Science Advisory Report 2008/046
Recovery potential assessment for the Salish Sucker (Catostomus sp.) in Canada
Summary
- Potential critical habitat includes all reaches in streams currently containing populations that contain more than 50 m of continuous pool that exceeds 70 cm depth at low flow. It includes all aquatic habitat and riparian reserve strips of native vegetation on both banks for the entire length of the reach. The most important riparian vegetation is mature forest to provide effective ecological function and protection to instream habitat.
- Current estimates of abundance of Salish sucker are unpublished, incomplete (some populations have not been not considered) and highly uncertain, and thus, insufficient to describe trends in abundance. For these reasons, population estimates presented in the original working paper could not be endorsed by all participants in the peer-review process.
- All estimates of current habitat capacity within individual watersheds are below the amount required to support 7000 adults, an average guideline for the minimum viable population (MVP) needed to ensure (with 99% probability) the long-term persistence of an isolated vertebrate population (Reed et al. 2003). Only 1 population (Chilliwack Delta) appears to have sufficient habitat capacity to support 4700 adults, the MVP for a 90% probability of long-term persistence. However, these estimates of habitat capacity are highly uncertain, and populations in different streams might not be as isolated from one another as the MVP guidelines assume.
- The geographic location of potential critical habitat for the known populations of Salish sucker is identified in Pearson (2007). Relationships between buffer width and maintenance of stream ecological function have not been developed that are specific to suckers. Recommended riparian buffer widths for potential critical habitat were therefore established using buffer-width ecological function relationships developed for salmonids, as described in the Riparian Areas Regulations methodology (Pearson 2007). Generalized buffer width-ecological function relationships developed for salmonids can be used for calculating biological and socio-economic tradeoffs until such time as research targeted at developing specific relationships for sucker are undertaken.
- Hypoxia, habitat loss, degradation, destruction and fragmentation are the most important factors jeopardizing survival or recovery.
- Population recovery depends on halting and reversing environmental degradation of Salish sucker habitat. The probability of recovery will be low if the impact on habitats from agricultural, industrial and urban development is not addressed through habitat protection and restoration, particularly in the presence of projected increases in human population growth in the Fraser Valley.
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