Reproduction 93 



of fry collected from each nest. He found that numbers of largemouth 

 bass fry varied between 751 and 11,457, with an average of 4375 per nest 

 (5 nests); rock bass from 344 to 1756 with an average of 796 per nest 

 ( 9 nests ) ; common sunfish 1509 and 14,639 per nest ( 2 nests ) ; and blue- 

 gills from 4670 to 61,815 per nest with an average of 17,914 (17 nests). 

 On the basis of the number of nests being used by these centrarchids 

 during the 1938 season, the minimum number of fry produced in Deep 

 Lake (surface area 14.9 acres) was estimated as follows: bluegill 6,610,- 

 000; common sunfish 1,518,000; rock bass 46,000; and largemouth bass 

 164,000. As this lake probablv would not support a fish population of 

 more than 8000 to 10,000 individuals of useful sizes, it is obvious that 

 any one of the 4 species listed above produced enough young fish in 1938 

 to overpopulate the lake. 



Other pan and sport fishes produce large numbers of eggs. Female 

 warmouths ranging in size from 3.5 to 7.0 inches contained from 4500 to 

 more than 50,000 eggs per fish."^- The female walleyes in Lake Gogebic 

 (Michigan) -^ ranging from 16.0 to 22.7 inches yielded from 37,000 to 

 nearly 155,000 eggs per fish. On the average, 34 walleye females from 

 Gogebic yielded 28,112 eggs per pound of body weight. Wisconsin muskel- 

 lunge from 25 to 53 inches in length were reported to produce 22,000 

 to 180,000 eggs per fish at each spawning, and northern pike are known 

 to produce about the same numbers. ^^ 



As mentioned above, only a small fraction of the young produced by 

 any fish species survives. For example, in the spring of 1941, Ridge Lake, 

 Coles County, Illinois (18 acres), was stocked with 100 sexually mature 

 largemouth bass.^^ Thirty-eight schools of young were observed in early 

 June, each containing at least 2000 individual free-swimming fry; a con- 

 servative estimate of the total was 76,000. When the lake was drained in 

 March, 1943, almost 2 years later, sHghtly more than 4000 of these young 

 bass were still present and even with this number, Ridge Lake was over- 

 populated with bass. 



Heaviest predation probably takes place during the first few weeks of 

 life when the fish are very small and relatively helpless. This was sub- 

 stantiated by studies on the spawning of northern pike in Houghton Lake 

 ( Michigan ) in 1939 and 1940.^^ Weirs were installed to catch fish in tlie 

 spawning migration of northern pike into the ditches tributary to the 

 north bav of Houghton Lake and to trap the returning young pike from 

 the ditches. In 1939, 125 female and 280 male adult pike migrated into the 

 ditches, and 7239 young pike were caught migrating toward the lake. 

 In 1940, 65 females and 81 males migrated into the ditches, and only 

 1495 young migrated out. In both years, newly-hatched pike fry were 

 about equally abundant in the ditches, but in 1939, minnows and perch 



