HATCHERY OPERATIONS 77 



supplemental feeding. Up to 2,000 pounds or more of fingerling fish per 

 acre can be reared with supplemental feeding. 



If fish larger than 4 inches are desired, stocking rates must be reduced. 

 Experimental evidence suggests that 1,500, 3- to 6-inch fingerlings per acre 

 will produce 1- pound fish in 180 days. 



HIGH-DENSITY CATFISH CULTURE 



Specialized catfish culture systems have received much publicity in recent 

 years, and several high-density methods are currently under investigation. 

 These include the use of cages; earthen, metal, or concrete raceways; vari- 

 ous tank systems; and recirculation systems. High-density fish culture 

 demands not only highly skilled and knowledgeable management but also 

 requires provision of adequate amounts of oxygen, removal of wastes, and a 

 complete high-quality diet. The methods used for calculating carrying 

 capacity in salmonid hatcheries can readily be used for intensive culture of 

 catfish. 



STRIPED BASS 



At present, most striped bass rearing stations receive fry from outside 

 sources. Eggs are collected and usually hatched at facilities located near 

 natural spawning sites on the Atlantic coast. Fry are transferred to the 

 hatchery at 1 to 5 days of age. There they are either held in special tanks 

 or stocked in ponds for rearing, depending on the age of the fry and 

 whether or not they have sufficiently developed mouth parts to allow 

 feeding. 



Earthen ponds are fertilized before stocking to produce an abundance of 

 zooplankton. In these prepared ponds, striped bass fry are stocked at a rate 

 of 75,000 to 125,000 per acre. A stocking density of 100,000 fry per acre, 

 under normal growing conditions, yields 2-inch fingerlings in 30 to 45 

 days. Survival is very erratic with this species, and may vary from to 

 100% among ponds at the same hatchery. As with most pond-cultured fish, 

 the growth rate of striped bass increases as the stocking density decreases. 

 If a 3- inch fingerling is needed, the stocking density should be reduced to 

 60,000 to 70,000 fry per acre. 



Culture of striped bass larger than 3 inches usually requires feeding for- 

 mulated feeds. Striped bass larger than 2 inches readily adapt to formulat- 

 ed feeds, and once this has taken place most of the procedures of trout cul- 

 ture can be applied. 



NORTHERN PIKE AND WALLEYE 



These coolwater species represent a transition between coldwater and 

 warmwater cultural methods. A combination of extensive and intensive 



