Gravel chub (Erimystax x-punctatus) COSEWIC assessment and status report: chapter 3

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Species Information

Name and classification

Common name

Morphological description

The gravel chub is a slender, round-bodied minnow (Figure 1) with an average length of 76 mm TL (Total Length) and a maximum length of approximately 100 mm TL (see Scott and Crossman (1998) for a detailed description). It is olive-green dorsally with silvery sides and a white belly. The scale margins on the back and sides of the gravel chub are randomly outlined in black resulting in distinct X-, Y- or W-shaped patterns. These markings are sometimes absent in large adults, and were usually faintly evident in Ontario specimens (Scott and Crossman 1998). A small black spot is usually predominant on the base of the caudal fin. The snout is rounded and long, overhanging the mouth, which has small but conspicuous barbels in each corner.

Genetic description

Two geographically distinct populations are recognized as subspecies (Gilbert 1980). The nominate subspecies (E. x. x-punctatus) occurs west of the Mississippi River, and E. x-p. trautmani in the east (Gilbert 1980). Hubbs and Crowe (1956) assigned Canadian populations of gravel chub to the subspecies E. x. trautmani, which is morphologically distinct from the subspecies E. x. x-punctatus. Genetic validation for the subspecies designation was confirmed by Simons (2004) based on the cytochrome b gene.

Designatable units

All Canadian specimens have been found within the Great Lakes-Upper St. Lawrence Biogeographic Zone of the freshwater Biogeographic Zone classification adopted by COSEWIC. There is no evidence to support the identification of designatable units below the species level.

Eligibility

The gravel chub is a recognized species (Nelson et al. 2004) that was formerly considered to be native to Canada, but has been absent from Canadian waters since 1958.

Despite the fact that this species has a disjunct distribution in the United States (U.S.), and is in peril in many areas throughout its range, there is a surprising lack of recent information regarding its habitat and ecology.

Attempts to obtain Aboriginal Traditional Knowledge (ATK) on the species have as yet failed to produce any new information.