Department of Environmental Sciences

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Browsing Department of Environmental Sciences by Advisor "Mfune, John K. E."

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    A comparative study on the fish species composition, diversity and catch rates among the fisheries reserves on the Zambezi and Kwando rivers, Zambezi region
    (University of Namibia, 2025) Namitaa, Tukelo Lavinia; Mfune, John K. E.
    The Zambezi and Kwando Rivers in northeastern Namibia support vital floodplain fisheries that provide food, income, and seasonal employment for many local communities. However, increasing pressure from overfishing, habitat degradation, and climate change has highlighted the need to establish fisheries reserves to promote sustainable resource use. This baseline study evaluated fish assemblages, specifically species composition, diversity, and catch per unit effort (CPUE); across five fisheries reserves located along the Zambezi River (Sitwela, Kabweza, and Makangala) and the Kwando River (Luhingi and Qhuqhumupa). Gillnet surveys using both experimental and monofilament gillnets were conducted between 13 November and 13 December 2021. A total of 3,360 individual fish, representing 32 species, were captured. On the Zambezi River, Makangala had the highest species richness with 24 species, followed by Sitwela with 21 species, and Kabweza with 20. On the Kwando River, Luhingi recorded 17 species, while Qhuqhumupa had 12. There was no statistically significant difference in species diversity among the reserves (H(4)=8.268, p=0.082). However, overall CPUE (by weight) varied significantly between sites (H(4)=46.621, p<0.001), with Luhingi showing the highest CPUE (0.704±0.78 kg/set) and Kabweza the lowest (0.209±0.14 kg/set). Significant differences in individual CPUE were observed for two commercially important species: Clarias gariepinus(H(4)=26.783, p<0.001) and Clarias ngamensis (H(4)=17.967, p=0.001), while no significant variation was found for Serranochromis macrocephalus (H(3)=0.260, p=0.967). Similarly, mean fish sizes for C. gariepinus (H(4)= 25.850, p<0.001) and C. ngamensis (H(4)=14.660, p=0.005) differed significantly across sites, whereas no difference was noted for S. macrocephalus (H(3)=0.779, p=0.885). Regression analysis showed that temperature had no effect on fish catch rates. However, reserve size explained 14% of the variation in catch rates. These spatial differences in catch rates for key commercial species may be influenced by factors such as the degree of protection, age, and size of the reserves. In particular, higher CPUEs in the Kwando River reserves may be attributed to stronger protection measures and longstanding conservation awareness compared to the more recently established reserves along the Zambezi River. These findings underscore the need for tailored, site-specific management strategies to ensure the sustainability of fish populations across all five newly established fisheries reserves in the region
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    Variations in the use of artificial waterholes by mammals at Okaukuejo and moringa in Etosha National Park, Namibia
    (University of Namibia, 2025) Mthethwa, Nomkhuleko Vangile Helen; Mfune, John K. E.
    The presence of artificial waterholes can alter local mammal biodiversity. Research on the impact of artificial waterholes on local mammal biodiversity and studies on the nocturnal patterns of water usage are limited in Namibia. In this study, large mammals that visited Okaukuejo and Moringa artificial waterholes in Etosha National Park were studied in the cool dry season in July 2022 to determine and compare their species richness, patterns of waterhole usage, duration of stay, and behaviors displayed at the waterholes. A total of 14 large mammal species were recorded at both waterholes. Species richness was significantly higher at Okaukuejo than at Moringa waterhole, with cape fox (Vulpes chama), blue wildebeest (Connochaetes taurinus), giraffe (Giraffa camelopardalis) and warthog (Phacochoerus africanus) sighted at either Moringa or Okaukuejo waterhole. Zebras (Equus quagga) and springboks (Antidorcas marsupialis) had the highest abundance at both waterholes and visited at all sampling sessions (03h00- 06h00, 07h00 10h00, 12h00-15h00, 17h00-20h00 and 22h00-01h00). This indicates more water dependence than other species and may be influenced by the diet and home ranges of these species. There was a temporal differentiation in the use of the waterholes; mammals mostly visited between 12h00-15h00 and least between 03h00-06h00. Low overlap in waterhole visitation times was observed between predators and potential prey, possibly due to predation risk. The duration of mammal stay was significantly higher at Okaukuejo than at Moringa for elephants (Loxodonta africana), springboks, and spotted hyenas (Crocuta crocuta). Duration of mammal stay was significantly higher between 22h00 01h00 at Okaukuejo, and significantly lower between 03h00-06h00 at Moringa than other sampling sessions. Black rhinos, elephants and giraffes stayed significantly longer at Okaukuejo, while black rhinos and elephants stayed significantly longer at Moringa, compared to other species. Vigilance and aggression were the most frequently observed behaviors among 13 behavior types recorded, possibly driven by the need for water, predation risk and competition for water. Behaviors occurred at a higher frequency at Okaukuejo waterhole due to higher species richness and abundance. This study provides valuable insights on the activity patterns of mammals around artificial waterholes. Repeated and seasonal observations, incorporating water quality tests at waterholes are recommended for year-round assessment of mammal waterhole use and for explaining variations in visitations, species distribution and behaviors of mammals at waterholes