FRENCH and BAKKALA: NEW MODEL OF OCEAN MIGRATIONS 

 180° ITCW I60°W 



55° N 



50°N 



50 100 150 50 100 150 



RELATIVE ABUNDANCE 



Figure 10. — Relative abundance of age .1 sockeye salmon along 

 cruise tracks fished in summer 1963. 



tains a broad east-west distribution throughout 

 the summer. Definition of the eastward limit of 

 this distribution is complicated by the inter- 

 mingling of Bristol Bay and other North 

 American stocks of immature sockeye salmon in 

 the northeastern Pacific. Some evidence of the 

 eastward range of Bristol Bay fish is provided by 

 the age composition of age .1 fish sampled 

 between long. 176" and 158"W in 1963 and 1966. 

 In 1963 systematic sampling along long. 176'' and 

 162"W from July to early September (Figure 

 10) showed that age composition of age .1 

 fish was very similar for the two areas as shown 

 in Table 2. Sockeye salmon in the following year's 

 Bristol Bay run was composed of approximately 

 66% age 1.2 fish and 34*!^ age 2.2 fish or very simi- 

 lar to the dominant ages of age 1.1 and 2.1 fish, 

 noted in each area the previous summer. This 

 suggests that in the summer of 1963, Bristol 

 Bay sockeye were distributed as far east as long. 

 162''W throughout the summer. 



Table 2. — Freshwater age composition of age .1 sockeye salmon 

 from samples along long. 162°W and 176°W in summer 1963. 



The age composition for the three lines fished 

 in 1966 (Figure 11) varied considerably as 

 illustrated in Table 3. Substantial differences 

 were shown between samples at long. 176''W 

 and samples to the east. The FRI purse seine 

 samples south of Adak Island were approximately 

 33% age 1.1 and 67% age 2.1 fish — very similar 

 to the age composition observed from gillnetting 

 in this area. The following year's run to Bristol 

 Bay, however, was composed of about 17% age 

 1.2 fish and 83% age 2.2 fish (Rogers, 1970). This 

 indicates that Bristol Bay sockeye (or age-groups 

 within the Bristol Bay stock) were distributed 

 differently in 1966 compared to 1963. Other pos- 

 sibilities were that non-Bristol Bay fish made up 

 a higher proportion of the catches in 1966 or 

 that there were differential maturity schedules 

 for the two major age-groups. 



Although age composition of the samples did not 

 clearly demonstrate the predominance of Bristol 

 Bay sockeye in the northeastern Pacific in 1966, 

 it seems likely that a large proportion of the fish 

 taken in this area as well as south of the 

 Aleutian Islands generally were of Bristol Bay 

 origin. This assumption is based on the 

 relative high abundance of sockeye shown by 

 catches south of the Alaska Peninsula and 

 Aleutian Islands, in view of the relative size of the 

 Bristol Bay stock compared to other North 

 American stocks and the evidence from tagging 

 studies on immatures (see Figure 3). 



180° 



— r- 



I70°W 



I60°W 



"1 r 



.^^- 







,^/' 



X 



JUNE 21-31 



JULY I -10 



I 1-20 



21-31 



AUGUST l-IO 



I 1-20 



AUGUST 21 -31 



n 



CRUISE TRACK 



I I I I I 1 I I I I 



CRUISE TRACK 



I 



CRUISE TRACK 



55°N 



50°N 



I I t I I I I I I 



50 100 50 100 50 100 



RELATIVE ABUNDANCE 



Figure 11. — Relative abundance of age .1 sockeye salmon along 

 cruise track fished in summer 1966. 



599 



