SALMON AND SALMON FISHERIES OF SWIFTSURE BANK 
815 
For the district north of Deception Pass, data were analyzed for seven traps 
catching 124,831 fish from 1902-34. For the district south of Admiralty Head, the 
six tiaps used caught 821,263 chums from 1900-1934. 
In the northern district the run really commences about the middle of September 
and reaches its peak by October 10. In the southern district there is a small early 
run in late August and early September, but the main run does not really start until 
nearly the end of September, and the peak is not reached until October 24, just 2 weeks 
later than the northern run. 
Because of the difference in time of run in the 2 districts, only a small fraction of 
the northern chums are protected by the closed season commencing November 11. 
This same closing date, however, protects about 20 percent of the southern run. 
ABUNDANCE FROM ADMIRALTY INLET TRAPS 
For the chum-trap index, 8 Admiralty Inlet traps were employed, 3 each from 
the Admiralty Bay and Bush Point areas, and 1 each from the Oak Bay and Point 
No Point areas. The total catch of each trap up to and including November 3 was 
used, as this period normally includes 70 percent of the southern run and it was not 
feasible to use a longer period as many of the traps ceased fishing by that date. In 
1934, 1921, and 1920 they all closed too early to be usable. The index was calculated 
in the same manner as that described for sockeyes. Three traps, over a 19-year 
period, were used for the standard curve. 
Because a small number of traps were used, and only a portion of the run occurred 
during the period they fished, the index is not especially reliable for any particular year. 
However, it does show that the chums of the southern district were very abundant at 
one time. In the last 12 years they were less than half as abundant as during the 
period just previous to the war (see table 57). 
ABUNDANCE FROM PURSE SEINES 
An estimate of the abundance of chums was made from the Puget Sound seine 
catches. The average catch per weighted delivery, each delivery was weighted by the 
efficiency weight given in the purse-seine section of this report, was first obtained for a 
6-week period from September 23-November 3. From 1910-34 data were available 
for 25,838 deliveries containing 5,322,546 chums. 
The first 2 weeks of the 6-week period chosen represented a large number of 
catches but only a few chums, the run having not yet attained any proportions. The 
efforts of the fleet up to this time had been almost wholly directed toward the capture 
of cohos. For this reason the average delivery was also obtained for a 4-week period 
from October 7-November 3, which, over the 25 years, represented 19,584 catches 
and 4,973,971 fisb (see table 58). 
The average catch per delivery obtained from the purse seine data appears to 
reflect economic factors as well as abundance. Thus 11 out of 12 of the even-num- 
bered years are higher than the year preceding them, whereas 8 out of 12 of the odd- 
numbered years are lower than the preceding year. Since the chums vary from 3-5 
years in age at maturity, there is no apparent biological reason for a higher level of 
abundance in the even years. 
