82 Carrying Capacity, Productivity, and Growth 



10 ounces. Growth calculations from scale measurements indicated a 

 growth to 9 inches the first year, then 15 inches, 18, 20, 21, 22 and 23 

 inches; its age was 7 years plus part of an additional summer. Official 

 record largemouth bass from Paarde Vlei Lake, Sommerset West, in 

 July, 1936, weighed 5 pounds 1 ounce, was 19 inches long and was stocked 

 in 1930 as a fingerling. These bass growth records are similar to examples 

 of maximum growth for largemouth in northern United States ( increment 

 of about one pound per year ) , but no example of largemouths of 8 to 10 

 pounds which are fairly common in the United States has been recorded 

 for South Africa. This may be related to the genetics of the original 

 stock, the source of which (in the U. S.) is unknown. 



A bluegill was caught on March 17, 1947, by Mr. H. F. Palmer that 

 weighed 3 pounds 1 ounce in a dam (pond) at Butha Buthe in Basutoland. 

 "The fish could not swim upright in 9 inches of water." It could not have 

 been more than 8 years old because the first bluegills were imported in 

 1938 and the first fingerlings were distributed in 1939. At least one bluegill 

 exceeding three pounds is recorded for the United States, so here again 

 maximum sizes may be comparable in South Africa and North America. 



Factors Affecting Rate of Growth 



In comparing growth rates of fishes in various parts of the United 

 States, fisheries biologists have emphasized the importance of (1) the 

 genetic growth potential of a given species, (2) a large available food 

 supply per individual fish, (3) and the length of the growing season, 

 e.g., length of the period when the water is warm enough to allow rapid 

 digestion and assimilation of food. All of these growth-controlling factors 

 are important, but in the production of fishes of above average size, a 

 large source of available food per individual fish seems to exceed in im- 

 portance the length of the growing season (Figure 4.5). Often a large 

 supply of available food is present for the few fish that are restocked in 

 renovated lakes, and they grow phenomenally during the first season 

 before population expansion has reduced the food supply per individual 

 fish.22 



In studying the growth of largemouth and smallmouth bass in Norris 

 Reservoir, Jones -^ concluded that although the agricultural growing 

 season at Knoxville, Tennessee, was almost 7 months, the bass growing 

 season was only 4 months. He assumed that because the bass stopped 

 growing they could not grow after late September or early October, even 

 though the water was still warm. Jones apparently misinterpreted the 

 effects of what presumably was a temporary fall shortage of bass foods 

 in Norris Reservoir, and he assumed that these effects represented a 

 definite bass growing season which was much shorter than the agricultural 

 growing season. Others have shown that bass may grow rapidly during 



