50 i)erceiit in November, liecause the (litfeience 

 between 41 and 50 percent survival is not statisti- 

 cally significant, I assume that no mortality oc- 

 curred in the lower area between September 2!) and 

 November 20 and use the averajje of the two esti- 

 mates, 46 percent survival, i'or the spawnin^r period 

 throujrh November 20. 



Equation (2) was used to calculate survival in 

 each period. Table 7 gives the results of these 

 calculations. 



Instantaneous mortality coefficients corresijond- 

 ing to survival i)ercentages given in table 7 were 

 also calculated. The equation (McNeil, 1966) is: 



M>„= 



t 



(0) 



where Mjn is the mortality coefficient for the jf'th 

 area and nth period, 

 Sjn is survival for the _;'th area and 7(tli 



period, and 



t is time. 



In computing values of M, the unit of time is 



taken as 1 month. Thus, i=1.3 for period 1; 



1.7 for period 2; and 4.2 for period 3. The values 



of Jl/ for each aiea and period are given in table S. 



T.VBLE 7. — Survival of pink salmon of the 1966 brood year in 

 three areas in Sashin Creek 



T.KBLE 8. — Instantaneous mortality coefficients for pink 

 salmon of the 1965 brood year in three areas in Sashin 

 Creek 



Changes in the number of live eggs and alevins 

 in eacli area and in the entire stieam arc sliown in 

 figure 1. The numbers declined in the up|)er and 



14 



12 



z 

 2 10 



z ° 

 o 



2 

 _) 



< c 

 tO fa 



z 



> 



o ENTIRE STREAM 

 UPPER AREA 

 ^ MIDDLE AREA 

 o LOWER AREA 



AUG. 'sept' OCT.'nOV.'dEC.IjAN.' FEB. 'mar.' APR.' MAY 'jUNE 



1965 



1966 



KiuuRE 1. — Xuuiber of Hve pink saliuon of the I'JGO brood 

 year in three area.s of Sashin Creeli and in the entire 

 .stream at bcginiiinf; and end of four pcriod.s in fresh 

 water. The dotted extensions in April and May are for 

 tlie period of fry inif;r:iti(iii and are diseiissed in tlie 

 text. 



middle areas at nearly uniform raters in periods 1, 

 2, and 3. In the lower area, the numbers declined 

 sharjjly in j^^riods 1 and 3 but did not decline in 

 period 2. Fry were not counted at the weir in the 

 spring of 1966 because it had been damaged in late 

 winter, but I have assigned 100-percent survival to 

 period 4 (dotted extensions of the curves in figure 

 1) in all areas on the basis of previous years' data 

 from Sashin Creek (table 9). 



Although the density of fry varied among the 

 three areas, the number of fry produced in each 

 was about the same because of differences in sizes 



Table 9. — Comparison of estimates of survival of pink 

 salmon fry in Sashin Creek before the fry emerge (hy - 

 draulic sampler) and at the time they migrate (weir), 

 1959-63 



' No estimate. 



580 



r.s. FISH AXD wii.Drji'i'; skrvice 



