Distribution of Spawning Pink Salmon in Sashin Creek, 

 Southeastern Alaska, and Survival of Their Progeny 



By 



WILLIAM J. McNEIL, Fishery Biologist 



Bureau of Commercial Fisheries Biological Laboratory 

 Auke Bay, Alaska 99821 



ABSTRACT 



The escapement of pink salnnon ( Oncorhynchus gorbuscha) to Sashin Creek, 

 southeastern Alaska, in 1963 was 16,757 fish, and fresh-water survival calculated 

 fronn potential egg deposition and nunnber of outmigrant fry was 20 percent. The 

 spawning ground was divided into three areas--upper, middle, and lower--for the 

 study of density of spawners and survival of progeny. The density of spawners was 

 highest in the nniddle area. Survival during spawning was low in each area; survival 

 between the end of spawning and the beginning of fry ennergence was variable among 

 the three areas; and survival during fry ennergence was high in each area. From 

 egg deposition to fry emergence, survival was estinnated to be 31 percent in the 

 upper area, 16 percent in the middle area, and 15 percent in the lower area. 



Although the upper area was highly productive of pink salmon fry, it has had 

 intensive spawning only in years when the density of spawners was high. When the 

 density was low, spawners tended to concentrate in the lower area. The validity of the 

 supposition that only highly productive spawning beds are used when escapements are 

 small is questioned. The observations at Sashin Creek indicate that relatively large 

 escapements help ensure complete use of productive spawning beds. 



INTRODUCTION 



The production of fry of pink salnnon 

 (Oncorhynchus gorbuscha) can vary greatly 

 among areas within a stream (Merrell, 1962; 

 McNeil, 1966). Much of this v a r i a t i o n may 

 be due to the distribution of spawners. 

 Frequently, small runs spawn in restricted 

 areas in a stream, whereas large runs spawn 

 throughout a stream (Kaganovskii, 1949; 

 Hunter, 1959; Merrell, 1962; Vasilenko- 

 Lukina, 1962). It has been postulated that 

 areas not used when runs are small have 

 relatively poor conditions for eggs and alevins 

 (Neave, 1953 and 1958; Pritchard, 1948; Semko, 

 1954; Ward and Larkin, 1964). 



Recent evidence from studies on Sashin 

 Creek, a small stream on Baranof Island, 

 southeastern Alaska, is not in full agree- 

 ment with this hypothesis. Merrell (1962) 

 demonstrated that a spawning area used little 

 in a year of low escapement was used in- 

 tensively in a year of high escapement; in 

 the year of high escapement this intermit- 

 tently used area had a high survival of eggs 

 and alevins and produced an exceptionally 

 large number of fry. 



To clarify the relations among the distribu- 

 tion of spawners, survival of eggs and alevins, 

 and production of fry in Sashin Creek, I 

 studied a relatively large run of pink salmon 

 that spawned there in the latter half of August 

 and in September 1963. Survival from deposi- 

 tion of eggs to emergence and migration of 

 fry was determined in three areas that to- 

 gether included 97 percent of the area used 

 by spawners in years of large escapements. 

 In this paper, estimates of survival of embryos 

 and alevins are compared with the density of 

 spawners in the three study areas, and sur- 

 vivorship curves are described for each area. 

 Also discussed is the concept that large 

 nunnbers of spawners are required to ensure 

 complete use of all productive spawning areas 

 within a stream. 



Only a small portion of Sashin Creek can 

 be used by salmon spawners. Although the 

 creek is about 4,000 m. long, a waterfall 

 1,200 m, from the head of tide prevents 

 further upstream movement of spawners. 

 Little spawning occurs in a narrow canyon 

 that extends 300 m. downstream from the 

 waterfall or in the intertidal zone, where 

 the gradient is steep and the bottonn is mostly 



