Abstract
The inadequate supply of tilapia fingerling is a major limitation to cage culture development in Ghana. Lake-based hapa systems are very efficient in nursing fingerlings although the process can be tricky due to inherent effects of stocking densities and environmental factors. This study aimed at assessing the growth, survival and profitability of Nile tilapia (Oreochromis niloticus) fingerlings of the Akosombo strain reared in nine 1 m3 Lake-based hapas at different densities. Each hapa was stocked with 2.12 ± 0.14 g sex-reversed tilapia fingerlings at varying stocking densities of 400 fish/m3, 800 fish/m3 and 1200 fish/m3 serving as treatments T1, T2 and T3 respectively. Each treatment was replicated thrice. Bi-weekly samplings were done and water quality parameters were measured. After the experiment, analysis of variance showed significant differences (p < 0.05) in the weight gained, specific growth rate, profit index and feed conversion ratio among treatments. The T1 fingerlings exhibited the highest specific growth rate (3.28 ± 0.10%/day) and FCR (1.42 ± 0.09) than others. Overall, profit index was affected by stocking density and varied significantly between treatments. Treatment T3 was found to be better for commercial fingerling production because survival rate (91.14 ± 3.23%) and profit index (3.96 ± 0.24) were the highest while treatment T1 recorded the least index of 1.31 ± 0.10. Survival rates ranged between 89% and 91% but no statistical differences were observed among treatments. It is concluded that the stocking densities used had significant effects on the specific growth rate, gain in weight and feed conversion ratio of fingerlings reared in Lake-based hapas. However, in fingerling production, not only profit but also rapid growth needs consideration, hence, T2 is highly recommended for nursery rearing of tilapia fingerlings in this system due to the relatively high profit index, growth rate and survival.
Highlights
With a nearly stabilized global fish production from capture, aquaculture has in recent times increased significantly throughout the world [1] and in most developing countries like Ghana
This study aimed at assessing the growth, survival and profitability of Nile tilapia (Oreochromis niloticus) fingerlings of the Akosombo strain reared in nine 1 m3 Lake-based hapas at different densities
Each hapa was stocked with 2.12 ± 0.14 g sex-reversed tilapia fingerlings at varying stocking densities of 400 fish/m3, 800 fish/m3 and 1200 fish/m3 serving as treatments T1, T2 and T3 respectively
Summary
With a nearly stabilized global fish production from capture, aquaculture has in recent times increased significantly throughout the world [1] and in most developing countries like Ghana. Aquaculture began in Ghana in 1950 [2] but only over the past two decades has the industry grown significantly, through the establishment of many fish farms across the country. Aquaculture, mainly fish farming in Ghana is primarily based on Nile tilapia and 90% of the reported volume is raised in cages on the Volta Lake [3]. A major challenge that continually limits the scale up commercialization of tilapia cage culture in Ghana is a lack of reliable quantity and quality fingerlings for stocking in grow-out facilities [7]-[10]. The growth in cage farming has stimulated an increase in the establishment of hatcheries along the Volta Lake [6] [10], the current supply of Nile tilapia fingerlings does not meet farm demands and an estimated 50 million seeds are lacking annually [10]
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