130 



Eatuarine Rearing 



Juvenile chinook, coho, and chum salmon use Grays Harbor for rearing before 

 entering the ocean; extent of use by each species has been well documented 

 (Simenstad and Eggers 1981). 



These authors concluded that: 



(1) Chehalis Basin Chinook migrate out of streams at age 0. 



(2) Regarding migration route, juvenile outmigrant Chinook 



(a) reach Sand Island above Cosmopolis by early April, 



(b) tend to concentrate in the inner Harbor, mainly near Cow Point on 

 the north bank opposite the Weyerhaeuser pulp mill outfall 

 (Figure 2) , and 



(c) reach Stearns Bluff on the south bank of Grays Harbor opposite 

 Point New by mid-April. 



(3) Chinook initially use the intertidal zone, but shift to open waters of 

 the Harbor by August. 



(4) Hatchery Chinook depend on the estuary for a shorter period than some 

 naturally-spawned individuals. 



(5) Chinook fingerlings released from hatcheries in early June were at 

 Westport by mid-June and left shortly thereafter. 



The authors speculate that early summer may be a critical time in their life 

 history, because growth was depressed until most fish left the area, at which 

 time the remaining fish resumed growing. In Oregon, late summer estuarine 

 residents contributed most heavily to the adult return (Reimers 1973). 



Coho yearlings were abundant in the inner Harbor from mid-April to early June 

 (Simenstad and Eggers 1981). In a sense, the Harbor is less important to coho 

 than to chinook because individual fic>h pass through more quickly and do not 

 take time to grow there (Moser et al. 1989). These investigators found that 

 radio-tagged coho released In the lower Chehalis River generally migrated in 

 the direction of the current; however, most tagged fish also tended to hold 

 their position in areas of low current velocity near large structures such as 

 pilings and docks, particularly around Cow Point. Holding periods ranged from 

 several hours to 12 days. Pish then used either the North or South Channel to 

 migrate to the outer Harbor. 



Juvenile chum salmon also rear in the shallow intertidal zone; migration into 

 the estuary probably starts in January and continues through mid-May 

 (Simenstad and Eggers 1981). Chum depend more on the shallow intertidal zone 

 than other juvenile salmon for food supply, since they enter the estuary at a 

 size too small to prey on large, open-water zooplanxton, depending instead on 

 relatively smaller epibenthic crustaceans (Hiss and Boomer 1986a). 



