Sockeye Salmon Utilization of Restored Okanagan River Habitat, BC

The Canadian portion of the Okanagan River supports the majority of the total sockeye salmon (Oncorhynchus nerka) production in the Columbia Basin. However, the Okanagan River is listed as one of the most endangered rivers in British Columbia. Approximately 84% of the river has been channelized, straightened, narrowed and dyked in the 1950’s and 90% of the riparian vegetation and wetland habitat has been lost. Furthermore, seventeen drop structures and three dams were constructed to aid in flow management but impeded or eliminated access to upstream habitat. McIntyre Dam (Oliver) has been the upstream fish migration barrier since its construction in 1954. Those modifications combined with other human impacts have lead to the Okanagan sockeye salmon population decline in the last decades.

In an effort to return portions of the channelized Okanagan River back to a more natural condition and regain the habitat quality and quantity that has been lost, the Okanagan River Restoration Initiative (ORRI) concept was conceived. ORRI is a collaborative ecosystem approach involving several Canadian and American partners and funding contributors. The first phase of ORRI was completed in 2009, restoring 1 km of floodplain and 0.5 km of river. A portion of the dyke was setback re-connecting the river to 15,000 m² of contiguous floodplains. A river dual channel was created re-connecting the river with its two historic oxbows. Spawning platforms, riffles and gravel bars were also built. On-going aquatic and terrestrial monitoring are measuring the biological impacts of the restoration. Spawning substrate, wetted depths and Froude numbers were improved for salmonids. Sockeye and Chinook used the spawning structures created only a month after they were built.

In an effort to regain salmon access to historic habitat, McIntyre Dam was refitted in 2009, providing adult salmon passage upstream and improving juvenile salmon migration downstream. The existing five undershot dam gates were replaced with five fish friendly overshot gates and a backwater riffle was built downstream the dam. The impacts on sockeye salmon migration were monitored over the 3-years project. In the two years after retrofitting the dam, spawner enumeration surveys and redd surveys have shown thousands of adult sockeye utilizing the newly available habitat. Acoustic surveys provided information on migration timing in the area. Biosampling surveys have shown no morphological variation, in term of fish size or population structure, between adult sockeye spawning above and below McIntyre Dam.