River Redhorse (Moxostoma Carinatum)
- Assessment Summary
- Executive Summary
- COSEWIC History, Mandate, Membership and Definitions
- Lists of Figures and Tables
- Species Information
- Population Sizes and Trends
- Limiting Factors and Threats
- Special Significance of the Species
- Existing Protection or Other Status Designations
- Technical Summary
- Acknowledgements, Information Sources, and Authorities Contacted
While the river redhorse has been reported from both lakes and rivers within its Canadian range, the persistence of this species relies upon access to suitable riverine spawning habitat. Past studies have indicated a preference for habitats with moderate to swift current, riffle-run habitat and clean coarse substrates (Hackney et al. 1967; Scott and Crossman 1973; Becker 1983; Yoder and Beaumier 1986; Parker 1988; Campbell 2001; Reid 2002; 2003). Yoder and Beaumier (1986) observed densities eight times greater in locations of preferred habitat than at pooled and impoundment locations in an Ohio River. Summer trap-net sampling on the Mississippi River resulted in the capture of river redhorse in run habitat, suggesting that its habitat requirements may be more extensive than previously thought (Campbell 2001). Summer sampling of river redhorse resulted in capture in areas of abundant aquatic vegetation, fairly slow current and soft substrates (Campbell 2001). Compared to the spawning period (June), lower catch per unit effort numbers in fall sampling of fastwater habitats along the Trent River suggest that deeper run/pool habitats are used during other periods of the year (Reid 2003).
In Quebec, river redhorse occurrence has been related to the presence of the copper redhorse, showing an affinity for lowlands rivers of medium size characterized by abrupt banks and uniformely deep channels (4-7 m) flowing over a solid clay, sand or gravel bottom exposed to rather slow currents and interspersed by sections of rapids suitable for spawning (Mongeau et al. 1986, 1992).
Depth preference for this species has not yet been determined with accuracy. However, there is a definite trend towards shallow water (less than 2 m deep) during spawning (Campbell 2001). In addition, fish captured during spawning were consistently captured in areas within 100 m of rapids (Campbell 2001). Lac des Chats (Ottawa River) sampling in August and September of 1998 (post-spawn) captured river redhorse at depths ranging from 3-12 m and consistently at distances greater than 10 km from the nearest rapids (Campbell 2001).
In the Richelieu River, YOY are found along vegetated shores where average depth is 1.5 m (maximum ≤ 3.0 m), the slope is shallow (≤ 20º) and the substrate consists of fine sediments (silt, clay and sand). In the early spring, age 1+ specimens are also found in greater abundance in vegetated areas. An important nursery habitat has been found in the Richelieu River in the Saint-Marc region (Vachon 1999a, 1999b, 2002). Jenkins (1970) suggested that moderate-sized streams or tributaries and backwater areas provide suitable juvenile habitat. In Quebec, it is clearly associated with medium-sized and large rivers, even at the juvenile stage (Mongeau et al. 1986, 1992).
The distribution of the river redhorse is restricted by the availability of its specific habitats, which are vulnerable to anthropogenic activities. For example, Mississippi River populations may be at risk due to intensive agricultural activities that increase the sediment load of the river and negatively affect the availability of the benthic invertebrate prey of the river redhorse (Campbell 2001). Poor water quality (i.e. excessive nutrients) as a result of agricultural activities and urban development likely contributed to the loss of some Quebec populations, at least in the Yamaska and Châteauguay basins (La Violette and Richard 1996; Moisan 1998; La Violette 1999; Vachon 2003a). Poor water quality (turbidity, excessive nutrients and high summer water temperatures) also affects the lower Grand River where river redhorse are found. Human population growth in the Grand River basin has been projected to be 30% over the next 20 years (www.grandriver.ca). Further impairment of habitat and water quality from upstream land use changes, water utilization and sewage disposal would likely have an adverse effect on resident river redhorse. Threats to river redhorse habitat quality in southwestern Ontario may in the future be mitigated through the recovery plan actions. For example, habitat improvement goals identified for the Thames River of benefit to the river redhorse include reductions in sediment, nutrient and toxic chemical loadings (Thames River Recovery Team 2003).
Riverine habitat in Canada is also threatened by the construction of hydroelectric dams and other barriers. Increased energy demands in Ontario and Quebec may result in the construction of new hydroelectric facilities, or the conversion of run-of-river facilities to peaking facilities. Dam construction has already heavily fragmented the Madawaska, Mississippi, Ottawa, Trent, Yamaska, Richelieu, and Châteauguay rivers and the lower reaches of the Grand River, increasing the risk of local extirpation due to limited immigration or emigration of the river redhorse population. Suitable spawning habitat is primarily limited to the tailwater areas downstream of these locks and dams. Maintenance of sufficient flows through these habitats during spawning is necessary for successful river redhorse reproduction (Reid 2002). In addition, due to the number of barriers, available habitat becomes limiting as movement between habitats and populations is restricted. Recovery of river redhorse populations after disturbances through emigration is expected to be limited by the number of dams along the rivers it inhabits (Reid 2002).
On a more positive note, recent emphasis has been placed on providing migratory fishes with access to previously unavailable habitat through the destruction of barriers, as well as through the construction of multi-species fishways. Recently, the Vianney-Legendre Fish Ladder was constructed on the Richelieu River in an effort to preserve fish biodiversity. The fish ladder enables species such as the river redhorse to reach spawning grounds and locate preferred habitat (Dumont et al. 1997). To determine the best operation procedures for maximizing fish passage, an experimental breaking-in period of 5 years was initiated in 2001. In 2002, 46 river redhorse (23-72 cm) were caught at the outlet between May 16 and July 4. In 2003, 555 individuals (20-70 cm) used the ladder between May 22 to June 24 (Fleury and Desrochers 2003, 2004).
The habitat of the river redhorse is protected under the habitat provisions of the federal Fisheries Act, particularly section 35 (1) which states that a development proposal must not cause a “harmful alteration, disruption, or destruction” of fish habitat. Habitat may also receive protection by other federal legislation, including the Environmental Assessment Act, Environmental Protection Act and Water Act. In Ontario, river redhorse may also receive protection under the Lakes and Rivers Improvement Act, Ontario Environmental Protection Act, Ontario Environmental Assessment Act, Ontario Planning Act and Ontario Water Resources Act.
Quebec legislation also provides general protection of fish habitat under the Environment Quality Act. The Act respecting the conservation and development of wildlife, under articles 128.1 to 128.18, controls activities that could modify biological, physical and chemical components peculiar to fish habitat. The Act respecting threatened or vulnerable species makes additional provision for the protection of the habitat of threatened or vulnerable species. Finally, the Pierre-Étienne-Fortin Wildlife Refuge, created in 2002 for the protection of the copper redhorse spawning grounds in the Chambly rapids (Richelieu River), also protects river redhorse habitat from activities that could disturb the river bed and flow characteristics. Access to the refuge sectors where the copper redhorse and river redhorse spawn is forbidden between June 20 and July 20 (Gendron and Branchaud 2001).
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