Spotted sucker (Minytrema melanops) COSEWIC assessment and status report: chapter 5

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Habitat

Habitat requirements

Throughout its range, the Spotted Suckerspotted sucker usually inhabits long, deep pools of small to medium-sized rivers over clay, sand or gravel substrates. Riffle areas are used for spawning (McSwain and Gennings 1972). Spotted suckers have also been collected from a variety of other habitats including large rivers (e.g. Mississippi River), oxbows and backwater areas, impoundments and small turbid creeks (Trautman 1981, Lehnen et al. 1997). Canadian collections of Spotted Sucker reflect this range of habitats. It has been collected from small to medium- sized rivers such as the Thames and Sydenham rivers, large riverine habitats in the St. Clair and Detroit rivers, and along the shores of Lake Erie and Lake St. Clair.

The Spotted Sucker is considered to prefer firm to hard substrates. Bottom substrates at capture sites in Ontario range from hard clays to sand, gravel and rubble (Parker and McKee 1984). Although specimens have been reported from areas with abundant aquatic macrophyte growths, records from Canadian collections lack habitat data and the relationships between this species and aquatic macrophytes cannot be substantiated (Parker and McKee 1984). In backwater and main channel habitats along the upper Mississippi River, a preference for sites with woody snags was reported by Lehnen et al. (1997).

The Spotted Sucker prefers clear, warm waters where turbidity is low (Trautman 1981). However, in Canada, it has been collected from rivers with moderate to heavy turbidity (e.g. East Sydenham River). It is considered more tolerant to siltation than other sucker species, especially if the siltation is only intermittently heavy (Parker and McKee 1984). Oxygen and temperature tolerances are not known for the Spotted Sucker.

Trends

Aquatic habitats within the Canadian range of the spotted sucker have undergone considerable historical transformation. Loss of wetlands and riparian vegetation, shoreline alteration, dredging, stream channelization, discharges of toxic chemicals, increased sediment and nutrient loading have been linked to alteredcompositionand lowerproductivity of regional fish communities(Dextrase et al. 2003, MacLennan et al. 2003, Ryan et al. 2003). Since the period between the first two spotted suckerstatus reviews (Parker and McKee 1984 and Campbell 1984), the invasion of the Great Lakes by dreissenid mussels (zebra and quagga mussels) has resulted in profound changes to primary production and the availability of rocky substrates (Ryan et al. 2003). Concurrent improvements to water clarity have resulted in dramatic increases in the abundance of aquatic macrophytes in Lake St. Clair and the Detroit River (Environment Canada and EPA 2003). It is not known what effect, if any, these changes have had on spotted sucker populations.

In response to these historic and ongoing stresses, Remedial Action Plans (RAP) and ecosystem recovery strategies are currently being developed and implemented. Populations of spotted sucker in the Detroit and St. Clair rivers are in two of 43 Great Lakes “Areas of Concern”. A Remedial Action Plan (RAP) has been initiated to address impaired uses, including degraded fish and wildlife populations and associated habitats (Hartig et al. 1996). If successfully implemented, the RAP is expected to improve water and habitat quality and therefore benefit local spotted sucker populations. The spotted sucker is one of nine fish species addressed in the Sydenham River Aquatic Ecosystem Recovery Strategy (Dextrase et al. 2003). One of the key objectives identified in the strategy is improved water and habitat quality through reductions in sediment loads, nutrient and chemical inputs and the maintenance of base flows. The application of agricultural best management practices, such as riparian buffers, conservation tillage and restricted livestock access, was identified as a key step to achieving this objective. The spotted sucker is also addressed in the draft Thames River Aquatic Ecosystem Recovery Strategy (Thames River Recovery Team 2003). Habitat improvement goals identified for the Thames River of benefit to spotted sucker populations include reductions in sediment, nutrient and toxic chemical loadings.

Protection/ownership

Spotted Sucker habitat may be protected by the Canadian Environmental Assessment Act, Canadian Environmental Protection Act, federal Fisheries Act, Canada Water Act, Ontario Environmental Protection Act, Ontario Environmental Assessment Act, Ontario Planning Act and Ontario Water Resources Act. Most of the lands adjacent to inland occurrences are privately owned and in agricultural production.