migration, the catch at Whale Bay would have 

 been approximately 45.626 pink salmon and 

 Q45 chum salmon. 



ABUNDANCE OF PRE-EMERGENT 



FRY IN INTERTIDAL AREA 



BELOW TRAPS 



Data collected at Beartrap Bay were treated 

 in the same manner. Fishing was continued 

 through May 16, when it was necessary to close 

 the station. By that time, 34.6 percent of the 

 pink and 40.1 percent of the chum salmon fry 

 had migrated at Olsen Bay, Fish Bay. Indian 

 Creek, and Cannery Creek. 



It is doubtful, however, that 34.6 percent and 

 40.1 percent had migrated at Beartrap Bay 

 when fishing ceased. This stream is con- 

 sidered atypical of other middle-run streams, 

 at least when considering the time of fry 

 migration in 1Q57. Fry migrations began about 

 April 10 at all middle-run streams studied 

 except Beartrap Bay. Ice prevented the instal- 

 lation of traps at that location until April 27, 

 at which time catches had greatly increased 

 at all other middle-run streams being sampled. 

 At Beartrap Bay, however, catches were small 

 during the first days of fishing, indicating that 

 the beginning of the migration was being 

 sampled. Also, daily catches remained rela- 

 tively small (310 pink and 142 chum salmon 

 fry) through May 16 when sampling had to be 

 discontinued. The peak migration at Beartrap 

 Bay, therefore, probably occurred at a later 

 date than at other middle-run streams. 



Number of Fry Migrating from 

 above Traps 



Estimates of the number of fry migrating 

 from above the traps in the eight study streams 

 (table 3) were calculated from the formula 



T = 



(l lO*^') /lOO^ / 100 \ 



\ b / XT') [wo^j 



The values of 100 percent in the column "Per- 

 cent of migration period fished" are some- 

 what arbitrary since a small but unknown 

 number of fry came downstream after our 

 studies were terminated. 



'Refer to formula pag^e 5 for explanation of column 

 headings. 



Table 4 summarizes the results of excava- 

 tions in intertidal areas where spawning was 

 known to occur. In deriving the estimates, we 

 assumed that the fry produced in the intertidal 

 area before the quadrat sampling emerged in 

 the same pattern as the upstream fry and that 

 the bulk of the fry estimated in the intertidal 

 area survived to migrate out of the gravel. 

 Data are not included for study streams at 

 Olsen Bay, Whale Bay, and Beartrap Bay, 

 since no intertidal excavations were accom- 

 plished at these stations. Rough estimates of 

 the abundance of fry in the intertidal zone at 

 these three locations were made on the basis 

 of the fraction of parent spawners observed 

 to use the area below the traps. 



The estimates of fry presented in table 4 are 

 minimal because: 



1. The studies were conducted late in the 

 migration, and the percent of the fry that had 

 already emerged in the intertidal area could 

 not be determined exactly. Also, some of the 

 fry may migrate from upstream and seek 

 refuge temporarily in the intertidal gravel. 



2. Stream velocities of about 2 feet per 

 second caused difficulties in placing the 

 sampling device and in keeping it stationary. 

 High velocities also causedgravel to be washed 

 into the area being sampled. 



3. Stream velocities of over 3 feet per 

 second made it impossible to sample some 

 areas. Velocities ranging above 3 feet per 

 second were recorded at times in Beartrap 

 Bay, Olsen Bay, Indian Creek, Pigot Bay, 

 and Whale Bay. 



4. Streambottom irregularities made it dif- 

 ficult to place the trap in some locations, and 

 removing boulders and gravel so that the trap 

 would be slightly submerged in the gravel may 

 have caused some fry to be washed from the 

 sample area without being detected. 



5. Digging in depths of 1 foot or greater 

 sometimes resulted in gravel sliding into the 



13 



