No abstract

This paper discusses the role of tilapia culture in rural development in Asia (Philippines, Thailand, Bangladesh and other Asian countries), Africa, and in Latin America and the Caribbean. It is stated that rural aquaculture is a multi-disciplinary practice, involving technical, socioeconomic, and policy aspects as well as extension services. It is necessary that all these factors be considered for efficient and sustainable development of rural aquaculture.

The effects of stocking density and feeding levels on larval survival, growth rates, feed utilization efficiency and body composition of Nile tilapia (Oreochromis niloticus L.) fry were investigated in two consecutive experiments. In experiment 1, swimup fry (0.016 g average body weight) were stocked in 20‐L fibreglass tanks, in a closed, recirculating indoor system, at five stocking densities (3, 5, 10, 15 and 20 fry L−1) and fed a larval test diet (40% crude protein) to apparent satiation, three times a day, for 40 days. Fish survival, percentage weight gain and specific growth rate (% SGR) were negatively correlated with stocking density. The best performance was achieved at 3 fry L−1. However, no significant differences in growth parameters were found between 3 and 5 fry L−1. Body composition was not significantly affected by stocking density. In experiment 2, fry (0.016 g average body weight) were stocked at 5 fry L−1, and fed a larval test diet (40% crude protein) at six feeding levels (10%, 20%, 25%, 30% and 35% BW day−1) and to satiation, three times a day for 40 days. Fish growth rates and survival were extremely poor at 10% feeding level, and improved significantly with increasing feeding levels up to 30%, and levelled off with further increase in feeding levels. On the contrary, feed conversion ratio (FCR) and protein production value (PPV) were negatively correlated with feeding level. The lowest feeding level (10%) produced significantly lower body lipid and higher protein and ash than other feeding levels. The present results suggest that the optimum stocking density and feeding level of Nile tilapia fry are 5 fry L−1 and 30% per day respectively.

The effects of total replacement of dietary fish meal (FM) with animal protein sources on the growth, feed efficiency and profit indices of Nile tilapia, Oreochromis niloticus (L.), were investigated. Shrimp meal (SM), blood meal (BM), meat and bone meal (MBM), BM ϩ MBM mix and poultry by-product meal (PBM) replaced FM in six isonitrogenous (30% crude protein), isocaloric (400 kcal GE 100 g -1 ) diets. The diets were fed to O. niloticus fingerlings (12.5 g) to satiation twice a day for 150 days. The growth of fish fed SM, PBM and MBM was not significantly different from those fed the FM-based diet, while feed conversion and protein efficiency ratios were significantly retarded. Further reduction in fish performance was noticed when BM or BM ϩ MBM replaced FM in the control diet. Cost-benefit analyses of the test diets indicated that these sources were economically superior to FM. The PBM-based diet produced higher carcass lipid than other diets. Fish fed SM, MBM and PBM diets had significantly higher ash contents (P Ͻ 0.05).

Taurine is a neutral β‐amino acid derived from the metabolism of sulphur‐containing amino acids. It is present in high concentrations in animal tissues, especially heart, retina, skeletal muscle, brain, large intestines, plasma, blood cells and leucocytes. Therefore, this amino acid plays significant roles in many physiological functions, including membrane stabilization, antioxidation, detoxification, modulation of immune response, calcium transport, myocardial contractility, retina development, bile acid metabolism, osmotic regulation and endocrine functions. Historically, taurine has not been considered as an essential nutrient for fish. However, recent studies have indicated that taurine synthesis widely differs between fish species and demonstrated that it plays a key role in aquaculture and nutrition of freshwater and marine fish and shrimp. Animal proteins are rich in taurine, whereas plant proteins are taurine‐deficient. Therefore, fish fed plant protein–based food may require exogenous taurine for maintaining their physiological functions. Nevertheless, taurine may be conditionally indispensable for fish and shrimp, depending on dietary protein source, fish species and size, feeding habits, previous histories and the rate of metabolism of its precursors, namely cysteine and methionine. It is my belief that taurine functions in, and benefits for, farmed fish and shrimp are now more than worthy of critical review and analysis. This review summarizes the current knowledge on the roles of taurine in fish, particularly farmed fish and shrimp, with emphasis on taurine structure and biosynthesis, physiological functions, the effects of dietary taurine on fish performance and health and live food enrichment with taurine.