EWING ET AL.: EFFECTS OF SIZE AND RELEASE TIME ON SALMON 



r l6 



TABLE 3. — Apparent growth rates of juvenile chinook salmon re- 

 leased into Pelton ladder, 1977 and 1978. 



I978 



Fic.l'RE 4. — Daily percent seaward migration from 8 May to 8 June 

 for groups released 14 February (solid circles) and 15 March (open 

 circles). Temperature (triangles) is the average daily temperature. 



20 



or 



or 



UJ 



o 



S 



UJ 



< 



or 



UJ 



4 - 



J I L 



JAN MAR MAY JUL SEP NOV 



FEB APR JUN AUG OCT DEC 



FIGURE 5. — Average monthly temperature in Pelton ladder 

 in 1977 (solid circles) and 1978 (open circles). 



TABLE 4. — Fork lengths of juvenile chinook salmon at time of release 

 into Pelton ladder and at time of recapture, 1977 and 1978. Values 

 are means ± standard errors. Number of samples is given in 

 parentheses. 



for fast-reared fish in 1977 and 1978, respectively. 

 Slow-reared fish in 1978 grew at 0.043 cm/d. 

 Apparent growth rates offish placed in Pelton ladder 

 varied from 0.034 to 0.124 cm/d (Table 3). These 

 apparent growth rates increased in later introduc- 

 tions, reflecting the increasing water temperature of 

 the ladder (Fig. 5). 



There was no evidence for differences in migration 

 timing by fish of different sizes. Fork lengths of fish 

 recaptured in the trap within a few days of release 

 were usually not significantly different (P > 0.05) 

 from those of fish at release (Table 4). However, fish 

 recaptured from the large group of juveniles released 

 on 1 4 February 1978 were similar over a 3-wk period 

 (Table 5), suggesting that faster growing fish were 

 migrating more rapidly that slower growing fish. 



Apparent growth rates of marked spring chinook 

 juveniles released below Pelton Regulation Dam in 

 1977 were calculated from fork lengths of recaptured 

 fish at the Dalles Dam, after a migration distance of 



TABLE 5.— Mean fork lengths of juvenile 

 spring chinook salmon recovered in 1978 

 after release into Pelton ladder on 14 Feb- 

 ruary 1978. Values are means ± standard 

 errors. Number of samples is given in 

 parentheses. 



Date of 

 recovery 



Fork length (cm) 



2/17 



5/15 



5/16 



5/18 



5/22 



5/24 



5/30 



6/1 



6/5 



6/9 



213 km (Table 6). This apparent growth rate is nearly 

 twice that of fish reared at Round Butte Hatchery. 



181 



