SALMON IN INLAND WATERS 



Salmon migrating between the sea and their spawning 

 areas have adapted to the estuariiie and fresh-water envir- 

 onment over thousands of years. In the space of a few dec- 

 ades, however, enormous changes have taken place to threaten 

 their survival. In our research on inland waters we anti- 

 cipate the environmental changes that will be detrimental 



to fish. We attempt to develop methods to increase survival 

 as the fish move between natural or artificial spawning areas 

 and the sea. Our research has application nationally and 

 internationally where water-use developments threaten the 

 production and development of aquatic organisms. 



THE CHANGING ENVIRONMENT 



During the past three decades, changes in the environ- 

 ment of the Columbia River were mainly brought about by 

 the construction of hydroelectric dams. These dams con- 

 stitute physical barriers to migration and are gradually 

 changing the river to a series of impoundments. The re- 

 lations of salmon to their predators, competitors, diseases, 

 and food organisms have been altered. Temperature regimes 

 have been modified. Freshets and floods, which play a major 

 role in migration, have been aff'ected. Young salmon mi- 

 grating to sea are often carried by water currents into tur- 



bines and are killed by the blades or other shear forces. Pre- 

 dators below the dams also cut down the number of survivors. 



At the present rate of construction, all sites for eco- 

 nomical production of hydroelectric power will have been 

 utilized by 1985. When dams in the upper reaches in Can- 

 ada are completed, the flow of the mighty Columbia will 

 be almost completely controlled. Little or no water will spill 

 over the dams. This change will influence the upstream mi- 

 gration of adult salmon and force most of the young fish to 

 pass through the turbines. 



THERMAL POLLUTION - A DEVELOPING PROBLEM 



In the future, most electricity in the Pacific Northwest 

 will Ije produced by thermal electric power plants (fig. 20). 

 Twenty such plants — over 1,000 mw. (megawatts) each — 

 are proposed for construction by 1990. The first will be 

 a fossil fuel (coal) plant; the remainder will be thermal 

 nuclear plants. Thermal plants use large volumes of water 

 to cool the condensors. The temjierature of the cooling water 

 at the point of return to the river may be 15° to 20° F. higher 



than at the intake. A series of power plants could produce 

 a severe cumulative eflfect. The proposed construction has 

 stimulated a controversy over the disposal of waste heat 

 from the nuclear power plants. 



Our biologists have been aware of the problem for some 

 years and have studied fish that have been subjected to the 

 temperatures of anticipated thermal regimes; research has 

 now been intensified. 



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