Page:Popular Science Monthly Volume 20.djvu/50

40 184,000,000 oysters; and by the estimate of 1879, over 89,000,000 oysters. The number of young growth removed would be, by the first estimate, 148,000,000; by the second, 36,000,000. The statistics collected in 1879, when compared with those collected in 1878, show that there were twice as many vessels at work in 1878 as in 1879, which accounts to a great extent for the difference of 95,000,000 mature oysters, as shown by the estimates for each season. The difference in the yield of young growth is due to the fact that, owing to the variations in temperature during the spawning-season, the summer of 1879 was a bad one for the "spat," and consequently there was a failure of "young."

So far as can be at present ascertained, the mortality among the young after attachment is about fifty per cent., and consequently only about 74,400,000 of the young removed in 1878-79 would have attained an age of one year, and perhaps the number would not reach even that figure. If none of the oysters had been removed from the beds during the dredging-season of 1878-'79, we would have had, when the last season's investigation was in progress, about 259,000,000 more oysters on the beds than was actually the case, and of that number seventy-one per cent, were mature and spawn-bearing. Now, as sixty-five per cent, of those in the beds are mature, the addition of the 250,000,000 would increase the percentage to sixty-eight, or the young growth would be in a more hopeless minority than before.

To prove more conclusively the effect of the fishery upon the ratio of young to mature oysters, I will take as examples the condition of two of the largest beds in Tangier Sound, where the number of young growth was much in excess of the number of mature oysters. The beds are known as the "Great Rock" and "Woman's Marsh." On the former the ratio of young growth to mature oysters was as three to one, or twenty-four per cent, were mature; on the latter the ratio was as one and seventy-four hundredths to one, or thirty-six per cent, were mature. By consulting the statistics collected, I find that of the oysters removed from the Great Rock in one year, sixty-four per cent, were mature, and of those removed from the Woman's Marsh sixty-nine per cent, were of the same class. If these oysters had not been removed, we would have on the Great Rock forty-four per cent, of the community mature, or the ratio of young growth to mature oysters would be as one and one tenth to one; and on the Woman's Marsh the percentage would be fifty-two instead of thirty-six, and the ratio would be as nine tenths to one. It is evident from the foregoing that a very large ratio of young growth to mature oysters is not an indication of an increased production, but, as explained, is due to the removal of too large a number of brood-oysters.

We have, then, three indications of the deterioration of the beds: the number of young is either much smaller or larger than the number