Table 4. — Foot survey estimates of pink salmon in intertidal and fresh-water areas of Olsen Creek, 1960-63 



Number Number Number Number Number Number 



Number 



Number Number Number Percent 



^ Late-run pink salmon of the even-year line do not spawn above the 14-foot (4.3-m. ) tide level (see fig. 1); there- 

 fore, the few fish that spawn between the 12-foot (3.7-m.) level (arbitrary division between intertidal and fresh- 

 water areas) and the 14-foot (4.3-m.) level are considered intertidal spawners. 



The timing and distribution of the pink salmon 

 runs in Olsen Creek in 1962 were nearly iden- 

 tical to the parent runs in 1960- -the runs in 

 both years were bimodal in time of appear- 

 ance in the stream. ' The early run spawned 

 in both the fresh-water and intertidal areas, 

 and the late run spawned only in the intertidal 

 area. In I960, 45 percent of the early run 

 spawned in the intertidal area, and in 1962, 41 

 percent spawned there (table 4). The few fish 

 of the late run that selected the fresh-water 

 area (fig. 5) spawned between the mean high 

 and extreme high tide levels--the 12- to 14- 

 foot (4.0- to 4.3-m.) tide zone, which is con- 

 tiguous to the arbitrarily established upper 

 limit of the intertidal zone. 



In July and August 1962 (peak of spawning 

 for the early run), pink salmon could not get 

 to some spawning areas in Olsen Bay because 

 of extremely low water caused by a drought. 

 Little Creek (fig. 1), for example, had so little 

 water that by July 27 all the water in the lower 

 half of the stream seeped through the gravel 

 (the surface of the bed was dry); between 

 August 10 and 21 the upper half of the stream 

 was also dry. Foot surveys of Little Creek 

 revealed 22 male pink salmon and one fenaale 

 on July 27 and seven males and two females 

 on August 6, These fish, which were in the 

 intertidal portion of the stream, were isolated 

 in small shallow pools when the tide was out 

 and were particularly vulnerable to predation 

 by black bears, Ursus americanus , and 

 glaucous -winged gulls, Larus glaucescens . 

 The first rainfall of any consequence was on 

 August 21, when the stream returned to its 

 nornnal flow. 



The effect of the drought was also evident in 

 Olsen Creek. The West Fork has two falls -- 



9 Fish of the first mode are termed the early run (or the 

 early escapement) and fish of the second mode the late run. 

 In the stream the two runs may overlap, but the fish are 

 easily recognized as early or late by their degree of physi- 

 cal degeneration. 



the first about 1 km. and the second about 2.5 

 km. above the confluence with the East Fork. 

 Pink salmon can usually negotiate the first 

 falls but never the second. As the stream level 

 fell during the drought, however, the firstfalls 

 became a barrier. On July 27, 5,924 pink salmon 

 were counted in the West Fork between the 

 confluence of the two forks and the first falls; 

 an additional 4,000 to 5,000 were crowded 

 in the pool below the falls; only 404 were 

 between the two falls. On August 6 the count 

 was still about 11,000 below the first falls but 

 only 179 above. The effects of the low water 

 on the migration of pink salmon spawners in 

 Olsen Creek in 1962 were discussed by Helle 

 (1966), 



The 1963 Spawning Population 



Figure 6 shows the results of the foot survey 

 counts of pink salmon in the intertidal and 

 fresh-water spawning areas in 1963. Because 

 these counts did not include fish in the pools, 

 the area under the curve was divided by the 

 mean redd life instead of mean stream life to 

 estimate the total spawning populations. I 

 assumed for these calculations that redd life 

 for males and females was the same and that 

 the sex ratio was 1:1. 



Redd life was determined by daily observa- 

 tions of 340 tagged female pink salmon that 

 had been captured off the mouthof Olsen Creek 

 with a beach seine and tagged with a Petersen 

 disk tag 1-1/4 inches (3.17 cm.) in diameter. 

 The numbers or letters on the tags were large 

 enough so that individual fish could be readily 

 identified from the bank of the stream (Hobart, 

 1964). The location of each tagged female 

 was recorded daily after she entered the 

 stream. Redd life was recorded as the time 

 in days from the first day that redd digging 

 and defense were observed until the female 

 was no longer near her redd. One day was 

 added to each estimate of redd life because 

 females were assumed to be present one-half 



11 



