Becker, George C. / Fishes of Wisconsin
Smelt family - osmeridae, pp. 377-384 PDF (3.4 MB)
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. 1971 DESCRIPTION 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 4-8. 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. DISTRIBUTION, STATUS, AND HABITAT 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. BIOLOGY 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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