PKOGRESS IN BIOI^OGICAL INQUIRIES, 1923. 3 



mercial importance. In years past the bureau has sponsored much 

 scientific work of the highest order but not bearing directly upon 

 problems connected with the conservation of our important fisheries. 

 Vahiable as this worlv in " pure science " is, it is felt at. the present 

 time, and in view of the limited funds available, that precedence must 

 be given to investigations relating to fishes of economic importance. 

 Happily, these practical investigations yield a considerable measure 

 of results of interest and value from the viewpoint of " pure science," 

 just as research in " pure science" has so frequently an ultimate, 

 though often unexpected, practical application. 



The general plans for the scientific investigation of our fisheries 

 are being made on as broad a foundation as possible. The funda- 

 mental problem is to determine the factors affecting the abundance 

 of any given species. One of the most important of these factors 

 obviously is the abundance of food. The food of all fish and shell- 

 fish is, either directly or indirectly, those minute forms of animals 

 and plants found floating in both fresh and salt waters and collec- 

 tively known as plankton. The abundance of plankton, however, is 

 directly determined by various physical factors, such as tempera- 

 ture, light, salinity, etc., and in the ocean the abundance of both 

 fish and plankton in any given locality is dependent in great measure 

 upon the oceanic currents in which drift the plankton and the eggs 

 and young of many fishes. It is evident that the abundance of fish 

 is determined to a considerable extent by various physical factors 

 acting, in part indirectly, through the medium of the plankton. A 

 comprehensive plan for the biological investigation of the fisheries 

 must therefore include a study of these physical conditions, a study 

 of the plankton, and finally a study of the fish and fisheries them- 

 selves. By this means we may hope eventually to understand the 

 ultimate and proximal causes of fluctuations in the abundance of any 

 given species, and this is the end of practical importance for which 

 economic fishery investigations should be designed. All of these 

 lines of inquiry are being given consideration, although emphasis 

 is naturally placed on those investigations dealing most immediately 

 with the fishes. 



During the past year many important investigations heretofore 

 begun were continued and some new ones were inaugurated. Out- 

 lines of the various studies that have been conducted will be found 

 in the following pages. 



The division has suffered a serious loss through the resignation 

 of Dr. R. E. Coker, who had been in charge of the division since 

 1915. Doctor Coker had been connected with the bureau since 1902 

 and was thoroughly familiar with the various problems pertaining 

 to the fisheries. The administration of the division has been aided 

 greatly during the year by the advice and help that he has freely 

 given. 



INVESTIGATIONS OF FISH AND FISHERIES. 



ATLANTIC COAST, 



FISHES OF THE GTLF OF MAINE. 



For a number of years the bureau, in cooperation with the Museum 

 of Comparative Zoology of Harvard University, has been conduct- 

 ing an oceanographic and biological survey of the Gulf of Maine. 



