numerous in Middle Slough. During higher high 

 tides starry flounder ( Platichthys stellatus ) 

 and Pacific tomcod ( Microgadus proximus ) 

 were observed just above the 9-foot level in 

 the main stream. 



CHARACTERISTICS OF THE SPAWNING 

 MIGRATION 



Timing 



The timing of the pink salmon spawning 

 migrations to Olsen Creek demonstrated dif- 

 ferent patterns with regard to utilization of 

 fresh-water and intertidal spawning areas on 

 the even- and odd-year cycles (1960 and 

 1961). In the 1960 run, the peak of the fresh- 

 water migration occurred about July 25 (fig. 6), 

 and by August 10 it was practically over. The 

 intertidal migration was bimodal, the first 

 peak occurring about August 8 and the second 

 September 4. The distinct separation of inter- 

 tidal and fresh-water spawners in relation to 

 tinne and space that occurred during the 1960 

 run did not take place in 1961 (fig. 6). A small 

 early run of both intertidal and fresh-water 

 spawners occurred in early July, but the 

 greatest portion of the migration developed in 

 late August and early September. 



The daily migrations of spawners into the 

 East and West Forks of Olsen Creek are 

 compared in figure 7. In both years the daily 

 migrations were almost identical. 



Federal management agents operated a weir 

 to count spawning escapement at Olsen Bay 

 in 1931 and 1932 (Bower, 1932 and 1933); and 

 in 1953, 1954, and 1955 (Thompson, 1955, 

 1956, 1957). Because of the position of the 

 weir in the intertidal area, data on the nvim- 

 bers of fish for these years are probably in- 

 accurate. However, they do provide compara- 

 tive information on the timing of the runs 

 (fig. 8). 



The counts for 1932 are not shown in ihe 

 figure because heavy rains washed out the 

 weir on August 14 after only 331 pink salmon 

 had been counted. Up to August 6 only 14 

 pink salmon had been counted, but from 

 August 7 \intil the washout the count was in- 

 creasingly daily. Connplete counts are avail- 

 able for only 2 even years (1954 and 1960) 

 but in these the run was bimodal. The peak 

 of the "early" run occurs in late July and of 

 the "late" run in late August or early Septem- 

 ber. Periodic stream surveys, fronn 1952 to 

 1956,' also have demonstrated the bimodal 



' Wallace H. Noerenberg of the Fisheries Research 

 Institute, University of Washington, made spawning ground 

 surveys of streams in Prince William Sound from 1953 

 to 1956. The results are reported In Fisheries Research 

 Institute Circulars 46, 58, 69, 81, and 90 (Fisheries 

 Research Institute, University of Washington, Seattle). 



occurrence of spawners at Olsen Creek on 

 the even-year cycle. Because of facts pre- 

 sented in these more recent data it would 

 seem that the "early" run in 1932 was ex- 

 tremely depressed or nonexistent. 



The location of the weir before 1960 in the 

 intertidal zone between the 9- and 10-foot 

 tide level makes separation of timing of inter- 

 tidal and fresh-water spawners impossible. 

 The records state, however, that when fish 

 were present considerable spawning took 

 place below the weir. 



The tinning of the late run in the odd-year 

 cycle in 1931, 1953, and 1955 (fig. 8) was 

 similar to the timing of the late run in the 

 even-year cycle, i.e., a gradual buildup of 

 spawners peaking in late August or early 

 September. No early run was evident in 1931, 

 1953, and 1955, but a small early rvm did 

 appear in 1961 (fig. 6). This was similar to 

 the even-year migration in 1932 when the early 

 run was either nonrecognizable or nonex- 

 istent. 



Conkle* stated that the commercial fishery 

 in Prince Williann Sound historically caught 

 mostly early-run fish, allowing a greater 

 number of late-arriving fish to spawn. On the 

 even-year cycle at Olsen Creek these late- 

 arriving pink salmon are predominantly inter- 

 tidal spawners. Conkle suggested that the 

 concentration of the commercial fishery on the 

 early run depleted that run, allowing a sub- 

 sequent buildup of intertidal spawners. 



There is some evidence that the late- run 

 fish in the odd-year cycle are available to the 

 commercial fishery. The weir attendant at 

 Olsen Creek in 1931' stated that a large 

 school of pink salmon appeared in the bay on 

 July 25 and did not start upstream until about 

 August 13. This same phenomenon was ob- 

 served at Olsen Creek in 1961. Most of the 

 fish in the early run spawned and died by the 

 first week in August, when large numbers of 

 pink salmon again appeared in the bay. They 

 stayed there for almost 2 weeks before 

 migrating upstream. When the upstream 

 migration did start the fish were ready to 

 spawn. This is in contrast to the early-run 

 fish which enter the stream while not yet 

 mature, and do not spawn immediately. 



Magnitude of Fresh-water Migration 



In 1960 and 1961 wooden picket weirs were 

 installed across the East Fork (fig. 9) and the 

 West Fork (fig. 10) of Olsen Creek atapproxi- 

 mately the 12-foot tide level. Both upstream 

 and downstream movements of pink salmon 

 through the weir gates were recorded from 

 counting houses located on the bank at each 



* See footnote 1, p. 1 



5 Unpublished management reports, 1931, on file at the 

 Bureau of Commercial Fisheries Biologfcal Laboratory, 

 Auke Bay, Alaska. 



