18 EEPOET OF THE COMMISSIONER OF FISHERIES. 



themselves on some of the banks and fishery grounds more adjacent 

 to our coasts, and it is not impossible that they are already present 

 obscurely. It will be highly important to recognize them promptly, 

 that corrective measures may be taken before conditions become so 

 critical as to require drastic action economically objectionable. For 

 these reasons compreliensive investigations of important fisher}- areas 

 north and east of Cape Cod were undertaken a number of years ago 

 and continued to the present time, with an interruption of several 

 years during the war. 



Tlie fundamental facts of the distribution of water temperatures, 

 and salinities, the horizontal and vertical circulation of the water, 

 the resulting production and distribution of the primary foods of 

 fishes, and the dissemination of their eggs and young have been 

 determined more accurately than on any other part of our Atlantic 

 coast. During the year the most important worl\«in this connection 

 has been the relt^ase of 1,500 drift bottles for current determina- 

 tions in cooperation with studies of like character conducted by the 

 Canadian Government in the home waters. Plans hav.> been laid 

 for supplementary work during the fiscal year 1924. Also, follow- 

 ing a project of cooperation with Canada, 2,396 cod, haddock, and 

 pollock were marked with metal tags and released, and the j)ractice 

 will be continued until a total of 10,000 fish has been so treated. 

 This experiment is to elucidate the facts of the migration, growth, 

 etc., of these important food fishes, and will h? supplemented by 

 other studies during the coming year that will develop the other 

 information necessary for the formulation of conservation measures, 

 which at any time may become necessary. 



A correlated investigation during the year was the study of th^ 

 seasonal changes of the plankton of the vicinity of Woods Hole, 

 based largely on the collections made by the bureau's laboratory at 

 that place over a long series of years. Plankton is composed of the 

 floating plants and animals, mostly minute, which constitute prac- 

 tically the sole food of most marine fish fry and direct^ or indi- 

 rectly the food of most of the adults. On it primarily depends the 

 fish production of the sea. 



During the year there was completed and submitted for publica- 

 tion a comprehensive report briefly describing all of the fishes known 

 to occur in the Gulf of Maine and epitomizing what is known of 

 their life histories. This work, and a large part of the other work 

 of the bureau in that region during the past 10 years, has been made 

 possible b.y the cooperation of the director of the Museum of Com- 

 parative Zoology at Cambridge, Mass., and Dr. H. B. Bigelow, of the 

 same institution. 



The field work of the investigation of the fisheries of Chesapeake 

 Bay was completed in June, 1922 : the collections and data have been 

 consigned to specialists, and considerable progress has bren made 

 toward a comprehensive report on the region. This investigation 

 repeats, in a more circumscribed area, the general features of that 

 conducted in the Gulf of Maine. The U. S. Coast and Geodetic 

 Survey, the U. S. Geological Survey, and the U. S. Weather Bureau 

 have all cooperated by furnishing valuable data respecting the hy- 

 drography and meteorology of the Chesapeake basin. 



