THE WHITEFISHES OF NORTH AMERICA. 301 



The whitefish makes regular migrations analogous to the movements 

 of anadromous fishes iu the coast rivers. These occur chiefly about 

 the spawning seasou and are impelled by the reproductive instinct. 

 There are also more or less regular movements at other times, but 

 these are not well understood. 



The whitefish rarely takes the hook. Its small mouth necessitates 

 the ingestion of minute food, and examination of the stomach contents 

 has shown that it subsists chiefly on crustaceans, mollusks, and insect 

 larva. 



Dr. S. A. Forbes, of Illinois University, has made a careful study of 

 the first food of the common whitefish in Lake Michigan, and has 

 reached the following conclusion: 



We are compelled to conclude that the earliest food of the whitetish consists 

 almost wholly of the smallest species of Entomostraca occurring in the lake, 

 since the other elements in their alimentary canals were evidently either taken 

 accidentally, or else appeared in such trivial quantity as to contribute nothing of 

 importance to their support. In fact, two species of Copepoda, Cyclops thomasi and 

 Diaptomus sicilis, are certainly very much more important to the maintenance of the 

 whitetish in this earliest stage of independent life than all the other organisms in 

 the lake combined. As the fishes increase in size, vigor, and activity they doubtless 

 enlarge their regimen by capturing larger species of Entomostraca, especially Daph n ia 

 and Limniaclanus. (Bull. 111. State Lab. Nat. Hist,, vol. i, No. ft, p. 108, 1883.) 



The common whitefish is generally regarded as one of the best food- 

 fishes of North America. In the regions in which it is taken it is 

 usually held in higher esteem than any other fish. Being a soft fish, 

 it spoils rapidly, and in the condition in which it usually reaches the 

 consumer its edible qualities have greatly deteriorated. 



7. Coregonus nelsonii Beau. 



Humpback Whitefish. 



Coregonus nelsonii Bean, Proc. U. S. Nat. Mus. 1884, 48, Nulato, Alaska. (Type, No. 

 29903.) 



Head, 5; depth, 4; maxillary, 4; D. 12; A. 12. Scales, 10-88-8 (or 

 10 counting to middle line of belly). Gillrakers about 20 in number, 

 the longest about 2 in eye. Body heavy forward; back greatly arched 

 and compressed. Head small, snout rather pointed. Mouth small, the 

 maxillary reaching front of eye. Distance from snout to nape about 

 2£ in distance from nape to origin of dorsal, the latter a little nearer 

 posterior base of adipose fin than tip of snout. Base of dorsal fin, 1| 

 in longest ray or 1£ in head. 



This species is allied to G. clupeiformis and G. labradoricus, from which 

 it may be distinguished by the greatly arched and compressed back. 



It was described by Dr. Bean in 1884 from specimens collected by 

 Mr. E. W. Kelson, at Nulato, Alaska; Mr. Townsend reports it from 

 the Kuwuk River. It is known only from Alaska, from Bristol Bay 

 northward. 



