768 
BULLETIN OP THE BUREAU OF FISHERIES 
As not all of these traps fished every year during the period under consideration, 
it was necessary to determine the relative efficiency of each trap, especially since no 
two traps are exactly alike in their potential capacity to catch fish. In determining 
these efficiencies it was, of course, necessary to use a base. 
The use of any one year as a base could not give a very accurate picture of their 
relative efficiencies, so a 28-year period was employed, from 1902-31; with the excep- 
tion of 1908 and 1922. Fifteen traps were found that had fished every year during 
this period, of which 1 was from the Point Roberts Area, 10 from Boundary Bay, 2 
from Birch Bay and 1 each from the Lummi Island and Salmon Bank Areas. For 
these traps an average annual catch per trap was computed. Using these average 
annual catches as a standard, or base, the proportion that the total annual catches of 
each of the 43 traps formed of the same annual catches of the standard was found. In- 
stead of using these proportions as weights, each trap was assigned an efficiency weight- 
ing which was the calculated average annual catch it theoretically would have caught 
had it fished for the whole 28 years represented by the standard, or base, curve. This 
was done for each trap by merely multiplying the average annual catch of the standard 
curve for the 28 years by the above-mentioned proportion. 
Having determined the relative efficiency of each of the 43 traps, the index was 
made by dividing for each year the total catch of such of the 43 traps as were driven 
by the total efficiency weightings of the same traps. The index figures are not actual 
numbers of fish but, as with most other indices, are to be considered in relation to one 
another. However, they give roughly the percentage that each year’s catches are 
of the average of the 28 years represented in the standard curve. 
Even though the trend of the base curve for the 15 traps rose or fell at a different 
rate than did the trend of the traps as a whole, this method of determining the effi- 
ciencies would prevent this difference in the trend from having any effect on the final 
index unless a large share of the traps selected fished for only a short number of 
years at one end of the period of time. Since this condition does not obtain, the 
index is believed to be a reliable measure of the changes that have occurred in the 
trap catches. 
Table 32 . — Sockeye index of abundance from traps, 1896-1934 
Year 
Catches 
Efficiency 
weights 
Num- 
ber of 
traps 
Index of 
abun- 
dance 
Index 
from 
stand- 
ard 
curve 
Year 
Catches 
Efficiency 
weights 
Num- 
ber of 
traps 
Index of 
abun- 
dance 
Index 
from 
stand- 
ard 
curve 
1896 
259, 512 
157, 152 
6 
165. 134 
1917 
1, 777, 158 
1, 361, 590 
43 
130. 521 
139. 225 
1897 
843, 303 
349, 089 
10 
241. 572 
1918 
350, 451 
1, 316, 830 
39 
26. 613 
23. 548 
1898 
821* 677 
381, 254 
11 
215, 520 
1919 
306, 114 
1, 161,984 
35 
26. 344 
29. 226 
1899 
2, 663, 376 
755, 475 
21 
352. 543 
1920 
499, 406 
932, 553 
27 
53. 553 
52. 306 
1900 
' 942* 721 
868', 394 
26 
108. 559 
1921 
621, 190 
1, 310, 431 
42 
47. 403 
47. 050 
1901 
5, 095, 464 
833, 241 
26 
611. 523 
1922 
328, 554 
802, 564 
20 
40. 938 
1902 
1 , 403' 869 
983, 037 
30 
142. 809 
132. 035 
1923 
276, 658 
1, 180, 625 
36 
23. 433 
24.950 
1903 
' 703' 336 
983', 037 
30 
71. 547 
70. 728 
1924 
555, 636 
972, 745 
27 
57. 120 
65. 769 
1904 
609, 681 
912, 297 
25 
66. 829 
68. 660 
1925 
679, 459 
1, 302, 442 
38 
52. 168 
59. 422 
1905 
4, 273, 212 
1, 033, 479 
31 
413. 478 
424. 986 
1926 
272, 170 
1, 171, 431 
33 
23. 234 
24. 999 
1906 
' 875, 782 
990, 361 
29 
88. 431 
90. 637 
1927 
392, 468 
1, 263, 574 
39 
31. 060 
36. 742 
1907 
512, 369 
976, 475 
28 
52. 471 
53. 652 
1928 
418, 199 
1, 121, 823 
32 
37. 279 
35. 085 
1908 _ 
907', 670 
824' 243 
23 
110. 122 
1929 
552, 836 
1,310,431 
42 
42. 187 
47. 686 
19C9 
4, 621, 094 
1, 095, 853 
31 
421. 689 
406. 717 
1930 
629, 889 
1, 195, 611 
36 
52. 683 
48. 720 
1910 
1, 058, 917 
1, 042, 569 
28 
101. 568 
98. 828 
1931 
298, 260 
1, 169, 332 
36 
25, 507 
23. 957 
1911 
657, 770 
1, 232, 865 
33 
53. 353 
56. 610 
1932 
338, 576 
743, 919 
21 
45. 513 
1912 
1. 082', 917 
1, 198', 760 
32 
90. 336 
86. 775 
1933 
753, 311 
1, 115, 144 
32 
67. 553 
1913 
5, 790, 820 
1, 226, 629 
35 
472. 092 
492. 264 
1934 
921, 829 
1, 076, 915 
33 
85. 599 
1915 
244, 628 
1, 342, 578 
40 
IS! 221 
20. 320 
Total. 
45, 110, 330 
1916.. 
487, 271 
1, 106, 225 
33 
44.048 
42. 167 
