Is the culture of exotic fish species the answer to low fish productivity? A case study on the use of Oreochromis niloticus in Zambia

Abstract

The study was conducted in the Copperbelt and North-Western Provinces of Zambia which represented the urban and rural strata respectively. A total of two hundred and forty farmers were randomly sampled from the farmer registers kept by the Department of Fisheries (DOF) in the Ministry of Fisheries and Livestock (MFL), Zambia. The main objective of the survey was to determine the productivity of the exotic fish species Oreochromis niloticus in comparison to closely related indigenous fish species (Oreochromis andersonii, O. machrochir and Tilapia rendalli) at farm level. Correlation analysis showed that stocking density was positively, though weakly, correlated (r = 0.31, N = 292, P< 0.05) with yield, with a higher stocking density associated with higher yield. Since the correlation coefficient was lower than 0.5, regression analysis was not performed. Sex reversed fingerlings gave almost double the yield (5.5 tons/ha/year) compared to mixed sex fish (3.8 tons/ha/year). Productivity was highest in those farmers using commercial feed (6.4 tons/ha/year) compared to those using single ingredients or fertilization or a combination of the two. There was no evidence to show that farmers who were using O. niloticus were performing better than those farmers using O. andersonii since the productivity of the farmers culturing the non-indigenous O. niloticus (4.7 tons/ha/year) did not differ significantly from those farmers using O. andersonii (4.6 tons/ha/farmer). There should be deliberate efforts to promote O. andersonii both at production and consumption levels in order to create demand for the fish species. Genetic studies should be conducted to establish the genetic variability and strains of the indigenous fish species in Zambia. Furthermore, there is an urgent need to establish gene banks for most indigenous fish species to conserve the genetic resources for aquaculture and capture fisheries. Key words: Exotic, indigenous, production, productivity, genetics.