NUTRITION AND FEEDING 249 



is distributed in the trough by automatic feeders set to feed at 5-minute in- 

 tervals from dawn to dusk (Figures 75 and 76). 



Coolwater fish will not pick food pellets off the bottom of the tank so it 

 is necessary to continually present small amounts of feed with an automatic 

 feeder. In some situations, coolwater fry are started on brine shrimp and 

 then converted to dry feed. Pennsylvania workers report that muskellunge 

 are extremely difficult to rear on artificial feeds. However, the tiger muskie 

 (northern pike male x muskellunge females) adapts readily to dry feeds. 

 Northern pike will accept a dry feed and also adapt to culture in tanks. 



Walleye fry have been observed feeding on the W-7 diet, but did not 

 survive well on it. Anemia developed in advanced fingerlings, indicating a 

 deficiency of some nutrient. 



Tiger muskie fry aggressively feed on dry feeds. Fry often follow a food 

 particle through the entire water column before striking it. Hand-feeding 

 or human presence at the trough does not disrupt feeding activity. How- 

 ever, when the fish attain a length of 5-6 inches, human presence next to a 

 trough or tank can disrupt feeding activity completely. Cannibalism gen- 

 erally is a problem only during the first 10-12 days after initial feeding, 

 when the fish are less than 2-3 inches in length. The removal of weak and 

 dying fry greatly reduces cannibalism. 



The methods developed for estimating feeding rates for salmonids can be 

 adapted for use with coolwater species. Michigan workers use a Hatchery 

 Constant of 40 to calculate feeding rates for tiger muskellunge raised in 

 70°F water. 



Feeding Guides for Warmwater Fishes 



CATFISH 



Newly hatched catfish fry live on nutrients from the yolk sac for 3-10 days, 

 depending upon water temperatures, after which they accept food from a 

 variety of sources. Generally, feed for trough- feeding of fry should be small 

 in particle size, high in animal protein, and high in fat. Salmonid rations 

 are well suited for this purpose. Palatability of lower-quality feed is 

 enhanced by having a high percentage of fish meal, fish oil, chopped liver, 

 egg yolk, or other ingredients that serve as attractants. 



Overfeeding in the troughs should be avoided and adequate water flows 

 must be maintained to avoid fouling the water. The fry should be 

 transferred to ponds with high zooplankton densities as soon as possible to 

 efficiently utilize the natural food source. 



Supplemental feeding of fry in ponds should begin soon after stocking. A 



