materials in the upper area suggest that 

 intragravel waterflow and oxygen supply are 

 favorable (Vaux, 1962; McNeil and Ahnell, 

 1964). The dissolved-oxygen levels of intra- 

 gravel water rennained relatively high in 

 the upper area throughout the period of spawn- 

 ing in both 1962 and 1963, whereas in the 

 nniddle and lower areas they were relatively 

 low in August (table 12). 



The existence of an environment favorable 

 for embryos in the upper area was also indi- 

 cated by a high percentage of live eggs in 

 the samples collected Septennber 25. In the 

 upper area, 86 percent of the eggs were 

 alive--3ignificantly more than the 64 per- 

 cent in the middle area or the 73 percent 

 in the lower. The better survival could have 

 resulted from the higher dissolved-oxygen 

 levels in the intragravel water in the upper 

 area (higher than 64-percent saturation). 

 Phillips and Campbell (1962) observed less 

 than 25-percent survival to hatching of ennbryos 

 of echo salnnon (O^ kisutch ) and rainbow trout 

 (Salmo gairdneri ) which had been buried in 

 streambed gravels and subjected to dissolved 

 oxygen levels averaging less than 7 mg./l. 

 (lower than 65-percent saturation). 



Although the density of spawners was highest 

 in the middle area, the density of eggs was 

 highest in the upper area; 78 percent of the 

 potential egg deposition wras estimated to 

 be in the upper area, as conapared with 31 

 percent in the nniddle and 38 percent in the 



lower area. Since the spawners retained only 

 4 percent of their eggs, it appeared that 

 losses from redd superimposition and other 

 factors that cause eggs discharged by females 

 to disappear from the spa'ATiing bed were 

 low in the upper area and high in the nniddle 

 and lower areas. I believe that the per- 

 centage of {potential egg deposition present 

 in the spawning bed at the end of spa'Aming 

 was highest in the upper area because of 

 the coarser bottom nnaterials there. 



Survival in period 1 (egg deposition) was 

 much higher in the upper area (67 percent) 

 than in the middle area (20 percent) or the 

 lower area (28 percent). The calculated in- 

 stantaneous mortality coefficients were 3 to 

 4 times higher in the lower and middle areas 

 than in the upper area during period 1. 



In period 2 (deposition to hatching), sur- 

 vival was high in the middle and lower areas 

 but low in the upper area, where large num- 

 bers of eggs and alevins disappeared. Factors 

 causing eggs and alevins to disappear from 

 the upper area were not identified, but scav- 

 engers or predators may have played an 

 important role. 



In period 3 (hatching to fry emergence) 

 survival was high in the upper and middle 

 areas but low in the lower area, where dead 

 alevins were considerably more abundant in 

 samples collected in late March than they 

 were in the other two areas. The low survival 

 in the lower area was not due to predation 



Table 12. — Dissolved-oxygen content of intragravel water in three areas in Sashin Creek, 



1962 and 1963^ 



Area and date 



Water 

 tenperature 



Concentration of 

 dissolved oxygen 



}/ean 



90-percent 

 confidence limits 

 of the oean 



Saturation 



Upper 



August 23, 1962 



August 7, 1963 



Septenber 13, 1963. 

 Septenfcer 27, 1963. 



ittddle 



August 23, 1962.... 



August 7, 1963 



Septentier 13, 1963. 

 Septentjer 27, 1963. 



Lower 



August 23, 1962 



August 7, 1963 



Septentier 13, 1963. 

 Septentjer 27, 1963. 



1^- 



13 



13 



12 



9 



13 



13 



12 



9 



13 

 13 



12 

 9 



6.9 

 7.3 

 8.8 



8.2 



5.0 

 5.1 

 8.4 

 9.2 



5.2 

 5.9 

 8.3 



3.7 



±0.8 

 + .6 

 + .6 

 + .6 



±1.0 

 ±.5 

 ±.6 

 ±.4 



±.7 

 ±.6 

 ±.6 



-^ .6 



Percent 



65 

 69 

 81 

 71 



47 

 48 

 78 

 79 



49 

 56 



77 



Methods of sanpling were described by fcfcNeil (1962). 



