caught at Bonneville from 231, 134 marked 2's 

 released by Leavenworth hatchery in October 

 and November (202, 353 were released into Lake 

 Wenatchee and 28, 781 were released into the 

 Wenatchee River) . Eleven marKed bluebacks 

 were caught from 29, 189 2's released by Leav- 

 enwortli hatchery in March into Icicle Creek . 

 A total of 107 bluebacks were caught at Bonne- 

 ville from an October release of 25, 351 marked 

 bluebacks released by Little White hatchery into 

 Drano Lake; 72 were caught from a March re- 

 lease of 25, 598 into Drano Lake. Table 13 

 shows hatchery releases of marked blueback 

 salmon and numbers captured at Bonneville. 



as hypothesized on page 17, if the fingerling 

 traps catch a higher percentage of the down- 

 stream migrants early in the spring, then 

 marked bluebacks released at that time would 

 be proportionally more numerous in the catches 

 than bluebacks that migrated during the peak 

 migration period later in the spring. 



The 119, U83 bluebacks marked A+LV, 

 released by Leavenworth hatchery in the fall of 

 1952, consisted of fish that had survived a virus 

 disease which had caused serious mortality in 

 the hatcheries. This factor could have affected 

 the subsequent survival of this group of fish. 



One reason for the greater apparent 

 survival of spring releases from Leavenworth 

 and Winthrop may be that the spring releases 

 were composed of larger fish that spent less 

 free time in fresh water. This would not ex- 

 plain why more fall fish were caught from a 

 Little White release, because the above state- 

 ment also applies to them. Perhaps the distance 

 from the point of release to Bonneville was 

 responsible for at least a part of the apparent 

 difference in catches of fish from Little White 

 and from Leavenworth and Winthrop. 



Some of the fall marked bluebacks were 

 released into rivers which could have caused a 

 higher mortality. Fall releases are usually 

 into lakes, where the fish spend the winter. 

 Comparison of fall releases of marked 2's from 

 Leavenworth into Lake Wenatchee in 1945 and 

 from Winthrop into the Methow River in 1948 

 and 1949 shows very little difference in captures 

 at Bonneville of these groups . Both the spring 

 and fall releases from Little White hatchery 

 were into Drano Lake, a part of the Little 

 White Salmon River . 



Marked bluebacks released in March 

 from Leavenworth and Winthrop hatcheries 

 appear at Bonneville before the catch of that 

 species has peaked. The river flow is less in 

 March than it is at the time of peak migration . 

 Also, since the spring marked bluebacks were 

 released into rivers, these fish would not be 

 distributed in the same manner as the rest of 

 the population. Therefore, if the proportion of 

 marked fish in the total number migrating past 

 Bonneville is greater early in the spring, and. 



Lengths of Marked Migrants 



Marked bluebacks are the only blueback 

 migrants caught at Bonneville that are definitely 

 Known to be from the hatcheries. Only one fall 

 release (planted in October and November 1952) 

 is available for comparison. The sample sent 

 by Leavenworth hatchery was from the Novem- 

 ber release and it ranged in length from 90 to 

 112 mm. (mean 98 mm.). A single 112-mm. 

 specimen from these releases was measured at 

 Bonneville (a second was caught but it was not 

 measured). There were three spring releases 

 that can be compared. The first was a release 

 from Winthrop on March 27, 1950. The sample 

 sent by the hatchery ranged in length from 1 13 

 to 138 mm. (mean 126 mm.). There were 11 

 recaptures at Bonneville, all within 19 days 

 after the date of release, which ranged from 122 

 to 160 mm. (mean 139 mm.). The fingerling- 

 trap catches averaged 13 mm. longer than the 

 sample sent by the hatchery. On April 18, 1951, 

 25, 000 1 's, marked adipose, were released 

 from Winthrop. The sample sent by the hatch- 

 ery ranged from 34 to 59 mm . (mean 45 mm .) . 

 Within 8 days 3 fish from this release were 

 caught at Bonneville. Their lengths ranged from 

 62 to 71 mm . (mean 66 mm .), or an average of 

 2 1 mm . longer than the hatchery sample . A 

 fourth fish from this release was captured on 

 September 11, 1953, and it measured 197 mm. 

 On March 25, 1953, 32, 692 2's, marked adi- 

 pose and right ventral, were released by the 

 Winthrop station. The hatchery sample ranged 

 from 115 to 148 mm. (mean 131 mm.). Within 

 39 days 15 of these fish were caught at Bonne- 

 ville; their lengths ranged from 138 to 193 mm. 



33 



