2 U. S. BUREAU OF FISHERIES. 



facts pertaining to the fisheries, which are discovered through scien- 

 tific investigation, are essential for the reason that adequate measures 

 of conservation must be based on a knowledge of the biology of the 

 fish. The actual administration of measures of conservation, how- 

 ever, devolves upon other governmental and State agencies, and it is 

 these agencies that directly perform the very necessary service of 

 conserving the various fishery resources. Without scientific investi- 

 gation, however, this direct service could not be properly conducted. 



The utilization of the fishery resources of the United States has 

 gradually increased since the Colonies were first established, and the 

 past decade or two has witnessed a remarkable growth in many of 

 our fishery industries. Certain fishery resources have shown more 

 or less marked signs of depletion for years; more of these resources 

 are showing evidences of depletion each j^ear ; and, with the increased 

 exploitation, which we can observe and which will in all probability 

 continue, we can only look forward to the depletion of resources at 

 present apparently unaffected and to the more serious affection of 

 those already showing evidences of depletion. Such exhaustion does 

 not necessarily become obvious to everyone while the process is going 

 on, and it is only through careful scientific investigation that it may 

 be determined before it has reached a dangerous stage. The work to 

 be done is of a distinctly practical nature, but must be interpreted 

 and conducted by means of biological and oceanographical knowl- 

 edge. Such investigations were never so essential to the preservation 

 of our fishery resources as they are to-day. 



The depletion of a fishery resource is not always the result of 

 overfishing, although this usually is an important factor and in some 

 instances apparently is the only one. Other factors of greater or 

 less importance are the pollution of coastal and inland waters and 

 the obstruction of streams by dams or other similar structures. 

 Without regulation it is to be expected that the amount of pollution 

 and the number of dams will tend to increase along with our in- 

 creasing population and industrialization. Efforts to combat the 

 various factors tending to deplete a fishery resource have been 

 confined mainly to artificial propagation and to various legal re- 

 strictions affecting the seasons in which, and the means whereby, 

 the fish may be taken, the discharge or treatment of pollutants, and 

 the construction of fishways over dams or of screens in irrigation 

 ditches. 



It is the primary function, of the division of scientific inquiry to 

 determine, if possible, when depletion is taking place — or, still bet- 

 ter, to determine when the condition of a fishery resource is such that 

 depletion is likely to occur — and then to devise and propose means 

 whereby such depletion may be prevented. Both of these are biologi- 

 cal problems and, to be adequately solved, require a reasonably com- 

 plete knowledge of the biology of the species in question. The more 

 complete our biological information, the more perfect can be made 

 the work of artificial propagation, and the better may the legal 

 regulations be adjusted to the normal life of the various species of 

 fishes so as to permit of the fullest possible exploitation of the re- 

 source without endangering the continuation of the supply. 



It is with these things in mind that the scientific activities of the 

 bureau are being directed more and more into studies pertaining to 

 the biology, or life history, of the various fish and shellfish of com- 



