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Transactions of the Highland and Agricultural Society of Scotland
On Developing the Oyster Fisheries of Scotland

By William Watt, 27 North Albert Street, Aberdeen.
[Premium—Five Sovereigns.]

The problem of how old oyster fisheries may be maintained and extended, and new oyster fisheries established, has long engaged the attention of naturalists and of men practically interested in fishery economics, but it cannot as yet be said to have been completely solved, and probably no solution of it will ever be found equally applicable in all the varying conditions of climate, soil, and surroundings in which oysters are found. In one or another of its forms oyster-culture has been practised from a remote antiquity. As exemplified in the English fisheries, from time immemorial, it has consisted in procuring young "brood" from beds in the open sea, or wherever it could be obtained, and laying it down upon certain well-known "fattening grounds," chiefly situated at the mouths of the Thames and Medway, of which those of Whitstable are the most widely celebrated. With reference to our present subject, it may be stated that these fattening grounds are situated in almost all cases in the estuary of a river or in a natural harbour, and with few exceptions they are held by individuals or corporations as private property. These oyster farms, as they may be called, have been subject to fluctuations and vicissitudes quite as serious, to say the least, as those that have affected agriculture and other industries. Where oyster beds have been common property, their usual fate has been destruction by over-dredging, the fishermen acting upon the principle that it is for their interest to obtain as many oysters as possible while they are to be found, and to leave the future to take care of itself. Where the beds are private property, the ruinous competition and scramble that have put an end to so many public oyster grounds are avoided, and self-interest is not altogether neglectful of thoughts of the morrow.

The oyster fisheries of the United Kingdom were included within the scope of the comprehensive inquiry into the sea fisheries generally, carried out about twenty years ago by a Royal Commission, consisting of Messrs Caird, Huxley, and Shaw-Lefevre. These Commissioners, as a result of their inquiry, recommended, as the only useful legislation applicable to oysters, that facilities should be given for the acquisition by individuals of portions of the sea-floor favourably situated for purposes of oyster-culture. And oyster-culture they defined, in accordance with old English practice, as the collection of "brood" or young, and its preservation by due skill and care, as a source of supply. This was the only remedy which these eminent Commissioners could suggest for the scarcity of which many of the witnesses examined before them made complaint; and beyond what might be needed, in order to give effect to this object, they were of opinion that no regulations or restrictions were likely to have any beneficial effect upon the supply of oysters for the markets. And such, it may be fairly allowed, was the best judgment that could be formed at the time. The main point is the appropriation of portions of the sea for oyster cultivation by individuals; and whether the oyster beds are natural or artificial, experience proves the absolute necessity of their having the protection of private property, if they are to be cultivated to profit, or even if they are to continue in existence. The principle of private property is the foundation of oyster-culture; and if this principle has not always been sufficient, in our Scottish waters or elsewhere, to preserve the beds from depletion, it has been because adequate knowledge has been wanting, or exceptional agencies of destruction have come into play, such as severe frost or the ice-water of rivers.

In discussing the best means of developing the oyster fisheries of Scotland, I do not profess to have discovered any royal road by which what has hitherto been a precarious enterprise can be made unfailingly certain and profitable. Experience in Scotland is very limited in regard to this mollusc, its existence in marketable quantity in Scottish waters being confined to a very few localities, chiefly in the Firth of Forth. In England the oyster industry is carried on at various points from Suffolk round by the Channel to the Welsh coast. There is considerable difference of practice at different places, and many of the cultivators are by no means communicative as to their experience.

One canon of practice that is well established is, that it is very unwise to lay out much money on breeding or fattening-grounds unless they have previously been proved by actual experiment to be suited to their purpose. If the grounds are already occupied by oysters, there is a presumption that well-considered expenditure may be undertaken with advantage; but if they are at present barren, there is a prima facie presumption that some of the requisite conditions are absent; and it is desirable, in the first instance, to verify conclusions as to suitability, based on general considerations, by tentative experiments to ascertain the behaviour of oysters at the proposed seat of their cultivation. Not only soil, but temperature, salinity, currents, and all the elements bearing on food, have to be taken into account, as well as the effect of storms, and, in estuarine waters, of floods and freshets. Both in England and in America, nourishing beds are occasionally all but destroyed by spring floods, caused by sudden thaws and the breaking-up of great masses of ice. This is a contingency which cannot absolutely be guarded against, though risk from it may be mitigated by a judicious choice of locality, and by having the oysters placed in water not too shallow prior to the season of icy floods.

Hitherto rearing and "fattening" has been a far less dubious enterprise than breeding, but recent discoveries point to a possible change in this respect. For a considerable number of years salmon have in this and other countries been systematically "hatched" from ova, artificially fecundated; and as method and manipulation have improved, it has been found that most of the fishes of commerce—both sea and fresh-water—can in like manner be multiplied at the will and under the control of man. Obviously a great step in advance would be made if oyster-culture could be so widened in scope as to include artificial propagation. The reproductive power of the oyster is very great. It is estimated that the larvae sent forth by a single parent oyster at a single breeding period reach in number a million or more. If this enormous reproductive power could be fully utilised there would be no scarcity, but, on the contrary, a too abundant supply. But only a very small proportion of the young oysters come to maturity, or become "fixed" where they can live. The difficulty is not in obtaining oyster larvae, but in the fixation of the spat. The larvae swim about in the water for a brief period of not very many days, the exact number being undetermined and perhaps variable. At the termination of its free-swimming career the young oyster settles down to the bottom of the water, there to pass the rest of its life. It alights, probably on the first solid object that comes in its path, generally the sea-floor. Should it have the good fortune to fall on a suitable object, its chief risk is that of being devoured by some other animal. In the vast majority of cases, however, the larvae are swept away by currents to be lost on unsuitable soil— choked or buried perhaps by sand or mud. To intercept these larvae or spat by means of faggots or branches of trees, tiles, or prepared wooden collectors, or even stones, or to lay down a culch or top-dressing of clean empty shells, where they are expected to fall, are familiar operations of oyster-culture. By these contrivances a certain proportion of the young oysters are, when other circumstances are favourable, preserved; but probably a far larger proportion are carried away by currents to stock new or replenish old banks, or perish, as the case may be. Uniformity of method does not prevail among British cultivators, but there has been an all but complete identity of experience among them in one respect. They have generally been unable to maintain their fisheries in a prosperous condition by means of natural increase. Spat either has not been produced, or it has perished from cold, or at least failed to adhere to the collectors prepared for its reception. The best localities for reproduction are situated in the English Channel, chiefly about the Isle of Wight; and the reason of their superiority, it seems pretty clear, is that the temperature is higher there at the breeding season than in the North Sea. A temperature approaching 70° is favourable to the fixation of spat, and while this is higher than the normal range of the waters of the Channel in early summer—the spatting time—it is still farther above the temperature of the Thames estuary and the east coast of these islands. The Channel receives a branch of the warm Gulf Stream, and responds more quickly than the colder North Sea to the warming rays of the summer sun. I have learned—though information of the kind is not an abundant commodity—that at some at least of the Channel oyster farms there have been exceptionally good falls of spat during the last two seasons, and that on the east coast it has also been better than the average. A very good spatting season in the Thames is quite phenomenal, and 1859 continues to stand out as the year of proverbial excellence in regard to the supply of young oysters. In the warmer waters of France considerable vicissitudes of fortune attend the oyster breeder's industry; but there such a thing as absolute failure is hardly known, whereas in these more northern latitudes it is by no means of rare occurrence. Still we have the important fact to remember that the oyster is indigenous all round these islands where localities that suit its habits are to be found; and the oyster industry has of late years undergone a great development in the estuary of the Scheldt, while it holds its ground in the cool waters of the Schleswig-Holstein coast—showing that the temperatures prevailing in these latitudes are not fatal to reproduction and development on a moderate scale, though it may perhaps be impossible to get the plethoric swarms of young that are successfully collected farther south in favourable seasons.

It is of great importance that the culch or collectors should be perfectly clean, and not covered with vegetable matter of any sort; in other words, they should not be put down until the reproductive season is close at hand. Wooden and even tile collectors should be covered over with a coating of hydraulic lime, or asphalt and sand, before being put down; and a culch of old shells, if previously used, should be bleached in the sun before being put down a second time, so that any kind of organic matter that may adhere to them may be rendered incapable of life and growth when they are put back into the water.

Another point connected with the reproductive process has likewise an all-important practical significance. The nature of that process has not been adequately explained as yet; but according to eminent physiologists, such as M. Davaine, Professor Huxley, and Professor Hoek of Leyden, it is clearly established that the same individual oyster (O. edulis) is alternately male and female, the milt being secreted in abundance after the ova are extruded, and ova in like abundance after the extrusion of the milt; but at any particular breeding time each oyster, as regards reproductive efficiency, is either exclusively male or exclusively female. As the ova in this species of oyster undergo incubation between the gill-plates and between the folds of the mantle, it is obvious that they must be fertilised there, and if the physiologists are right the fertilisation must take place from without. This can occur only in one way. When the milt is fully matured it must be shed into the sea as in the case of fishes, and must reach adjacent oysters and come into contact with the slimy mucus in which the ova are imbedded. This must occur some little time before the female is unburdened of her brood, and manifestly there must be a great deal of waste, while an incredible number of spermatozoa must reach the ovaries if anything like full effect is to be given to the reproductive power of the female. And in proportion as the oysters on a bank are distant from each other are the chances of fertilisation lessened. A few oysters, in close proximity to each other, might soon, in favourable circumstances, replenish a whole bank, but when the dredge has done its worst and only a few stragglers remain, the work of destruction is complete, and another is added to the long list of exhausted beds. If the industry is to thrive, careful attention must, therefore, be given to the conditions governing the reproductive process, and especially to the most essential condition that a sufficient breeding stock should be left gregariously crowded together in accordance with the plan of nature. In France this has been recognised for a considerable number of years, and the Government insists on reserving a portion of the natural beds exclusively for breeding purposes, only allowing a little dredging in order to clean the ground and clear away enemies at intervals. From these natural banks the larvae spread all over the neighbouring waters, and myriads fix on the collectors laid down on private grounds for their reception. Of late years there has been, as already said, a great revival of the Dutch oyster fishery of the Scheldt—due exclusively to the abundant collection of spat on particular parts of the Yerseke bed. This revival at first caused some surprise, and nobody knew very well how to account for it. Various parts of the bank were dredged for the purpose of ascertaining the source of the spat, but only with negative results. At last some one thought of the fringe of 500 metres from the dykes by which the country is protected from the inroads of the sea. Within this fringe dredging is prohibited, and is besides rendered almost impracticable by the presence of large stones. Divers were sent down to explore the ground, with the result that almost everywhere the stone-works which jut out from the dykes were found to be covered with oysters that had never been disturbed. These natural beds were undoubtedly the explanation of the great abundance of spat in regions some little distance off, but found by actual experiment to be connected with them by currents. It may be added that the portion of the Scheldt in which these beds are situated has been cut off by a railway embankment from all direct connection with the freshwater stream, and is to all intents and purposes a sheltered bay or creek filled with the waters of the sea.

An analogous order of things is observed at some of the principal seats of oyster cultivation in the east and south of England. The Blackwater, in Essex, is a wide estuary or arm of the sea, and though many of its oyster-grounds are public and frequented by large numbers of dredgers, they nevertheless maintain their productiveness. The reason is that they are every year replenished by spat brought down by currents from the well-stored private grounds in the upper creeks and reaches of the estuary. These private layings are stocked with young oysters from the public grounds lower down; and thus a mutually beneficial reciprocity exists, and the industry is successfully carried on from year to year. In the same district, a similar condition of mutual dependence is observed on the Roach River, the upper portion being carefully stocked as an oyster farm, while lower down much of the bed is, before the breeding season, strewn over with culch for the reception of spat. And off Whitstable the public grounds undoubtedly benefit by the well-stocked fattening grounds of the bay; but as the water is here an open expanse, unconfined by banks, very much of the spat is dissipated and lost, while experience also proves that the best fattening places are not the best breeding places. The best brood oysters are the produce of natural banks, though artificial layings also yield satisfactory supplies in average seasons, and in localities favourable to collection.

These facts, and were it necessary they might be multiplied., tell us somewhat of the conditions that must be observed if a large oyster-industry is to be developed in Scotland. With regard to breeding, the best practical measure that can be adopted, is to conserve with jealous vigilance every existing natural bank. It is very difficult to create a good breeding place, but not quite so difficult to utilise to its utmost a breed-jug place already in existence. This utilisation is to be effected by restricting, or altogether preventing, the removal of breeding stock, by clearing away occasionally the whelks, starfishes, boring-sponges, and other "enemies" by which the banks are apt to be infested, and by adopting measures for the collection of as much as possible of the spat. The work of "cleaning" is done by means of the dredge. Collection of spat must be preceded by experiments or observations to ascertain, as far as possible, where the spat is likely to fall; and except in waters more or less hemmed in by land, there is not, it must be confessed, much hope of succeeding with this branch of the business.

In American and Portuguese oysters (O. virginiana, O. angulata) the process of embryonic development is effected not within the shells of the parent, but, as in the case of most fishes, in the water of the surrounding sea. The ova are cast into the water, and are there fertilised, and there the larvae come forth as free-swimming creatures. With these oysters some progress has been made towards establishing artificial propagation corresponding to the fundamental operation of fish-culture, as now extensively practised in Europe and America. The pioneer in this art was Dr W. K. Brooks of Baltimore, director of the Chesapeake Zoological Laboratory, and chairman of the Maryland Oyster Commission; and other early labourers in the same field have been Professor Pice and Mr Ryder in America, and M. Bouchon-Brandely in France. Dr Brooks's experiments in 1879 were witnessed by Lieut. Winslow, of the United States Navy, who, being stationed next year at Cadiz, repeated them with the Portuguese oyster, which he found to be likewise capable of artificial propagation. Stimulated also by Dr Brooks's experiments, M. Bouchon-Brandely has for some years been carrying on an important series of researches with the Portuguese oyster, and has succeeded in raising a large number of young from artificially fecundated ova through all the early stages, as is fully detailed in his Reports to the French Government, which have been translated and issued by the Board of Trade in this country. The practicability of raising Portuguese and American oysters—which indeed are one species—from artificially fertilised eggs, is therefore clearly established. It is true that these oysters differ not a little from the Ostrea edulis, and are in by no means so high repute; still they have a good commercial value, and their cultivation artificially from the earliest stage is an important step in advance. As regards the common oyster, which is incubated within the shells, the difficulty is not in obtaining larvae, but in getting the spat to adhere to the collectors or culch. In confined waters, food conditions and want of aeration are difficulties as well as temperature ; and whatever reasonable hopes there may be that these difficulties will sooner or later be overcome, we must for the present rely upon the old methods, and look forward with hope to the progress of experiment and research into the conditions of oyster life. The requisite aeration of confined water can be provided by mechanical means ; but food conditions are more unmanageable, because, for one thing, they are less perfectly known. They are no doubt affected by aeration, and probably also by temperature. The temperature of a sea water tank of moderate dimensions can of course be raised by artificial means, but the art of cultivating the microscopic organisms, upon which the oyster feeds and fattens and its larvae are sustained, has still to be learned. Old oysters are sometimes supplied with a sprinkling of oatmeal, and appear to benefit by imbibing particles of this food, but we have still to learn how to provide the natural food of the larvae, or whether any substitute is available. These speculations, however, pertain to the scientific branch of the subject. The life history of the oyster is still known only in part, and we are but on the threshold of the art of propagating this mollusc through the intervention of human contrivance. Within certain narrow limits we can assist nature. We can also refrain from thwarting nature by dredging away the parent stock, instead of leaving sufficient breeding places intact.

As a practical means of developing the oyster fisheries of Scotland, we must, I think, look first to an extension of the system of granting leases of oyster grounds for short terms, on condition of a certain amount of money being annually expended on their cultivation. The proceedings to this end, though they might with advantage be further simplified, have been facilitated by the Sea Fishery Act for 1885. Having found a promising locality, and obtained a lease from the Secretary for Scotland, on the recommendation of the Fishery Board, the grantee would set about preparing the ground, putting up a rough fence, perhaps, to mark it off and afford some protection, or at least surrounding it with a few stout posts to which brushwood or hurdling might be attached, at the proper season, for the collection of spat. If the nature of the ground permitted, or rendered it desirable, sloping ridges might be formed so as to give the allotment more or less of an undulating surface, as is done on many of the American oyster layings of Chesapeake Bay; and it should also be strewn over with a layer of old shells, or if these cannot be procured the smaller debris from a stone quarry would be a fairly good substitute. At sundry places on the Adriatic it is customary to drive branches of oak into the bed of the sea round oyster grounds, in 1½ fathom of water, every spring; and in the autumn these branches, which meanwhile have become laden with young oysters, are transferred with their burden into deeper water. There the branches are sunk, and the oysters left to develop and mature—safe alike from the heat of summer and the frosts of winter. At other Adriatic stations the branches, instead of being staked, are simply laid down in the water. This, it may be added, is substantially the method of oyster-culture pursued at Lake Fusaro on the Gulf of Taranto, since the old Roman days—the breeding oysters being placed on heaps of stone with wooden stakes or piles planted around them. It is to an examination of this method by M. Coste that the modern development of the French oyster industry is in great measure due. On M. Coste's recommendation, the Fusaro system was introduced at different points on the Bay of Biscay, and its adoption soon became general. About the same time, however, the system of artificial parcs and claires had its inception. The parcs are simply portions of the foreshore walled round roughly with stones, and having a clay foundation, which retains water, are strewn with a covering of stones or shells. These pares are covered by the sea at every tide, and much labour is expended in keeping them in good order, and in clearing away intruding marine animals. They are used as stores and breeding places, and at the breeding season, collectors—generally tiles— are laid down in them. The claires are similar ponds, but, beyond the range of the ordinary ebb and flow of the tide, though reached by the high water of spring tides. They are used for fattening and "greening" oysters, the comparative stagnation of the water being favourable, as would seem, to the growth of the microscopic organisms by which these processes are effected. Much, however, depends on the character of the soil; British "natives" are not the sickly produce of stale ponds.

The sensitiveness of the oyster to frost renders the French system unsuitable to Scotch conditions, and the model for Scotland is rather the old Italian system. But with a view to commercial results, attention will naturally be directed to rearing fully as much as to breeding. Supplies of brood, ready for "planting out," can be procured at Auray or Arcachon, at a price that need not be regarded as prohibitive. To some people it may sound like rank heresy, but I must also mention the American oyster as deserving of notice. Large numbers of the kind known as "East Rivers," which are those most in repute in this country, are imported every year at the young stage, and "planted out" in the Conway, the Menai Strait, and, I understand, certain places in the south of England. The American oyster trade seems to prosper in this country; at all events, the Transatlantic bivalve is gaining for itself every year a more and more important place in the English market. The most noteworthy trait in its character is, that while it grows and thrives in British waters, it does not reproduce itself; and thus the grounds as they are cleared have always to be replenished by new importations of young from America, Whether "natives," or Americans, or Portuguese are dealt with, the beds where they are to winter must be protected by having always a few feet of water over them. Four feet is a sufficient minimum in sheltered localities, but where the beds are more or less in the current of a river, a greater depth than this is necessary. To attempt to raise oysters on a sandy beach would be no less absurd than to attempt wheat growing among the moving sands of the Sahara. Soft mud is equally to be avoided. A somewhat firm alluvial or clayey soil, with a certain admixture of calcareous matter in some form, is a general description applicable to very many oyster beds; and there must be a good deal of organic matter on the ground or in its neighbourhood. Rocky localities, though not always unsuitable to oyster growth, are undesirable on account of the difficulty of dealing with them. To enlarge and improve existing beds, I repeat, is a far more certain way of attaining success than to attempt to establish new ones. The usual method of taking up oysters is by the use of the dredge, but in America the "tongs" is employed, and in moderately shallow water it is preferable for ridged grounds, as causing less disturbance.

These are the main points bearing on the development of the Scottish oyster fisheries. The scale of the present essay does not allow them to be adequately discussed, but the outline that has been given may not be altogether without utility. I have not attempted any specific account of actual or potential oyster localities in Scotland, because anything like a comprehensive report of that kind must be preceded by local inquiries of a somewhat extensive nature. On this head it may be said generally, however, that there are a great many arms of the sea running into Scotland and its islands in which promising spots are to be found. The Firth of Forth contains extensive dredging grounds. The Tay, notwithstanding its sand and silt, is not without comparatively pure and hopeful localities. There are some oysters in the Cromarty Firth. The "voes" of Shetland, the sounds of Orkney, and the Loch of Stenness offer advantages to the ostri-culturist which will probably some day be turned to account; and in some of the sea lochs of the West Highlands and Hebrides, where the oyster is indigenous, a sufficiency might be grown to supply extensive markets. Even in Scotland, therefore, oyster culture is not without great possibilities. The demand for oysters is far greater than the supply, and were the business properly developed in the various seats of actual or possible production, it should be highly remunerative, even after a concession has been made to the consumer in the matter of price. At present the industry, except in the Firth of Forth, is almost entirely undeveloped. Occasional desultory experiments in oyster cultivation have been made in Scottish waters, but they have not come to much. Experiments are not needed to show that the common oyster thrives in these waters, and the common oyster will probably always remain the prime favourite in the markets. The experiments to be desiderated are not biological but economic, and from the teachings of experience elsewhere, and the fact that the oyster is indigenous in Scotland, it can hardly be doubted that the first who choose their ground with judgment, and lay out their capital to good purpose, will reap an abundant harvest, and virtually add one more to the list of Scottish industries. The east coast, except in the estuaries, is for the most part impracticable, but a great deal might be done on the west coast and among the islands. There the climate is mild and suitable, while nowhere are well-sheltered places more abundant. The establishment of an oyster industry, moreover, would be of public and national importance, as a means of employing labour in regions where remunerative employments are by no means numerous. The first step is to simplify and cheapen the process preliminary to the granting of concessions of ground, and the rest must be left to the energy, sagacity, and knowledge of capitalists prepared to embark their resources in the enterprise, and to the industry of the workers prepared to co-operate with them in turning the forces of nature to account in a new way for the production of wealth.

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