COSEWIC Assessment and Update Status Report on the Redside Dace in Canada
- Assessment Summary
- Executive Summary
- COSEWIC History, Mandate, Membership and Definitions
- Lists of Figures, Tables and Appendices
- Species Information
- Population Sizes and Trends
- Limiting Factors and Threats
- Special Significance of the Species
- Existing Protection or Other Status Designations
- Technical Summary
- Acknowledgements, Authorities Contacted, and Information Sources
- Biographical Summary of Report Writers and Collections Examined
- Appendix: Results of Early and Recent Sampling in Canadian Watersheds (Tables 1 - 22)
The redside dace is a colourful minnow that reaches a maximum length of 12 cm. In the spring it develops a bright red stripe along the front half of the body and a brilliant yellow stripe above. It is distinguished from other Canadian cyprinids by its very large mouth, protruding lower jaw, and large pectoral fins on the male. It is one of two species in the genus Clinostomus which is currently believed to be most closely related to Richardsonius, a genus of western dace.
The redside dace has a discontinuous distribution ranging from southeastern Minnesota in the west; north to the Lake Superior drainage in upper Michigan, and the north end of Lake Huron in Ontario; east to New York in the Susquehanna drainage; and south to West Virginia and Kentucky.
In Canada, it is found only in Ontario in tributaries of western Lake Ontario from Oshawa to Hamilton, in tributaries of the Holland River (Lake Simcoe drainage), in a tributary of the Grand River (Lake Erie drainage), and three tributaries of Lake Huron.
Historically in Ontario, the species was found in small (< 10 m wide), isolated tributaries of 24 watersheds. It was most likely extirpated from seven of these tributaries between 1940 and 1980. Although one population (Humber River) appears to have undergone a range expansion between 1950 and 1980, most of the remaining populations have been restricted to, or become fragmented into, small isolated sections of an earlier, wider distribution in most watersheds. There is recent (2000-2004) sampling evidence that two populations (West Don and Morrison Creek) are close to extirpation, or have been extirpated.
The redside dace is found in pools and slow-flowing sections of relatively small, clear headwater streams with both pool and riffle habitats and a moderate to high gradient. These streams typically flow through meadows, pasture or shrub overstory, and have abundant overhanging riparian vegetation. Redside dace occupy pool habitats and spawn in riffles or the slow-flowing water at the bottom end of pools. Populations have been lost from several streams that have had major habitat changes associated with intensive urban development and the construction of reservoirs. Approximately one-half of the extant sites are in or near areas expected to be developed over the next 16 years. The beds of the streams inhabited by redside dace are either privately owned or, if navigable, are generally owned by the Crown. The majority of adjacent lands are privately owned, but those in urban subdivisions are usually returned to public ownership.
The redside dace is relatively short-lived, reaching a maximum age of 4 years, with most fish maturing at age 2. Redside dace spawn in gravel riffles in May when water temperatures reach 16-18 °C. The non-adhesive eggs are normally laid in the gravel nests of co-occurring minnow species such as creek chub (Semotilus atromaculatus) and common shiner (Luxilus cornutus) while these species are still on the nest. The fecundity of redside dace ranges from 409-1971 eggs/female. The redside dace is a surface feeder and often leaps several centimetres out of the water to capture aerial insects. It feeds primarily on terrestrial insects, especially adult flies (Diptera). No long distance movements have been reported for redside dace populations. In Ontario, the redside dace usually co-occurs with tolerant, common coolwater fishes such as creek chub, common shiner and blacknose dace (Rhinichthys atratulus species complex). It occasionally co-occurs with various trout species that may compete with, and prey upon, redside dace.
Population Sizes and Trends
Absolute population sizes have not been estimated. Analysis of data on sampling at historical sites of occurrence indicates that redside dace have declined in most of the river systems in Canada with few exceptions. Large declines have occurred in 8 watersheds that were thought to have healthy or stable populations when the status was reviewed in 1985. This conclusion was based on the presence of healthy populations in the 1970s and 1980s. Redside dace populations are strongest in tributaries of the Humber River, the Rouge River and Sixteen Mile Creek. Search efforts have failed to find them, and they are likely extirpated, from the following streams: Pringle Creek, parts of Duffins Creek (main stem, Urfe Creek and Reesor Creek), Highland Creek, the lower Rouge River, middle sections of the Don River, German Mills Creek, Mimico Creek, Etobicoke Creek, a creek in Clarkson, and Mountsberg Creek, a tributary of Bronte Creek. Surveys also suggest declines in Lynde Creek, parts of the upper Rouge River, tributaries of the Credit River (Silver Creek and its tributaries, Huttonville Creek and Fletcher’s Creek), Fourteen Mile Creek, the upper parts of all three branches of Sixteen Mile Creek, Spencer Creek, the Holland River tributaries Kettleby Creek and Sharon Creek, the Grand River tributary Irvine Creek, the Saugeen River and its tributary Meux Creek. The West Don and Morrison Creek populations are likely close to extirpation. There is no possibility of rescue from populations in the U.S.
Limiting Factors and Threats
The major threats to redside dace in Ontario are habitat alteration and degradation, resulting in changes in water quality and quantity and riparian vegetation, associated with urban development and agricultural activities and the introduction of non-indigenous species.
Special Significance of the Species
Redside dace feed primarily on terrestrial insects thereby importing terrestrial energy into stream ecosystems. Redside dace may be useful as an indicator of ecosystem health as they are more sensitive to environmental disturbance than most fish species in the Ontario streams where they occur.
The habitat of the redside dace receives general protection under the habitat provisions of the federal Fisheries Act. The harvest of redside dace is prohibited in Ontario as it is a specially protected fish under the Ontario Fisheries Regulations. The species is listed as Threatened in Ontario and as Endangered in Michigan and Indiana.
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