82 COMMUNITIES OF LARGE LAKES 



2. The sand-depositing shores are without animals, at least to a depth 

 of i . 5 meter, and life is scanty to 8 meters, on account of the shifting 

 character of the bottom. 



3. Animals are abundant in protected bays; the species inhabiting 

 these situations are commonly found in sluggish streams and small 

 lakes, and a few of them have been recorded below 8 meters also, which 

 is relatively quiet water. 



4. The animals of the upper shore belt, 0-8 meters, are found also 

 in swift streams. 



5. The animals of the lower shore and upper deep-water zone are 

 below effective wave-action and are those found in still waters. 



6. The animals of the deep-water zone are not found outside of deep 

 lakes, and cannot be compared with any others of our Chicago area. 



7. We have, then: swift-water animals in the upper belt, still-water 

 animals in the middle belt, and deep-water animals in the lowest. 



8. The fish are migratory and deserve special comment. 



DISTRIBUTION OF WHITEFISH AND DEEP-WATER FISH IN LAKE MICHIGAN (75) 



Argyrosomus artedi, the lake herring, is near the surface. 



Coregonus clupeiformis, the whitefish, lives most commonly between 21 and 



36 meters; it spawns in water between 3 and 28 meters, most commonly 



between 15 and 19 meters. It makes migrations into the 9-meter belt 



in summer, supposedly on account of bad aeration; has disappeared 



where breeding-grounds have been destroyed. 

 Argyrosomus prognathus, the long-jaw, is found mainly in from 36-66 meters. 

 Argyrosomus nigripinnis, the blackfin, is found in from 70-80 meters, coming 



up to 60 in December. 

 Argyrosomus hoyi, Hoy's whitefish, is usually recorded below 115 meters. 

 Triglopsis thompsoni is confined below 115 meters. 

 Cristivomer namaycush, the lake trout, is confined below 25 meters, except 



during the breeding season. It breeds between 2 and 25 meters on rock 



or other hard bottom. 

 Lota maculosa, the lawyer, appears to be distributed throughout, but no 



account is to be found regarding its movements or their causes. 



An interesting truth is illustrated by the species of whitefishes 

 (Argyrosomus and Coregonus). If a group is to be successful and become 

 extensive in its distribution, it must so differentiate in habits as to bring 

 the different races out of competition with each other. We usually 

 find that different species which are closely related have different habitats. 

 Here we have these species of fish arranged one above the other. The 

 separation in such cases is usually horizontal. 



