Characterisation of Oreochromis niloticus fish species of Lake Kariba, Zambia, using morphological, meristic and genetic methods

Abstract This study aimed at characterising Oreochromis niloticus fish species of Lake Kariba and was premised on the hypothesis that there are different types of O. niloticus fish species in Lake Kariba. Oreochromis niloticus fish specimens (n = 409) were collected from both culture fisheries (Yalelo fishery, Fwanyanga fishery and Choombwe fishery) and capture fisheries (Siavonga and Sinazongwe) based at Lake Kariba from April to November 2020. All the collected fish samples were used for phenotypic characterisation, while 98 were used for genetic characterisation. A total of 23 morphometric measurements and seven meristic counts were used to generate morphometric data which were analysed using multivariate analysis. In order to delineate the sampled specimens, dendrograms were generated. Further, microsatellite data were generated from 98 samples using a panel of five microsatellite markers and analysed using microsatellite toolkit, GenAIEx, Fstat and LIAN software. Meristic results of culture fisheries showed that the sampled fish could be characterised into two strains, while samples from capture fisheries could be characterised into four strains. On the other hand, morphometric characterisation of fish from both culture and capture fisheries grouped the fish into three strains. In addition, population genetic analysis also showed that aquaculture farmers of Lake Kariba are rearing three populations of O. niloticus, while those from capture fisheries are composed of many distinct variant fish strains but can be roughly grouped into two types of O. niloticus fish species. The population of O. niloticus from the wild are genetically diverse, sub‐structured with an absence of panmixia and are present in all fisheries. In conclusion, the fisheries understudy possessed potentially three strains of O. niloticus segregated in approximately three populations.