REPORT OF THE COMMISSIONER OF FISHERIES. y 



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 fisherias. A comprehensive report embodying the results 

 of observations gathered during a number of preceding j-ears 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 

 harmon}' in methods of marine investigations. 



AID TO THE SHELLFISH INDUSTRIES. 



The Bureau is rendering every practicable service to the oyster 

 growers in the difficult cirfumstaiicos which confront them in certain 

 regions because of the failure of natural seeding. The conditions 

 during the season of 1920 were very unfavorable ?o experimentation, 

 and the work was further hampered by the loss in course of the 

 season of the assistant charged with major responsibility for tlie 

 investigations. The natural conditions in the beginning of the 

 season of 1021 .seemed favoial)le 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 



filanters in the waters where investigations were bein<j^ conducted. 

 *rogress has been made in the investigations to determine the effect 

 of pollutions upon oyster propagation, both through direct action on 

 the larvsn and through impairment of the vitality of oyster larvae 

 or of the fertility of breeding oysters by exhaustion of oxygen supply 

 in the water. 



Invcslif^ations of previous years had opened the way for artificial 

 propagation f)n a commercial sf^ale of fresh-water mussels, on which 

 a very important button industry depends. The nature and extent 

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