Fish Hatchery Management - fisheries & aquaculture

2t6FISH HATCHERY MANAGEMENTfeed that contains at least 5070 protein; at 6-8 weeks the requirement decreasesto 40% of the feed and to about 35% of the feed for yearling salmonids.Recommended protein levels in trout feeds as percent of the diet are:Starter feed (fry)Grower feed (fingerlings)Production feed (older fish)The level of protein required in feed varies with the quality and proportionsof natural proteins that make up the feed. Between 0.5 and 0.7 poundof dietary protein is required to produce a pound of trout fed a balancedhatchery feed. The requirement for protein is also temperature-dependent.The optimal protein level in the feed for chinook salmon is 40% at 47"Fand 55'li at 58'F.PROTEIN IN CATFISH FEEDSThe natural foods of catfish are rich in protein. Catfish may metabolizesome dietary protein for energy. Protein utilization is affected by the proteinsource and water temperature. Channel catfish convert the best animalprotein source, fish meal, two times better than they do the best plantsource, soybean meal. It is noteworthy that a combination of proteinsources yields better conversion rates than any single source. In catfishfeeds, at least 50'li of the dietary Protein requirement should be animalprotein.Better efficiency is obtained for all proteins when they are fed at temperaturesbetween 75'F and 88'F than at 65'F or below. However, a mixtureof animal protein is utilized almost equally at both extremes. The particlesize of the protein sources in the feeds has no measurable effect onprotein utilization at any temPerature.The protein requirements for catfish are also size-related. The recommendedtotal protein levels in percent of the feed for different-sized catfishat a 75'F water temperature are:Fry to fingerlingsFingerlings to subadultsAdults and broodfish45-55Y035-5'fo30-40'/oWhen catfish are fed as much as they will eat, and the feed is balancedin amino acids and energy, lower protein levels are adequate' When thefeeding rate is restricted, as in pond culture, higher protein levels haveproved beneficial. Fish on higher protein rations require less energy perpound of gain.35-40'/o25 35',i028 32ui,tThe role of carbohydrates and fats in protein-sparing has not been adequatelystudied, but indications are that these nutrients in catfish diets are