Carrying Capacity and Standing Crop 69 



The standing crops of fisli recorded in the 1947, 1949, 1951, and 1959 

 censuses (which are most nearly comparable to one another, with both 

 bass and bluegills present and no drawdowns ) ranged from 140 to 256 

 pounds per acre. The liighest poundage (256) represented more tlian 

 an 80 per cent increase over the lowest poundage ( 140 ) . 



After each census, oil of the cotchahle bass icere returned to the lake, 

 and the bluegill populations were drastically reduced, usually to less 

 than 200 per acre of the larger fish. The population after two, three, or 

 four growing seasons ( 1959 census ) reflected the struggle for dominance 

 between the bass and bluegills. From Table 4.2 one is led to believe that 

 fall drawdowns of the lake affect both species: the bass througli a 

 poundage decrease with litde change in numbers, the bluegills through 

 a decrease in both numbers and poundages, but with a more severe 

 effect on numbers. Thus, the drawdowns were more favorable to bass 

 than to bluegills. 



The eight censuses of Ridge Lake parallel the four censuses of Arrow- 

 head Pond in exposing what appears to be competition, primarily between 

 largemouth bass and bluegills in which the bass would rather quickly 

 lose out except for the culling of bluegills on each census. Ridge Lake 

 is a highly favorable habitat for bluegill reproduction and survival, but 

 poor in nutritional resources for bluegills of desirable sizes. 



Growing Season. Swingle and Smith ^^ state: "After the fish used in 

 stocking have spawned once, more small fish are present than can be 

 adequately supported by the food that the pond is producing. Hence a 

 pond rapidly reaches its maximum carrying capacity, usually within one 

 year." 



The length of the fish growing season in the southern part of the United 

 States may be more than 10 months long, whereas in the northern states 

 the fish growing season may be less than 4 months (Figure 4.3), and 

 northern lakes and ponds may be covered with ice from 3 to 5 

 months. The length of the growing season affects the time of population 

 growth required for it to approach the carrying capacity of an un- 

 populated body of water. RalP found that the total weight of fish re- 

 corded at the end of the third year did not vary greatly from that of the 

 second year. This indicates that two growing seasons are usually sufficient 

 for a population to approach the carrying capacity of a body of water 

 in the northern part of the United States. 



Other Factors Related to Standing-Crop Size. The relationships be- 

 tween the standing crops of fishes and certain environmental and fish 

 population characteristics have troubled fishery biologists for years. Re- 

 cently, using regression methods, Carlander ^^ attempted to determine 

 whether certain environmental factors may affect standing crops of fishes. 

 He found no relationship between standing crop and lake area; an in- 



