VI REPORT OF THE COMMISSIONER OF FISHERIES 



region was continued. Closely cocndinated with this work has been 

 an investioation of the minute animals and })lants, collectively known 

 as plankton, which are found everywhere, but in varyino- abundance, 

 in the sea water. Larval fish feed exclusiveh' on these planktonic 

 forms, and the larger fishes and other aquatic animals depend either 

 directly or indirectly on the plankton for their nourishment. A 

 study of the food and feeding habits of the larval fish was begun 

 during the latter part of the fiscal year. This investigation will be 

 extended to include a study of the young fish during the postlarval 

 stages, between the larval stages and the time the fish first appear in 

 the commercial catch. In these investigations special attention is^ 

 being given to the cod, and Avhen completed this study of the earlj?^ 

 history of the cod will supplement the study of the migrations and 

 growth of the adult and provide a fairly complete life history of 

 the species. 



The abundance and distribution of the plankton on which all other 

 animal life in the sea depends are profoundly influenced by such 

 physical and chemical factors as currents and the temperature and 

 salinity of the sea water. The study of these factors constitutes the 

 science of oceanography, and oceanographic studies are of the great- 

 est importance if we are to understand fully the fluctuations in 

 abundance of our food fishes. Slight changes in temperature or 

 shifts in the oceanic currents may cau.se extensive migrations, or may 

 spell destruction to an entire brood of young fish. During the year 

 oceanographic studies haA'e been made in the region of Woods Hole, 

 Long Island Sound, Chesapeake Bay, and the Gulf of Maine. In 

 each case special attention has been given to the bearing of the 

 oceanographic data upon fishery problems. 



During the past year a report on the fisheries of Key West, Fla., 

 was prepared and published as Bureau of Fisheries Document Xo. 

 962. It describes the various fisheries of the Florida Keys and in- 

 cludes a detailed account of the clam industry of southwest Florida. 

 An annotated list is given of all the known conmiercial food fishes 

 of the region, a total of 83 species. 



The study of the salmon, trout, and smelts of the New England 

 coast has been continued throughout the year, and has yielded addi- 

 tional data bearing on the biology of these species. 



For a number of years ]:)ast the bureau has enjoyed the association 

 of Dr. H. B. Bigelow. of the ^fuseum of Comparative Zoology, Har- 

 vard I'niversity. Recently he has been concerned Avith a com])lete 

 ()ceanogra])hic and biological survey of the (xulf of Maine, a body 

 of water that supj^orts some of our most valuable fisheries. A report 

 dealing with the fishes of this region is now in press. It includes a 

 complete account of the distribution of the fish and as much as is 

 now Icnown of their life histories. Another report, dealing Avith the 

 plankton, is in an advanced stage of ])rei)aration, and progress has 

 been made Avith the ])rei)aration of a paper dealing Avith the ocean- 

 ography of the Oulf of ]\raine. When completed these three i-epoi*ts 

 AA'ill })rovide a com])rehensive survey of what is at pi-esent kjiown of 

 the |)hysical and biolo<rical factors influencing the distribution and 

 abmidance of the food fishes of this region, and will form a con- 

 tribution of first importance to our knoAvledge of the fisheries. 



A comprehensive hydrographic and biological survey of Chesa- 

 peake Bay Avas undertaken several years ago and field observations 



