occur nevertheless, with peak escapements 

 approaching 10,000. Harris River and Indian 

 and Old Tom Creeks may be somewhat repre- 

 sentative of numerous Southeastern Alaska 

 pink salmon streams which, when taken as 

 a whole, contribute significantly to the total 

 catch. Although the volume of fine sands and 

 silts in these streams varied, it was apparent 

 that each contained considerably larger vol- 

 umes of fine materials and was less per- 

 meable than the area of Anan Creek sampled. 



SILT REMOVAL BY SPAWNERS 



In view of the nearly conclusive evidence 

 that silt is harmful to salmon eggs and larvae 

 (see the review by Cordone and Kelley, 1961), 

 it is likely that redd digging benefits progeny 

 through removal of fine particles and organic 

 detritus from spawning beds. Changes occur- 

 ring in the composition of bottom materials 

 during the spawning period were studied. 



Volumes Removed 



The intertidal Harris River sampling area 

 was sampled randomly before and after spawn- 

 ing in 1959 and 1960. The number of females 

 spawning between the sampling dates was 

 estimated to be 2.4 per 100 square feet in 

 1959 and 4.6 per 100 square feet in 1960. 

 It was found that the percentage of solids 

 passing through an 0.833-mm. sieve decreased 

 significantly over the spawning period in both 

 years (table 3). The greatest decrease occurred 

 among settleable solids passing through a 

 0. 104-mm. sieve and classified as "pan" in 

 these studies. Other studies suggested that a 

 considerable portion of fine particles removed 

 by spawners consisted of light organic ma- 

 terial. 



Organic Content 



The organic content of pan materials was 

 determined for samples collected before 

 spawning in the summer of 1958. Nine samples 

 from spawning riffles in Harris River and In- 

 dian and Twelvemile Creeks were dried and 

 sorted. Materials passing through a 0. 104-mm. 

 sieve (pan) were divided into two groups before 

 being weighed — those retained by a 0.074-mm. 

 sieve and those passing through a 0.074-mm. 



sieve. The organic fraction of each group was 

 burned off, and the samples reweighed. Solids 

 retained by the 0.074-mm. sieve had an average 

 organic content of 3.9 percent (range, 1.7 - 

 7,2 percent); whereas the average organic 

 content of solids passing a 0.074-mm. sieve 

 was 12.4 percent (range, 7.9- 19.0 percent). 



Specific gravity of materials retained by 

 and passing through the 0.074-mm. sieve was 

 also determined. Mean values of four samples 

 were 2.68 g./cc. for materials retained by the 

 0.074-mm. sieve and 2.38 g./cc. for materials 

 passing through the 0.074-mm. sieve. Thus 

 it appeared that the highest organic fraction 

 was in the finest size groups, which were also 

 most susceptible to complete removal from 

 spawning beds. 



SPAWNING BED SILTATION 



During our studies, we observed one instance 

 where siltation of spawning beds occurred in 

 association with logging. We also observed 

 that flooding removed most if not all of the 

 silt accumulating from logging. 



Silt Pollution from Logging 



Land areas contiguous to the upstream sam- 

 pling area of Harris River were logged in 

 late summer and autumn 1959. From personal 

 observation, it was apparent that tributary 

 streams draining the logged areas carried 

 unusually heavy silt loads during freshets. 

 Water samples collected from three tributary 

 streams during freshets contained, on the 

 average, two to four times more inorganic 

 sediment after logging then before. The av- 

 erage amount of organic sediment in samples 

 collected after logging was only fractionally 

 more than the amount in samples collected 

 before logging. Because of the high variability 

 observed in the amount of sediment carried 

 by the tributary streams and the small num- 

 bers of samples collected, it is not possible 

 to show conclusively that the content of in- 

 organic sediment increased because of logging. 

 However, the data, which are summarized in 

 table 4, lend support to this conclusion. 



