88 



e 8. Juvenile coho production from the Upper Chehalis River system (Brlx 

 Seller 1977, 1978; Seller et al. 1992b; WDF unpublished records). 



er (Table 8) was estimated by trapping downstream migrants in 1976, 1977, 

 from 1986 to 1991 (Brix and Sailer 1977, 1978; Seller et al. 1992b). The 

 er Chehalis is producing roughly as many coho smolts per square mile and 



■pawner as other western Washington streams (Seller 1987, 1989). The 

 ■er Chehalis system produces exceptionally large, healthy smolts compared 

 -Eft neveral other western Washington rivers (Schroder and Fresh 1992). 



* production from the 1974 brood year was lower than other years perhaps 

 e smolt trapping was not begun until April 15 (Brix and Seiler 1977), by 

 w time some of the smolts had already migrated past the trap site, (T&ble 

 6 ix and Seiler 1978). Smolt production from the 1984 brood year 

 et ponds to full seeding of the spawning grounds (Seiler 1987). 



Tc unate the total Chehalis Basin coho run size for an average water year, 



asr -g the "pollution block" were removed, Seiler (1987) used the smolt 



pr: -ion of Bingham Creek, where 5 years of trapping showed production 



av.- ed around 34,900 per year. Expanding this number in direct proportion 

 to number of accessible miles of stream in the upper Chehalis system 

 sue ed that the system would produce 1,000,000 smolts in a normal water 



yea: -th adequate spawning. Since the upper Chehalis covers 920 square 

 mil. and the whole Basin is 2,500 square miles, the Basin should produce two 



to t- '-e million smolts (Seiler 1987). At a 10 percent smolt-to-adult 



surv. al, this would create a total run — that is, marine interception plus 



term: tl run — of 200,000 to 300,000 adults. This exceeds even the estimated 

 historic high run size described below. 



31 



