Fish Hatchery Management - fisheries & aquaculture

NUTRITION AND FEEDINC 251high-quality, 36()/i protein catfish feed (Appendix F) is an adequate supplementalfeed for fry and small fingerlings as they will get a large portion oftheir nutrients from natural pond organisms.Feed first should be pelleted or extruded before it is reduced to smallerparticle sizes. Fat sprayed onto the feed after processing reduces the loss ofwater- soluble vitamins.Growth of channel catfish fingerlings is similar with either sinking orfloating pellets, provided that the nutrient contents are the same. Floatingfeeds are a valuable management tool to help determine the effects of lowdissolved oxygen content and low or high water temperature on feeding,general vigor, and health of fish during the feeding season. It also is helpfulin determining amounts of feed to give fish in special culture systemssuch as cage feeding, raceway feeding, and ponds having abundant rootedvegetation.Table 28 presents a feeding guide for channel catfish in ponds, andTable 29 offers one for catfish in raceways. The pond feed is a supplemental,361iprotein diet; that for raceways is a complete formulation. See AppendixF for ingredients.Low dissolved oxygen levels depress feeding activity of catfish, and fishshould not be fed in early morning for this reason. Neither should they befed late in the day because their increased metabolic oxygen requirementduring active feeding and digestion will coincide with the period of lowdissolved oxygen in the pond during the night and early morning. Thebest times to feed are between mid-morning and mid-afternoon.The optimal temperature for catfish growth is approximately 85"F; astemperature decreases, food consumption decreases proportionally. Generally,catfish do not feed consistently in ponds when the water temPeraturedrops below 60"F; below 50"F they will feed, but at greatly reducedlevels and frequencies. Below (i0'F, the efficiency of digestion and metabolismdrops markedly.During colder months, feed catfish only on warm days and only what thefish will consume readily. A recommended guide for winter feeding of catfishin ponds is to feed the fish 0.75-1'li of their estimated weight dailyonlv when the water temperature is above 54"F, and not to feed at lowertemperatures.There are no reliable data on the best feeds for catfish in the winter.Catfish do not respond as well to high-protein diets in cool weather as inwarm weather. This may indicate that lower-protein feeds (b"lo* 32'li) aremore economical in cold water. Digestibility of carbohydrates is suppressedeven more at low temperatures than the digestibility of proteins and fats,indicating that high-grain feeds are not utilized by catfish in cool weather.Therefore, winter rations should contain less protein and carbohydratesthan those fed durine the summer.