REPORT OF THE COMMISSIONER OF FISHERIES. 9 
SURVEYS OF PARTICULAR WATERS. 
For the proper conservation of fishery resources and for gauging 
the necessity for and results of fish-cultural work it is important to 
have the most complete knowledge of the natural conditions in waters 
where fish propagate, grow, appear, and disappear under the con- 
trol of factors now but little understood. During the past year 
such general investigations and surveys have been conducted both in 
the North Atlantic Ocean and in Chesapeake Bay—two of the most 
important sources of fish food and the locations of some of our 
principal fisheries. A comprehensive report embodying the results 
of observations gathered during a number of preceding years in the 
Gulf of Maine is now in preparation, special consideration being 
given to the life histories of the useful fishes and the conditions 
governing their distribution. In Chesapeake Bay the field work of 
the general survey has been completed, and it remains to compile and 
report upon the large mass of data accumulated. The special field 
studies of the occurrence and distribution of fish in the bay and 
tributary waters is being actively prosecuted. Other studies of a gen- 
eral nature have been conducted at relatively small expense in certain 
interior lakes, in cooperation with the Wisconsin Geological and 
Natural History Survey, and in the Mississippi River as a part of 
the work of the biological station at Fairport. 
An event of interest and promise was the formation during the 
year of an international committee on marine fishery investigations 
composed of three representatives from Canada, one from New- 
foundland, and three from the United States. The function of this 
committee is not to engage in joint work, but to serve as a ready 
means of effecting interchange of counsel, coordination of plans, and 
harmony in methods of marine investigations. 
AID TO THE SHELLFISH INDUSTRIES. 
The Bureau is rendering every practicable service to the oyster 
growers in the difficult circumstances which confront them in certain 
regions because of the failure of natural seeding. The conditions 
during the season of 1920 were very unfavorable to experimentation, 
and the work was further hampered by the loss in course of the 
season of the assistant charged with major responsibility for the 
investigations. The natural conditions in the beginning of the 
season of 1921 seemed favorable for experimental work, and the 
Bureau was able, as the results of the methods of study worked out 
and followed during preceding years, to render direct service to 
planters in the waters where investigations were being conducted. 
Progress has been made in the investigations to determine the effect 
of pollutions upon oyster propagation, both through direct action on 
the larve and through impairment of the vitality of oyster larve 
or of the fertility of breeding oysters by exhaustion of oxygen supply 
in the water. 
Investigations of previous years had opened the way for artificial 
propagation on a commercial scale of fresh-water mussels, on which 
a very important button industry depends. The nature and extent 
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