Colorado Fish Species: Gizzard Shad

Description: A fish that is strongly compressed lateraly, body thin and deep; mouth small and subterminal, upper jaw with a deep notch at center, upper jaw extends past lower jaw; dorsal fin with 10-13 rays, last ray of dorsal fin modified into a long, thin filament; 29-35 rays in anal fin; more than 55 scales in lateral line. Adults are silver or silvery-blue on the back, fading to silver on the sides, with a whitish belly. Young have a large purple-silver spot on the sides behind the upper edge of the operculum. Mature fish range from 9-13.5 inches in length and weigh about 12 ounces. Specimens longer than 18 inches have been taken in eastern Colorado.

 Range in Colorado: Gizzard shad in Colorado are restricted to reservoirs and mainstem river reaches in the Arkansas and South Platte drainages. Every life stage, from larvae to spawning adults, is found in many eastern plains reservoirs. Immature fish, to five inches in length, may be encountered in the mainstem South Platte River from Greeley upstream to the Saint Vrain River, and in the lower reaches of that tributary (Propst 1982). Wiltzius (1981) indicated that gizzard shad may be native to Colorado since specimens were collected in the Arkansas drainage prior to any known introductory plant of the species. Gizzard shad have been stocked in many eastern plains reservoirs as a forage species.

Habitat: Gizzard shad are found in many diverse Colorado waters, but principally in highly productive impoundments. Traveling in schools which generally are in continual motion, gizzard shad are found in areas of little or no current. This avoidance of current could explain the absence of mature shad in the mainstem South Platte River where low fall and winter flows leave few large pool areas.

Courtesy of NDIS Colorado Parks and Wildlife