Fish Hatchery Management - fisheries & aquaculture

NU'I'RITION AND F[L,DINGbeneficial in this regard. The amino acid requirements for catfish have notbeen established, but appear to be similar to those for salmonids'Catfish feeds-or any feeds fed in extensive culture-are classified aseither complete or supplemental diets. Complete feeds are formulated tocontain all the vitamins, minerals, protein, and energy needed by the fish.Usually these complete feeds contain 30 to 40% total crude protein, ofwhich fish meal may make up l0 to 25(x, of the feed. Complete feeds aremore expensive than supplemental feeds. Complete feeds are fed to fry,and also to larger fish raised intensively in raceways, cages, or otherenvironments where the intake of natural feeds is restricted.Supplemental feeds are formulated to provide additional protein, energy,and other nutrients to fish utilizing natural food. Generally, the fish areexpected to eat natural food organisms to supply the essential growth factorsabsent in the feed. Usually supplemental feeds contain a lower level ofcrude protein than complete feeds, and soybean meal is the principal proteinsource.Low stocking rates and low standing crops of fish result in more naturalfood (and protein) being available to each fish. The above factors and others,such as season, fish size, feeding rate, water temPerature, oxygen levels,and disease influence the dietary protein levels required for maximumefficiency in growth. Consequently, no one protein level in feeds will meetall conditions and it remains for the fish culturist to choose the feed with aprotein level that will satisfy production needs.PROTEIN IN COOLWATER FISH FEEDSFeeding trials with northern pike, chain pickerel, muskellunge, walleye,and the hybrid tiger muskellunge showed that the hybrid and, to a lesserdegree, northern pike will accept a dry pelleted, formulated feed. A 50'l1rprotein experimental feed (Appendix F) formulated specifically for coolwaterfish provided the highest survival and growth with fingerlings. Troutfeeds and experimental feeds that contain less protein were inadequate'Therefore, it appears that the protein requirement for the fingerlings ofthese species is about 50'X, of the feed. It is also noteworthy that 60-809[ ofthe dietary protein was supplied by animal protein sources in feeds thatproved satisfactory. Only limited testing has been conducted on feedingadvanced fingerlings of coolwater species, but indications are that the proteinlevel of the feed can be reduced. This follows the similar pattern fortrout and catfish.C ar bo hy dra te R eq uirementsCarbohydrates are a major source of energy to man and domestic animals,but not to salmonids or catfish. Only limited information is available on