FISHES OF DOUGLAS LAKE, MICHIGAN. 



231 



located for a single average fish, would be higher and of different form from that for the 

 pike of Douglas Lake. Such a hypothetical curve is sketched in broken lines in figure 3 

 to show how cur\-es for single species might be characteristic of localities. A comparison 

 of our curve for the pike with that for the sucker shown in figure 2 shows that they 

 differ. The sucker increases less rapidly in weight with increasing length than does the 

 pike. A sucker of 12 inches weighs about 14 ounces; a pike of 12 inches, if our curve 

 is correct, about 10 ounces. This is for Douglas Lake. With data enough for many 

 species from many localities, one might be able to say, from a study of such curves, for 

 what species of fish the conditions of each locality were most favorable. By defining or 

 describing these conditions one might then possibly use them as a guide in the practical 

 operations of fish culture. 



It is interesting to note that pike 22 of our list had a large hump on the back due to 

 curvature of the spine. If this was the result of an injury it had been inflicted so long 

 before that no external scars remained. The deformity may even have been congenital. 

 In spite of it the fish had thriven. The conditions of existence were not severe enough 

 to eliminate it. Its position is shown at 22 on figure 3. 



Percopsis guttaTus Aggassiz, trout perch, is known only from the numerous 

 specimens thrown up on the beach of South Fishtail Bay. It has not been taken in 

 nets. In one specimen 2)4 inches long the intestine contained the chitinous parts of 

 an insect larva. This indicates that its habitat is the vegetation zone. 



July 17, 1912, following a storm, many adults were picked up on the beach. Among 

 these were females that gave up eggs freely on slight pressure. On the following day 

 a search was made of the shoals in the hope of locating the breeding fish, but without 

 result. 



Ambloplites rupESTris (Rafinesque), rock bass. — The data collected concerning 

 this fish are brought together in table iv. 



Table IV. — Records of Ambloplites rupestris Taken in Douglas Lake in 1912. 



Although the records show it from but two localities, it is taken wherever there is 

 vegetation in the lake. We have taken it at no greater depth than ^yi feet, a depth 

 which is usually reached a little beyond the edge of the terrace. It may go deeper. I 

 believe it is sometimes taken at greater depth on the hook, but not beyond the vegetation. 



