Science Advisory Report  2011/047

Assessment of Methods for the Identification of Critical Habitat for Freshwater Mussels

Summary

• The identification of critical habitat for mussels is comprised of two main components; a geospatial component and a functional description.
• The geospatial component can be delineated using either recovery target-dependent or independent methods. Recovery target-dependent methods have been historically applied using the concept of Minimum Viable Population (MVP), while the recovery target-independent method follows an Area of Occupancy approach.
• Very limited data are currently available to apply the concept of MVP to freshwater mussels; therefore the area of occupancy approach is often more applicable.
• The species-specific functional description plays an important role in the delineation of critical habitat for freshwater mussels by providing a summary of the basic life history and habitat needs of a freshwater mussel to successfully complete each life stage. The functional description should be based on research and literature on the species, if available, or by inference from knowledge of closely related species.
• Guidance related to data quality and quantity, specifically to asses if a record(s) should be considered a population, can be obtained from the Recovery Potential Assessment (RPA) for the species, if a RPA has been completed. If this information is not available from a RPA, or if the recovery team does not agree with the results presented in the RPA, consensus should be reached by the recovery team on what data to include in the delineation of critical habitat.
• Including a buffered area around the area of occupancy should account for the following: (1) uncertainty related to sampling artifacts, taking into account spatial and temporal issues related to sampling; (2) biological considerations, including movement of the mussel and potential movement of the host fish; and (3) that an individual has habitat needs that vary seasonally, and that extend beyond the point of capture.
• The ecological classification buffering approach is generally favoured over a fixed-distance buffer because it provides an opportunity to consider freshwater mussel distribution on a larger spatial scale. Case-specific, appropriate buffering techniques should be applied at the discretion of the recovery team.

This Science Advisory Report is from the Fisheries and Oceans Canada, Canadian Science Advisory Secretariat, regional advisory meeting of April 28, 2011 on the assessment of methods for the identification of critical habitat for freshwater mussels.  Additional publications from this process will be posted as they become available on the DFO Science Advisory Schedule.

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