Q.100 



2 



o 



UPPER CHATHAM STRAIT/ 



I ' I — I — r 



I I I I I WEEK FROM BEGINNING OF SEASON 



30 7 U 21 28 U 11 18 25 31 30 7 1U 21 28 •! 11 18 25 31 



NE JULY AUGUST JUNE JULY AUGUST 



DATE AT END OF WEEK 



Figure 18.— Average number of pink salmon caught per trap per 

 week in each major statistical area in 1940. The approximate 

 dates on which the catch per trap per week reached 10,000 Hsh 

 and 20,000 fish are shown by the vertical lines. 



lower Chatham Strait reached the 10,000- and 20,000- 

 fish levels before traps in middle Chatham Strait, it is 

 unlikely that many fish moved from middle to lower 

 Chatham Strait. The movement from middle 

 Chatham Strait into Frederick Sound shown by the 

 tagging experiments is not immediately apparent 

 from trap catch data. Average catches reached the 

 10,000-fish level in Frederick Sound and Stephens 

 Passage shortly after that level was reached in lower 

 Chatham Strait and shortly before it was reached in 

 middle Chatham Strait, except in 1939. In that year 

 Frederick Sound reached the 10,000-fish level 2 days 

 after lower Chatham Strait, 1 day after outer Icy 

 Strait, and 16 days before middle Chatham Strait. 

 Catches in Frederick Sound probably contained fish 

 from both middle and lower Chatham Strait, for the 

 catch buildup would have been less rapid if fish had 

 come from only one source. 



A rough estimate of the rate of migration was ob- 

 tained by dividing the distance between the mid- 

 points of two areas by the time difference between 

 fixed catch levels in the areas. The rates of travel 

 between outer Icy Strait and inner Icy Strait, upper 

 Chatham Strait, and middle Chatham Strait; and 

 between lower Chatham Strait and Frederick Sound 

 and Stephens Passage were calculated. Results of the 



1 



I 



29 

 JUNE 



56789 10 I23H5 



I WEEK FROM BEGINNING OF SEASON I 



I 



13 20 27 3 10 17 21 31 

 JULY AUGUST JUNE JULY 



DATE AT END OF WEEK 



9 10 



I I 



29 6 13 20 27 3 10 17 21 31 



AUGUST 



Figure 19.— Average number of pink salmon caught per trap per 

 week In each major statistical area in 1941. The approximate 

 dates on which the catch per trap per week reached 10,000 fish 

 and 20,000 fish are shown by the vertical lines. 



first set of calculations are shown in Table 12 and of 

 the second set in Table 13 in the columns headed 

 M/D. The rate between outer Icy Strait and lower 

 Chatham Strait was not calculated, for the data in- 

 dicated few fish from Icy Strait entered lower 

 Chatham Strait. 



The rate of travel seemed to increase as the bulk of 

 fish moved south. For example, in 1939 the rates 

 between outer and inner Icy Strait were 3.3 and 4.1 

 miles per day, whereas the rates between outer Icy 

 Strait and middle Chatham Strait were 5.8 and 7.0 

 miles per day. 



The rates between lower Chatham Strait and 

 Frederick Sound and Stephens Passage (Table 13) are 

 much higher than those calculated for more northern 

 areas. In 1939 the rates between lower Chatham Strait 

 and Stephens Passage were 72.0 miles per day at both 

 the 10,000- and 20,000-fish levels. The second greatest 



27 



