58 UNIVERSITY OF WISCONSIN STUDIES 



in Lake Geneva. The present generation is awake to the im- 

 portance of "conservation," but few people realize how impor- 

 tant it is to preserve the completeness of the environment. The 

 Mississippi cannot continue to furnish buttons and food fishes 

 if the swamps along its borders are drained and used for agri- 

 culture. The ultimate value of changes which involve the elim- 

 ination of great living natural resources should be carefully 

 considered before being undertaken. Sometimes two branches 

 of commerce help each other. The chief clam-eating fishes in 

 Lake Pepin are the carp and sheepshead. The same two fishes 

 are yielding the best profits to fishermen. The growth of clams 

 for buttons is fostered by commercial seining in the Mississippi. 



The productiveness of a lake depends on various combina- 

 tions of the factors just considered. Lake Pepin, which has in- 

 timate association with the Mississippi River, according to the 

 writer's catches contained the greatest number of species, but 

 the smallest number of fishes per unit of area. The largest 

 numbers of fishes per unit of area were found in the inland lakes 

 with considerable vegetation and rich bottom faunas. The two 

 deep, clear inland lakes with little vegetation and plankton both 

 rank ahead of Lake Michigan in this respect. Lake Geneva has 

 the most limited fauna in species. 



From these facts it appears that the factors which make 

 fishes numerous in a lake are abundant food and vegetation. 

 But these factors, while they permit numbers to exist, do not 

 necessarily allow fishes to reach their maximum degree of per- 

 fection. Lake Wingra contains more fishes than Lake Mendota 

 per unit of area, but its lake fishes are small in size. Lake Men- 

 dota with its varied shores and greater depth offers a more fav- 

 orable environment in which fishes may develop to large size. 

 Lake Michigan, which is thinly populated, produces some gigan- 

 tic fishes. 



Lake Geneva and Green Lake present the most monotonous 

 environments of any of the lakes studied, and, probably on that 

 account, contain the smallest number of species. However, 

 Lake Geneva contains the largest number of desirable game 

 fishes (wall-eyed pike, smallmouth black bass, and pickerel) 

 of any of the lakes. In this respect Green Lake ranks second 

 with many pickerel and good numbers of smallmouth black 

 bass. The clear deep lakes are apparently the most desirable 



