FAMILY COREGONIDAE 95 



Whitefishes hybridize, but to what extent is not at present known. 

 Such hybridization accounts for some of the great difficulty in identi- 

 fying the fishes of this family taken from different lakes. The common 

 whitefish and the cisco, or lake herring, are the most common species 

 found in Lake Superior. Five other species belonging to the same genus 

 as the cisco and one species, the Menominee whitefish, belonging to the 

 genus Prosopium, are also found in Lake Superior. Although several 

 species of whitefish and tullibee have been described and reported for 

 various Minnesota and Wisconsin lakes, it is doubtful whether more 

 than one species of whitefish and one species of cisco occur inland. Many 

 of the inland lakes of Minnesota, Wisconsin, and other northern states 

 contain whitefish that are subspecies of the common whitefish and 

 tullibee that are subspecies of the Great Lakes cisco, or lake herring. 



Key to Common Species of Family COREGONIDAE* 



1 . Two flaps between openings of a nostril; gill-rakers of first arch more than 23 



2 



Single flap between openings of a nostril; gill-rakers of first arch less than 20 



Common 



Menominee Whitefish, Prosopium cylindraceum quadrilaterale (Richardson) 



2. Premaxillaries longer than wide, not turned backward (antrorse) in position; 

 premaxillary forms angle of less than 90° with horizontal axis of body; gill- 

 rakers more than 31 (Diagram 4) 3 



Premaxillaries wider than long, turned backward (retrorse) in position; pre- 

 maxillary forms angle in excess of 90° with horizontal axis of body; gill-rakers 

 fewer than 32 (Diagram 4) 



. .Great Lakes Whitefish and subspecies, Coregonus clupeaformis (Mitchill) 



3. Lower jaw more or less hooked (symphysial knob) 7 



Lower jaw not hooked (no symphysial knob) 4 



4. Gill-rakers of first branchial arch usually more than 43 



Lake Superior Cisco and subspecies, Leucichthys artedi (LeSueur) 



Gill-rakers of first branchial arch usually less than 43 .5 



5. Body ovate (deeper anterior to center) ; mandible tip distinctly pigmented 



Bluefin, Leucichthys nigripinnis cyayiopterus Jordan and Evermann 



Body elliptical (deepest at center) ; mandible tip never more than faintly 

 pigmented 6 



6. Gill-rakers of first branchial arch usually less than 39 



Superior Shortnose Chub, Leucichthys reighardi dymondi Koelz 



Gill-rakers of first branchial arch usually 39 or more 



Shortjaw" Chub, Leucichthys zenithicus (Jordan and Evermann) 



7. Body ovate; scales in lateral line usually more than 75; gill-rakers of first 



branchial arch usually less than 41 



Michigan Kiyi, Leucichthys kiyi kiyi Koelz 



Body elliptical: scales in lateral line usually less than 76; gill-rakers of first 



branchial arch usually more than 40 



Great Lakes Bloater, Leucichthys hoyi (Gill) 



*The characters of the Coregonidae are variable and render a key difficult to use. 

 Further reference should be made to Koelz (1929) and to Hubbs and Lagler (1941). 



