mortality rates reflect current passage conditrons. Juvenile passage conditions have been 

 improved by installation of bypass systems and spilling of water over some of the dams. 

 These rates do not include higher survival that may be attainable by transporting juvenile 

 fisfraround the dams, c) Mixed-stock fishery . In a mixed-stock fishery, upriver and wild 

 runs already weakened by habitat and passage losses are fished at the same rate as 

 hatchery-supplemented lower-river runs. Weakened upriver runs may be overfished. 



(e) Effects of Mitigation 



Efforts have been made to mitigate the effects of development. Some of these efforts 

 have had major implications for the salmon and steelhead fisheries. First was a series of 

 fishing regulations that contributed to a shift from inriver harvest to ocean harvest of some 

 stocks. Ocean fisheries (including those in Canada and Alaska) now account for about 73 

 percent of total Columbia River Chinook harvested. Second was the development of large- 

 scale hatchery production of salmon and steelhead. In 1949. hatchery programs were 

 developed with federal appropriations under legislation called the Mitchell Act (16 U.S.C. 

 755). The majority of Mitchell Act hatchery fish are raised and released in the lower river, 

 supporting the expansion of the lower river and ocean commercial fisheries. By the late 

 1960s, hatchery production of fall Chinook and coho salmon and steelhead far surpassed 

 natural production Extensive production of hatchery fish has, along with permanent 

 blockage by dams which eliminated some stocks, probably changed the genetic character 

 of Columbia River Basin stocks. In addition, as noted above, availability of large numbers 

 of lower-river hatchery fish led to overfishing of wild and upriver stocks in the mixed-stock 

 harvest. [Source: Council] 



