Popular Science Monthly/Volume 20/November 1881/Deterioration of American Oyster-Beds I
By Lieutenant FRANCIS WINSLOW.
A WRITER in a recent number of "Lippincott's Magazine" has called attention to the failure of the oyster-beds of the New England and Middle States, to the deterioration of those lying in Southern waters, and to the necessity for some effort, either upon the part of the national or State Governments or by individuals, to maintain the supply of oysters in sufficient numbers to satisfy the large and increasing demand of the consumers. This very desirable end, it is suggested, can be obtained by a system of oyster-culture similar to that adopted by the French Government and by various foreign oyster companies. The author's statements of facts, especially those relating to the foreign fisheries, are both interesting and in accordance with what is known by those interested in and possessing knowledge of the history of the oyster-fishery, either in the United States or abroad. The inferences drawn from the statistics collected can be accepted as just, inasmuch as they relate to the destruction or deterioration of the American beds; but that they logically lead to a belief that oyster-culture in the United States, if conducted as in France, can either supply the demand or be financially successful, is open to serious question.
There is no doubt, as stated in the article at present under review, that the natural beds of the North are practically exhausted; neither is there any doubt of the greatly diminished production of the Southern beds—that is, those of Maryland and Virginia. That the area of the latter has decreased is, however, improbable, the estimates of Governor Wise and of the officers of the "Merchants' and Mechanics' Exchange," of Norfolk, to the contrary, notwithstanding. Why the reduction of the area of the beds is considered improbable will be shown subsequently. The writer states various reasons for his belief in the early failure of the oyster-supply, none of which are sufficiently plausible to justify his assertion, unless supported by other facts of which he has made no mention. For instance, though the increased price of oysters may be, as he states, an indication of a diminished supply, yet an increase of the demand would have the same effect. Similarly with regard to the laws relating to the use of dredges and scrapes: the beds might be in their normal state, yet the increased demand or knowledge of the inhabitants of the fore-shores might call for protection of the beds. The action of natural enemies and of natural causes, also mentioned in the article in question, may be neglected. Such causes existed in the past as well as in the present, and yet the beds increased and multiplied as they have done nowhere else in the world.
"But the primary cause of the threatened destruction of this industry," says the author of Lippincott's article, "is the failure to cultivate the oyster." It would have been better had he said "the failure to protect the oyster-beds." Oyster-culture is one thing, no doubt an admirable one, but an expensive, laborious undertaking of doubtful financial success. Oyster protection is a matter easily achieved, with but small expenditure of money, and with but little distress to those depending upon the fishery for support.
It is presumable that our author was not aware of the contributions to the literature relating to oysters and oyster-beds, contained in the "Report of the Commissioners of Fisheries of Maryland," for 1880. Had he examined that report, he would have found matter which would more directly have supported his opinion regarding the deterioration of the Southern oyster-beds, and have suggested to him means of restocking the impoverished areas, other than by the expensive and laborious methods detailed in his paper. The tentative steps taken toward the latter end, by successfully propagating the oyster artificially, are detailed by Dr. Brooks, of the Johns Hopkins University, in the abovementioned report, and the general condition of certain areas covered by oysters are described in extracts from official reports made by myself to the Superintendent of the Coast and Geodetic Survey. It is from those reports, the paper of Dr. Brooks, and the various works relating to oysters and oyster-culture here and abroad, that the material for this report is drawn.
While few will dispute the assertion that the Northern oyster-beds are practically exhausted and have become mere fattening-places for the transplanted Southern oyster, many will dispute the assertion that the beds of Maryland and Virginia are in a nearly similar condition, or in danger of soon becoming so. It rests with us, then, to determine that question with as much accuracy as possible, and, should we find the evil an existing one, to show the best means of removing it.
First, are the beds of Maryland and Virginia deteriorating?
It is only possible to speak with entire accuracy of a limited portion of the entire area covered by oysters in these States, but, as the influences affecting the beds are very similar, it may be assumed with safety that the condition of the beds of one district will be, approximately, that of all; at least, it is certain that beds or localities presenting like peculiarities will be in a similar condition as regards reproduction. The only locality in this country which has been thoroughly studied lies on. the eastern shore of Chesapeake Bay, opposite the mouth of the Potomac River. The investigation was carried on by the Coast and Geodetic Survey during the summers of 1878 and 1879, and included the survey of the beds of Tangier and Pocomoke Sounds, the measurement of the depth of water over the beds, and direction and force of currents; the ascertainment of the character of the bottom, the constituents and specific gravity of the water on both flood and ebb tides; the temperature during the summer months or spawning-season; the effect of gales, ice, and freshets; and of the fishery either with dredges or tongs. In general terms, as elaborate a study of the beds of the locality was made as was possible.
Tangier and Pocomoke Sounds were selected on account of the immense extent of their oyster-beds, and because they permitted the study of all the varying conditions affecting the oysters.
The two sounds are arms of Chesapeake Bay, and lie opposite the mouth of the Potomac River, on the eastern side of the bay. Tangier Sound extends north from Watt's Island, at its entrance, about thirty-six miles, and is separated from the bay by a chain of low, marshy islands; it receives from the eastern peninsula the waters of several creeks and rivers, all of considerable importance. The shoals on each side of the channel are covered with oyster-beds, and, where the beds do not exist, the oysters are scattered either in groups or singly. They are also found as continuations of the beds, or scattered in the straits separating the different islands and joining the waters of the sound to those of the bay. On each side of the channels of the tributaries of the sound oyster-beds are also found, and, generally speaking, it may be said that throughout Tangier, in depths between one and six fathoms, oysters may be taken in varying numbers. The entrance to Tangier Sound is also the entrance to Pocomoke Sound, Watt's Island lying between the two at their confluence. Pocomoke stretches to the northward and eastward, extending into the peninsula, while Tangier lies along its western boundary.
Pocomoke Sound is twelve and a half miles long and about nine miles broad near the middle, decreasing in breadth near the head and entrance. The channel is narrow and tortuous, and the main body of the sound is shoal, and these shoals covered with oysters scattered singly and in small groups, or existing in large, well-defined beds. Several small creeks empty their waters into this sound, and one large river, the Pocomoke, discharges into it also. The majority of the beds were found on the eastern side of the sound, and the largest were about the middle and near the mouths of the creeks. The beds in both sounds were located and defined during the summer of 1878, and the area upon which oysters were scattered was also ascertained approximately. The entire area in both sounds upon which oysters were found amounts to fifty-four square miles. The area covered by oysters, but only very thinly, they being scattered in small groups or singly, comprises in Tangier Sound fourteen square miles, and in Pocomoke Sound twenty-nine square miles. The area of the beds proper, or those grounds where the oysters are to a great extent uniformly spread and where the majority of the dredging-vessels work, amounts to six square miles in Tangier Sound and to four square miles in Pocomoke Sound.
The information obtained in 1878, so far as it related to the condition of the beds, may be summarized as follows: The number of oysters on the beds had been very much diminished since the commencement of the fishery, or during the last thirty years. The area of the beds had been greatly increased since the commencement of the fishery. There had been during the period alluded to no change of the usual natural conditions to which the animals are subjected.
Before attempting to draw any conclusions from the above, it will be well to see if the extension in area of the beds and diminution of the number of oysters can be accounted for by the action of natural, unassisted causes.
After the original formation and growth of the beds, they would at some time, the same conditions continuing to operate, cease their development, neither increasing in size nor in number of oysters, there being a natural limit to expansion in either direction. Suppose, then, a bed to have extended itself as far as the conditions of bottom and water or other natural limit would allow, all future expansion could be only in the number of oysters on the bed, and this is limited by the amount of food and room for development, the question of enemies not being considered, as, there being no increase, if they were not in sufficient numbers to prevent the growth of the bed and number of oysters, they would not be sufficient to cause its destruction or deterioration. The number of oysters on a limited bed would then steadily increase, as long as there were sufficient room and food supplied them, until they had reached their limit, a rather undefinable one, in that direction. Having reached that point, the number of oysters would to all intents remain the same as long as the conditions under which they had previously lived were not changed. To cause, then, either an increase or diminution of the number of oysters or the size of the bed, a new factor must be brought into operation, when, all conditions 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 hydrographic 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 impairment 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 specimens would be sufficient to determine the question. If, however, the destruction of the mature oysters or the non-production of the young is accomplished by means that are harmful only to those individuals directly affected, a cause for the diminution is discovered in harmony with the existing facts.
Considering first the destruction of young, large numbers, immense when compared with the production of the higher orders of animals, are annually destroyed by the falling of the "spat" upon unfavorable ground, the prevalence of heavy freshets which would drive the brood into the bay and probably cause its loss, the ravages of various enemies, and unusual changes of the temperature and density of the water. But all these causes have been in operation continually since the first discovery of the beds, and the animals have survived and increased while contending with them. Therefore, some increase of power must be assigned to one or all of these causes, in order to account for the diminished number of oysters, and there is no reason to suppose that there has been such increase. Thus, by reviewing all the natural causes which affect the beds, we can assign to none of them the destruction of either young or old oysters, or the extension of the beds which has been coincident with the diminution of the number of animals. Remaining, then, as the only other operating cause, is the agency of man.
The oyster-fishery in these localities is carried on in two ways, either by "tonging" or "dredging." The first method, being confined to small areas and to a limited number of fishermen, and susceptible of use but in shoal water, need not be considered. The second method of taking the oysters is as follows: the implement used is called a dredge, or scrape, and resembles a large iron claw, the nails representing the teeth of the dredge. To the back of this claw, or the dredge, is fastened a bag of iron mesh-work, large enough to hold two or three bushels. When the dredge is dragged along the bottom the teeth or claws dig up the oysters and shells, which pass between them and into the network behind. The action is somewhat like that of a harrow. The dredges vary greatly in size, being from two to five feet across the mouth, and of greater or less weight, according to the depth of water in which it is intended to use them. The dredging-vessels vary in size from five to thirty tons, and all use two dredges. When on the oyster-ground the dredges are dropped one from each side, and a sufficient amount of line paid out to insure the "taking" of the teeth; the vessel is then kept under easy sail and at a moderate speed until the dredges are full, that being indicated by the strain on the dredging-line and by other signs known to the fishermen. The instrument is then hauled in by means of a small winch, the contents emptied on the deck, and the dredge put over again. This is continued until the vessel is near the edge of the bed, when the dredges are recovered, the vessel put about, and the dredging resumed in an opposite course. While the dredges are in the water, the mud, sand, sponge, grass, or other débris brought up arc separated from the oysters, and, 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.
Theoretically, then, the dredging would—1. Extend the beds; 2. Destroy their fecundity by removing the brood-oysters and by destroying their progeny. Practically, has this been the case?
In the absence of previous surveys of the beds, the testimony of the fishermen must be accepted with regard to the extension of area, and the testimony was unanimous to that effect, some of the beds having doubled in size during the last thirty years. The testimony was also to the effect that all the beds in question had materially deteriorated, the general opinion being that, with the improved appliances now in use, there could have been taken twenty-five years ago from two to seven times as many oysters as at present! But we are not compelled to rely solely upon these statements. A comparison of the results obtained from an investigation of newly discovered beds in the Chesapeake Bay with those beds in the sounds that had long been subjected to the dredging influence shows marked differences, and affords more certain methods of proving the deterioration of old beds. In 1879 areas were discovered in the bay upon which oysters existed, and the locality of which was known to but few of the fishermen; the beds were thus practically in a natural state. The following differences were observed between them and the beds in the sounds: On the new beds in the bay the oysters were generally found in clusters of from three or four to twelve and fifteen; the shells were clean and white, and free from worms; the spaces between the larger oysters were filled with the young growth and barnacles; usually the clusters had a large tuft of red sponge attached to them, and sponges were very plentiful over the beds; the mature oysters were long and narrow, with the lower valve very deep and bills very thin and sharp; the animal itself was much larger and thinner than those of the same age on the worked beds in the sounds; and this last difference is probably due to the difference of water and to the fact that, growing as they do in clusters, food is not so readily obtained. The oysters taken from a bed which has been worked for some time are usually single or in clusters of two or three; they are larger than the corresponding class on the unworked beds—that is, broader in comparison to their length and of greater thickness; the valves are blunt and thick about the lips; and the animal fatter and thicker than those of the same age in the new beds. The shells are dirty, with much mud or sand clinging to them. There is but little sponge attached to the shells; but they are covered with worms, and bored in many places by the boring pholad; and the older the bed and oysters, the larger the number of worms and the less healthy is the appearance of the shell.
The new beds were hard, and the clusters seemed more firmly attached to the bottom, and required greater force to detach them than was necessary on the beds in the sounds. There was comparatively but a small number of broken shells, and the bottom was usually too hard to be penetrated by an iron probe. The beds in the sounds were soft and easily penetrated. The dredge took the oysters readily, and without great effort. There was much mud among the oysters, and the amount of old broken shells and other débris was quite large. It is evident that in any community there must be in the life of a given generation a depletion of number in each successive stage of existence, or, in other words, as the age of the generation increases, the number of individuals decreases. Therefore, on an oyster-bed we should have a larger number of young than mature oysters, provided that we include as "young" the offspring of a sufficient number of spawning-seasons to guard against irregular production in any one season; and, if, having taken that precaution, we find the number of mature oysters to exceed the number of young growth, we may safely decide that there is a deficient production due to some cause, natural or otherwise.
On a natural bed which has not been worked, and which has had no abnormal conditions to contend with, the number of young oysters should, then, exceed the number of those mature. Let us see if this was actually the case on the unworked beds in Chesapeake Bay.
All the oysters examined during the season of 1879 were measured and distributed into four classes. The first two classes comprised the mature oysters; the last two, the young growth. During the season several areas which had never been dredged over were carefully examined, with the following result: Over twenty thousand oysters were measured and classified, and the ratio of young growth to mature oysters was found to be as three to two, or one and five tenths of the former class to one of the latter. This ratio was accepted as a standard, and the ratios of young oysters to mature on all the beds in the sounds were compared with it separately and collectively. Over one hundred thousand oysters were taken from those beds, measured and classified in a similar manner to that adopted for the oysters from the beds in the bay, and the ratio of young growth to mature oysters was found to be as three to six, or five tenths of the former class to one of the latter. Thus, on the new beds the young growth outnumbered the mature, while on the worked beds in the sounds the mature oysters outnumbered the young growth.
The action of the dredge is very destructive to the oysters remaining on the bed. They are not only roughly detached from each other and from the different objects to which they cling, but are, no doubt, frequently left in such positions as will prevent the opening of the valves without allowing the entrance of mud or sand, and thus insuring destruction. The teeth of the dredge also break the lips of the valves, and thus prevent their complete closure, which is the only defense of the oyster against its numerous enemies. Thus, the dredge causes the destruction indirectly of a large number of oysters that remain after its passage, and hence the number of old empty shells should be greater upon a bed that has been dredged than upon one that has not; and, if that number is very large, it shows that the population of the bed has been destroyed. Upon an unworked bed the number of old shells will show approximately the number of oysters perishing from natural causes; and, should the number on any worked bed exceed this on the undredged one, it may be concluded that Nature is being assisted in her work of destruction.
The quantity of matter brought up in the dredge was measured in all cases during the season of 1879, as was also the quantity of oysters and of débris. On the unworked beds in the bay this débris was found to equal thirty per cent, of the whole amount of matter brought up. On nearly every bed in the sounds the percentage of débris was greater than that on the unworked beds, and in Pocomoke Sound it was extraordinarily large, amounting in some of the beds to as much as ninety-seven per cent.!
During the season of 1878 a method was devised by which the number of oysters to the square yard could be determined approximately; and, though this number was not near the true one, yet, as the measurements were always made in the same manner, it was useful as affording a standard for comparing the results of subsequent seasons or of different localities.
The number of oysters to the square yard obtained by this method depended mainly upon the number of oysters brought up by the dredge; and, as already explained, the difficulty of obtaining the animals was much greater on the new and unworked beds than upon those which had been dredged for many years; therefore, the number to the square yard, other things being equal, should be much greater on the old beds than upon those recently discovered. To make this plainer, a very simple illustration will suffice: Any person knows that the plowing or harrowing of a field frequently subjected to that process is much easier than the breaking up of entirely new ground, and the dredging of an oyster-bed is very similar to the harrowing of a field.
The number of oysters to the square yard, as shown by the method used, should then be greater upon the old beds than upon the new, and, comparing the results of successive seasons on the same bed, if it is found that the number of oysters to the square yard is decreasing, it may be concluded that too large a number of the animals is annually removed. The investigation of the beds in 1879 showed that on sixty per cent, of the beds in Tangier Sound there was a decrease in the number of oysters during the season of 1878-'79, and that on sixty per cent, of the beds the number of oysters to the square yard was less than on the newly discovered beds in the bay, and in no case was the number much greater. In Pocomoke Sound, on every bed the number of oysters to the square yard was considerably less than in 1878, and also much below the number on the new beds in the bay.
On several of the beds in the sounds the ratio of young growth to mature oysters was found to be considerably larger than that on the unworked beds, and there was thus, apparently, a much increased production upon the former areas, or the ratio apparently indicated that, instead of deteriorating, the beds were improving, though all other indications were the reverse.
It is evident that, if the number of young growth falls below the number of mature oysters, the fecundity of the bed is impaired; but it does not follow that, if the young greatly outnumber the mature, it is a sign of increased production, for, though the ratio may be increased by increasing the antecedent, or the number of young, it may also be increased by diminishing the consequent, or number of mature oysters. We know that from the beds in question many millions of oysters are annually removed, and that a large percentage of them are mature; and, if this removal of one class is excessive, it might show itself in the increased ratio of young oysters to mature. Supposing this to be the case, the young would then greatly outnumber the mature for about three years, or the period necessary to pass from youth to maturity. During this period there is a constant removal of the brood-oysters, and, as the reproduction depends upon them principally, the number of young spawned during that period will constantly decrease, so that at the end of three years the mature oysters would probably outnumber the young, and the ratio be as abnormally small as it was abnormally large. Now, with the large number of mature oysters there would be an increased production, and at the end of the second period of three years the ratio would again change, and in this way will increase and diminish alternately, while the number of oysters will constantly diminish. In time, however, the brood-oysters will become so scarce and so widely separated that the fertilization of the eggs will be more and more improbable, and the young will consequently remain in the minority, and, the fishing continuing, the entire destruction of the breeding power will be but a matter of time.
During both seasons of the investigation of the question here discussed, every effort was made to collect statistics of the oyster-fishery, and from these statistics has been estimated the number of oysters removed in a day and in the season. In 1878 this number was over 1,500,000 per day; in 1879, over 700,000 per day. In the sounds the dredging continues throughout the year, though comparatively little is done during the summer months. As the law sanctions the working of the beds only from October 1st until May 1st, in order that any error may be in under-rather than in over-estimation, I will consider the dredging to be confined to that period, and will make the very liberal allowance of three days in each week for bad weather which would prevent work. The dredging-season would then be one of one hundred and twenty days, and in that time there would be removed from the beds, by the estimate of 1878, over 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 of mature oysters, and in the latter case it is so large as to be abnormal; the amount of débris found on the beds is much greater than in the newly discovered areas; and the number of oysters to the square yard not only falls below what it should be, but has decreased since the first examination in 1878. The testimony of all persons living in the vicinity of the sounds is to the effect that there has been a marked deterioration of the beds since they were first discovered and worked, and it is the general opinion that, had the improved implements and appliances now used in the fishery been available when the beds were first discovered, from three to five times as many oysters as are taken at present could have been obtained in Tangier Sound, and about seven times as many in Pocomoke Sound; that even with the insufficient implements then in use more oysters were taken, per sail, in the same time than was possible at present.
Considering this testimony, and the results of the comparison of the worked beds in the sound with the unworked ones in the bay, it may be concluded that the former areas are much impaired in productive power, and, the same causes continuing to operate, there will be a constant deterioration until that productive power is entirely destroyed. As there is no indication of any natural cause influencing the beds in the sounds and not the contiguous ones in the bay, we are compelled to assign, as the cause for the deterioration and impaired fecundity of the beds in Tangier and Pocomoke Sounds, the excessive and exhaustive fishery peculiar to them, and from which the beds in the bay have heretofore been free.
The fishery in the sounds is not more extensive than it is in many other localities in Chesapeake Bay: the conditions under which the beds exist are nearly the same; the laws governing the fishery are the same; and about the same amount of attention is paid to them. It is probable, then, that were the remaining beds of the Chesapeake examined carefully, they would present indications of deterioration similar to those shown by the Tangier and Pocomoke beds. That this deterioration is due to the severe fishing can not be doubted. That in time it will amount to utter exhaustion is a fact well known to those who have given any attention to the matter. To those who have not, the following information may be interesting. Only a few of many cases are cited, but enough, it is hoped, to show that the experience is not confined to small areas or one country; that one result follows invariably upon the heels of over-fishing, and that result is, exhaustion.
The records of the production of the beds of Cancale Bay, on the northwest coast of France, which extend over a period of sixty-eight years, from 1800 to 1868, are perhaps the most instructive:
The beds in the bay comprise an area of about one hundred and fifty acres, and, from 1800 to 1816, produced annually from 400,000 to 2,000,000 oysters. This, however, was the period of the Napoleonic wars, and the fishery was much disturbed by the English cruisers. During this time the beds became so thickly stocked that the oysters were in some places a yard thick. After the close of the war the fishery improved, and the oysters were removed in larger and increasing numbers until 1843.
From 1823 to 1848 it is supposed that the dredgers were living upon the animals accumulated during the period of enforced rest, from 1800 to 1816. In 1817 the number of oysters produced was 5,600,000, and until 1843 there was a constant increase, the number taken in that year being 70,000,000. In 1848 it was 60,000,000, and thenceforward there was a constant decrease. From 1850 to 1856 the decrease was from 50,000,000 to 18,000,000, and was supposed to be the effect of over-dredging. From 1859 to 1868 the decrease was from 16,000,000 to 1,079,000, the oysters having almost entirely disappeared from the beds, though on account of the suffering condition of the inhabitants of the shores it was impossible to prevent it or restrict the fishery. In 1870 there was a complete wreck of the bottom, which could only be remedied by a total prohibition of the fisheries for several years.
From the beds of the districts of Rochefort, Marennes, and Isle d'Oléron, on the west coast of France, there were taken, in 1853-'54, 10,000,000 oysters; in 1854-'55, 15,000,000. On account of exhaustive fishing, in 1863-'64 only 400,000 could be obtained.
According to Mr. Webber, Mayor of Falmouth, England, about seven hundred men, working three hundred boats, were employed in a profitable oyster-fishery in the neighborhood of Falmouth until 1866, when the old laws enforcing a close-time were repealed, under an impression that, owing to the great productive powers of the oyster, it would be impossible to remove a sufficient number to prevent the restocking of the beds. Since 1866 the beds have become so impoverished, from the excessive and continual fishery, that in 1876 only forty men and less than forty boats could find employment, and, small as that number is, they could not take more than sixty or one hundred oysters a day, while formerly, in the same time, one boat could take from ten to twelve thousand.
According to the statement of Mr. Messum, an oyster-dealer and secretary of an oyster company in Emsworth, England, there were in the harbor of Emsworth, between the years 1840 and 1850, so many oysters that one man in five hours could take from twenty-four to thirty-two thousand. In consequence of over-fishery in 1858, scarcely ten vessels could find loads, and in 1868 a dredger, in five-hours, could not find more than twenty oysters!
The oyster-fisheries of Jersey, in the English Channel, afforded employment to four hundred vessels. In six or seven years the dredging became so extensive and the beds so exhausted that only three or four vessels could find employment, and the crews of them had to do additional work on shore in order to support themselves, the returns from the beds being so inadequate.
The evil of excessive fishery then exists, and, continuing, can have but one effect, and we have seen how disastrous is that result. Our oyster-beds are, however, so extensive, the animals are so widely distributed, and are so easily transported and transplanted, that the total failure of the American oyster-beds must be postponed for some time. But the failure of the beds of different localities may occur at any time, and it is more than probable that those of Chesapeake Bay will be practically exhausted before many years. The deterioration and final exhaustion of the beds, either of particular localities or of the whole country, would, however, cause far greater distress, discomfort, and inconvenience in the United States than the failure of the foreign beds caused abroad. With us the oyster is no luxury, but a means of subsistence to a large number of people. Oysters are consumed from Maine to Texas, and from the Atlantic to the Pacific, and immense numbers are also annually exported. In supplying this great demand numbers of the poorer classes of citizens find a constant and profitable employment, and thus the deterioration of the beds, or extinction of the oysters, would not only be felt by the consumer in the much-increased price of a desirable and nutritious article of food, but by the producer, in a loss of employment, and that loss occurring in localities where there is hardly any other resource.
[The natural history of the oyster with especial reference to the process of reproduction and the conditions influencing its rate of increase will form the subject of a concluding article.—Ed.]