FISHERY BULLETIN: VOL. 74, NO. 4 



toward earlier migration in the soutliern part of 

 the range (Table 11). 



To compare yields of coho salmon smolts 

 between strearns, we express yield in numbers per 

 unit area. Estimates of the annual yield of coho 

 salmon smolts from Sashin Creek for the period 

 1956-68 (except 1964-66) ranged from 5.5 to 

 16.9/ 100m- of rearing area (Table 10). The yield of 

 smolts for a 5-yr period in three streams tributary 

 to Drift Creek ranged from 18 to 67/100 m- 

 (Chapman 1965). The much lower yield of smolts 

 from Sashin Creek probably reflects increased 

 mortality accompanying the additional 12 mo of 

 freshwater residence for most smolts from Sashin 

 Creek. The number of nonmigrant yearling coho 

 salmon in Sashin Creek in early summer 

 (determined from population studies) approx- 

 imates the yield of smolts from Drift Creek 

 tributaries more closely than does the yield of 

 smolts (all ages) from Sashin Creek. 



Early Emigration and 

 Salinity Tolerance of Fry 



The number of fry entering the estuary is great 

 enough (Table 10) that the question of their fate in 

 salt water is important. Many factors such as 

 predation, failure to find adequate food, failure to 

 adjust physiologically to salt water, and disease 

 may act alone or in combination to determine the 

 survival of fry entering marine waters. We had 

 opportunity to explore adjustment to salt water as 

 a factor in survival of migrating fry. 



Early-migrating coho salmon fry might have 

 reentered Sashin Creek undetected, although they 

 could not have done so while the fry and smolt weir 

 was in operation. In addition, a low waterfall 

 immediately downstream from the weir is a bar- 

 rier to upstream migration of coho salmon fry 

 except for several days each year when above- 

 average high tides inundate the falls. Our popula- 



Table U. -Timing of seaward migration of coho salmon smolts from streams and lakes in Alaska, British Columbia, Washington, 



Oregon, and California. 



Location 



Migration period 



Peak of migration 



Source of data 



South-central Alaska: 



Fire Lake (lat. 61°2rN) 



Bear Lake (lat. 60°12'N) 



Little Kitoi Lake, Afognak Island 

 (lat. 58-12'N) 



Karluk Lake, Kodiak Island 

 (lat. 57'^'27'N) 



Lake Margaret (lat. 57'46'N) 



Lake Genivieve (lat. 57'"46'N) 

 Souhteastern Alaska: 



Taku River (lat. 58°33'N) 



Eva Lake (lat. 57"'24'N) 



Hood Bay Creek (lat. 57°20'N) 



Sashin Creek (lat. 56°23'N) 

 Central coastal British Columbia: 



Port John (Hooknose Creek) 

 (lat. 52^08'N) 

 Southern British Columbia: 



Cultus Lake (lat. 49°03'N) 

 West-central Washington: 



Minter Creek (lat. 47°22'N) 

 Northwestern Oregon: 



Gnat Creek (lat. 46°12'N) 

 Northern coastal Oregon: 



Spring Creek (lat. 45"36'N) 

 Central coastal Oregon: 



Drift Creek tributaries: Deer, 



Flynn. and Needle Branch Creeks 



(lat. 44°32'N) 

 Crooked Creek (lat. 44°25'N) 



Southern coastal Oregon: 



Sixes River (lat. 42°51'N) 

 Central coastal California: 



Waddell Creek (lat. 37°06'N) 



Mid May-early July 

 Late May-early Aug. 



Late May-late July 



Mid May-early July 

 Mid Mar. -early July 

 Mid May-mid July 



Mid Apr-mid June^ 

 Mid May-mid June 

 Early May-late June 

 Apr. -early July 



Mid Apr. -early June 

 Apr. -June 

 Feb. -early June 

 Apr.-early June 

 Late Feb. -May 



Feb. -May 

 Feb. -early June 



Mar.-June 

 Apr.-early June 



Late May-early June 

 Early June 



Mid June 



Late May-early June 

 Late May-early June 

 Late May-early June 



Mid May-early June 

 Late May 



Mid May-early June 

 Late May-early June 



May 



Late May-early June 



May 



May 



Late Mar.-early May 



Late Mar.-early Apr. 

 Apr. -May 



Apr.-May 

 Late Apr.-May 



Wallis (1967, 1968) 

 Logan (1963) 



Parker and Vincent (1956) 



Drucker (1972) 

 Van Hulle (1971) 

 Van Hulle (1971) 



Meehan and Siniff (1962) 

 Armstrong (1970) 

 Armstrong (1970) 

 Table 10, this report 



Hunter (1948, 1949) 

 Foerster and Ricker (1953) 

 Salo and Bayliff (1958) 

 Willis' 

 Willis et al." 



Chapman (1962, 1965) 

 Harry H. Wagner (pers. commun. 

 9 July 1973) 



Reimers' 



Shapovalov and Taft (1954) 



'Trapping facilities were completed after the beginning of the migration. 



^Period when a sampling trap was operated. 



'Willis, R. A. 1962. Gnat Creek weir studies. Final Rep., BCF Contract 14-17-0001-469, Fish Comm. Oreg., Res. Div., 71 p. 



"Willis, R. A., R. N. Breuser, A. L. Oakley, and R. W. Hasselman. 1959. Coastal Rivers Investigations Prog. Rep., August 1957-June 1958, 

 Fish Comm. Oreg., 24 p. 



sReimers, P. E. 1971. The movement of yearling coho salmon through Sixes River estuary. Coastal Rivers Investigations Prog. Rep. 71- 

 2, Fish Comm. Oreg., 15 p. 



908 



