XXXVIII REPORT OF THE COMMISSIONER OF FISHERIES 



servation were recommended. A thorough study of the biology of 

 the important commercial species is now being conducted with the 

 active cooperation of the State, and plans for regulating the fishery 

 are being developed. 



OYSTER INVESTIGATIONS 



The oyster industry of the Atlantic coast yields $14,000,000 worth 

 of products annually. In many ways this is the most important 

 fishery on the Atlantic coast. It is prosecuted in every coastal State 

 from Massachusetts to Texas, but in many localities it has declined 

 to an alarming extent, the total decrease in yield in the last 20 years 

 amounting to almost 60 per cent. While this decline may be due 

 mainly to overfishing, the progress of civilization and the indus- 

 trialization of rivers and harbors, with the attendant pollution, may 

 be looked upon as important, if not the most important, causes of the 

 decline. However, the oyster is so well adapted to cultivation that 

 relief from the present scarcity may be sought through perfected 

 methods of farming and regulated exploitation. 



Despite the fact that the oyster has been cultivated for hundreds 

 of years and is one of the best-known mollusks, there is a surprising 

 lack of exact information concerning its life history. These prob- 

 lems are being attacked in a systematic manner at the bureau's 

 Woods Hole laboratory, where careful experiments on the physi- 

 ology of feeding, growth, and reproduction are being conducted. 

 By means of specially constructed apparatus it was possible to 

 measure accurately the rate of flow and the volume of water passed 

 through the gills of the oyster. This was found to vary with the 

 temperature of the surrounding water, reaching a maximum at 

 77° F. and ceasing at 45° F., when the condition of hibernation is 

 said to exist. The feeding of the oyster was studied, and it was 

 found that over 99 per cent of the microscopic organisms carried 

 in by the current of water were consumed. Experiments on the 

 problems of sanitary control of oyster beds also were conducted, 

 and it was found that but very few of the bacteria in the water are 

 retained as food by the oyster. Lately, studies on the physiology of 

 spawning have been undertaken, with the view of determining the 

 concentration of adult oysters necessary to produce an abundant 

 set of spat. 



In addition to the laboratory studies, controlled field experiments 

 in the Long Island Sound region at Milford, Conn., have been car- 

 ried on. Studies in spat collection resulted in the devolopment of a 

 particularly successful type of collector, which it is believed will in- 

 crease the total yield of seed oysters that can be produced upon a 

 given area. The factors affecting the set of spat, such as current, 

 depth, and character of surface, as well as the habits of the larvae 

 were studied carefully. The discovery of an entirely unknown habit 

 of the young larvae to settle upon and burrow in the bottom enables us 

 better to understand the relation between spawning beds and setting 

 areas and the effect of tides, waves, and currents upon distribution. 

 Extensive studies made in previous years resulted in the perfection 

 of methods of hatching and rearing oysters in tanks and troughs. 

 While this method of propagation is entirely feasible, more recent 

 studies have indicated that the greatest return in the Long Island 



