DETERIORATION OF AMERICAN OYSTER-BEDS. 33 



bed, a new factor must be brought into operation, when, all condi- 

 tions being changed, the life of the animals begins anew and progresses 

 differently. 



As already stated, the character of both beds and oysters in the 

 locality under consideration has undergone great changes during the 

 last thirty years, and the causes for those changes must be sought 

 among such as it is known would produce like effects. Disregarding 

 for the present the agency of man in the matter, the question is, What 

 natural cause or causes would both expand the beds and diminish the 

 number of oysters ? 



A" bed is extended, naturally, by the drifting " spat " or young 

 brood attaching themselves to any appropriate "cultch" contiguous to 

 the bed. This manner of extending the area is much assisted by the 

 current, and consequently natural extension is greatest in the direction 

 of the currents. The principal expansion of the beds, so far as could be 

 effected by Nature, must, however, have been accomplished long ago, 

 for as far back as can be remembered the beds have been surrounded 

 by soft bottoms of a character most destructive to the young brood. 

 Unless, then, some substance is interposed between this soft bottom 

 and the drifting "spat," they will sink into it and be destroyed. 

 Nature has no means of offering such a substance except to a very 

 small extent, and consequently the great expansion of the beds could 

 not have been the result of natural causes, but must be assigned to 

 other agents. 



The diminution of the number of oysters might have been effected 

 by several natural causes. An increased deposit of earthy or vegetable 

 matter upon the beds would, if in sufficient quantities to bury the 

 oyster, effect the destruction of old and young. No such deposit has 

 been noticed, nor could it well occur without showing its presence in 

 other ways, principally by changing the channels and causing shoals, 

 but no such changes have 'occurred ; the deviations in channels, shoals, 

 and character of bottom, from those established by the first hydro- 

 graphic survey of the locality, being very slight indeed. 



A change in the character of the water and bottom which would 

 probably follow a change of channel, and possibly occur without such 

 change, might, by depriving the animals of their proper food, cause 

 their deterioration and destruction ; but such a change, though it 

 would certainly diminish the number of oysters, would do so suddenly, 

 and the evil effects would be noticed in the oysters remaining, their 

 quality, flavor, and vitality being very much impaired. No such im- 

 pairment has been observed, however, the animals being at present 

 much larger and finer than when the beds were first discovered. 



That fact alone will eliminate many quantities from the equation, 

 for any natural cause injurious to all the oysters on a bed would show 

 its effects upon those remaining, and an examination of a few speci- 

 mens would be sufficient to determine the question. If, however, the 



TOL. XX.' 3 



