FAMILY ESOCIDAE 189 



black mottling on the body. Undoubtedly, as proved by the experi- 

 mental evidence, this type is breeding true in nature, for in the lakes 

 where this fish occurs pure silver-colored individuals of all ages continue 

 to appear and possible hybrid types are uncommon. This fish is appar- 

 ently a true-breeding mutant of Esox lucius and has definitely estab- 

 lished itself in several lakes, where it breeds with others of its kind 

 rather than with the accompanying northern pike and muskellunge. 

 Properly, the common name should be '"silver pike" rather than "'silver 

 muskellunge." 



NORTHERN MUSKELLUNGE (Wisconsin Muskellunge) 

 Esox inasquinongy immaculatus (Mitchill) 



The general shape of the muskellunge is very similar to that of the 

 northern pike. The species is said to be readily distinguishable because 

 of the absence of scales on the lower part of the cheek, but many Min- 

 nesota specimens show more or less developed scales on the lower cheek. 

 As in the northern pike, the opercle bears scales on the upper half only 

 and the lower half is naked. The branchiostegals number 16-19. The 

 dorsal fin has from 19 to 21 rays. The body is usually more or less 

 silvery, though some muskellunge from the Lake of the AYoods drain- 

 age are dark brown. The markings vary considerably, but always con- 

 sist of dark markings on a light background. The total number of pores 

 on the ventral surfaces of both mandibles varies from 11 to 18, but 

 always exceeds 10. Minnesota specimens have from 130 to 157 lateral- 

 line scales, but most specimens counted ranged from 147 to 155. 



Three subspecies of muskellunge have been described by various 

 authorities. Of these the subspecies immaculatus (Figure 32B) is as- 

 signed to the region of Minnesota and Wisconsin. The subspecies E. 

 masquinongy masquinongy (Mitchill) is reported to range through the 

 Great Lakes but at present seems to be absent from the Minnesota 

 waters of Lake Superior. Greene (1935) reported it from the Apostle 

 Islands in Lake Superior and from Lake Michigan. 



The markings and other characters of the muskellunge in this region 

 indicate that further study is needed to determine the relations of the 

 various types. The typical markings consist of a more or less silverj' 

 background with broad and more or less distinct dark bars on the sides. 

 This variety is called locally the "'tiger musky.'" On some older speci- 

 mens the bars become so faint as to be almost indiscernible. Other 

 muskellunge are marked with more or less distinct spots on a light back- 

 ground and are called locally '"leopard muskies." Whether they con- 

 stitute distinct varieties is doubtful, for all are sometimes found in the 

 same lake and many individuals showing intergradations are found. 



Muskellunge are seldom abundant in any one lake in Minnesota. They 

 are found in Lake of the Woods and tributary waters and in certain 



