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tagging studies will begin in 1992 to indicate whether the pollution block has 

 been reduced. A number of years of fish tagging will be required to make 

 final conclusions about the success of cleanup. 



Current Harbor Dredging and Pish Survival 



Regulatory agencies thoroughly examined the current harbor deepening and spoil 

 disposal project and ultimately agreed that operations would not significantly 

 diminish fish survival (USACE 1990, Ging 1989). Potential negative effects 

 were considered and either minimized by requiring judicious operating plans or 

 mitigated through habitat enhancement. 



The USACE (1990) arguments against negative effects of dredging and spoil 

 disposal notwithstanding, sediment contamination with potentially toxic 

 chemicals is widespread enough to be a concern (Table 15). Their own argument 

 that winds and tides resuspend sediment throughout the harbor (USACE 1990) 

 implies that dioxin and other contaminants, even though bound to sediment 

 particles, remain available to the food chain that may lead to salmon and 

 shorebirds . 



Parasitise in the lower Chehalii 



Parasitism was identified by Schroder and Fresh (1992) as the only contributor 

 to low survival aside from the inner Harbor environment. Biopsies indicated 

 that both Chehalis and Humptulips systems had low pathogen infestation 

 overall, and similar species composition of parasites. One notable exception 

 was the kidney fluke Nanophyetus salmmcola, which occurred more frequently in 

 the lower Chehalis system and the inner Harbor than in the Humptulips or North 

 Bay. The authors stated that parasitism alone could not account for 

 differential survival between the two systems because (1) infestation was 

 highly variable within and between watersheds; (2) no linkage had previously 

 been noted between parasite infestation and survival in the absence of 

 additional stressors; and (3) other coho populations that had high survival 

 rates had higher levels of the parasite. However, heavy parastism by 

 Nanophyetus coupled with additional stressors can cause coho to die 

 prematurely (Schroder and Fresh 1992). 



CHEHALIS-CENTRALIA TEMPERATURE AND OXYGEN BLOCK 



Chinook salmon attempt to hold in the Chehalis River between Centralia and 

 Chehalis before gradually moving upstream to spawn in early fall; important 

 Chinook spawning grounds lie upstream. In late summer, a complex combination 

 of natural and human- induced conditions often results in the reach being 1) 

 unsuitable for Chinook holding and/or 2) impassable for adults migrating 

 upstream, because of high temperature and/or low dissolved oxygen (Hiss et &1. 

 1983a). The marginal conditions also make fish particularly susceptible to 

 mortality from pollution, such as sudden spills of toxic material or oxygen- 

 robbing waste (Pickett 1992). 



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