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Becker, George C. / Fishes of Wisconsin

Smelt family - osmeridae,   pp. 377-384 PDF (3.4 MB)

Page 379

Rainbow Smelt    379 
Rainbow Smelt 
Osmerus mordax (Mitchill). Osmerus-Greek for odor- 
     ous; mordax-biting. 
Other common names: smelt, American smelt, fresh- 
     water smelt, frost fish, ice fish. 
Adult male 155 mm, L. Superior, Ashland (Ashland Co.), 29 Apr. 
Body slender, slightly compressed laterally. Average 
length 178 mm (7 in) TL. Depth into TL 7.2 (6.5-8.0). 
Head into TL 4.9 (4.6-5.4). Snout elongate and 
pointed. Mouth large, lower jaw protruding; maxil- 
lary extending to middle of eye or beyond. Teeth on 
upper and lower jaws, and on tongue and front of 
vomer where teeth are especially enlarged. Gill rak- 
ers long and slender 26-35. Branchiostegal rays 5-7. 
Scales cycloid; lateral scales 62-72, lateral line incom- 
plete. Dorsal fin rays 8-11; anal fin rays 12-16; pec- 
toral fin rays 11-14; pelvic fin rays 8. Pyloric caeca 
  Breeding tubercles extensively developed on head, 
body, and fins of males; seldom on females. 
  Silvery; dorsal half of head and body steel blue, 
with sides lighter and belly white. A faint lateral 
stripe present in some large individuals. Fins gener- 
ally clear. 
Although essentially a marine species with primary 
distribution along Canadian coastal waters, the rain- 
bow smelt has intruded into fresh waters of the 
northeastern states and into the Great Lakes. It oc- 
curs in all major drainage systems in Wisconsin. In 
the Lake Superior basin it inhabits the lake proper 
and its tributaries; in the Lake Michigan basin, the 
lake proper, its tributaries, and Lake Lucerne (Forest 
County). In the Mississippi basin its presence has 
been established in Diamond, Sand Bar, and Toma- 
hawk lakes (all within Bayfield County), and in Fence 
Lake and adjacent streams (Vilas County). The smelt 
was introduced "inadvertently" into the Fence Lake 
system in 1968 (M. Bailey, pers. comm.). The origin 
of the Lake Lucerne population is not known (A. 
Oehmcke, pers. comm.). 
   The rainbow smelt is an escape into Wisconsin wa- 
 ters. The seed stock, which came originally from 
 Green Lake, Maine, contained a native freshwater 
 race of the marine species common along the North 
 Atlantic coast. Attempts to introduce this species in 
 the upper Great Lakes go back to 1906, but it is gen- 
 erally accepted that the present strain spread from 
 the 1912 stocking of 16.4 million smelt in Crystal Lake 
 (Benzie County), Michigan. The rainbow smelt was 
 first taken in Lake Michigan off the east shore near 
 Frankfort, Michigan, in 1923 (Van Oosten 1936); by 
 1924 it had crossed the lake to Big Bay de Noc, an 
 arm of Green Bay. It was first observed in Wisconsin 
 waters in 1928 when a few were caught in gill nets 
 near Little Sturgeon Bay (Door County). In 1929 a 
 few smelt were taken in Lake Michigan off Gill's Rock 
 and the Sturgeon Bay Canal. By 1930 it had reached 
 Manitowoc, Port Washington, and Racine, and in 
 1931 it reached Kenosha, Wisconsin, and Michigan 
 City, Indiana. 
 In Lake Superior the rainbow smelt appeared first 
 at Whitefish Bay, at the eastern end of the lake, in 
 1930; it appeared in Keweenaw Bay in 1936, and 
 probably reached the Wisconsin waters of Lake Su- 
 perior in the late 1930s. 
 The rainbow smelt is common in lakes Superior 
 and Michigan and is occasionally taken in large tribu- 
 tary streams. 
 In the Great Lakes, rainbow smelt inhabit waters 
 14-64 m deep and are most abundant in the 18-26 m 
 zone. Occasionally they occur in small numbers to 91 
 m. The adults move inshore and congregate in dense 
 schools in April, and, when spawning, some may 
 move short distances up tributary streams. 
 The spawning season (late March through early May) 
 normally lasts about 2 weeks, but climatic conditions 
 such as cold rains and cold nights may extend it to a 
 month (Daly and Wiegert 1958). Because of temper- 
 ature differences between northern and southern 
 Wisconsin waters the start of the spawning run may 
 vary as much as 3 weeks between southern Lake 
 Michigan and Lake Superior to the north. The run in 
 southern Green Bay is normally a week to 10 days 
 later than the run in northern Lake Michigan because 
 the bay freezes over in winter and therefore warms 
 up later. 
 Spawning is initiated when the water temperature 
 reaches 4.4°C (40'F) or higher-shortly after the ice 
breaks up and moves out. At this time the bulk of 

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