4 



Carrying Capacity, 

 Productivity, and Growth 



The carrying capacity of a container (a pail or basket) is hmited by 

 the height of its sides and its diameter. Not so well defined, however, is 

 the ability of an environment to support life. The term "carrying capacity" 

 was probably first used in game management to express the maximum 

 population of game animals supported by a limited range during a period 

 covering at least the four seasons of one year.^^ Before we define carrying 

 capacity further, it is important to distinguish between this term and 

 saturation. An adult animal population that tends to be uniform over a 

 wide area may reach a saturation point. Saturation point is defined as a 

 uniform maximum density of grown individuals attained by a species, 

 even in the most favorable local environments. However, saturation also 

 implies a degree of intolerance of animals to "piling up," an interaction 

 between individuals that may have little connection with other environ- 

 mental conditions. Thus, saturation should not be confused with carrying 

 capacity, which always implies a tendency toward uniformity over a 

 wide area. 



Carrying capacity when applied to fishes in aquatic habitats may be 

 defined as the maximum pounclage of a given species or complex of species 

 of fishes that a limited and specific aquatic habitat may support during a 

 stated interval of time. Since adverse environmental factors during certain 

 seasons might actually control the maximum poundage of fish, seasonal 

 adversity could establish the carrying capacity. However, as fishes rarely 

 can be seen readily, or estimated by direct observation, little is known 

 of the effects of seasonal adversity on fish populations. We believe that 

 food is often limiting to population size in fishes, but other factors may 

 be of equal importance. Therefore, at present the concept of carrying 

 capacity is largely theoretical. 



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