Science Advisory Report 2020/040

Guidance on the identification of Critical Habitat in the riparian zone for freshwater species at risk

Summary

• A science-based guidance document on the identification of Critical Habitat in the riparian zone for listed freshwater fishes and mussels that builds upon and complements DFO’s existing approach to identify Critical Habitat was reviewed.
• A review of Recovery Potential Assessments (RPA) and Recovery Strategies of currently listed freshwater fishes and mussels identified inconsistencies in the assessment of riparian habitat.
• A systematic approach to identify processes that affect listed freshwater fishes and mussels, such as the example in the Appendix 1, would provide a consistent way of identifying the role of riparian habitat on survival and recovery of these species.
• The proposed guidance suggests that riparian features should be considered as Critical Habitat when they 1) are necessary to maintain aquatic features and/or water quality attributes of aquatic features identified as Critical Habitat; and/or 2) support life cycle functions necessary for the survival or recovery of listed freshwater fishes and mussels species or their host species.
• For the purpose of the guidance, riparian zone was defined as the area located between a waterbody’s high water mark and the upland area. However, other features such as groundwater recharge areas that may extend further than the riparian zone but still affect aquatic and/or riparian features may also be considered.
• The influence of riparian features on aquatic features and/or water quality can be represented by seven main processes: erosion, filtration, infiltration, isolation, meandering, shading, and subsidization. The importance of each process will be dependent on specific freshwater fish and mussel life history requirements.
• Literature regarding the widths of riparian habitat required for the processes was reviewed and showed that increasing width protected a greater number of processes. However, in this guidance specific widths of riparian zone for the different processes were not recommended due to species-specific habitat requirements and regional differences in underlying factors such as geomorphology, slopes, land use practices, and site potential vegetation height. When determining riparian Critical Habitat width, reference should be made to regional and species-specific guidance as appropriate.
• Riparian Critical Habitat may be located adjacent to aquatic Critical Habitat, but strong longitudinal connectivity in streams means that riparian Critical Habitat can also be identified upstream of the aquatic Critical Habitat if it is necessary for the survival and recovery of freshwater fishes and mussels.
• Processes that allow for the survival and recovery of an aquatic species have a range of natural variation. In the description of the extent of riparian Critical Habitat, the natural variation in the processes should be considered on a species- and site-specific basis, and be robust to environmental and climate change with the goal of maintaining or restoring the natural function of the riparian zone.
• There is a broad scientific consensus that riparian zones are essential habitat for natural aquatic ecosystem structure and biophysical functioning and are therefore important for all aquatic species.

This Science Advisory Report is from the CSAS national science advisory meeting of March 3–4, 2020 entitled “Guidance on the identification of Critical Habitat in the riparian zone for freshwater species at risk”. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Scheduleas they become available.

Science Advisory Report 2020/040 (PDF, 1,132 KB)

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