competes with living organisms for oxygen in 

 the water flowing within the gravel bed. 

 Hunter (1959) suggested that dead eggs some- 

 times remained in spawnlngbeds for a year 

 or more; with live eggs of the following brood 

 year, these dead eggs placed an additional 

 demand upon the available oxygen supply. 

 Rlcker (1962) also considered the question of 

 residual decomposing eggs fouling spawning- 

 beds after eggs of a subsequent brood year 

 had been deposited, but he indicated that 

 further study of the problem would be required 

 before Hunter's hypothesis could be accepted 

 or dismissed. 



Changes in abundance of dead 1961 brood 

 year pink salmon eggs and larvae were ob- 

 served in Sashin Creek. The observations 

 were made primarily to determine whether 

 or not dead eggs or larvae remained in 

 spawnlngbeds for a period of sufficient length 

 to compete with eggs of a subsequent brood 

 year for the available supply of dissolved 

 oxygen. 



Heavy spawning by pink salmon in Sashin 

 Creek in 1961 produced a potential deposition 

 of about 2,000 eggs per square meter. This 

 was followed by an exceptionally light spawn- 

 ing in 1962, when the potential deposition by 

 the three salmon species found in Sashin 

 Creek (pink, chum, 0. keta, and coho,0.h is utch) 

 was less than 50 eggs per square meter in 

 the most heavily spawned segments of the 

 spawning ground. ^ It was thus possible to ob- 

 serve changes in abundance of residual dead 

 eggs and larvae from a large spawning brood 

 year which had only minimum disturbance 

 from the spawning of adults in the subsequent 

 brood year. The abundance of dead salmon 

 eggs and larvae in Sashin Creek spawnlngbeds 

 was measured in October 1961 (shortly after 

 spawning); in March, July, August, and Octo- 

 ber, 1962; and in March 1963. Observations 

 were also made on stream hydrology and 

 water quality in spawnlngbeds. The findings 

 are presented in this paper. 



iJhe small pink salmon run of 1962 was the result 

 of deliberate attempts to eliminate the even-year cycle 

 from Sashin Creek. 



METHODS 

 The Study Area 



The study area encompassed 4,067 square 

 meters (about 30 percent of the total available 

 spawning area) and was centrally located in 

 the parts of Sashin Creek accessible to adult 

 salmon. The average gradient was 0.3 percent. 

 The stream bottom was composed of materials 

 containing 48 percent of particles larger than 

 25 mm., 44 percent between 1 and 25 mm., 

 and 8 percent finer than 1 mm. The method 

 of determining size composition of bottom 

 materials is described in McNeil and Ahnell 

 (1964), 



Egg and Larval Abundance 



Parents of 1961 brood year pink salmon 

 spawned in Sashin Creek in September, and 

 most of the surviving fry emerged the follow- 

 ing April and May. The total potential egg 

 deposition calculated from the average fecun- 

 dity of adult females counted entering the 

 stream was 29,425,000.* Twenty-nine percent 

 of the calculated total deposition was estimated 

 to have been available for deposition in the 

 study area. This estimate was calculated from 

 the fraction of total sightings of spawning 

 adult pink salmon tagged at the weir and sighted 

 in the study area. Results of the tagging in- 

 dicated that spawners were distributed fairly 

 uniformly throughout the Sashin Creek spawn- 

 ing ground, and the expected density of eggs 

 was assumed to be nearly equal for all seg- 

 ments of the Sashin Creek spawning groimd 

 both Inside and outside the study area. 



Two areas outside of the boundaries of the 

 study area were sampled in October 1961 

 to estimate the density of eggs present in 

 spawnlngbeds at the end of spawning; but the 

 study area was not sampled at this time. One 

 of the areas sampled was located downstream 

 and the other upstream from the study area. 

 Potential egg deposition was estimated to be 

 near 2,000 per square meter in these two areas 

 as well as in the study area. Of the 2,000 eggs 

 per square meter potentially available for 



t Ninety-five percent confidence limits were ± 990,000. 



