158 PAPERS ON ZOOLOGY OF MICHIGAN. 



prolonged periods of quiet. Residents say, however, that herrings are 

 thrown ashore at times bj' the waves. Water movements in all prob- 

 ability disturb the sand down to a depth of twenty -six feet as they do 

 in Lake Michigan (Shelf ord 1913, page 74). 



Bottom material. No definite relations of bottom soil to fish could 

 be made out, yet certain types of bottom were preferred to others by 

 certain fish. In Lake Superior the submerged pebble zone was avoided 

 by the schools of free swimming young herring, perch, and suckers, as 

 well as by sticklebacks and some others, while sculpins and burbots 

 evidently preferred the stony area. In the marsh lakes, there was 

 noted a marked preference for the muck bottoms on the part of all 

 species. The loose, black soil undoubtedly harbored much food and 

 furnished hiding places for the small fish, although none were seen 

 retreating into it. 



Plants. The larger aquatic plants are used by the fish for protection 

 and seclusion. Growths of stonewort, water weeds, tape grass, and pond- 

 weeds were found utilized in this way. Partly submerged sweet gale, 

 sedges, and many other plants of similar habits also furnished con- 

 cealment for fish; pike lie in ambush about their submerged bases. 

 Filamentous algae was eaten by common suckers, young whitefish, 

 brook sticklebacks, and sculpins, according to the wTiter's observations, 

 and diatoms were found in many digestive canals, especially those of 

 common suckers, Cayuga minnows, silvery minnows, and black-head 

 minnows. The food value of these little plants is questionable. 



Invertebrates. The invertebrates are an important part of the fish 

 environment when they serve as food or become parasites. The prin- 

 cipal forms eaten by fish in the region are entomostracans, chironomid 

 larvae, black-fly larvae, May-fly larvae, caddice-worms, amphipods, 

 and leeches. Entomostracans constituted the chief food of j^oung 

 herring, young whitefish, and nine-spined sticklebacks on the Lake Su- 

 perior shoal. All were feeding on the same forms, which belonged chiefly 

 to the Crustacean genera, Diaptomus, Bosmina, and Cyclops. Small 

 suckers, and perch, on this shoal, were also eating these forms to a 

 considerable extent. Chironomid larvae are extensively taken by the 

 fish of the Whitefish Point region; they seemed especiall}' important 

 to bottom feeders, suckers, sculpins and burbots. Black-fly larvae 

 appeared to be the sole food for the colony of long-nosed dace living 

 near the mouth of Vermilion Creek. Sculpins were also eating them in 

 Shelldrake River. Amphipods made up most of the stomach contents 

 of the few whitefish caught in the deeper part of the shoal. Leeches 

 were eaten by large perch in the marsh lakes. 



Vertebrates. The vertebrates are especially marked factors in the 

 fish environment when they prey upon fish. Brook trout, rainbow 



