780 
BULLETIN OF THE BUREAU OF FISHERIES 
therefore that so large a catch was made at so low a level of abundance, or that the 
abundance had declined an additional 47 percent by 1907. 
In 1907 only three-quarters as many traps and one-half as many gill nets were 
employed as in 1903. The catch of 1,700,000 doubtless permitted a larger escape- 
ment than in 1903. This is reflected by a slightly increased abundance in 1911. In 
1911 the number of traps remained about the same as in 1907 and the gill-net intensity 
was slightly lower, yet the yield was larger, being 2,200,000. 
According to the combined index of abundance there was a fall of 39 percent 
between 1911 and 1915, but this figure is undoubtedly too large. The trap index for 
1915 was the lowest of the whole 39 years, but that it was so low chiefly on account 
of the failure of the run to pass by the traps is shown by the gill-net catch. This 
was nearly twice that of 1911, or about what one would have expected if the number 
of sockeyes reaching the gill nets in 1915 had been somewhat comparable to the 
number reaching them in 1911, as the gill-net fishing effort was about twice that in 
1911. Since the number removed by the traps before reaching the gill nets was 
much greater in 1911 than in 1915 it is probably true that the 1915 level of abundance 
was slightly lower than that of 1911. 
Between 1915 and 1919 the abundance declined another 30 percent, according 
to the combined index, and probably more if the 1915 level were higher than shown. 
The spawning ground reports claim that in 1915 fewer sockeyes passed through Hell’s 
Gate to the spawning grounds of the upper Fraser than in any year since observations 
were started in 1901. On the other hand, the number spawning in the tributaries 
below the canyon, Lillooet Lake, Harrison Lake, Cultus Lake, Pitt Lake, etc., was 
estimated as being the largest for some years, even including 1913. Because of the 
failure of the traps to take many sockeyes, the total catch of 1915 was but 1,800,000. 
Considering the catch of 1915 in relation to the abundance, it does not appear 
to have been sufficiently large to have been the sole cause of the drop in 1919. Rather, 
it would appear that the extremely cold weather early in 1916, when the eggs deposited 
in 1915 were incubating (see table 35), had some part in it. The temperatures pre- 
vailing early in 1916 were even colder than in 1913. The reason for tnis second 
instance not showing as great a fall in abundance as in the first instance, when the 
temperatures were not quite as low, probably lies in the fact that in 1912 by far the 
larger portion of the spawning escapement went to the lakes above Hell’s Gate, in 
1915 most of the spawning was below Hell’s Gate where it would not be affected by 
the cold temperatures of the upper Fraser. 
This is borne out by the 1919 escapement estimates, which for the region below 
the canyon were as high as in 1915, whereas practically none were found above the 
canyon. The survey was more thorough than usual and the dearth of up-river fish 
was very marked. 
In 1923 the abundance level was about on a par with 1919. There were only 
two-thirds as many traps and slightly fewer gill nets than in 1919, resulting in a 
eaten of 850,000 compared to 1,250,000 in 1919. Since 1919 was able to bring back 
a comparable run in 1923 witn a larger catch it is not surprising that 1927 showed a 
much improved condition. 
