DEVELOPMENT OF FISH HABITAT FOR MITIGATION BELOW HYDRO DIVERSIONS

In 1987 the Government of Canada, the Province of British Columbia, an d Alcan Aluminium Ltd. entered into a tripartite agreement establishin g a program of measures to conserve chinook (Oncorhynchus tshawytscha) and sockeye (Oncorhynchus nerka) salmon stocks in the Ncchako River. Large-scale applications of habitat measures are planned to manage the risks caused to chinook salmon by potential reductions in habitat qua lity associated with the reduction of flows. The reduction of flows re sult from the planned diversion of an additional portion of the upper Nechako River drainage. Experimental placements of debris structures a nd channel modifications were conducted from 1988 to 1993. Juvenile ch inook salmon highly colonized debris structures, particularly the swee pers and rail-debris catchers installed in 1991, and fry density was s imilar to sparse natural debris cover. Channel modifications, point ba rs, and a side channel were durable, but were not as well utilized by young chinook. Physical assessment indicated that durability was mediu m to high where debris catchers and bundles withstood peak flows of 25 0-283 m(3)/s.