Browsing by Author "Libala, Stellah Naumi"

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    Fish species composition, fish sizes and diversity in the Kamutjonga floodplain, Kavango river, Namibia
    (University of Namibia, 2023) Libala, Stellah Naumi; Hay, Clinton
    Floodplains are amongst the most productive aquatic environments on earth providing valuable ecosystem services to communities such as being a valuable protein source for marginalized communities. This study ultimately aims to provide information on the fish species composition, fish sizes and species diversity in the Kavango River’s Kamutjonga floodplain as a basis to provide management advice to ensure the sustainable use of the fisheries. The fish species composition and relative abundance were assessed in the Kamutjonga floodplain along the Kavango River between February and April 2017, February to June 2018 and February to June 2020. Fish sampling was carried out once weekly using a seine net. A total of 2924 fishes were collected in 2017, 1678 fishes in 2018 and 4461 in 2020. The catch per unit effort (CPUE) by number was higher in 2017, followed by 2018 and lastly 2020. 31 fish species from 10 families, 37 species from 11 families and 31 species from 9 families were identified in 2017, 2018 and 2020 respectively. The Cyprinidae family was most prominent in the catches in 2017 and 2020, whereas the Cichlidae family dominated the catches in 2018. According to the index of relative importance, the most important species according to number in 2017, 2018 and 2020 were Oreochromis andersonii comprising of 47.7%, 27.1% and 49.6% of the total catches, respectively. The total weight of fishes collected in 2017, 2018 and 2020 were 6.404 kg, 5.963 kg and 11.456 kg respectively. The two most important fish species according to weight throughout the sampling period were O. andersonii (2.990 kg in 2017, 2.300 kg in 2018 and 6.273 kg in 2020) followed by Hydrocynus vittatus (1.546 kg in 2017, 1.915 kg in 2018 and 1.076 in 2020). The highest weight of fish was found in 2020, however, the catch per unit effort (CPUE) by weight was highest in 2018, followed by 2017 and then 2020. The majority of Oreochromis andersonii sampled were between the length classes 41 mm to 50 mm (n = 489) in 2017, 61 mm to 70 mm (n=89) in 2018 ii and 31 mm to 40 mm (n=606) in 2020. The majority of Coptodon rendalli sampled were found between the length classes 51 mm to 60 mm in 2017, 21 mm to 30 mm, 41 mm to 50 mm in 2018, and 41 mm to 50 mm in 2020. The majority of Hydrocynus vittatus sampled were found between the length classes 51 mm 59 mm (n = 54 mm) in 2017, 71 mm to 80 mm (n = 48) in 2018 and 31 mm to 34 mm (n = 68 mm) in 2020. This study found no significant difference in fish species diversity between years. The water level of the Kamutjonga floodplain had an influence on the catch rates, however, the water temperature did not affect the catch rates (catch per unit effort by number) in all the three years of sampling