Figure 9. — Debris deposited in intertidal Indian Creek by the December 1959 flood. 



in early December appeared to result in little ad- 

 ditional loss of eggs or larvae from intertidal 

 Harris River. 



The period of heavy rain in November was not 

 associated with high egg mortality in intertidal 

 Indian Creek, but the period of heavy rain in 

 December was associated with high mortality of 

 eggs and larvae. After high water had receded in 

 December, large numbers of eggs and larvae 

 scoured from the Indian Creek, streambed were 

 observed by workers along the banks. About 90 

 percent of live eggs and larvae in the intertidal 

 Indian Creek spawning bed at the time of high 

 water in December 1959 were probably destroyed. 

 A factor contributing to this high mortality ap- 

 peared to be the breaking up of a natural log jam 

 located a short distance above the intertidal 

 Indian Creek spawning area and the subsequent 

 deposition of debris from this jam in the spawning 

 area. Figure 9 shows some of the debris deposited 

 in intertidal Indian Creek. Turbulence created 

 by the stream flowing around this debris was be- 

 lieved to have been mainly responsible for causing 

 the stream to alter its course at several locations, 



washing out or burying deeply a large percentage 

 of eggs and larvae present. 



There was evidence that gravel movement 

 caused high mortality in upstream Harris River. 

 No live or dead eggs or larvae were collected from 

 68 points sampled in February 1960. Other 

 evidence of widespread gravel movement in up- 

 stream Harris River was obtained from studies on 

 size composition of bottom materials. There was 

 a significant reduction in volumes of fine sands and 

 silts in bottom materials during high water in 

 autumn 1959 (McNeil and Ahnell, 1964). 



I960 Brood Year 



Periods of highest intensity rainfall occurred 

 between October 9 and 22. Intertidal Harris 

 River, Indian Creek, and Twelvemile Creek were 

 sampled in autumn 1960 before and after high 

 water (table 12). 



Estimated total abundance of eggs in inter- 

 tidal Harris River, as in the previous 2 years, 

 declined about 50 percent in association with high 

 water. The mean fraction of points containing 

 fewer than 35 eggs per in.- increased 0.16 after 



516 



U.S. FISH AND WILDLIFE SERVICE 



