penetrate deeply enough to consume eggs or 

 larvae. More recent evidence has shown, 

 however, that a varied fauna is often asso- 

 ciated with eggs and larvae in streambeds, 

 McDonald (1960) found lamprey larvae, stone- 

 fly nymphs, and dlptera larvae associated 

 with masses of sockeye salmon (0. nerka) 

 eggs burled in spawning gravel. He also ob- 

 served that the rate dead eggs disappeared 

 was related to gravel size, being higher in 

 coarse than in fine gravel. Briggs (1953) 

 found oligochaetes to be abundant in redds 

 containing large numbers of dead eggs; and 

 at Old Tom Creek, Southeastern Alaska, Ahnell 

 (1961) found a variety of invertebrates to 

 depths of 21 inches in salmon spawning riffles. 



In Sashin Creek it would appear that dis- 

 appearance of dead eggs from decomposition 

 and scavenging progresses slowly between 

 the end of spawning (October) and beginning 

 of fry emergence (March), and dead lairvae 

 seem to disappear more rapidly than dead 

 eggs. The evidence also suggests that in Sashin 

 Creek the fraction of the total B.O.D. attrib- 

 utable to decomposing eggs may not be en- 

 tirely satisfied before eggs of the following 

 brood year are deposited. Dissolved oxygen 

 levels of intragravel water were observed 

 to be only 50 percent of saturation at a time 

 when the population of residual dead eggs 

 was estimated to be about 100 per square 

 meter. Additional research will be required 

 before it can be determined if the B.O.D. of 

 this population of dead eggs was sufficient 

 to reduce oxygen levels significantly. High 

 levels of free carbon dioxide and ammoniacal 

 nitrogen in intragravel water were also ob- 

 served at a time when the population of dead 

 residual eggs was estimated to be about 100 

 per square meter. High levels of free carbon 

 dioxide are known to reduce the blood's 

 affinity for oxygen (Bohr effect), and am- 

 moniacal nitrogen when in the form of ammonia 

 or un-ionized ammonium hydroxide is known 

 to be highly toxic to fishes. Further research 

 is required to establish the rates at which 

 these waste metabolites are produced during 

 the decomposition of dead eggs and larvae. 



Although the carryover of residual dead 

 eggs for at least 1 year beyond the date of 

 spawning was observed to occur in Sashin 



Creek, the results of other studies suggest 

 that the redd construction activities by female 

 salmon cause the removal of organic detritus 

 such as egg fragments from their nests. 

 McNeil an(J Ahnell (1964) and Semko (1954) 

 found that spawning salmon removed signifi- 

 cant volumes of fine materials from spawning 

 beds, and they gave evidence that the materials 

 removed Included much of the organic detritus 

 present in the streambed at the time of spawn- 

 ing. However, the capability of a population of 

 spawning adults to cleanse a spawning bed of 

 fouling organic matter is unquestionably di- 

 rectly related to the density of females spawn- 

 ing. Small populations (similar to the one 

 observed in Sashin Creek during 1962) would, 

 therefore, be expected to remove only a small 

 fraction of the organic detritus present; where- 

 as large populations could conceivably remove 

 nearly all organic matter in the streambed. 

 Ricker (1962) was cognizant of this relation- 

 ship when he pointed out that residual decay- 

 ing eggs could possibly have an adverse effect 

 on a subsequent brood year of small size. 

 Additional study is needed to establish more 

 clearly relations among density of spawning 

 adults, conditioning of spawning beds, and 

 survival of eggs and larvae. 



SUMMARY 



1. Pink salmon deposited an estimated 29.5 

 million eggs in Sashin Creek during summer 

 and autumn 1961, giving a potential egg deposi- 

 tion in excess of 2,000 per square meter of 

 spawningbed. 



2. Changes in size and composition of the 

 population of dead eggs and larvae of the 1961 

 brood year were observed over the period 

 October 1961 through March 1963 in a selected 

 study area encompassing about 30 percent of 

 the total area available for spawning in Sashin 

 Creek. 



3. Residual dead larvae disappeared from 

 the streambed within 2 months after fry 

 emergence. 



4. Residual dead eggs were collected in sig- 

 nificant numbers 18 months after spawning, 

 but decomposition had caused them to dis- 



11 



