Modeling dolly varden habitat in the western Arctic, Canada in support of ecosystem based management (O-CCFFR)

Dolly Varden (Salvelinus malma) is a char native to western North America that is harvested by northern communities for subsistence purposes. Populations occur in eight river systems across northern Canada have experienced significant declines. Therefore, local communities, co-management boards, and government agencies agreed to implement conservative harvest quotas. Several stakeholders believe that changes to habitat, specifically low water levels observed over successive years, are partially responsible for declining stocks. Winter habitat is limiting for this species as it is restricted to several small areas in headwater sections of freshwater streams. Spawning and winter habitats typically overlap and both are associated with perennial groundwater sources. We surveyed two spawning and overwintering reaches from Fish Hole Creek, a tributary to the Babbage River, and Little Fish Creek, a tributary to the Big Fish River. Depth, velocity, substrate, and cover were measured at positions in the stream where fish were observed and also at spawning redds. The two-dimensional hydrodynamic and fish habitat model River2D (www.river2d.ca) was used to determine the minimum discharge thresholds for spawning and winter habitats. These discharges can be used as a guideline to help stakeholders manage Dolly Varden stocks more effectively by monitoring water levels in these rivers annually.