. The Canadian field-naturalist. 1984 Parker and McKee: Status of the River Redhorse 111. Figure I. River Redhorse (Moxostoma carinatum). Courtesy of D. E. McAllister, National Museum of Natural Sciences. specimens captured in 1971. Siltation and pollution may have degraded water quality to a level unsuitable for this species. A single collection of two adults in 1936 is the only indication of this species occurring in the Ausable River system. Quebec populations in the Yamaska and Richelieu Rivers are small. It was listed at all stations on the Richelieu River and abundant at only 2 out of 26
. The Canadian field-naturalist. 1984 Parker and McKee: Status of the River Redhorse 111. Figure I. River Redhorse (Moxostoma carinatum). Courtesy of D. E. McAllister, National Museum of Natural Sciences. specimens captured in 1971. Siltation and pollution may have degraded water quality to a level unsuitable for this species. A single collection of two adults in 1936 is the only indication of this species occurring in the Ausable River system. Quebec populations in the Yamaska and Richelieu Rivers are small. It was listed at all stations on the Richelieu River and abundant at only 2 out of 26 stations on the Yamaska River (Parker and McKee 1980). Jenkins (1970) stated that River Redhorse comprised only 5 per cent of all redhorse taken in the Yamaska River. Collections in other parts of south- western Quebec are few and population centres have not been identified. Habitat The River Redhorse has been captured in lakes and rivers within its Canadian range. This species prefers moderate to large rivers with gravel, rubble and bed- rock bottoms where siltation is minimal (Trautman 1957; Jenkins 1970). River Redhorse captured in the Mississippi River were taken from fast-flowing pools in a 300 meter- long chute and a catch-pool of a 1 to 2 meters high waterfall. Stream gradient was approximately m/km over the entire river, but rapid changes in elevation are evident at both capture localities. Water flow volumes fluctuate in the Mississippi River from cubic m/s in late summer to 142 cubic m/s dur- ing spring floods (Ontario Ministry of the Environ- ment, 1977). The river bed in these areas is composed of limestone and granite bedrock, and rubble. A 1 to 2 cm layer of detritus covered the bottom in areas of slackened current. This species was not observed in slow-moving stretches of the Mississippi River which had abundant macrophyte growth and soft substrates. Jenkins (1970) also noted that this species is rarely captured in deeper waters of slow flows which have
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