Comparative study of growth rates, condition factors and natural mortality of Oreochromis niloticus fish from culture fisheries and capture fisheries at Lake Kariba, Zambia

Oreochromis niloticus were sampled from culture fisheries (Yalelo, Fwanyanga and Choombwe) (n = 211) in April and May, 2020. Capture fisheries (Siavonga and Sinazongwe) (n = 198) were sampled between April and November, 2020. The research was aimed to study the population parameters (growth rates, condition factors and natural mortality) of O. niloticus at Lake Kariba. The results showed that fish at culture fisheries exhibited positive growth (b > 3; b = 3.093) while fish at capture fisheries exhibited negative growth/negative allometry (b < 3; b = 2.24). The study established that fish at all the aquaculture farms were in good condition (Fulton’s condition factors were: Yalelo fishery KF = 1.95; Fwanyanga fishery KF = 1.77 and Choombwe fishery KF = 1.83). Fulton’s condition factors at both capture fisheries (KF = 1.91 at Siavonga and KF = 1.81 at Sinazongwe) were above the optimal value of 1.0, hence the studied fish were healthy and in good condition. Culture fisheries were in better condition than capture fisheries (KF for culture fisheries was 2.24 while KF for capture fisheries was 1.93). Fish from culture fisheries were growing faster than fish from capture fisheries (culture r2 was 0.960 while capture r2 was 0.555). It can be further concluded that the habitats at Lake Kariba are favourable for fish production and they are supporting healthy fish stocks. Natural mortality values at capture fisheries and culture fisheries were similar (MW capture = 0.142, MW culture = 0.122). The larger condition factors at culture fisheries than capture fisheries and the higher growth rates of fish from culture fisheries than capture fisheries coupled to the lower natural mortality values at culture fisheries than capture fisheries entail that the aquatic habitat at culture fisheries are better than those at capture fisheries at Lake Kariba. Key words: Lake Kariba, Oreochromis niloticus, captures fishery, culture fishery, condition factor, natural mortality.