On the other hand, the correlation between 

 high streamflows during spawning and total 

 fresh-water survival of pink salmon in the 

 Fraser River system was negative (Inter- 

 national Pacific Salmon Fisheries Commis- 

 sion, 1968). Low survival in this system was 

 attributed to the death of the eggs spawned 

 on gravel bars at high water and later ex- 

 posed during low water. In neither British 

 Columbia study was survival determined from 

 potential to actual deposition of the eggs. 



Neave (1953) listed three major causes 

 of death of salmon eggs preceding burial: 



(1) predation on adult unspawned fish, (2) death 

 of adult unspawned fish through other causes, 

 notably as a result of barriers or insuf- 

 ficient water, and (3) loss of eggs through 

 retention in the body or failure of fertiliza- 

 tion. I would add a fourth cause: inefficiencies 

 in spawning that cause eggs not to be properly 

 buried and therefore to be lost to predators 

 and scavengers or washed from the stream. 



I believe that most of the difference between 

 potential and actual deposition in 1966 was 

 due to the inability of the females to bury 

 their eggs because of high waterflow rather 

 than to removal of the eggs from the gravel 

 by subsequent spawnings. This view is sup- 

 ported by comparing the results of spawn- 

 ing in 1965 and 1966; 82 percent of the poten- 

 tial egg deposition was in the gravel at the 

 end of spawning in 1965, but only 37 percent 

 in 1966. These markedly different "spawning 

 efficiencies" occurred even though (l)the 

 1965 escapement contained more than twice 

 as many females as the 1966 escapement, 



(2) the maximum spawning ground counts in 

 1965 were more than twice those of 1966, 

 and (3) the females remained on the redd 

 for 12 days on the average in 1965 and 19 

 days in 1966- -the greater longevity would 

 give better protection to the redds from sub- 

 sequent spawners. 



SURVIVAL OF EGGS AND ALEVINS 



Survival of the progeny of the 1966 escape- 

 ment was calculated from estimates of the 

 numbers of eggs and alevins in the three 

 study sections of Sashin Creek at three 

 periods: (1) during spawning (early Septem- 

 ber), (2) after spawning (late September), and 

 (3) shortly before the alevins became fry and 

 emerged from the gravel to migrate to the 

 ocean (early March 1967). The estimate of 

 the number of eggs in each section during 

 spawning (the potential egg deposition) was 

 based on the average fecundity determined 

 at the weir and the estimated number of 

 females that spawned in each section. The 

 numbers of eggs or alevins at the end of 

 spawning and in March (before the fry emerged) 

 were estimated by sampling randomly selected 

 0.1-m.^ areas with hydraulic sampling gear 



(McNeil, 1964). The number of fry leaving 

 Sashin Creek is usually estimated by trapping 

 at the weir, but this was not done in 1967. 

 Females voided nearly all of their eggs--I 

 examined the body cavities of 38 dead or 

 dying females and found only 423 eggs, or 

 less than 0.5 percent of their potential fecun- 

 dity. 



Estimates of the number and density of 

 eggs or alevins present during spawning and 

 just before emergence of the alevins from the 

 gravel, and estimates of survival are presented 

 for each section and for the entire stream 

 in table 8. So few eggs were deposited in 

 the Upper section (because of few females) 

 that the results of sampling have little mean- 

 ing. No data are available on the fate of the 

 small number of eggs deposited outside the 

 study sections ("remainder of stream" in 

 table 8). I have therefore used the weighted 

 mean of the fresh-water survival in the 

 Middle and Lower sections to estimate the 

 number of fry produced in the Upper section 

 and the remainder of the stream. 



The potential egg deposition for the entire 

 stream in September 1967 was 6,255,000 eggs 

 and the estimated number of live alevins in 

 the stream on March 10, 1968, was 744,000- -a 

 total fresh-water survival of 11.9 percent 

 (table 8). 



I consider details of the fresh-water sur- 

 vival only for the Middle and Lower sections. 

 Four factors are of special significance: 



(1) Most (99 percent) of the successfully buried 

 eggs were alive on September 25 (table 9); 



(2) none of the eggs found in March were 

 alive (all had either died or hatched); (3) most 

 (99 percent) of the alevins found in March 

 were alive; and (4) a much greater portion 

 of the eggs or alevins disappeared from 

 the Middle than from the Lower section 

 from September 25 to March 10 (68 percent 

 versus 20 percent). The similar ratios of 

 live to combined live and dead in the Middle 

 and Lower sections on March 10 (63 and 65 

 percent — table 9) might be interpreted to 

 mean similar hatching success in the two 

 sections, but such a view may not be justified. 

 A dead egg with an intact chorion is highly 

 resistant to bacterial action 2 and probably 

 to scavenging by invertebrates and may per- 

 sist in the stream for 18 months (McNeil, 

 Wells, and Brickell, 1964). Dead alevins, how- 

 ever, do not have the protection of a chorion 

 and may decompose rapidly and also be 

 more available to scavengers. 



The much greater disappearance of eggs 

 and alevins from the Middle section than 

 from the Lower section (table 9) might be 

 explained in three ways: (1) A greater portion 



2 Brickell, David C. 1967. Oxygen consumption by dead 

 pink salmon eggs in salmon spawning beds. Manuscript 

 on file Bur. Commer. Fish. Biol. Lab., Auke Bay, 

 Alaska 99821, 107 pp. 



