FISHES OF DOUGLAS LAKE, MICHIGAN. 243 



inclusion of Percopsis guttatus and Pcrcina caprodcs in the list is provisional. We have 

 found insect remains in the stomach of the former, while Forbes and Richardson (1908) find 

 the latter to feed on entomostracans and insects, and we found it always on the bottom 

 near vegetation. What we know of the food of both forms, therefore, suggests the 

 vegetation habitat. The small-mouthed bass, the sucker, and the pike are found in 

 the vegetation habitat, but chiefly about its edges, while they are characteristic of the 

 deep-water community in which we have placed them. The whereabouts of the young 

 of these forms is unknown to us, but there is little doubt that they will be found in the 

 vegetation. Here also we are likely to find the young of Lota maculosa. 



With the possible exception of the log perch and the trout perch, the forms listed 

 above are confined to the vegetation. We do not ordinarily find them elsewhere. 

 They invade the shoals only, so far as known, when they afford them shelter similar 

 to that to be had amongst vegetation. From the laboratory on South Fishtail Bay a 

 dock consisting of planks supported on spiles extends from the shore to the seaward 

 edge of the terrace, which is here an unprotected sand shoal. Beneath this numerous 

 fishes found shelter — small black bass, both large and small mouthed; bluegills, rock 

 bass, adult spot-tailed minnows, and small perch. To this retreat they had been able 

 to make their way readily from the adjacent vegetation, and from it they were able to 

 harrj' the schools of young fishes on the shoals. Such shelters were no doubt formerly 

 afforded by the trunks and branches of fallen trees. With the destruction of the forests, 

 fallen trees have become rare along the shore and are removed by those who use the 

 shore as a roadway. When they were more abundant, fish must have been more plenti- 

 ful on the shoals, for they were then able to find there the shelter conditions of the 

 vegetation. 



Short forays into deeper water in search of food are probably made by several of 

 the fishes of the vegetation community. By the extension of these the 6-inch perch no 

 doubt attain in time to a membership in the deep-water community. The breeding 

 season finds certain of the vegetation fishes outside of the vegetation. The log perch 

 then betakes itself to the sand shoals and is there closely associated with the adult 

 suckers, which come to the shoals to feed on its eggs. The common shiner and the 

 small-mouthed bass must also leave the vegetation to breed. 



That the larger small-mouthed bass and the pike make raids from deeper water into 

 the vegetation in pursuit of prey we can not doubt, for they are captured at its borders. 

 Moreover, in the stomachs of the pike are found 4-inch perch, which are not known to 

 occur outside the vegetation. 



Three factors suggest themselves as determining the make-up of the vegetation 

 community — food, shelter from enemies, and breeding habits. All 10 forms, of course, 

 find their food within the vegetation. Three members of the community — the bullhead, 

 the rock bass, and the large-mouthed bass — reach a considerable size, feed in part on fishes, 

 and might obtain these outside the vegetation. But, of these, the bullhead is largely 

 nocturnal or crepuscular and is slow of movement. It tends to lie in wait for its prey 

 rather than to seek it actively. The conditions within the vegetation zone are favor- 

 able for this method of getting food. The rock bass and the large-mouthed bass 

 include a considerable proportion of small fishes in their diet, and these are most 

 abundant in the vegetation. The remaining forms feed on invertebrates, largely 



