The Mooneye Cisco 



The species reaches a foot in length. It seems most closely 



related to the lake herring, from which it differs chiefly in the 

 fewer gillrakers. 



Nothing is known regarding its abundance, distribution, or 



habits. 



Mooneye Cisco 



Argyrosonins Jioyi Gill 



This fish, which is thus far known only from Lake Michi- 

 gan and, possibly from Lake Superior, does not appear to be 

 an abundant species. Until 1894 only 2 specimens were known, 

 but in that year the investigations of the United States Fish 

 Commission showed it to be one of the principal fishes taken 

 in the deep-water gillnet fishery in the western part of Lake 

 Michigan. 



Very little is known as to its habits. It seems to be a deep- 

 water species and it is not known to come into shallow water. 

 Examples taken between November 5th and 20th were all ripe or 

 nearly so, indicating that to be their spawning time, and its 

 spawning beds are probably in deeper water than those of other 

 species. Among other names by which this species is known are 

 mooneye, cisco, kieye, chub, and Hoy's whitefish. It reaches a 

 length of 12 or 13 inches and is one of the smallest and hand- 

 somest of our whitefishes. 



From A. prognathns, which it resembles. Hoy's whitefish may 

 be distinguished by the larger eye, the shorter maxillary and the 

 darker colour. 



Head 4^; depth 4^; eye 4\ to 4t; snout 3f to 3I; maxillary 

 2f to 3, reaching vertical of middle of pupil; mandible 2^; D. 10; 

 A. II or 12; scales 8 or 9-73 to 80-7; gillrakers 14+25 or 26, 

 slender, about 2 in eye; vertebrae 56; B. 8 or 9. Body rather 

 slender, compressed, the back somewhat elevated; mouth large, 

 subterminal, the lower jaw shortet- than the upper even when 

 the mouth is open; tip of muzzle rather bluntly truncate, some- 

 what as in a true Coregonus: head rather long, slender, and 

 pointed; suborbital and preorbital long and narrow; distance -from 

 tip of snout to occiput 2\ to 2f. in distance from occiput to 

 origin of dorsal fin; fins low; free margin of dorsal very oblique, 

 the length of anterior ray if in head, that of last ray less than 



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