Table 1. — \ umber of adult pink salmon in each escape- 

 ment, potential egg deposition, number of fry produced, and 

 fresh-water sunival for brood years 1934-65, Sashin 

 Creek, southeastern Alaska 



' The term "brood year" refers to the year of spawning. 



2 Based on 2,000 eggs per female except when actual fecundity was calculated 

 in 1942 (1.936 eggs). 1957 (1.988 eggs). 1959 (2.040 eggs). 1960 (1.903 eggs). 1961 

 (1.991 eggs). 1963 (1.908 eggs). 1964 (1.709 eggs), and 1965 (1,782 eggs). 



3 An attempt was made to aestroy the spawners. 



* Natural escapement (327) was reinforced by introduction of 1,866 adults. 



* Fry weir was not functioning; estimate based on number of preemerged 

 aleviiis in spawning beds. 



MIGRATION, DISTRIBUTION, AND 

 DENSITY OF SPAWNERS 



Fresh-water survival of pink salmon eggs and 

 alevins in Sashin Creek is inversely related to the 

 time of migration of the spawners (Skud, 1958; 

 Merrell, 1!)62). Because pink salmon are ma- 

 ture when they enter Sashin Creek, early entry into 

 the stream means early spawning and late entry 

 gives late spawning. The date by which 50 per- 

 cent of all of the spawnei-s had entered the Creek 

 is used in this paper to index the time of spawn- 

 ing. In 1965, 50 percent of the spawners had en- 

 tered the Creek by August 26, which was the fourth 

 earliest date of record. I had expec;ted, therefore, 

 that sur\ival of the eggs and alevins would be 

 high. 



The distribution and density of spawners in 

 1965 were analyzed to detennine if .spawners con- 

 centrated in areas that afforded the best habitat for 

 embryos and alevins. Ninety-seven jjercent (13,084 



m.-) of the Sashin Creek spawning ground was 

 divided into thi-ee areas — upper (2,945 m.-), 

 middle (4,067 m.= ), and lower (6,072 m.= ). The 

 upper area has a relatively high gradient and 

 coai-sc materials in the bed; the middle area has 

 an int«rmediat« gradient and medium-sized mate- 

 rials; and the lower area has a low gradient and 

 relatively fine materials (table 2). 



T.\BLE 2. — Average gradient and size composition of bottom 

 materials' in three areas in Sashin Creek 



' Procedures tor sampling bed materials to measure size composition were 

 described by McNeil and .\hneU (1964). 



2 Coarse particles are >12.7 mm. diameter; medium particles are 1.68 to 

 12.7 mm.; fine particles are <1.68 mm. diameter. 



In years before 1965, when spawners were 

 abundant they used the entire Sashin Creek 

 spawning ground but concentrated in the middle 

 area. Nevertheless, tlie upper area produced more 

 fry per unit area of streambed than tiie niiildle 

 or* lower area (Merrell, 1962; McNeil, 19(;(;). 

 When spawners were scarce, they usually concen- 

 trated in the lower area and did not use the upper 

 area at all. The failure of spawners to use the po- 

 tentially most productive upper area raises im- 

 portant questions about factors that control their 

 distribution. 



In 1965, 14,813 pink salmon spawners, includ- 

 ing 7,109 females, entered Sashin Creek. Two 

 hundred of the females were captured as they 

 jjassed tiie weir and were tagged with plastic Pe- 

 tei-sen disks 1.6 cm. in diameter, fastened below the 

 dorsal fin. Fifty fish were tagged with white disks 

 on August 18, 50 with red di.sks on August 24, 50 

 with yellow disks on August 28, and 50 with green 

 disks on Sei)tember 12. The dates of release of the 

 tagged females were selected to ensure represen- 

 tation of the early, middle, and late portions of 

 the migration to fresh water. Seven percent of 

 the total number of females (7,109) had entered 

 Sashin Creek before the first date of tagging 

 (August 18); 37 percent i)efore the second date 

 (August 24) ; 70 percent before the third date 

 (August 28) ; and 95 percent before the fourtii 

 date (September 12). An observer on foot 



576 



U.S. FISH AND WILDLIFE SERVIfK 



