Fish Hatchery Management - fisheries & aquaculture

2t0FISH HA'I'CIIERY MANAGEME,NTpellets provide for more complete consumption of the feed. Feeding rates of0.5 to l09t of fish weight per day reduce the chance for feed wastage. Lessfeed wastage results in far less pollution of the water during feeding and acomparable reduction in cleaning of ponds and raceways. Pelleted feeds areadaptable for use in automatic feeders.Many combinations of feedstuffs were tested as pelleted feeds; somefailed because the pellets were too hard or too soft; others did not providethe nutrient requirements of the fish.Along with the testing and development of dry feeds, fish nutritionresearchers, relying largely on information concerning nutrition of other animalssuch as chicken and mink, began utilizing and combining more andmore feedstuffs.Commercial fish feeds were pelleted and marketed in advance of openformulafeeds. A few commercial feeds failed to produce good, economicalgrowth and to maintain the health of the fish but, by and large, most werevery satisfactory.Several items must be considered in developing an adequate feeding programfor fish. These include the nutrient requirements for different fishsizes, species, environmental conditions, stress factors, types of feed, andproduction objectives. General feeding methods are important and will bediscussed extensively in the last part of this section.It would be difficult to determine which factor has the greatest effect ona hatchery feeding program. In all probability, no one factor is more importantthan another, and it is a combination of many that results in an efficientfeeding program. Application of the available knowledge of fish nutritionand feeding will result in healthy, fast-growing fish and low productioncosts. A fish culturist must be able to recognize the factors affectingfeed utilization and adapt a feeding program accordingly.Factors Influencing Nutritional RequirementsThe physiological functions of a fish (maintenance, growth, activity, reproduction,etc.) govern its metabolism and, in turn, determine its nutritionalrequirements. Metabolism is the chemical processes in living cells by whichenergy is provided for vital processes and activities.WATER TI]MPT]RATUREApart from the feed, water temperature is probably the single most importantfactor affecting fish growth. Because fish are cold-blooded animals,their body temperatures fluctuate with environmental water temperatures.Negligible growth occurs in trout when the temperature decreases to 38'F.The lower limit for catfish is about 50"F. As the temperature rises, growth