Studies on intensive snakehead (Channa Spp.) culture with special reference to their nutrition

Abstract

The aim of this thesis was to conduct preliminary studies into the intensive culture of snakeheads (Channa spp.) with special reference to their nutrition. In order to assess the current culture and management techniques employed, identify problematic areas and to guide research needs a field survey of Channa striata farming in Thailand was carried out. Results showed that, at the time of the survey (1980), the C. striata farming industry in Thailand was experiencing difficulties which threatened to undermine the economic viability of the industry. In particular, problems associated with the use of trash fish as feed, especially its ever increasing cost and diminishing supply, was identified to be the major factor regulating the profits of snakehead farms. Dry pelleted food was suggested as a replacement for trash fish. Simple economic analysis of the net returns of a C. striata farm showed that potential economic benefits can be gained by utilization of dry pelleted feeds. However, at present, such feeds are not available and the basic nutritional requirement data for snakeheads, needed for diet formulation, is almost non existent. Therefore, in Chapter 3, a series of experiments were designed to determine the basic nutritional requirements of Channa striata and Channa micropeltes. In Experiment 1, the dietary protein requirements of C. striata and C. micropeltes juveniles were investigated. As expected, for carnivorous species. C striata and C. micropeltes required high levels of dietary protein, approximately 46% and 52% of the diet respectively. Quantitative essential amino acid requirements of C. striata and C. micropeltes juveniles were determined using the daily tissue essential amino acid deposition method, in Experiment 2. The essential amino acid requirements of both C. striata and C. micropeltes were comparable to those of other fish species, with the exception of the amino acids methionine and phenylalanine. The effects of dietary essential fatty acid intake on growth and fatty acid composition of the liver and muscle were investigated with C. micropeltes juveniles in Experiment 3. Results showed that C. micropeltes are not very demanding in their essential fatty acid requirements during the on-growing phase. Fish fed either dietary linoleic acid, a combination of linolenic and linoleic acids or cod liver oil all grew equally well. Analysis of the fatty acid composition of liver and muscle indicate the C. micropeltes possess some capacity to chain elongate and desaturate linolenic acid producing long chain (n-3) polyunsaturated fatty acids but seem unable to similarly modify linoleic acid. Dietary lipid, and to a lesser extent dietary carbohydrate, were shown to spare dietary protein for growth in C. striata juveniles in Experiment 4. However, the improvements in growth and feed conversion efficiency with increasing dietary lipid at constant dietary protein level, were achieved at the expense of fattier fish carcass. Incidental studies on the disease problems associated with the translocation of snakehead juveniles were performed. High mortalities were recorded with newly arrived consignments. It was postulated that the high mortality rate was caused either directly by the traumatic effects of the stress induced by the translocation process or by the attacks of ectoparasites on fish weakened by the induced stress. Successful treatments for the ectoparasitic infections were developed. In the final chapter, on the basis of the nutritional studies conducted with C. striata and C. micropeltes, a practical diet for on-growing snakeheads was formulated and its cost of production estimated. Suggestion for future work were also presented.