SALMON AND SALMON FISHERIES OF SWIFTSURE BANK 
769 
The index would appear to be extremely reliable for trap-caught sockeyes, as, 
during the period from 1896-1934 the 43 traps caught 45 million sockeyes while 
the total trap catch since the beginning of the fishery totals but 94 million. During 
the past 20 years, when complete figures for trap catches are available, our sample 
comprised as high as 82 percent of the trap catch in 1924, and fell only as low as 54 
percent, in 1915 and 1917. 
The index (table 32 and fig. 24) shows a marked decline in abundance in all four 
age cycles, comparing favorably with the average catch per unit of gill net effort, 
except in a few years. In 
1897 the abundance shown 
by the trap index is decid- 
edly lower than that shown 
by the gill net averages, 
but a large part of this 
discrepancy may be due to 
the fact that a great many 
of the traps were driven 
for the first time in 1897 
and so had not yet been 
efficiently located. The de- 
tails of the levels of abun- 
dance shown will be dis- 
cussed under the various 
cycles. 
PURSE SEINES 
1897 1901 1905 1909 1913 1917 (921 1925 1929 1933 
Figube 24— Sockeye index of abundance calculated from the catches of Puget Sound 
traps for the 39-year period from 1896-1934. A decrease in abundance has occurred 
in all cycles. 
In the 26 years since 
1909 when purse seines be- 
came an important factor 
in the sockeye fishery, their catch has exceeded that of the traps in only 3 years: 1930, 
1931, and 1934. Their success in 1930 was due to the heavy schooling, especially at 
Point Roberts, of the abundant late run which, massed in the shallows off the river 
mouth, were easily seined. The 1931 catch exceeded that of the traps because the 
seines had their second most successful season on Swiftsure Bank. In 1934 the purse 
seiners were prepared for a repetition of the abundant late run of 1930 and, although 
they did not do as well in the inside waters, they caught over three times as many 
sockeyes on Swiftsure Bank as in any previous season. In 7 of the 26 years their 
catch in both inside and offshore waters totaled less than 150,000 sockeyes per year. 
Six of these were even-numbered years when no pink salmon were running. The 
seiners fished during the early season for cohos in the offshore waters, and during the 
late season for both cohos and chums in the inside waters. 
