Table 5. — Potential egg deposition, number of live and dead eggs and alevins, ratio of live to combined live and dead eggs and 



alevins, and survival of 1965 brood pink salmon in three areas of Sashin Creek 



' This estimate is uncorrected for egg retention. The estimate corrected for egg retention is 82 percent. 

 2 These estimates do not differ significantly and are averaged to give 46 percent survival for each date. 



measuring the presence of eggs in sampling units 

 at the end of spawning. To measure the presence 

 of eggs, I classified samples with more than three 

 eggs and alevins as points used by spawners and 

 those with fewer eggs as unused. The classification 

 of sample points with three or fewer eggs and 

 alevins as unused is arbitrary, but some small value 

 greater than zero helps correct for the presence of 

 drifted eggs at points not actually used by 

 si^awners. 



It is probable that the density of eggs in the 

 middle area at the end of spawning was over- 

 estimated. The percentage of samples containing 

 more tlian three eggs and alevins (table G) did not 

 change significantly for any area from immedi- 

 ately after spawning (September 29) to hatching 

 (Xovember 20). The percentages of samjjles with 

 more than three eggs or alevins were similar in the 

 upper and middle areas in both September and 

 Xovember, and these similar measures of use in tlie 

 two areas agree with observed densities of females. 

 Furthermore, the upper and middle areas were 

 similar in terms of the density of eggs and alevins 

 in both Xovember and March (table .o). The poten- 

 tial egg deposition was also about equal in tlie two 

 areas, and together these observations sujiport 

 strongly the conclusion that density of eggs was 

 overestimated in the middle area at the end of 

 spawning. 



Relatively few eggs were unspawned in tlie body 

 cavities of females. Spawned females retained 5 

 percent of the potential egg deposition (based on 

 an examination of 17.'5 females). 



Table 6. — Percentage of 0.1 m.^ sampling units in three 

 areas in Sashin Creek with more than three eggs and 

 alevins, after spawning and during hatching 



i Sampling units with more than three eggs or alevins— 



Estimates of survival at the end of spawning 

 include allowance for .5 percent retention of eggs 

 by females in the upper and lower areas. In the 

 middle area, however, the density of live and dead 

 eggs at the end of spawning was calculated to be 

 100 percent of potential egg deposition (equation 

 3). This estimate is too high and requires further 

 correction for the retention of eggs by females. 

 Because only 95 i)ercent of potential egg deposition 

 was voided during spawning, the estimated 86 per- 

 cent of live eggs in the middle studj- area in late 

 September (table 5) pertains to 95 percent (or 

 less) of potential egg deposition. The survival esti- 

 mate corrected for egg retention is, therefore, 



0.95X0.86 = 82 percent. 



Correction is also required for two estimates of 

 survival in the lower area wliere survival was esti- 

 mated to increase fiom 41 percent in September to 



PIXK S.iLMON SPAWXERS IX SASHIN CREEK 



579 



