FLUCTUATIONS IN THE SUPPLY OF HERRING 
23 
CHANGES IN THE PURSE SEINES 
Besides these changes in the boats there have been some slight changes in the 
purse seines. From about 170 fathoms in length a few years ago the seines gradually 
increased in length and depth, especially on the larger boats until some were over 
200 fathoms in length. In 1926 (p. 18) a regulation was promulgated restricting 
seines to 180 fathoms in length and 1,230 meshes in depth. This decrease in length 
of a few of the larger seines is not of sufficient importance to be taken into considera- 
tion, but it may in the future serve as a restriction on the building of very large seine 
boats. 
EFFECT OF IMPOUNDING ON THE UNIT OF EFFORT 
The use of the purse-seine boat as a x 
of the fishery is somewhat invalidated by 1 
(described in a previous report, Rounse- 
fell, 1930, p. 231). For example the Pacific 
Fisherman for September, 1917, says that 
Alaska Herring & Sardine Co. at Little 
Port Walter reported enough herring im- 
pounded in the harbor to last them all 
season, and the Alaska-Pacific Herring Co. 
had approximately 12,000 barrels of her- 
ring impounded at Big Port Walter. (See 
fig. 6.) 
Since 1925 practically no impounding 
has been done in southeastern Alaska (ex- 
clusive of that for bait) except in Surprise 
Harbor. The change has probably been 
due largely to several causes — as the in- 
creased carrying capacity of the newer 
boats; the increase in the percentage of the 
catch taken in deeper water and around 
Cape Ommaney where impounding is im- 
practicable; and the increase in the num- 
bers of the fleet; which, taken together wii 
it highly inconvenient for each seine boat 
ut of fishing effort during the early years 
ie then prevailing practice of impounding 
Figure 8.— Showing the combined capacity of all herring re- 
duction plants (solid line), except the S. S. Peralta in 1927 and 
1928, and the number of purse-seine boats (dotted line), plotted 
on a logarithmic (proportional) scale so that the slopes of 
the two curves are comparable (see text) 
i the ever increasing cruising radius, make 
o have a towboat for impounding. 
CAPACITY OF THE HERRING PLANTS 
A knowledge of the variations in the capacity of the herring plants as determined 
by the sizes of herring needed and the quantity capable of being used is important 
to this study. Previous to the building of additional reduction plants in 1919, all 
of the herring companies (with the exception of Killisnoo) were limited in their use 
of herring to what they could salt or can. They fished only for herring of a size 
large enough to fulfill their requirements; consequently the catch per boat of this 
period would be in no way comparable to that of later years, even were one sure 
what type of gear was employed in every case. 
The total capacity in tons of raw fish per hour of all of the reduction plants 
(except the S. S. Peralta in 1927 and 1928) and the number of boats fishing each 
year are shown in Figure 8. The two curves have been plotted on a logarithmic 
scale to show the relative changes. It is obvious that the relation between boats 
