66 FISH HATCHERY MANAGEMENT 



400^ 



2 4 6 



FISH LENGTH IN INCHES 



8 



Figure 26. The weight of different sized fish that would receive the 

 same quantity of food (5 pounds) at a Hatchery Constant of 10. 

 (Source: Piper 1972.) 



water temperatures. These two graphs do not depict optimum stocking rates 

 but rather what we believe to be the maximum loading or density that must 

 not be exceeded if normal growth rates are to be maintained. 



There is a relationship between the amount of feed that can be metabo- 

 lized in a given rearing situation and the pounds of fish that can be carried 

 in that rearing unit. There is much support for two major premises 

 presented by David Haskell in 1955: 



1. The carrying capacity is limited by (A) oxygen consumption, and (B) 

 accumulation of metabolic products. 



2. The amount of oxygen consumed and the quantity of metabolic prod- 

 ucts produced are proportional to the amount of food fed. 



Haskell postulated that the accumulation of metabolic products and the 

 consumption of oxygen are the factors that limit the carrying capacities of 

 rearing units. If this is true, metabolism is the limiting factor because both 

 the utilization of oxygen and production of metabolic products are 



