|Robinson, E -|
|Li, M -|
Submitted to: Journal of Applied Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 1, 2008
Publication Date: January 1, 2009
Citation: Robinson, E.H., Li, M.H. 2009. Effects of Feeding Diets With or Without Fish Meal on Production of Channel Catfish, Ictalurus Punctatus, Stocked at Varying Densities. Journal of Applied Aquaculture. 21:1. Interpretive Summary: Proteins of animal origin, particularly fish meals prepared from whole fish, are considered to be nutritionally superior to proteins of plant origin. Although there are exceptions, the superiority of animal proteins is primarily based on the fact that they generally contain a higher level of indispensable amino acids and are more highly digestible by channel catfish than plant proteins. Commercial channel catfish diets have traditionally contained relatively high levels of protein supplied in part by animal protein supplements, but there is a growing body of evidence that animal protein can be reduced or eliminated in diets for food-size catfish. The studies that we have conducted thus far concerning eliminating animal protein from catfish diets have been conducted with channel catfish stocked at rates from about 14,820 to 24,700 fish/ha. Since catfish stocking densities vary greatly from farm to farm and from time to time, we wanted to see if fish meal becomes a limiting factor on fish growth at high stocking densities. Therefore, we conducted the study to evaluate diets with and without menhaden fish meal fed to channel catfish stocked into earthen ponds at densities of 14,820, 29,640, and 44,460 fish/ha. Based on results from this study, it appears that at stocking densities typically used in the commercial catfish industry, animal protein does not appear to be needed in the diet for growing stocker-size catfish to food fish. However, at densities two to three times higher than generally used, animal protein (fish meal) may be beneficial. In regard to stocking densities, high stocking results in higher overall production but the average fish size decreases as stocking density increases. At the highest stocking density, average fish size was at the low end of the desirable range for a marketable catfish even after two growing seasons.
Technical Abstract: Animal protein, generally fish meal, has traditionally been used in the diet of channel catfish. However, our previous research indicates that animal protein is not needed for growing stocker size catfish to food fish when the fish are stocked at densities typical of those used in commercial catfish culture. Whether this holds when fish are stocked at high densities is not known; thus, we conducted an experiment to evaluate the effect of feeding diets with and without fish meal to channel catfish stocked in earthen ponds at different densities. Two 32% protein practical diets containing 0% or 6% menhaden fish meal were compared for pond-raised channel catfish, Ictalurus punctatus, stocked at densities of 14,820, 29,640, or 44,460 fish/ha. Fingerling channel catfish with average initial weight of 48 g/fish were stocked into 30, 0.04 ha ponds. Five ponds were randomly allotted for each fish meal level x stocking density combination. Fish were fed once daily to satiation for two growing seasons. There was a significant interaction between stocking density and fish meal for net production; net production increased in fish fed a diet containing fish meal compared with those fed an all-plant diet at the highest stocking density, but not at the two lower stocking densities. Net production of fish fed diets with and without fishmeal increased as stocking density increased. Viewing the main effect means, weight gain decreased and FCR increased for fish stocked at the two highest densities, and survival was significantly lower at the highest stocking density. Visceral fat decreased in fish at the two highest stocking densities. Body composition data were largely unaffected by experimental treatment except for a reduction in percentage of filet fat in fish at the highest stocking density, and fish that were fed diets containing fish meal had a lower percentage of fillet protein and a higher percentage of fillet fat. It appears that at stocking densities two to three times higher than generally used, animal protein (fish meal) may be beneficial in the diet of channel catfish. In regard to stocking densities, high stocking results in higher overall production, but the average fish size decreased as stocking density increases.