Terms of Reference

Ecological Impact of Water-Level Drawdown on Lake Chubsucker (Erimyzon Sucetta) in the St. Clair National Wildlife Area

Regional Peer Review – Central and Arctic Region

May 14, 2020
Virtual meeting

Chairperson: Dave Andrews

Context

The St. Clair National Wildlife Area (NWA) is a 352 ha wetland complex located on the east shore of Lake St. Clair in the municipality of Chatham-Kent, Ontario. Between 1940 and 1980, a series of dykes, pumps, and other water control structures were installed within the St. Clair Unit to maintain water levels in the East and West wetland cells. Dyking was necessary to maintain wetted area and other habitat functions in the face of drainage modifications to the surrounding landscape and due to ongoing water level fluctuations of Lake St. Clair (ECCC 2018).

Management of the St. Clair NWA is the responsibility of the Canadian Wildlife Service of Environment and Climate Change Canada (ECCC). Currently, thirty five species (birds, reptiles, insects, fishes, vascular plants) listed under the Species at Risk Act occur within the NWA. The area is also internationally recognized as an important migratory stopover for numerous waterfowl and other migratory bird species. The management plain for the St. Clair NWA (ECCC 2018) identifies periodic water-level drawdown through the dyke and pump system as a necessary activity to maintain a diverse, native aquatic vegetation community, similar to the water level fluctuations experienced in an undyked coastal wetland. Periodic drying of soils is aimed at rejuvenating the seed bank of native aquatic plants and achieving hemi-marsh condition (described as an equal ratio of vegetated and open water), but may also allow for targeted removal of exposed invasive plants, such as European Common Reed (Phragmites australis subsp. Australis) and American White Water-lily (Nymphaea odorata).

Water-level drawdown has been proposed for 2020, which is intended to achieve a 95% reduction of water volume over a five month period in the East cell of the St. Clair Unit. Although the long-term maintenance of native aquatic vegetation imposed by such a drawdown may benefit fishes within the cell, concern exists that drawdown will impose substantial mortality or other negative effects on Lake Chubsucker (Erimyzon sucetta), SARA listed as Endangered, owing to stranding or other effects (e.g., increased predation by shorebirds; Bouvier and Mandrak 2011). DFO’s Species at Risk and Fish and Fish Habitat Protection programs have requested that DFO Science provide advice on the potential impact of water-level drawdown on Lake Chubsucker; namely, to identify the relationship between drawdown increment and available refuge habitat for Lake Chubsucker in the East cell, as well as the potential for deepwater habitat creation in advance of drawdown to increase available refuge.

Objectives

The objective of this review is to determine the relationship between drawdown increment and available refuge habitat for Lake Chubsucker in the East cell of the St. Clair Unit; and, to determine the potential effect that deepwater habitat creation in advance of drawdown could have on the availability of refuge habitat.

Expected Publication

• Science Response

Expected Participation

• Fisheries and Oceans Canada (DFO) (Science, and Ecosystem Management sectors)
• Environment and Climate Change Canada, Canadian Wildlife Service

References

Bouvier, L.D., and Mandrak, N.E. 2011. Information in support of a Recovery Potential Assessment of Lake Chubsucker (Erimyzon sucetta) in Canada. DFO Can. Sci. Advis. Sec. Res. Doc. 2011/048. vi + 24 p.

Environment and Climate Change Canada (ECCC). 2018. St. Clair National Wildlife Area Management Plan 2018. Environment and Climate Change Canada, Canadian Wildlife Service, Ontario Region. 75 p.

Vlasman, K.L., and Staton, S.K. 2007. Recovery Strategy for the Lake Chubsucker (Erimyzon sucetta) in Canada [Proposed]. Species at Risk Act Recovery Strategy Series, Fisheries and Oceans Canada, Ottawa. vi + 29 p.