FISHES OF THREE WISCONSIN LAKES 55 



cussed in this paper, Lake Geneva has the most strikingly 

 rocky shores. The rock bass is most abundant in this lake as is 

 its favorite food the crayfish which commonly hides among 

 stones alongshore. 



Transparency of water. In all but one of the lakes more 

 species of fishes were found in the first five meters below the 

 surface than in any deeper zone. In Lake Pepin a comparatively 

 large number of fishes was caught per hour in the upper five 

 meter zone. In the most transparent lake studied (Table V) 

 the preponderance of the fishes in the second five meters below 

 the surface was very striking. The more transparent the water 

 in a lake is, the deeper can the aquatic vegetation migrate. 

 Most shore fishes are associated with the zones where water 

 plants are found. 



Depth. The depth of a lake is important in many ways. 

 The summer temperature may be gradually less at greater 

 depths; the pressure increases downward; the dissolved gases are 

 influenced by the stagnation due to thermal stratification. 

 Though more species are usually found in the shallower parts of 

 lakes, there are some true deep-water fishes which are not 

 found except in cool depths where the pressure is great: certain 

 ciscoes, lawyer, etc. Some fishes, though they commonly feed 

 on the bottom and are found in lakes where there is abundant 

 bottom food and oxygen at all depths, are perhaps kept from 

 feeding on the bottom by some factor associated with depth. 

 Apparently the perch in Green Lake and Lake Michigan would 

 gain much by feeding on the bottom everywhere, as they do in 

 other lakes which are not so deep, but they do not do so. 



Vegetation. Many of the shore fishes spend most of their 

 lives in or near the shore vegetation. The bluegill is caught in 

 lakes much more than the pumpkinseed, which has similar 

 habits apparently because it feeds more from the surface. The 

 pumpkinseed is always found among vegetation and the writer 

 has never seen it in an "open" lake. Vegetation supplies food, 

 directly and indirecly, and furnishes shelter for fishes. Kofoid 

 (1903, p. 496), in speaking of lakes has stated that, "whenever 

 the depth of the water, the currents, the winds, or other factors 

 prevent the development of a submerged aquatic flora the en- 

 tire production of the lake takes the form of plankton and, in 

 turn, of those larger species, insect larvae, molluscs, and fish, 



