BECKER: PARAMETERS OF JUVENILE CHINOOK SALMON 



at Richland (below Hanford) in 1969 largely 

 because of thermal discharges from operating 

 plutonium-production reactors on the Hanford 

 reservation. 3 Solar radiation also contributes 

 heat to the free-flowing river above Richland 

 during the summer (Moore, 1968). Maximum 

 daily temperatures recorded in 1969 at Priest 

 Rapids Dam and Richland were 19.7° and 

 20.6 °C, respectively. These peaks were well 

 below the apparent upper incipient lethal level 

 of 25.1°C for juvenile chinook salmon, experi- 

 mentally determined (Brett, 1952). 



The annual volume of river flow in the 

 central Columbia River ranges from about 

 40,000 to over 300,000 cfs (1,133-8,500 m^/sec). 

 Flows are low during the fall and winter, 

 but increase and peak during April, May, and 

 June due to the seasonal runoff of the spring 

 freshet. In 1969, flows increased about 6 weeks 

 earlier than normal because of operational 

 releases at Grand Coulee Dam on the upper 

 Columbia River. High flows were sustained 

 for about 3 mo, then decreased sharply in 

 July, and minimum summer flows occurred 

 in late August and September. 



The discharge data illustrated in Figure 2 

 are based on weekly means and fail to reveal 

 the extent of either weekly or daily fluctua- 

 tions in river levels that occur from flow 

 regulation at Priest Rapids Dam. Flows are 

 generally reduced on weekends and increased 

 during the week in response to consumer 

 demands for hydroelectric power (Figure 3). 

 Similar but less extreme variations are induced 

 daily. Water in excess of reservoir capacity 

 is discharged over spillways at Priest Rapids 

 Dam during the spring spate. Weekly fluc- 

 tuations in river volumes are more variable 

 at other seasons because greater need exists 

 to conserve reservoir water supplies for hydro- 

 electric production. At these times, such as 

 in March and August 1969, flow regulation 

 on weekends may result in changes of water 

 level in the Hanford area of up to 2 m in 24 hr. 



MWOAY WAY 17t 



10 15 20 25 30 



3 Four reactors were discharging heated water in 1968 

 and the spring of 1969. The effluents issued as point 

 discharges from subsurface locations in midriver at 

 depths exceeding 6 m, and the mixing zones extended 

 downstream in narrow bands prior to dispersal. Juvenile 

 salmonids feeding in inshore areas below the reactors 

 were not directly exposed to thermal increments. 



Figure 3. — Weekly and daily fluctuations in flow volumes 

 in the central Columbia River due to regulation at Priest 

 Rapids Dam, above Hanford, March-August 1969. 



Juvenile fall chinook salmon occur in the 

 Hanford area of the Columbia River from 

 late March to mid-July (Figure 2) (Mains 

 and Smith, 1964; Becker, 1970b). During this 

 span the eggs hatch, fry leave the gravel 

 of the riverbed, and juvenile fish occupy 

 inshore feeding areas for indeterminate periods 

 of feeding and growth before departing sea- 

 ward. Most juveniles lingering at Hanford 

 emigrate by the end of July. The short resi- 

 dence span is a historical characteristic of 

 juvenile fall chinook salmon originating in 

 the central Columbia River. However, the 

 timing of the seaward migration of juvenile 

 salmonids passing through the upper and lower 

 Columbia River system is now delayed by the 

 reservoir complex (Park, 1969; Raymond, 

 1969). 



METHODS 



Juvenile chinook salmon of the 0-age group, 

 produced by adults spawning during the fall 

 of 1968, were collected by seines at stations 

 along the river banks from 4 March to 29 

 July 1969. The sampling span corresponded 

 to the annual presence of fish following emer- 

 gence from the gravel and preceding seaward 

 migration. Stomach analyses of 769 fish were 

 made from samples collected at roughly weekly 

 intervals, when available. All samples were 

 collected between 0900 and 1500 hr, and pre- 

 served in 10% buffered Formalin ^ immediately 



•* Reference to trade names does not imply endorse- 

 ment by the National Marine Fisheries Service, NOAA. 



389 



