HATCHERY OPERATIONS 75 



Warmwater Fish Rearing Densities 



Channel catfish have been reared at densities of up to eight pounds per cu- 

 bic foot of water. Stocking density and water turnover both had substantial 

 effects on growth and food conversion. Reduced growth due to the increase 

 in stocking density was largely compensated by increased water exchange, 

 and growth rate data indicated that production of over 20 pounds per cu- 

 bic foot of water was possible in a 365-day period. High-density culture of 

 catfish in tanks or raceways can be economical if suitable environmental 

 conditions and temperatures are maintained. 



Fish weight gain, food utilization, and survival may decrease as fish den- 

 sity increases, but faster water exchanges (inflow) will benefit high stocking 

 densities. The best stocking densities and water exchange rates will take 

 into consideration the various growth parameters as they affect the 

 economics of culturing channel catfish. Stocking densities between five and 

 10 fish per cubic foot have been suggested as feasible and production can 

 be increased to higher densities by increasing the oxygen content with 

 aeration, if low oxygen concentration is the limiting factor. 



Acceptable stocking densities for warmwater fish are related to the type 

 of culture employed (intensive or extensive) and the species cultured. The 

 appropriate density is influenced by such factors as desired growth rate, 

 carrying capacity of the rearing facility, and environmental conditions. 

 Most warmwater fish, other than catfish, normally are cultured extensively. 

 The following paragraphs cover representative species of the major groups 

 of commonly cultured warmwater and coolwater fishes. Stocking rates for 

 related species can be estimated from these examples. 



LARGEMOUTH BASS 



Production methods used for largemouth bass are designed to supply 2- 

 inch fingerlings. 



Fry are stocked in prepared rearing ponds at rates varying from 50,000 

 to 75,000 per acre. If a fingerling size larger than 2 inches is desired, the 

 number of fry should be reduced. Normal production of small bass ranges 

 from 30 to 150 pounds per acre depending on the size fish reared, the pro- 

 ductivity of the rearing pond, and the extent to which natural food has 

 been consumed and depleted. 



The length of time required for the transferred fry to grow to a harvest- 

 able size depends mainly upon the prevailing water temperature and the 

 available food supply. Normally, it is 20-30 days in southeastern United 

 States at a temperature range of 65-75°F. A survival rate of 75 to 90% is 

 acceptable. A higher survival suggests that the number of fry stocked was 

 estimated inaccurately. Less than 75% survival indicates a need for 



