XXIV REPORT TO THE SECRETARY OF COMMERCE 
the natural reefs, and particularly as to whether or not dredging 
oysters on certain reefs would be harmful. Observations indicated 
that dredging north of the line extending from Alabamaport to Fish 
River not only would do no harm but would improve the condition of 
the reefs and increase their productiveness, provided the culling laws 
were observed. 
FISHERIES OF THE PACIFIC COAST AND ALASKA 
Besides successfully discharging the duties of protecting and 
administering the salmon fisheries of Alaska, based on present knowl- 
edge of the life histories and biology of the various species, the 
bureau is making rapid progress toward a more complete understand- 
ing of the factors that regulate the abundance of salmon from year 
to year and in checking the depletion. The salmon fisheries of 
Alaska depend upon five distinct species of wide distribution, each 
of which is represented by an independent, self-perpetuating colony 
in every stream that affords suitable conditions for its existence. 
Each colony is independent of all others, and, inasmuch as it secures 
no recruits from adjacent streams, its maintenance depends on an 
adequate spawning reserve to produce the eggs for succeeding genera- 
tions. The regulatory function of the Bureau of Fisheries, therefore, 
consists in adopting and enforcing regulations of the fisheries that 
will permit a sufficient number of adults to reach the spawning 
grounds of each salmon stream throughout the region. 
A program of investigation was adopted in 1921 with the purpose 
of discovering how large a spawning reserve is necessary, and this 
program has been followed assiduously and has been extended under 
the auspices of the Pacific Salmon Investigation Federation to in- 
clude the entire salmon fisheries on the Pacific coast. The essential 
part of the problem is to ascertain the complete returns from spawn- 
ing colonies of known size. The Karluk and Chignik Rivers have 
been selected because of favorable natural conditions in which to 
conduct the studies. Weirs have been constructed, and investigators 
have been stationed at them to make necessary observations, and it is 
confidently expected that a reliable basis for the prediction of the 
magnitude of future runs of salmon will be developed. A report on 
this subject has been prepared. 
In order to determine the migration routes of fish, extensive tagging 
experiments have been continued for several years. A report cover- 
ing these operations in Alaska in 1926 adds much to our knowledge 
of the routes of travel of the salmon from the sea to their spawning 
grounds and indicates the source of supply. Plans have been made 
for the spring and summer of 1927 to extend the tagging of salmon 
caught by trolling in the ocean. The work will be conducted by 
representatives of the bureau in Alaska and various State authorities 
along the coasts of Washington, Oregon, and California. Specific 
studies on Karluk Lake have been instituted to determine the reason 
for the unusually rich production of salmon in the Karluk River 
system. 
During the past 10 years the Bureau of Fisheries, in cooperation 
with the Oregon Fish Commission, has conducted marking experi- 
ments as a means of studying the life history of the salmon in the 
