Bigmouth shiner (Notropis dorsalis) COSEWIC assessment and status report: chapter 5

Update
COSEWIC Status Report
on the
Bigmouth Shiner
Notropis dorsalis
in Canada
2003

Species Information

Taxonomy

Class:

Actinopterygii

Order:

Cypriniformes

Family:

Cyprinidae

Scientific name:

Notropis dorsalis (Agassiz)

Common name:

bigmouth shiner

Other names:

Gilbert’s minnow, central bigmouth shiner, big-mouthed shiner

French:

Méné à grande bouche


Description

The bigmouth shiner (Notropis dorsalis) is a cyprinid of the plains that reaches a maximum size of 75 mm (Figure 1). The species is most commonly found in shallow waters in creeks and small rivers, but can occur rarely in larger rivers. They feed mainly on aquatic insects, but plant material, benthic ooze, and terrestrial insects can also form a portion of the diet. The bigmouth shiner has a distinctive body form, being slender, relatively flat-bellied, with a back that is more arched than other related Notropis species. The eyes appear to focus upward, when viewed from above, due to the pupil being skewed dorsally. The body colour is olive-yellow on the back and silvery on the sides and belly. A mid-dorsal stripe is continuous around the dorsal fin base.


Figure 1. Fresh specimen of a Bigmouth Shiner (Notropis dorsalis)

Figure 1: Fresh specimen of a Bigmouth Shiner (Notropis dorsalis)

Photo courtesy of Ken Stewart.

In Manitoba, the bigmouth shiner, sand shiner, mimic shiner, and river shiner are similar to one another in appearance. K.W. Stewart, Department of Biology, University of Manitoba, Winnipeg, Manitoba (pers. comm., 2003) gives the following description for identification of the four species: Collectively, the four species differ from all other shiners in Manitoba in the combination of: (1) the lack of a lateral dark stripe that continues onto the head, (2) the lack of a black spot at the base of either the caudal or dorsal fin, (3) location of the base of the dorsal fin over the base of the pelvic fins and, (4) not having the scales on the sides more than twice as high as long. Superficially, the bigmouth shiner and sand shiner share the presence of dark markings (“mouse tracks”) above and below each lateral line pore. “The bigmouth shiner differs from the sand and mimic shiners in having an arched back and flat ventral profile, having an inner row of pharyngeal teeth and the mid dorsal dark band is uniform in width anterior to the dorsal fin and continuous around the base of the dorsal fin. The bigmouth shiner differs from the river shiner in having only one inner row pharyngeal tooth on both sides instead of two on at least one side, usually seven anal fin rays instead of eight and in having the “mouse tracks” described above” (K.W. Stewart, pers. comm., 2003). Bigmouth shiners in Manitoba have scales covering the nape. In this respect, they conform to the subspecies N. d. dorsalis (K.W. Stewart, pers. comm., 2003).

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