African Zoology

Understanding the translocation dynamics of Nile tilapia (Oreochromis niloticus) and its ecological consequences in East Africa

Papius Dias Tibihika, Harald Meimberg, Manuel Curto — Mon, 02 Jan 2023 00:00:00 +0000

The Nile tilapia (Oreochromis niloticus) is the second-most economically important fish species in East African countries (EAC), surpassed only by the Nile perch (Lates niloticus). It is the most-farmed freshwater fish species in EAC and the second-most-farmed worldwide. Currently, in EAC, through direct stocking activities and likely indirectly via aquaculture escapees, Nile tilapia are present in waterbodies where it is not native and where it is thought to have contributed to the fish biodiversity loss observed in recent decades. Introduced Nile tilapia may hybridise with native, congeneric species, promoting genetic introgression that can be detrimental to the sustainability of biodiversity. Moreover, the translocation dynamics and escapes from aquaculture can contribute to artificial geneflow between Nile tilapia stocks, compromising their gene pool and the sustainability of the species as a fishery resource. In the current work, we review some examples of these phenomena in EAC. Additionally, we explore the importance of collecting genetic data to define baseline knowledge for native and non-native Nile tilapia populations that can be used in monitoring programmes for development, management and conservation of tilapia genetic resources.

Testing the efficacy of bat monitoring methods for identification and species surveys in KwaZulu-Natal province, South Africa

Alexandra Howard, Ara Monadjem, Duncan MacFadyen, Christian T Chimimba — Mon, 02 Jan 2023 00:00:00 +0000

Multi-method sampling approaches are becoming increasingly popular for investigating species occurrence at specific sites, as there is a need to accurately monitor species with limited time and resources. In this study, a multi-method comparative approach was used to survey bat species in the foothills of the Drakensberg Mountain range in KwaZulu-Natal province, South Africa. We used historical museum records and species distribution modelling (SDM) to predict which species would likely occur in our study area. We then compared physical capture (by deploying mist nets) with acoustic surveys (using an Anabat bat detector) to assess the bat species assemblages present. Species distribution models predicted eight bat species to occur from the historical checklist of 28 species recorded in the broader region, as no museum records existed for the specific study area. Species detection by acoustic data yielded the highest number of detected species (n = 11) while active trapping yielded nine species from 54 individuals of four families, namely, Laephotis botswanae, L. capensis, Myotis tricolor, Pipistrellus hesperidus, Rhinolophus clivosus, and Tadarida aegyptiaca with molecular confirmation required for Miniopterus fraterculus, R. darlingi and R. swinnyi. These complementary sampling methods may be necessary for accommodating the limitations of each individual method for a more inclusive assessment of bat species richness in a targeted landscape. The present study could be used as a model approach to assess the biodiversity and demographics of other taxa and in other habitats.

Endohelminth parasites of male and female tigerfish, Hydrocynus vittatus (Castelnau, 1861), from the Sanyati basin in Lake Kariba

Nyasha Mabika, Maxwell Barson, Cobus Van Dyk, Annemariè Avenant-Oldewage — Mon, 02 Jan 2023 00:00:00 +0000

Tigerfish (Hydrocynus vittatus Castelnau, 1861) is of considerable importance in both the commercial and recreational fishery activities of Lake Kariba. In our previous paper (Mabika et al. 2019) we provided information on the seasonal occurrence of metazoan parasites of H. vittatus. This communication provides endohelminth infection statistics of male and female H. vittatus across two seasons not previously included. A total of 80 H. vittatus individuals consisting of 56 females and 24 males were examined for endohelminth parasites during the period October 2014–July 2015 in the Sanyati basin, Lake Kariba. Parasites were recovered from the abdominal cavity, mesentery and intestines. Most of the parasites were harboured in the abdominal cavity in both sexes. Parasite infection was more prevalent during the dry season in comparison to the rainy season for both sexes. Contracaecum larval infection was significantly higher in female (84%) than in male tigerfish (24%), whereas larval cestode infections were significantly higher in male tigerfish (59%) than female fish (16%). The mean condition factor of the male tigerfish (1.68) was not significantly higher than that of the female (1.64). The results of the study indicate that female tigerfish were more suitable hosts to Contracaecum larval infection than the male fish. Further parasitological and histopathological research on tigerfish is recommended to contribute to knowledge on endohelminth diversity and conservation.