20 THE OYSTER AND THE OYSTER INDUSTRY. 



also eaten. The recent work of Dr. T. C. Nelson "■ shows that a 

 larger proportion of the oyster's food is of this nature than was 

 formerly supposed. Copepods, or ' 'water-fleas," the free-swimming 

 larvse of snails and bivalves (including the oyster), worms, rotifers, 

 and protozoa have been found in the stomach of the oyster. These 

 animals, like the plants, are found in greater or less abundance in 

 all w^aters. A systematic effort to ascertain the food content avail- 

 able for oysters in any particular Avater should include the determi- 

 nation of the quantities of the suitable animal as w^ell as plant forms 

 present. 



Dr. Nelson kept under observation a number of oysters in water 

 shallow enough for a system of wires and levers to be connected 

 with the shells in such a way that the opening and closing of the 

 valves were recorded on a revolving smoked drum or cliimograph 

 in the floating laboratory above. It was found that, during the 

 summer months at least, the 03^sters remained open, and conse- 

 quently feeding, for 19 to 20 hours out of 24. Feeding is thus evi- 

 dently a fairly continuous process during the warmer months. 



Organic detritus or debris resulting from the decay and disintegra- 

 tion of plant and anunal life undoubtedly contributes to the food 

 of the oyster. As the diatoms and other plant forms become broken 

 up some of their fragments are ingested by the oyster, and a certain 

 amount of nutriment is derived therefrom. After death, animal 

 forms disintegrate and release fats, albumens, etc., into the water. 

 It has been found that the fresh-water mussel may make use of 

 such products, and probably the same is true in the case of the 



oyster. 



NATURAL BEDS. f> 



DEVELOPMENT AND DESCRIPTION. 



A natural oyster bed is an area of the bottom on which oysters 

 have become established without the voluntary and intentional 

 agency of man. In law, the term is usually held to include only 

 such bottoms as bear oysters in sufficient quantities to make fishing 

 for them by legitimate methods a means of reasonable livelihood 

 or areas which have formerly been such and whose present char- 

 acter indicates a reasonable likelihood that they may again become 

 productive. The only difference between natural and artificial 

 beds lies in the fact that the latter originate by the intentional act 

 of man, whereas the former arise from natural conditions purely, 

 from accident, or from unintentional human agency incidental to 

 other works and purposes. In most cases the natural beds, and 

 especially the larger ones, have been produced by the operation of 

 factors in which man has no part, and we know nothing of their 

 origin. In a few instances, small beds have been caused by ship- 

 wrecks and other accidents; but on the other hand there are many 

 beds, some of them very productive, which have grown on ashes 

 and similar material thrown overboard from vessels and upon shells 

 culled from the live oysters by oj^stermen and strewn at random 

 over the bottom. Whatever their origins, all oyster beds, if left to 



a Nelson, T. C. Forthcoming report, N. J. Agricultural College Experiment Station. 

 6 Moore, H. F. Proposed revision of " Oysters and Methods of Oyster Culture" (1897). 



