Water Quality 



Near the beginning of the 1962 spawning 

 season, mean levels of dissolved oxygen, free 

 carbon dioxide, and ammoniacal nitrogen in 

 the intragravel water' were estimated from 

 water samples collected at randomly selected 

 points. Water samples were obtained from 

 standpipes similar to those described by Mc- 

 Neil (1962b) except that 1-inch inside diameter 

 pipes were used instead of 3/4-inch. 



OBSERVATIONS OF EGGS AND 

 LARVAE 



Potential egg deposition by pink salmon in 

 the study area during 1961 was estimated to 

 be 8,533,000, an average density of 2,100 per 

 square meter, A small undetermined number 

 of chum and coho salmon also spawned here; 

 but, as already reported, their progeny were 

 only about 1 percent of the eggs and larvae 

 collected in March 1962. 



The unmodified Winkler method was used 

 to measure the amount of atmospheric oxygen 

 dissolved in water samples. Samples were 

 titrated with 0.022 N sodium thiosulfate solu- 

 tion delivered from a microburette. Final 

 readings were corrected for the volumes of 

 fixatives added to each sample. 



Samples for free carbon dioxide were col- 

 lected in sequence in two 30-ml. samples 

 from each standpipe. Twenty-five ml. from 

 each of the two samples were combined in a 

 Nessler tube, giving a 50-ml. sample which 

 was titrated to a phenolphthaleln endpoint 

 with N/88 sodium hydroxide to determine the 

 amount of free carbon dioxide present. 



A model 900-3 Klett-Summerson photoelec- 

 tric colorimeter was used to determine am- 

 moniacal nitrogen. Thirty-ml. water samples 

 were collected from standpipes, and 25 ml. 

 of the sample were carefully transferred 

 from the collection vial to a 100- ml. test 

 tube by pipetting. Two ml. of Nessler reagent 

 were added to each sample, and color was 

 permitted to develop for 5 minutes. The solu- 

 tion was then transferred to a 40-mm. color- 

 imeter cell, and readings were taken with 

 a 420-mM color filter. Zero settings were 

 made, using 25 ml. of ammonia-free distilled 

 water plus 2 ml. of Nessler reagent. Zero 

 was reset after each four samples. 



The methods used are described further 

 in "Standard Methods for the Examination 

 of Water and Sewage" (10th edition, 1955). 



JThe term "intragravel water" is used here to 

 describe water flowing through Interstitial spaces within 

 the spawning bed. 



Changes in Abundance of the 1961 

 Brood Year 



Estimated densities of 1961 brood year eggs 

 and larvae in the study area through mid- 

 August 1962 and before deposition of 1962 

 brood year eggs are summarized in table 1. 

 Mean values of estimated densities of living 

 and dead eggs or larvae are plotted in figure 

 1 to show trends in their abundance. 



Total Population. — The total population of 

 live plus dead 1961 brood year eggs and 

 larvae in the gravel appeared to undergo two 

 periods of sharp decline (fig. 1) — one corre- 

 sponding to the period of spawning and the 

 other to the period of fry emergence. Because 

 of fairly high spawning densities in 1961 (1.1 

 females per square meter in the study area), 

 losses from redd superimposition and other 

 factors associated with spawning may have 

 been high and probably accounted for much 

 of the difference observed between estimated 

 potential egg deposition and estimated density 

 of eggs in the spawning bed at the end of 

 spawning. 



Evidence was obtained that the second period 

 of sharp decline was caused by emergence 

 of fry from the gravel. The total population 

 of preemergent fry in Sashin Creek in March 

 1962 was estimated to include 6,300,000 live 

 pink salmon.* At the termination of fry migra- 

 tion in mid-June 1962, 5,940,000 pink salmon 

 fry had been counted leaving Sashin Creek. 

 Hence, there was no evidence of high mor- 

 tality during emergence and migration, and 



* The 90-percenl confidence limits of this estimate 

 were ±1.090,000. 



