Carrying Capacity and Standing Crop 65 



concluded that the difference in the poundages of fish in the two censuses 

 was due to the fact that the perch is largely piscivorous in its feeding 

 habits, whereas the blucgill is largely dependent on invertebrates for 

 food and thus is closer to tlie primary food chain. 



Fork Lake, a pond of 1.38 acres in central Illinois, was censused at 

 the beginning of a cropping experiment when an undesirable population 

 of fish was poisoned, and again 4 years later when the pond dam was 

 washed out.» At the time of the first census. Fork Lake contained 5350 

 fish weighing 774 pounds or 539 pounds of fish per acre. By weight, carp 

 and bigmouth buffalo made up 47.5 per cent, bullheads (plus 4 channel 

 catfish) 41.2 per cent, and largemouth bass and panfish, 6.3 per cent. 

 At the time of the dam failure, an estimate of the population was 10,300 

 fish weighing 260.9 pounds or 189.1 pounds per acre. By weight, 64.7 

 per cent of the population was largemouth bass and 35.3 per cent blue- 

 gills. This population had been subjected to heavy wing net-fishing for 

 bluegills. The earlier population containing carp, buffalo, and bullheads 

 was 2.85 times as heavy as that composed of bass and bluegills. 



Duck Pond (3.05 acres), an isolated part of an old flooded stripmine 

 in Vermilion County (Illinois), was censused at two widely separated 

 times. At the time of the first census in 1940, the pond contained 11,269 

 fishes of 30 species weighing 2051 pounds or 672.5 pounds per acre. Tlie 

 population was composed of 3.0 per cent bass, 12.2 per cent pan fish, 

 0.6 per cent catfish, 23.5 per cent rough fish (largely quillbacks and 

 carp), and 60.7 per cent forage fish (gizzard shad). In a second census 

 made in 1945, the population consisted of 3150 fishes of 18 species weigh- 

 ing 689.1 pounds or 229.7 pounds per acre. This population was composed 

 of 2.6 per cent largemouth bass, 33.1 per cent pan fish, 1.3 per cent 

 catfish, 41.0 per cent rough fish, and 22.0 per cent forage fish (gizzard 

 shad). The wide discrepancy in the total poundages of fishes in the two 

 censuses is difficult to explain. There were more pounds of bass in the 

 first census (62.4 pounds as compared with 18.2 pounds) and more 

 pounds of pan fish (251.2 pounds to 205.2 pounds). However, the large 

 differences were in the poundages of rough fish (479.8 pounds in the 

 first census, 282.2 pounds in the second) and forage fish (1245.0 pounds 

 of gizzard shad in the first census, 150.0 pounds in the second). Ap- 

 parently at the time of the second census, the populations of rough fish 

 and gizzard shad were considerably below the carrying capacity of the 

 pond for these species. 



Arrowhead Lake, an artificial pond of 2.6 acres on the grounds of the 

 Ilhnois State 4-H Club Camp, University of Illinois Allerton Estate near 

 Monticello, Illinois, was stocked in 1948 with 22 fingerling bass, 26 adult 

 bluegills, 7 adult warmouths, and 103 black bullheads. This pond was 

 censused by drainage in the springs of 1950, 1952, 1953, and during 



