FISHES OF DOUGLAS LAKE, MICHIGAN. 225 



back is thin and sharp instead of round, and the head is disproportionately large com- 

 pared to the body. This is because the head is made up largely of bone, and emaciation 

 can not so greatly reduce its bulk as it does that of the more fleshy body and tail. The 

 emaciated fish do not appear to be diseased and are not usually parasitized heavily 

 enough to account for their emaciation. Death seems to be due to stan'^ation. 



Hankinson {1908) collected 41 suckers in Walnut Lake and gives their average 

 weight as 2.5 pounds. Their average length, including the caudal fin, is, from Hankin- 

 son's tables, 16.2 inches. From Forbes's and Richardson's (1908) figure of the common 

 sucker, the length from tip of the snout to the base of the caudal is found to be 0.88 

 of the total length from tip of snout to tip of caudal fin. Applying this correction 

 to Hankinson's average length, we get an average length of his suckers of 14.3 inches, 

 measured in the usual way from tip of snout to base of caudal. In contrast to this the 

 14 fish taken in Douglas Lake have an average length of 9.5 inches and an average weight 

 of 0.48 pound. 



From the fact that all stomachs of the common sucker were found empty, from their 

 habit of feeding on the comparatively innutritious materials of the lake bottom and 

 on those covering the stems and leaves of plants, from the large number of deaths among 

 them in midsummer, and from their relatively small average size, it may be inferred 

 that the fish get insufficient food. 



In Walnut Lake Hankinson (1908) found, as the result of the examination of the 

 alimentary canals of 13 common suckers, caddis-worms and cases, small bivalve mollusks, 

 amphipods, insects, marl, midge larvae, and Daphnia. Of these, the caddis-worms, 

 amphipods, and midge larvae are commonly associated with vegetation. It is not 

 unUkely that the relatively slight development of vegetation in Douglas Lake makes 

 it an unfavorable habitat for suckers. 



The breeding grounds of the Douglas Lake suckers are unknown. According to the 

 writer's unpubUshed observations, suckers breed in streams where there is swift water 

 and gravel bottom. These conditions are found in Maple River and in Bessie Creek. 

 Young suckers less than 2 inches long are found in June on the shoals of South Fishtail 

 Bay, about 6 miles by the shore from either of these streams. They are doubtless fish 

 of the season and, if the breeding habits of the suckers of Douglas Lake are the same 

 as elsewhere, the young must have wandered to the shoals from the breeding grounds 

 in Maple River and Bessie Creek. It is possible, however, that the essential requirement 

 for breeding is suitable bottom, not running water. Bottom suitable for suckers is 

 plentiful in Douglas Lake on the shoals, and the young suckers found there may be still 

 on the breeding grounds. 



In figure 2 the lengths and weights of the suckers included in table i have been 

 plotted and a curve sketched to show their relation. It is clear that there is a definite 

 relation of such a sort that, after a weight of 4 or 5 ounces has been reached, length 

 increases less rapidly than weight. Thus between the weights of 4 and 5 ounces the 

 increase in length is about 0.75 inch, while between 14 and 15 ounces it appears to be 

 scarcely o.i inch. At the 15-inch length the line is nearly horizontal. Our data are not 

 enough to make it advisable to draw the length-weight curve mathematically or to 

 determine its formula. (See Hecht, 1913.) 



PiMEPHALES NOTATus (Rafinesque) , hlimt-noscd minnow. — Ten specimens, 2^4 to 2% 

 inches long and evidently adult, were taken in the seine at Bryant's dock (location 9 



