HATCHERY OPERATIONS 



73 



in Figure 28. There is no effect on the rate of length increase or food 

 conversion of rainbow trout as fish density increases from less than I to 5.6 

 pounds per cubic foot. 



A rule of thumb that can be used to avoid undue crowding is to hold 

 trout at densities in pounds per cubic foot no greater than 0.5 their length 

 in inches (i.e., 2-inch fish at one pound per cubic foot, 4-inch fish at two 

 pounds per cubic foot, etc.). A density index can be established that is the 

 proportion of the fish length used in determining the pounds of fish to be 

 held per cubic foot of rearing space. Fish held at densities equal to one- half 



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8 12 16 20 



BIWEEKLY GROWTH PERIODS 



24 



Figure 28. Relationship of cumulative length increase, food 

 conversion, and pounds per cubic foot (ft ) of rainbow trout 

 reared in aluminum troughs for 10 months. (Source: Piper 

 1972.) 



