FISHERY BULLETIN; VOL. 87, NO. 4, 1989 



from the Priest Rapids Dam rearing facility, 

 and 3) late summer migrant fish from wild 

 stocks that spawn above Priest Rapids Dam or 

 from hatchery releases at Wells Dam. Peak 

 abundance of these three gi'oups occurred at dif- 

 ferent times (Fig. 4). Juvenile fall chinook salm- 

 on originating from the Hanford Reach were 

 collected in higher numbers than any other sal- 

 monid group. These fish were already present in 

 the river when sampling began in late April 



Spring Outmigration 



Wild and hatchery 0-age chinook salmon oc- 

 curred throughout the river cross section at 

 Hanford, but the highest concenti'ations oc- 

 curred at nearshore barge stations (Fig. 5). 

 About 45% of the fish (n = 6,281) were collected 

 at barge 4. In contrast, only 7% of the 0-age 

 chinook salmon were collected in the shoreline 

 nets. 



1800 

 1600 

 1400 

 1200 



w 



t 1000 



E 



Z 



800 

 600 

 400 

 200 

 



0-Age Hatchery 



0-Age Wild 



Figure 4. — Seasonal patterns of abundance for 0-age chinook salmon 

 populations captured by fyke net near the study site. Sampling effort was 

 uniform throughout the collection period. 



1984. Populations peaked in late May, and small 

 numbers were still present in late June when 

 sampling ended. About 60% of the 0-age fall 

 chinook salmon collected in 1984 were wild fish 

 that originated from the Hanford Reach. Hatch- 

 ery-reared fish appeared in nets within 24 hours 

 of their release from the Priest Rapids rearing 

 facility. These fish differed from wild salmon 

 because of their larger size and deeper body. 

 Most salmonids collected during June were 

 hatchery-released fish. Small numbers of 0-age 

 summer or fall chinook salmon were also col- 

 lected from July to September 1983 and in July 

 1984. These fish probably originated in the 

 Wenatchee River, with lesser contributions from 

 the Entiat, Methow, and Okanogan Rivers. Only 

 Hmited spawning of fall and/or summer chinook 

 salmon occurs in the mainstem Columbia River 

 above Priest Rapids Dam (Horner and Bjornn 

 1981). 



Table 2. — Summary of average catch per unit effort for 

 0-age chinook salmon caught by fyke nets in spring 1984. 



Station 



Depth Number/h Number/m=' >■ 10^ 



Shoreline 1 ' Surface 



0.3 



669.0 



780 



