish representing 10 families, 17 genera and 31 species sampled from the Kamutjonga floodplain. The five most important fish species according to the percentage index of relative importance (%IRI) were Oreochromis andersonii (76.7%), S. altus (5.1%), P. philander (4.5), T. sparrmanii (3.2%) and Coptodon rendalli (3.2%) cumulatively contributing to 92.7% of the catch.

According to percentage IRI, Cyprinidae represented 11 species contributing 35.5%, Cichlidae contributed 32.3%, Clariidae and Hepsetidae contributed 6.5% each, Poecillidae, Schilbeidae, Characins, Mochokidae and Mormyridae all contributed 3.2% each. These results suggest that the floodplain at KIFI is not only exploited for subsistence fisheries but is potentially utilized as feeding, nursery grounds and could provide refuge for the Okavango River fish communities. Furthermore, from both the fishermen and experimental gear catches it was observed the species abundance was dominated by O. andersonii for the flood period. Species diversity for the different flood prod showed no significant differences for the fishermen catch, however there were significant differences observed for the experimental dragnet catch. There was a statistically significant difference (P=0.00) in surface water temperature during the flood rising phase, peak and receding phase in the floodplain and river. The floodplain and the river’s conductivity was observed to be significantly different (P=0.03) during the different flood phases. There was a significant difference (P=0.00) in water clarity during the flood rising, peak and receding phase in the floodplain as well as in the river.

For the sustainability of the fishery seine netting and mosquito netting in the floodplains at KIFI should be discouraged to avoid recruitment overfishing particularly for fish species namely; O. andersonii, H. vittatus C. rendalli that are commercially important species. This management approach will ensure that smaller fish sizes are not harvested before they mature and recruit into the fishery.