188 



A1TACHMKNT 4 



June. 1994 



CRA issue briefing paper 



It's ti me to be factual-Dams don't kill 95% of the salmon 



A Closer Look at Salmon Mortality 



Salmon lead a perilous life, with some Snake 

 River Spring Chinook traveling almost 900 miles 

 from central Idaho to the Pacific Ocean, spending 

 years in the ocean and finally the lucky ones return 

 to points of origin. Anbcipating high mortality, a 

 female salmon may lay 4500 eggs, with the 

 objective of returning only two spawning adults. 

 Mortality occurs through several life stages of the 

 Snake River salmon migration path. Some of this 

 mortality is due to lutural system mortality arxl 

 some is related to human-caused mortality, such as 

 spawning habitat impacts, dam passage and harvest 

 of some stocks. In almost all life stages, natural 

 and human-caused mortality impacts are difficult to 

 separate. 



Rtarine sites to Lower Granite R eservoir: 

 Percentage of total mortality - 25% (A.E.)* 



From the juvenile rearing sites in Idaho to the 

 head waters of the Lower Granite Reservoir a 



juvenile salmon may travel up to 400 miles. 

 Biologists estimate only about SO percent of 

 hatchery and wild fish survive this Tusl stage. 



Lower GrtmUe Reservoir to Bonne vilU Dam: 

 Percentage of total mortality - 20% (A.E.)* 



Survival rates through the Lower Granite 

 Reservoir are relatively high, estimates to be 95 

 percent or greater, as recorded in reservoir passage 

 experimeris conducted by a joiru University of 

 Wasfaington/Natiooal Marine Fisheries Service 

 (NMFS) research team. The majority of Snake 

 River salmon do not pass directly through the 

 Snake and Cohmibia River hydroelectric dams and 

 reservoirs. Most salmon are transported in 

 specially designed barges from collection sites at 

 Lower Granite, Little Goose, Lower Monumental 

 and McNary projects to release stes below 

 Bonneville Dam— as many as 85 percent in recent 



DOWNRIVER MIGRATION 



PACIFIC OCEAN 



UPRIVER ADULT MIGRATION 



INniVlR ADULT HANve*T AND INTeR-DAM LOSS 

 lai.oee ii4,ooo iia.ooe 



WILD SNAKe Riven 



•AtMON 



1990-1992 conditions 



10 SOCKEVe 

 ■eo W.P.CHIN. 

 It.OOe W.S/a CHIN. 



