Science Advisory Report 2017/018

Information needed in support of the identification of the habitat necessary for the survival and recovery of Rocky Mountain Ridged Mussel (Gonidea angulata)

Summary

• In Canada, Rocky Mountain Ridged Mussel (G. angulata) is found only in the Okanagan Valley where it is considered to be at the northern extent of its range.
• Rocky Mountain Ridged Mussel (RMRM) has been assessed by COSEWIC as endangered. If listed under the Species at Risk Act, critical habitat will have to be identified for the species.
• Habitat necessary for the survival and recovery of the species has been determined based on a bounding box approach, including the geo-spatial identification and a description of associated biophysical functions, features and attributes.
• Two distinct habitat features (lacustrine and riverine) have been recommended for this species, as both support completion of all life stages of RMRM.
• Key habitat attributes for RMRM include water quality, water depth and site slope, exposure/fetch, substrate size and embeddedness, available food supply and availability of a host fish to support development and transportation of larvae.
• Sculpin have been determined to be the most likely host fish (other possible hosts include Longnose Dace, Leopard Dace and Northern Pikeminnow); however the specific host fish species and their required abundance is unknown.
• Historical occupancy data, habitat suitability modeling and recent observations were used to identify areas that would meet the criteria for critical habitat.  However, only areas that have been surveyed since 2005 and have RMRM present are recommended as critical habitat at this time.
• Activities identified as most likely to destroy critical habitat of RMRM include: land development, channel alterations and dredging, water level changes in the Okanagan Valley and introduction of invasive species.
• The main knowledge gaps that need to be addressed for this species include: determination of minimum viable population size, confirmation of the host fish species and associated ranges and migration patterns, flow measurements at areas with and without mussel beds and determination of the maximum sediment load tolerance for RMRM.

This Science Advisory Report is from the February 10-11, 2016 regional peer review on Information in support of the identification of critical habitat for Rocky Mountain Ridged Mussel (Gonidea angulata). Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

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