Abstract
Unaffordability of commercial feeds to semi-intensive Nile tilapia, Oreochromis niloticus farmers has led to reliance on supplemental feeding and fertilization for nutrition of their fish without a scientific basis. This study compared the growth, survival, condition factor and yield performance of O.niloticus fed on mixed ingredients (MI) and rice bran alone (RB) diets reared in fertilized earthen ponds in small scale farmers’ ponds. The study also determined phytoplankton composition, biomass and abundance in the experimental ponds. Quadruplicate ponds were stocked with O. niloticus and African sharptooth catfish, Clarias gariepinus at a stocking ratio of 1:3. The initial mean weights of O. niloticus and C. gariepinus were 14.62 ± 0.61 and 20.34 ± 1.44 g respectively. The fish were fed on MI and RB diets with protein content of 184.74 and 126.06 g kg−1 respectively for 270 days. The results showed that growth performance, survival rate and condition factor of O.niloticus were not affected by either feeding with MI or RB diet (p > 0.05). Moreover, there were no significant differences obtained in phytoplankton biomass and abundance in O.niloticus ponds fed on the two diets (p > 0.05). Furthermore, feeding O.niloticus either on MI or RB diet did not affect the net and gross fish yields (p > 0.05). The study revealed that the use of either MI or RB diet does not significantly affect the performance of O.niloticus cultured in semi-intensive earthen ponds where natural food organisms are an integral part of the culture system. Rice bran could be used for semi-intensive culture of O.niloticus in fertilized ponds to boost the production based on its availability and low cost.
Highlights
The majority of fish farmers in developing countries practise semi-intensive culture ofNile tilapia (Oreochromis niloticus L.) by feeding them with on-farm made feeds due to unavailability and high cost of commercial feeds
Water quality parameters and phytoplankton composition, biomass and abundance Water temperature, dissolved oxygen and pH were found to be almost similar between treatments (Table 2)
The abundance of Chlorophyceae was 34,022.65 ± 4417.19 and 32,499.24 ± 7477.50 individuals L−1 in ponds with O. niloticus fed on mixed ingredients (MI) and rice bran alone (RB) diets respectively (Fig. 2)
Summary
The majority of fish farmers in developing countries practise semi-intensive culture ofNile tilapia (Oreochromis niloticus L.) by feeding them with on-farm made feeds due to unavailability and high cost of commercial feeds. Farmers stock O. niloticus and African sharptooth catfish (Clarias gariepinus) in polyculture system (Shoko et al 2014a, b; Limbu et al 2015) In both cases, the culture of O. niloticus in earthen ponds entirely depends on supplementary feeds such as rice, maize and wheat bran; and sunflower and cotton seed cakes with or without fertilization using animal manure. The culture of O. niloticus in earthen ponds entirely depends on supplementary feeds such as rice, maize and wheat bran; and sunflower and cotton seed cakes with or without fertilization using animal manure The latter is commonly used where pond fertilization is practised. When cultured in semi-intensive earthen ponds, O. niloticus has been shown to thrive on supplementary diets made from agro-byproducts augmented with fertilization based on its omnivorous feeding behaviour (Charo-Karisa et al 2006; Abdel-Tawwab et al 2007). Phytoplankton availability has a synergistic effect in promoting high growth performance, survival rate and yield of O. niloticus cultured in semi-intensive ponds (Li and Yakupitiyage 2003)
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