4 o THE POPULAR SCIENCE MONTHLY. 



184,000,000 oysters ; and by the estimate of 1879, over 89,000,000 oys- 

 ters. The number of young growth removed would be, by the first 

 estimate, 148,000,000 ; by the second, 36,000,000. The statistics col- 

 lected 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 varia- 

 tions 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 addi- 

 tion 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 oys- 

 ters 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 



