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Family Osmeridae SMELT RAINBOW SMELT Osmerus mordax (Mitchill) An elongate, laterally-compressed fish; mouth large, terminal with lower jaw pro- truding past upper jaw; dorsal fin located at the middle of the body; well developed adipose fin; caudal fin deeply forked; anal fin long in comparison to other fins; stom- ach lining silver with dark speckles, intes- tine short. Smelt in Colorado range from dark green to silver on the back, fading to silver-white on the stomach. Freshly killed smelt may have a purple-pink coloration on the sides. Adults can exceed 8 inches in length. Range: The rainbow smelt is found throughout the northern portions of North America, Europe and Asia in coastal areas (Scott and Crossman 1973). Rainbow smelt are found in both fresh and salt water. Like salmon, smelt living in the ocean migrate up rivers to spawn. In Col- orado, smelt have been introduced to Quincy, Rampart, Trinidad, and Horse- tooth reservoirs to determine if the species can provide an adequate prey base for fish desired by anglers. Habitat: In fresh waters, rainbow smelt are found in open, middle depths of a lake or reservoir during the summer months. In the spring and fall the fish venture into shallow waters close to shore. Usually, rainbow smelt are carnivorous, taking a wide variety of crustaceans and small fish (Scott and Crossman 1973). In Colorado, rainbow smelt feed on zooplankton and dipteran larvae and appear to spawn during April with the fish first attaining sexual maturity at one or two years of age (J. Goettl, personal communication). Because this is an open water fish it is being introduced to some Colorado reservoirs in an attempt to create a forage base for large predatory fish. Most Col- orado impoundments are rather shallow and lack underwater structure or vegeta- tion required by many forage species. Suc- cess or failure of the program has not yet been determined though smelt are suc- cessfully reproducing and are being preyed upon by largemouth bass, rainbow trout and brown trout (J. Goettl, personal communication). Adult rainbow smelt. --r r'- -- i - -----rte--pp -----?J _ L - :r - Distribution by County of the rainbow smelt. Colorado's Little Fish 14