The nutritive potential of watermelon (Citrullus lanatus) seedmeal as dietary protein source in the diet of Nile tilapia (Oreochromis niloticus) using economics was evaluated in a 56 day feeding trial. One hundred and fifty tilapia fingerlings of 6.12±0.05g average weight were acclimatized for a week, weighed and allotted into five dietary treatments; containing 0, 15, 30, 45 and 60% Citrullus lanatus replacement levels with soybean meal. The diets were isonitrogenous and isolipidic. Each treatment was replicated three times with ten fish per replicate. Fish were fed 5% body weight on two equal proportion per day. Economic analysis was carried out using incidence of cost, profit index, profitability ratio, cost and return analysis as analytical tools. The results of the study indicated the profitability of using watermelon seedmeal with positive gross margin and net returns. The average gross ratio, benefit cost ratio, return on investment (ROI) and the Rate of Return (ROR) values on capital invested on producing O. niloticus with diets containing watermelon seedmeals across the different dietary treatment groups were 0.57, 1.76, 0.77 and 0.55 respectively. It can be concluded from this study that it is economically viable to produce Nile tilapia with diets containing watermelon seedmeal.
Keywords: Incidence of cost; profit index; profitability ratio; cost and return analysis; Nile Tilapia