82 REPORT OF THE COMMISSIONER OF FISHERIES. 



a method of artificially producing these fattening beds in localities 

 where they do not naturally exist. 



A bight of Lynnhaven Bay, embracing a water area of 2.6 acres 

 and an average depth of about 2 feet, has been cut off from the open 

 waters of the bay by a dam, excluding all but the highest storm tides. 



The food of the oyster consists mainly of microscopic plants, of much 

 beauty of form and color and remarkable motility, known as diatoms. 

 These, like the higher plants, are dependent for their growth or mul- 

 tiplication upon the supply of inorganic salts in the water. Ordinarily 

 this is obtained by the natural drainage from the land, and consequently 

 oyster food is generally more abundant in the neighborhood of the 

 mouths of streams having rich and extensive drainage basins. Warmth 

 during at least a part of the year is also an important factor in the 

 multiplication of diatoms, and consequently shallow waters, rather 

 than deep ones, are usually better for fattening beds, other conditions 

 being equal. Under the system in vogue in France shallow ponds 

 apparently of themselves satisfy the conditions, but this was not the 

 case at Lynnhaven, There was evidently a dearth of useful saline 

 constituents in the water, and to supply this commercial fertilizers 

 were introduced. The result was prompt, and there was an almost 

 immediate increase of diatomaceous growth in the pond. 



This abundance of food having been secured, oysters were placed 

 in various parts of the pond, but the results were mainly negative, and 

 a study of the conditions indicated that this, in a measure at least, was 

 due to the absence of currents to waft the food within reach of the 

 sessile oj^sters. In the following year a remedy was found. At one 

 side of the pond, or claire, a canal 150 feet long and about 8 feet wide 

 was constructed of sheet piling. A circulation of water through this 

 canal, and returning via the open waters of the pond, was secured by 

 the use of a propeller operated by means of a gas engine, thus simu- 

 lating the conditions supplied on the natural beds by tidal movements. 

 The result of this arrangement was very satisfactory, and oysters 

 placed in the canal were fattened, in some cases within a period of 

 eight days, much improving their value on the market. 



New difficulties were encountered, however, and to the present time 

 these have not been removed. There developed at times in the fat- 

 tened oysters a decidedly marshy taste, which was eventually traced 

 to an abundant growth of filamentous algoB in certain portions of the 

 claire. The same saline richness of the water which proved so favor- 

 able for the diatoms was equally favorable, to the growth of other 

 vegetable matter. It was found that a limited application of lime 

 water retarded or destroyed the algal groAvth, but it was necessary to 

 exercise constant watchfulness and frequently the affection would 

 develop suddenly and stop the shipment of oysters at a time when 

 they were bringing the best prices. During the present year it was 



