218 THE FISHERIES OF THE UNITED STATES. 



Ill Long Island sound it is considered tbat from the 5th to the 10th of July is the time -when shells should be 

 spread, with the design of immediately catching the spawn, which is not emitted to any extent before that date in 

 those northern waters. The method of making these artificial beds is described in the chapters relating to that 

 region. 



Seasonal vaeiations in abundance of spawn. — ^But the most intelligent care is not always rewarded 

 with a profitable catch, nor does every season bring a uniform addition of young to the natural growth on the 

 native reefs. This variability is all the more marked in regions where oysteriug has been extensively pursued, 

 and natural conditions and environment are disturbed. Nor are these variations widespread along a whole coast ; 

 they seem essentially local, confined, often, to very limited areas, indeed, and are marked by occasional seasons 

 of extraordinary fertility, followed by total blanks or only a partial " set". Thus the last highly productive 

 season in the Monument river, Massachusetts, was in 1S74 ; at Pocasset, Massachusetts, 1876 ; in the Somerset, 

 1877 ; yet all these localities are close together. This failure may not always be a failure to spawn, but generall3", 

 perhaps, a waste and loss of all or nearly all the young, through rough weather or an unclean condition of the 

 shores where they should have found resting places. Nevertheless, as Mr. Winslow observes, many i^ersons of 

 experience areof oinuion, and I now concur with them in thinking, that not only the attachment of young may not 

 be general nor occur each year, but that the emission of the products of generation may also be frequently confined 

 to partial areas, and that by a combination of circumstances there can be a total failure of impregnation on all 

 beds of any locality. Further, on this head, Mr. Winslow records some quotable observations, as follows, as 

 resulting from his Chesapeake studies : 



We have only been able to investigate the spatting of three seasons, and it may be found by subsequent observations, that two similar 

 seasons of success, moderate success, or failure, will follow each other, but so far this has not been the case, and in the period of three 

 years we have, comparatively to the other seasons, one at least of successful attachment. 



I can see no rfeason for supposing that there is any regular recurrence of the spattiug-seasons, but am inclined to beliere that the 

 success or failure is due to two causes — variations of temperature and vari.ations of density. I have no means of ascertaining either the 

 changes of temjierature or density in the years preceding those in which I have been engaged upon this investigation, and in both seasons 

 I arrived in the sounds too late for the temperatures or determiuations of density obtained by the ])arty to be of jiractical value. 



Oysters will and do live in very dissimilar temperatures, and in waters of very different densities, as is shown by their existence in 

 the -waters of North America, from Nova Scotia to the Gulf, and on both the Atlantic and Pacific coasts. That the mature oyster is a hardy 

 animal, readily adapting itself to new conditions and environment, is shown by the ease with which it is transplanted from the warm 

 ■waters of the Chesapeake to the colder ones of New England ; from the dense and salt waters of the ocean and bay to the brackish 

 waters of the creeks and rivers, or vice fersa, and from soft bottoms to hard or the reverse, but uatui-ally this hardiness is not a quality of 

 the immature oysters or the swimming embryos. 



The influence of increased or dimiuished temperature upon the formation of the ova and spermatozoa, mnst be very serious and very 

 considerable, and, judging by analogy, it would seem probable that the formation would be more rapid during a warm spring than during 

 a cold one. 



Whether the formation has been late or early, when once formed a sudden change of density or of temperature may so affect the 

 oyster or the generative matter, that the latter would not be expelled, and only upon this hypothesis can be explained the retention of 

 the products of geueration noticed in so many oysters, and which is said to be so common, for none of the other conditions are subject to 

 violent ch.anges, such being peculiar to the density and temperature alone. 



Probably the influence of changes of environment, especially of density and temperature of the water, is most severely felt by the 

 embryos when in their free swimming state, and, iu connection with the want of success of the spatting-seasons in the sounds, it is 

 noticed that the temperature curves show a maximum change about the time when it is supposed that the young would attach fti Largest 

 numbers, or about the period when they were swimming about in the water. It is also worthy of notice that Professor Brooks, about 

 this time, met with the maximum amount of success iu his etibrts to artificially raise the embryos. 



In consideration of the foregoing, I am of the opinion that the success or failure of any spatting-season is dependent upon the 

 equability of the temperature, and that the higher the temperature during the spring months, the earlier the advent of the spawning- 

 season, and that an increased temperature will also hasten the development of the spat, and of the young oysters after they have become 

 attached. I also infer that sudden and extensive changes of density will likewise affect the advent, duration, and success of the spawning, 

 though to a less extent. 



Subsequent to the attachment of the animal, changes of the condition surrounding it are not of so much importance, though 

 natur.ally such changes will more severely affect the delicate organism of the young oyster than that of the older and more hardened 

 adult. During the first six months of its existence, the oyster is exposed to the greatest danger from the numerous enemies which 

 surround it. The thin, delicate shells, from one-sixteenth of an inch to one inch in diameter, are readily bored by the drills or t(u-n off 

 by the crabs, and the immense numbers of both of thi'se, leave no room to doubt their destructive efl'ects. The inspection of the spat- 

 collectors iu the Big Annemessex river, shows that during the e.arly months of their existence about 50 per cent, of the young oysters are 

 destroyed, and futiu'e inspections of the hurdle will, I hope, give the rate of decrease in other periods of time. 



Naturally, as the animal progresses, it becomes more hardy and better able to resist the .attacks of enemies .and changes of 

 environment, .and thus we find on the uuworked beds, where the oysters .are pr;ictically in a natural st.ate, that the decrease in passing 

 from young growth to mature oysters is about 30 per cent., or about one-third of a given number perish in passing from the first to the 

 fourth year of their existence. 



Here <mr information ceases, but enough has been gafhcnd to indicate the proportion which nature has assigned as necessary 

 between the young and the luatnie oysters. For every l,U(Jt) of the latter there should lie 1,500 of the former, if the number of brood- 

 oysters uecess.ary to maintain t In^ f.M'.nndity of the bl^ds is to be kept up, anil though this jiropiu-tion is based upon (lula whii^i is not quite 

 siillicicnt, y.^t, as I liavt^ said, it is all that has been alfonli'd as yet, and may bi^ accepted within certain limits. Certainly, wh.atevcr it 

 should be, the number of the rising generation of the animals should never be less than that of the older, or there should always be as 

 many young as mature on any bed. A greatly increased proporl ion of young to in.atme oysters would show either one of the two things— 



that the 1 lality in passing from youth to nuitiiiity was minh greater than shown by the dredging results in the bay, or that a very 



large numUr ut nialnie oysters hail been unioved liy ollii-r than natural causes. 



Iu considering these several beds, the question of food and other necessary supplies has not been considered, as it is evident that 



