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Mooneye Cisco
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This fish, which is thus far known only from lake Michigan 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 handsomest of our whitefishes.
From A. prognathus, which it resembles, Hoy's whitefish may be distinguished by the larger eye, the shorter maxillary and the darker colour.
Head 4 1/2; depth 4 1/2; eye 4 1/5 to 4 2/3; snout 3 2/5 to 3 5/6; maxillary 2 3/5 to 3, reaching vertical of middle of pupil; mandible 2 1/6; D. 10; A. 11 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 shorter than the upper even when the mouth is open; tip of muzzle rather bluntly truncate, somewhat as in a true Coregonus: head rather long, slender, and pointed; suborbital and pretrial long and narrow; distance from tip of snout to occiput 2 1/5 to 2 2/5 in distance from occiput to origin of dorsal fin; fins low; free margin of dorsal very oblique, the length of anterior ray 1 3/5 in head, that of last ray less than half that of first; longest anal ray 2 3/5 in head, and more than twice as long as the last; pseudobranchiae very large; tongue with traces of teeth. Colour, light iridescent blue on back, with a few fine dark punctulations reaching about 2 scales below lateral line; sides and under parts rich silvery, brighter than in any other of our Coregoninoe, much as in Hiodon and Albula; top of head light olivaceous; cheeks silvery; dorsal, caudal and pectorals with some dark on their margins; anal and ventrals white, with some dark dustings; the male perhaps a little richer, more iridescent blue on back, and with the scales a little thicker and less closely imbricated.