Percina evides (Jordan and Copeland, 1877)
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Basis for Listing
In Minnesota, the gilt darter, also known as the gilded darter, occurs only in the St. Croix River and several of its tributaries (Snake, Kettle, Sunrise, Tamarack). Its limited distribution makes it vulnerable to decline and possibly extirpation through catastrophic events. The closest stable populations are in the Chippewa and lower Black rivers of Wisconsin, but the Mississippi River does not offer an avenue for recolonization. The Minnesota-Wisconsin St. Croix population is disjunct from those of the Ozarks and the Tennessee uplands. Elsewhere across its range, the gilt darter has greatly declined or become extirpated. It was listed as a special concern species in Minnesota in 1996.
The gilt darter is a robust, stout darter. Seven saddle bands straddle the dorsal ridge, joining dark blotches midside. In breeding males, the bands turn an iridescent blue-green, while areas between the blotches as well as the head, spinous dorsal fin, and ventral portions of the body turn brilliant yellow and orange. At the height of the breeding season, a blue-black pigment accumulates in the breast, pelvic and spinous dorsal fins, and at the base of anal fin. Adult gilt darters average 78.5 mm (3.1 in.) in total length (Becker 1983).
The gilt darter occurs in riffles of medium- to large-sized streams with strong to moderate currents, and is generally most abundant in the deeper portions of its habitat. The species also requires streams with relatively strong, year-round flow and clean gravel and cobble substrates for spawning (Hatch 1985/86).
Biology / Life History
In summer, the gilt darter is found most frequently in rubble riffles and cobble or boulder raceways where currents are moderate to swift. It rarely occurs in pools or in association with rooted aquatic vegetation. In fall, it moves to deep chutes of rubble and boulder riffles where it over-winters. Mature individuals return to shallower areas to spawn in mid-May to late July. Males establish territories around cobble or boulder stones. In the Sunrise River, specimens have been observed feeding during the day. The gilt darter's diet includes mayfly, caddisfly, and diptera larvae (Hatch 1982, 1985/86).
Conservation / Management
Gilt darters are sensitive to sediment loading and probably organic loading from sewage effluents, making them important indicators of degraded water quality. High levels of suspended sediments can smother spawning habitats and likely have an adverse effect on the gilt darter's ability to feed (Hatch 1985/86). Their distribution has become fragmented over the past century. Elsewhere in North America, the gilt darter has greatly declined or been extirpated. In Minnesota, the species' required combination of habitat characteristics (low siltation, strong, year-round flow, clean substrate for spawning) occurs only in the St. Croix River drainage. Silting of spawning habitats has likely prevented gilt darter populations from becoming established in streams of central and southern Minnesota (Hatch 1985/86). Additional research needs for the gilt darter in Minnesota include identification of habitat guilds and population stressors.
Conservation Efforts in Minnesota
The DNR's Minnesota Biological Survey and Division of Fisheries and the Minnesota Pollution Control Agency record any occurrences of gilt darters found while conducting their annual fish surveys.