FAMILY COREGONIDAE 101 



its pale coloration and its bluish caudal and dorsal fins, on which the 

 black is confined to the tips. 



Like the kiyi, the bluefin is a deep-water species. Bluefins are some- 

 times abundant in Lake Superior from Duluth eastward to Two Harbors 

 and intermittently to Beaver Bay, and thence to Grand Marais and 

 shghtly beyond. James Scott of Grand Marais is responsible for the 

 report that these fish spawned offshore at this point in September 

 (Koelz, 1929) . Both the bluefin and the kiyi appear to inhabit depths 

 where the water has a uniform temperature of 40° F. In midsummer, at 

 least in the west end of Lake Superior, this habit would at times keep 

 them deeper than 200 feet. Koelz states that they are seldom found in 

 water shallower than 60 fathoms, or 360 feet, but this datum does not 

 apply to the North Shore. They are commonly found in the stomachs of 

 fat trout or siscowets caught at depths of 75 fathoms. Although they 

 are caught in commercial nets, bluefins are not now abundant enough 

 in Lake Superior to be of economic importance. Koelz states that fish- 

 ermen report them as spawning in September at depths of 60 to 100 

 fathoms. 



GENUS Coregomis Linnaeus 



The genus Coregonus contains the true whitefishes, only one species 

 of which is found in central North America, although other species 

 have been recognized farther north. Other species of this genus are 

 found in northern Europe and Asia. 



GREAT LAKES WHITEFISH (Common Whitefish, Labrador 

 Whitefish, Ah-de-com-egg of the Red Lake Chippewas) 



Coregonus clupeajorinis clwpeajorTnis (Mitchill) 



The common whitefish (Figure 10) is a large, more or less ovate fish 

 with silvery sides that shade to a dark olive-brown back. It is character- 

 ized by the presence of two flaps between the openings of each nostril 

 and by the snout which distinctly overhangs the lower jaw. The upper 

 jaw is characterized by a wide premaxillary greater in width than in 

 length. The mandible usually is contained from 2.4 to 2.7 times in the 

 head. Vestigial teeth may be present on the premaxillaries, palatines, 

 mandible, and tongue. The gill-rakers number more than 23 and less 

 than 32. During the spawning season pearl organs are developed by 

 both sexes on the sides of the body and on the head. 



These fishes are among the most important of the commercial fishes 

 in Lake Superior and in other Great Lakes, though they are not as 

 abundant as formerly. Subspecies of the whitefish live in the open waters 

 of some northern inland lakes and range to considerable depth. In Min- 

 nesota they have been taken at a depth of over 100 feet in Lake 



