FISHERY BULLETIN: VOL. 82, NO. 1 



PELTON REGULATION DAM< 



P€LTOn\ 

 PELTON DAM<^~ - LADOER 



c^., k .^ D .,-r-r,- ^... jUrOUND BUTTE HATCHERY 

 ROUND BUTTE DAM^SS 



-V-I80 



FIGURE 1.— Map of the lower 175 km of the Deschutes River and its 

 confluence with the Columbia River. Numbers refer to kilometers 

 from the mouth of the Deschutes River. 



Round Butte Hatchery (river km 175 from the 

 Columbia River) in 1976 and 1977 were used for 

 experiments in 1977 and 1978, respectively. Eggs 

 from 1976 brood fish were incubated in Heath 4 

 incubators in 10 U C spring water, and the resulting fry 

 were reared in raceways using the same water source. 

 Eggs from 1977 brood fish were divided into two 

 groups. One group was reared under conditions as 

 described above and referred to as "fast-reared". 

 The second group of eggs was incubated in Heath 

 incubators in spring water chilled to 5°-6°C. The 

 resulting fry were transferred to raceways and reared 

 in 7°-8°C tail-race water from Round Butte Dam. 

 After 2 mo, the group was transferred to 10°C spring 

 water and reared there until release. This group was 

 referred to as "slow-reared" and was released in 

 March 1979 as yearlings. 



■"Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



In May and June, production lots of fast-reared 

 spring chinook juveniles were released into the 

 Deschutes River below Pelton Regulation Dam. At 

 this time, experimental groups were transferred to 

 oval fiber glass ponds supplied with 10 U C spring wa- 

 ter at 9.5 1/s. In May 1977, 5,600 fast-reared spring 

 chinook juveniles (average fork length 10.0 cm) were 

 transferred to a fiber glass pond and reared there 

 through June 1978. In late March 1978, 2,500 fast- 

 reared fish (average fork length 8.5 cm) were 

 transferred to a fiber glass pond and reared there 

 through August. 



All fish were reared under a natural photoperiod 

 and fed to repletion daily with Oregon Moist Pellet. 



Seaward Migration 



Migratory behavior of the spring chinook salmon 

 was assessed by the release and recapture of 

 hatchery-reared juveniles from two groups. Migra- 

 tion tendency of the experimental groups was 

 assessed by monthly release of about 200 fish into 

 the upper end of Pelton ladder during 1977 and 1978 

 (Fig. 1). The ladder is 3.7 km long and is constructed 

 with concrete walls and bottom except for a 1.1 km 

 central section which is a natural stream channel. It is 

 supplied with water from Lake Simtustus (directly 

 above Pelton Dam) at a constant flow rate of 1,130 

 1/s. Maximum depth of the ladder is 2. 1 m. The ladder 

 is closed by revolving screens at both the upper and 

 lower ends. A trap located at the lower end of the lad- 

 der was used to capture migrants. Temperature of 

 the water at the lower end of the ladder was measured 

 by a thermograph placed near the trap. 



Fish from the various experimental groups were 

 identified upon recapture in the trap at the lower end 

 of the ladder by unique combinations of polystyrene 

 dye (Phinney et al. 1967) and fin clips. The trap was 

 checked 5 d a week during May and June and 2 d a 

 week during the remainder of the year. Fish captured 

 in the trap were considered migrants while those 

 remaining in the ladder following the date of peak 

 recapture were assumed to be residuals. Fork lengths 

 and marks of each migrant were recorded upon cap- 

 ture. In January 1978, the ladder was drained and all 

 residual fish from the 1977 studies were removed 

 before the 1978 releases. 



The second group of hatchery-reared fish used for 

 assessment of migration were production lots of fast- 

 reared juvenile chinook released into the Deschutes 

 River immediately below Pelton Regulation Dam 

 (river km 161). These fish were marked with coded 

 wire tags (Jefferts et al. 1963). In 1977, 62,000 fast- 

 reared fish were released on 2 May and 73,000 fast- 



158 



