Page:Popular Science Monthly Volume 20.djvu/45

Rh together with all oysters unfit for market, thrown back into the water. The limits of the dredging-grounds are not accurately defined, and the vessels frequently drag large numbers of shells and oysters some distance beyond the boundary of the beds. The dredge, especially when full, acts as a scrape, and carries before it much that would be collected in the network attached to it, had that receptacle been open. After "culling" the oysters, or separating them from the old shells, those shells are thrown back again and with them many young oysters. Should they fall on suitable ground, and any which is sufficiently consistent to support them is suitable, they form a small colony which, by action of natural causes, or the dredges, soon becomes attached to the main bed and the area of the latter is thus enlarged. The exposure of suitable "cultch" on bottoms contiguous to the bed is effected by the dredges in the above manner, and they are thus mainly instrumental in extending the area, especially by their direct action in raking down the bed and spreading the shells and oysters. Will the dredging also account for the diminution of the oysters?

Without, for the present, going into the question of propagation, which will be subsequently discussed, it may be stated here that both male and female of the American variety of oyster expel the generative matter into the water, where the eggs must meet the male fluid in order to be fertilized. That being the case, it is evident that the more compact the bed, the more closely settled the community of oysters, the greater the chance the ova and spermatozoa have of coming in contact; or the chance of fertilization of the eggs is inversely proportional to the distance separating the oysters. Hence, should the mature, spawn-bearing oysters on any bed become very much diminished in number or widely separated from each other, there would be but a slight chance of contact of ova and spermatozoa, and a consequent failure of reproduction. Should the bed be so situated that the currents passing over it did not also pass over other more plentifully stocked beds, it would receive no outside support, and the mutual assistance generally rendered would not be obtained. This is the case with one of the largest beds in Pocomoke Sound, and, as would be inferred, the most extensive deterioration was noticed on that bed.

The removal of mature brood-oysters would, then, cause a diminished fecundity, and, should this removal continue, the fecundity will naturally diminish, until there is virtually no reproduction on the bed. But the removal of brood-oysters is not the sum total, by any means, of the effects of the dredging. Millions of young oysters, unfit for market, are carried off sticking to the shells of the mature oysters, and with those shells find a final resting-place on the shell-heaps of the packing-houses. Nearly as many young are destroyed by being thrown from the dredging-vessels upon soft or unfavorable bottoms, no care being exercised, in the hurry and press of work, to see that the young are returned to the beds or other suitable ground.