LAKE MANAGEMENT REPORTS 



4. A SECOND YEAR OF FISHERIES 

 INVESTIGATIONS AT FORK LAKE, 1939 



George W. Bennett, David H. Thompson, 



Illinois Natviral History Survey, 



and 



Sam A. Parr, 



Illinois State Department of Conservation 



This report covers the fisheries investigations done at Fork Lake, near Mount Zion, 

 Illinois, in 1939. Although our conclusions are intended to apply to Fork Lake itself, a 

 body of water of 1.38 acres, they may be extended to include other similar, small artifi- 

 cial lakes. In an earlier report (Thompson & Bennett 1939a) investigations In Fork Lake 

 during 1938 and recommendations for future management were discussed. It may be well to 

 repeat here the principal points. Poison was applied to the lake and a fish census was 

 made which showed 744 pounds of fish, of which 37 pounds were hook-and-line fish of legal 

 length. The lake was then restocked with 1,440 largemouth bass fry, Huro salmoides 

 (Lacepede), and with 270 breeder bluegills, LepoiJiis maorochirus (Rafinesque); the latter 

 spawned during the summer of 1936. Throughout the grov/ing season of 1939, fish were 

 removed at the rate of about 25 pounds per acre per month. The percentage of fish of 

 desirable sizes was greatly increased after one year as a result of the practices set up. 



This improvement was accomplished without additional stocking, without the construc- 

 tion of spawning beds, without forage fish, without the planting of aquatic vegetation, 

 without fertilization and without the addition of brush piles. 



Illustrations covering certain phases of our study on Fork Lake are shown in plate 1. 



ACKNOWLEDGADBNTS , 



Mr. Paul S. Smith, owner of Fork Lake, has continued to make these investigations 

 possible by permitting the Survey staff full use of the lake. He has also helped in many 

 phases of the work. Dr. D. F. Hansen, Dr. C. L. Schloeraer, Mr. L. H. Krumholz and Mr. 

 F. X. Lueth of the Survey staff assisted with the fishing and the collection of data. 

 Mr. Krumholz drew graphs or figures. Mr. Lueth made preliminary stomach analyses and 

 assisted in the tabulation of data. 



Aid in moving fish, planting trees and supervision of road construction and levee 

 work was received from Mr. Alvin C. Tuggle of the Illinois State Department of Conserva- 

 tion, under the directorship of Mr. Thomas J. Lynch. 



Mr. Sam A. Parr, District Inspector with the State Department of Conservation, has 

 contributed to the completeness of this paper through collection of important field data. 



SmUIARY OF THE 1939 YIELD 



A total of 1,289 fish, weighing 223.4 pounds, was removed from Fork Lake during 1939. 

 This is equivalent to 934 fish, or 162 pounds, per acre and is about half of the theoreti- 

 cal carrying capacity of the lake for hook-and-line fish. The catch is listed in table 1. 



TABLE l.~FISH REMOVED FROM FORK LAKE DURING 1939. 



This catch includes 60 per cent of the original bluegill breeders, 24 per cent of the 

 original bass fry and an unknov/n percentage of the bluegills produced in the lake in 1938, 

 It is evident that the 1938 brood of bluegills furnished the greatest part of the catch, 

 both in numbers and in weight. M 



For comparison: fish stocked in the summer of 1938 consisted of 270 bluegills weigh- 

 ing about 40 pounds and 1,440 largemouth bass fry weighing 0.15 pound. 



