Distribution of FisJies 



233 



these forage in the shoals, especially at night. The 

 catfishes are more strictly bottom feeders, and these 

 feed mainly at night. A few species keep to the close 

 shelter of thick vegetation at the water's edge, and one 

 species, the least darter, prefers to lie over mottled 

 marl-strewn bottoms at depth between fifteen and 

 twenty feet. 



So it appears that some two-thirds of the species 

 have their center of abundance in the pondweed zone: 

 here, doubtless they best find food and escape enemies. 



FT 



20 

 40 

 60 



80 



100 



J^\,- 'pondweted zone 



n>^ 



a, whitefish, i species. 



c, pike, i species. 



e, sucker, i species. 



n, perch and wall-eye, 2 species. 



o, bass, sunfish, minnow, etc., 



19 species. 



r, catfishes, 2 species. 

 5, mudminnow, etc., 3 species. 

 x, least darter, i species. 



FIG. 140. Diagram illustrating the habit- 

 ual distribution of the thirty-one species 

 of fishes in Walnut Lake, Michigan. 

 Data from Hankinson. 



Only a few of the stronger and swifter species venture 

 much into the deeper water: the weaklings and the 

 little fishes frequent the weed-covered shoals. 



The eggs of fishes are cared for in a great variety of 

 ways. Their number is proportionate to the amount of 

 nurture they receive. No species scatters its eggs 

 throughout the whole of its range, but each species 

 selects a spot more or less circumscribed in which to lay 

 its young. Carp enter the shoals and scatter their eggs 

 promiscuously over the submerged vegetation and the 

 bottom mud with much tumult and splashing. A 

 single female may lay upwards of 400,000 eggs a season. 



