Erimystax x-punctatus (Hubbs and Crowe, 1956)
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Erimystax x-punctatus, Erimystax x-punctata, Hybopsis x-punctata
Basis for Listing
The gravel chub, also referred to as the spotted chub, is declining rangewide and has been extirpated from some portions of the northern part of its range. It is presumed to reach its current northern range limit in Minnesota, where it is restricted to two rivers in the Mississippi River drainage in the southeastern part of the state: the Upper Iowa River and the Root River. The specialized habitat of this species is at risk of degradation through siltation from sediment loading in the lower Mississippi River (Hatch et al. in preparation). For these reasons, the gravel chub was listed as a special concern species in Minnesota in 1984.
A medium-sized minnow, the gravel chub is usually less than 10 cm (3.9 in.) in total length and has a prominent barbel at the end of its maxillary (bone of the upper jaw). Its pointed snout extends slightly beyond the upper jaw. The gravel chub body has a faint, lateral stripe, and the sides are marked with small, X-shaped spots (Eddy and Underhill 1974).
Large creeks and small rivers are the preferred habitat of the gravel chub. It is found in riffles over fine gravel and over pea-sized, limestone gravel in clear to slightly turbid waters.
Biology / Life History
Little is known about the life history of the gravel chub. Indications are that spawning occurs sometime in May in Minnesota, and possibly into early June (Hatch et al., in preparation). Spawning takes place adjacent to gravel bars, probably stimulated by rising water levels following heavy rains (Harris 1986). The gravel chub probes bottom crevices with its barbeled snout in search of food. Its diet likely includes plant matter, diatoms, gastropods, and miscellaneous aquatic insects (Hatch et al. in preparation).
Conservation / Management
Gravel chubs require permanent flow and silt-free riffles. Sediment loading in streams of the lower Mississippi River drainage in Minnesota and the continued interference with flow regimes puts this species at great risk. Efforts to maintain and improve the water quality of southeastern Minnesota streams should be encouraged.
Conservation Efforts in Minnesota
Surveys by the Minnesota DNR in 1992-2000 (Schmidt 2000) and by the Minnesota Pollution Control Agency in 2004 recorded spotty distribution of this species in Fillmore and Olmsted counties. More surveys are needed to determine the species' full distribution in the state and to obtain accurate population estimates. Additional research needs for the gravel chub in Minnesota include life history studies, genetic analysis, identification of habitat guilds, identification of limiting factors and opportunities for fish passage around the Lidtke Mill Dam on the Upper Iowa River, and the determination of specific habitat impacts and stressors.