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OYAMA, IWAO, PRINCE (1842– )
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See also:OYAMA, IWAO, See also:PRINCE (1842– ) , See also:Japanese See also: How many times the See also:alternation of See also:sex may take See also:place in a See also:season is not known. It must be See also:borne in mind that in what follows the See also:species of the See also:European coasts, Ostrea edulis, is under See also:consideration. The ova are fertilized in the genital duct, and before their See also:escape have undergone the earliest stages of segmentation. After escaping from the genital See also:aperture they find their way into the infra'branchial See also:part of the See also:mantle cavity of the See also:parent, probably by passing through the suprabranchial chamber to the posterior extremity of the gills, and then being conducted by the inhalent current caused by the See also:cilia of the gills into the infra-branchial chamber. In the latter they accumulate, being held together and fastened to the gills by a See also: In an oyster containing white spat microscopic examination of the genital organs shows nothing but a few unexpelled ova. An oyster in this condition was kept in an See also:aquarium by itself for a fortnight, and after that See also:period its genital organs were found to contain multitudes of spermatozoa in all stages of development.
The breeding season of the European oyster lasts from May to See also:September. The See also:rate of growth of the See also:young oyster is, roughly speaking, an See also:inch of diameter in a See also:year, but after it has attained a breadth of 3 in. its growth is much slower. See also:Professor Maims is of See also:opinion that oysters over twenty years of See also:age are rare, and that most of the adult See also:Schleswig oysters are seven to ten years old.
The development of the See also:American oyster, 0. virginiana, and of the Portuguese oyster, O. angulata, is very similar to that of 0. edulis, except that there is no period of See also:incubation within the mantle cavity of the parent in the See also:case of these two species. Hence it is that so-called artificial fertilization is possible; that is to say, fertilization will take place when ripe eggs and milt are artificially pressed from the oysters and allowed to fall into a vessel of See also:sea-water. But if it is possible to procure a See also:supply of spat from the American oyster by keeping the swarms of larvae
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in confinement, it ought to be possible in the case of the European oyster. All that would be necessary would be to take a number of mature oysters containing white spat and See also:lay them down in tanks till the larvae escape. This would be merely carrying oyster culture a step farther back, and instead of See also:collecting the newly fixed oysters, to obtain the free larvae in See also:numbers and so insure a fall of spat independently of the uncertainty of natural conditions. This method has been tried several times in See also:England, in See also: In nature the beds are liable to See also:variations, and, although Huxley was somewhat sceptical on this point, it seems that they are easily brought into an unproductive condition by over-dredging. Oysters do not flourish in water containing less than 3 % See also:salt; and hence they are absent from the Baltic. The See also:chief enemies of oysters are the See also:dog-whelk, See also:Purpura lapillus, and the whelk-tingle, Murex erinaceus, which See also:bore through the shells. Starfishes devour large numbers; they are able to pull the valves of the See also:shell apart and then to See also:digest the body of the oyster by their everted See also:stomach. Cliona, the See also:boring sponge, destroys the shells and so injures the oyster; the boring annelid Leucodore also excavates the shell. The wandering See also:life of the larvae makes it uncerain whether any of the progeny of a given oyster-See also:bed will See also:settle within its area and so keep up its numbers. It is known from the See also:history of the Liimfjord beds that the larvae may settle 5 m. from their place of See also:birth. The genus Ostrea has a See also:world-wide See also:distribution, in tropical and temperate seas; seventy species have been distinguished. Its nearest See also:allies are Pinna among living forms, Eligmus among fossils. For the so-called See also:pearl-oyster see PEARL. Oyster See also:Industry.—Oysters are more valuable than any other single product of the See also:fisheries, and in at least twenty-five countries are an important See also:factor in the See also:food-supply. The approximate value of the world's oyster See also:crop approaches £4,000,000 annually, representing over 3o,000,000 bushels, or nearly io billion oysters. Not less than 150,000 persons are engaged in the industry, and the See also:total number dependent thereon is fully See also:half a million. The following table shows in See also:general terms the yearly oyster product of the world: See also:Country. Bushels. Value. See also:United States 26,853,760 £2,533,481 See also:Great See also:Britain See also:Ireland 113,700 54,7 113,700 22 154,722 France. 3,260,190 716,778 Holland See also:ioo,000 84,400 See also:Italy 68,75o 44,000 Other European countries 29 930 40,250 See also:Asia, See also:Africa arid See also:Oceania . 275,000 1 11,400 Total . 30,835,470 £3,728,436 United States.—The oyster is the chief See also:fishery product in the United States. The states which See also:lead in the quantity of oysters taken are See also:Maryland, See also:Virginia, New See also:York, New See also:Jersey and See also:Connecticut; the See also:annual value of the output in each of these is over $1,000,000. Other states with important oyster interests are Rhode See also:Island, See also:North Carolina, See also:Louisiana and See also:California. The oyster fisheries give employment to over 56,000 fishermen, who See also:man 4000 vessels, valued at $4,000,000, and 23,000 boats, valued at $1,470,000; the value of the 11,000 dredges and 37,000 See also:tongs, rakes and other appliances used is $365,000. The quantity of oysters taken in 1898 was 26,853,760 bushels, with a value of $12,667,405. The output of cultivated oysters in 1899 was about 9,800,000 bushels, See also:worth $8,700,000. See also:Canada.—Oyster See also:banks of some importance exist in the Gulf of St See also:Lawrence and on the See also:coast of See also:British See also:Columbia. All of the grounds have suffered depletion, and cultural methods to maintain the supply have been instituted. The oyster output of the Dominion has never exceeded 200,000 bushels in a single year, and in 1898 was 134,140 bushels, valued at $217,024. United See also:Kingdom.—The natural oyster beds of Great Britain and Ireland have been among the most valuable of the fishery resources, and British oysters have been famous from time immemorial. The most important oyster region is the See also:Thames See also:estuary, the site of extensive planting operations. The See also:present supply is largely from cultivated grounds. Important oyster-producing centres are +26 See also:Whitstable, See also:Colchester and See also:Brightlingsea. The oysters landed on the coasts of England and See also:Wales in 1898 numbered 35,809,000, valued at £122,320, and in 1899, 38,978,000, valued at £143,841. The Scottish fishery has its centre at See also:Inveraray and Ballantrae, and in 1905 yielded 218,000 oysters, valued at £865. Public oyster grounds of Ireland in 1903 produced 2,532,800 oysters, valued at £5030. The fishery is most extensive at See also:Wicklow, See also:Queenstown, Ballyheige, See also:Galway and Moville. Planting is carried on in seven counties; the oysters taken from cultivated beds in 1903 numbered 2,687,500 oysters, valued at £5420. France.—The industry owes its importance to the See also:attention given to oyster cultivation. In the fishery on public grounds in 1896 only 6370 fishermen were engaged, employing 1627 vessels and boats, valued at 1,473,449 francs, and apparatus worth 211,495 francs, while only 13,127,217 kilograms of oysters were taken, or about 320,000 bushels, valued at 414,830 francs. In the parks, claires and reservoirs the private culture of oysters has attained great perfection. Fully 40,000 men, See also:women and See also:children are employed, and the output in 1896 was 1,536,417,968 oysters, worth 17,537,778 francs. The See also:principal centre is See also:Arcachon. Oyster Culture.—The oyster industry has passed from the hands of the fisherman into those of the oyster culturist. The oyster being sedentary, except for a few days in the earliest stages of its existence, is easily exterminated in any given locality; since, although it may not be possible for the fishermen to See also:rake up from the bottom every individual, wholesale methods of See also:capture soon result in covering up or otherwise destroying the oyster banks or reefs, as the communities of oysters are technically termed. The See also:main difference between the oyster industry of See also:America and that of See also:Europe lies in the fact that in Europe the native beds have long since been practically destroyed, perhaps not more than 6 or 7 % of the oysters of Europe passing from the native beds directly into the hands of the consumer. It is probable that 6o to 75% are reared from the spat in artificial parks, the See also:remainder having been laid down for a time to increase in See also:size and flavour in shoal See also:waters along the coasts. In the United States, on the other See also:hand, from 30 to 40% are carried from the native beds directly to See also:market. The oyster fishery is everywhere, except in localities where the natural beds are nearly exhausted, carried on in the most reckless manner, and in all directions oyster grounds are becoming deteriorated, and in some cases have been entirely destroyed. At present the oyster is one of the cheapest articles of See also:diet in the United States; and, though it can hardly be expected that the See also:price of American oysters will always remain so See also:low, still, taking into consideration the great See also:wealth of the natural beds along the entire See also:Atlantic coast, it seems certain that a moderate amount of See also:protection would keep the price of See also:seed oysters far below European rates, and that the immense stretches of sub-merged See also:land especially suited for oyster planting may be utilized and made to produce an abundant See also:harvest at much less cost than that which accompanies the complicated system of culture in See also:vogue in France and Holland. The simplest See also:form of oyster culture is the preservation of the natural oyster-beds. Upon this, in fact, depends the whole future of the industry, since it is not probable that any system of artificial breeding can be devised which will render it possible to keep up a supply without at least occasional recourse to seed oysters produced under natural conditions. It is the opinion of almost all who have studied the subject that any natural bed may in time be destroyed by overfishing (perhaps not by removing all the oysters, but by breaking up the colonies, and delivering over the territory which they once occupied to other kinds of animals), by burying the breeding oysters, by covering up the projections suitable for the reception of spat, and by breaking down, through the See also:action of heavy dredges, the ridges which are especially fitted to be seats of the colonies.' The ' Even' Huxley, the most ardent of all opponents of fishery legislation, while denying that oyster-beds had been permanently annihilated by dredging, practically admitted that a bed may be reduced to such a condition that the oyster will only be able to recover its former See also:state by a long struggle with its enemies and competition—in fact that it must re-establish itself much in the same way as they have acquired See also:possession of new grounds in See also:Jutland, a See also:process which, according to his own statement, occupied See also:thirty years (Lecture at the Royal Institution, May 11th, 1883, printed with additions in the See also:English Illustrated See also:Magazine, i. pp. 47-55, 112-121).immense oyster-beds in Pocomoke See also:Sound, Maryland, have practically been destroyed by over-dredging, and many of the other beds of the United States are seriously damaged. The same is doubtless true of all the beds of Europe. It has also been demonstrated that under proper restriction great quantities of mature oysters, and seed oysters as well, may be taken from any region of natural oyster-beds without injurious effects. Parallel cases in See also:agriculture and forestry will occur to every one. See also:Mobius, in his most admirable See also:essay See also:Die Auster and Die Austernwirthschaft, has pointed out the proper means of preserving natural beds, declaring that, if the See also:average profit from a bed of oysters is to remain permanently the same, a sufficient number of See also:mother oysters must be See also:left in it, so as not to diminish the capacity of maturing. He further shows that the productive capacity of a bed can only be maintained in one of two ways: (I) by diminishing the causes which destroy the young oysters, in which case the number of breeding oysters may safely be decreased; this, however, is practicable only under such favour-able conditions as occur at Arcachon, where the beds may be kept under the See also:constant See also:control of the oyster-culturist; (2) by regulating the fishing on the natural beds in such a manner as to make them produce permanently the highest possible average quantity of oysters. Since the annual increase of half-grown oysters is estimated by him to he four See also:hundred and twenty-one to every thousand full-grown oysters, he claims that not more than 42% of these latter ought to be taken from a bed during a year. The Schleswig-See also:Holstein oyster-beds are the See also:property of the state, and are leased to a See also:company whose See also:interest it is to preserve their productiveness. The See also:French beds are also kept under See also:government control. Not so the beds of Great Britain and America, which are as a general See also:rule open to all corners,' except when some See also:close-time regulation is in force. Huxley has illustrated the futility of " close-time " in his remark that the See also:prohibition of taking oysters from an oyster-bed during four months of the year is not the slightest See also:security against its being stripped clean during the other eight months. " Suppose," he continues, " that in a country infested by wolves, you have a See also:flock of See also:sheep, keeping the wolves off during the lambing season will not afford much protection if you withdraw shepherd and See also:dogs during the See also:rest of the year." The old close-time See also:laws were abolished in England in 1866, and returned to in 1876, but no results can be traced to the action of See also:parliament in either case. Huxley's conclusions as regards the future of the oyster industry in Great Britain are doubtless just as applicable to other countries—that the only See also:hope for the oyster consumer lies in the encouragement of oyster-culture, and in the development of some means of breeding oysters under such conditions that the spat shall be safely deposited. Oyster culture can evidently be carried on only by private enterprise, and the problem for legislation to solve is how to give such rights of property upon those shores which are favourable to oyster culture as may encourage competent persons to invest their See also:money in that undertaking. Such property right should undoubtedly be extended to natural beds, or else an area of natural spawning territory should be kept under constant control and surveillance by government, for the purpose of maintaining an adequate supply of seed oysters. The See also:extension of the area of the natural beds is the second step in oyster culture. As is well known to zoologists, and as has been very lucidly set forth by Mobius, the location of oyster banks is sharply defined by See also:absolute See also:physical conditions. Within certain definite limits of See also:depth, temperature and salinity, the only requirement is a suitable place for attachment. Oysters cannot thrive where the ground is composed of moving See also:sand or where mud is deposited; consequently, since the size and number of these places are very limited, only a very small percentage of the young oysters can find a resting-place, and the remainder perish. Mobius estimates that for every oyster brought to 'Connecticut has greatly benefited its oyster industry by giving to oyster-culturists a See also:fee See also:simple See also:title to the lands under control by them. market from the Holstein banks, 1,045,000 are destroyed or die. By putting down suitable "cultch " or " stools " immense quantities of the wandering See also:fry may be induced to settle, and are thus saved. As a rule the natural beds occupy most of the suitable space in their own vicinity. Unoccupied territory may, however, be prepared for the reception of new beds, by spreading sand, See also:gravel and shells over muddy bottoms, or, indeed, beds may be kept up in locations for permanent natural beds, by putting down mature oysters and cultch just before the time of breeding, thus giving the young a See also:chance to fix themselves before the currents and enemies have had time to accomplish much in the way of destruction. The collection of oyster spat upon artificial stools has been practised from time immemorial. As See also:early as the 7th See also:century, and probably before, the See also:Romans practised a See also:kind of oyster culture in See also:Lake See also:Avernus, which still survives to the present See also:day in Lake See also:Fusaro. Piles of rocks are made on the muddy bottoms of these salt-water lakes, and around these are arranged circles of stakes, to which are often attached bundles of twigs. Breeding oysters are piled upon the rookeries, and their young become attached to the stakes and twigs provided for their reception, where they are allowed to remain until ready for use, when they are plucked off and sent to the market. A similar though ruder See also:device is used in the Poquonock See also:river in Connecticut. See also:Birch trees are thrown into the water near a natural bed of oysters, and the trunks and twigs become covered with spat; the trees are then dragged out upon the See also:shore by oxen, and the young fry are broken off and laid down in the shallows to increase in size. In 1858 the methods of the See also:Italian lakes were repeated at St Brieuc under the direction of Professor P. Coste, and from these experiments the See also:art of artificial breeding as practised in France has been See also:developed. There is, however, a marked distinction between oyster-culture and oyster-breeding. In considering the oyster-culture in France it is necessary to distinguish the centres of See also:production from the centres of rearing or fattening. The chief centres or regions of oyster production are two, (i) Arcachon, (2) See also:Brittany. The See also:basin of Arcachon has an area of about 38,000 acres at high water, and only about 15,000 acres are under water at low See also:tide. The water is See also:salter than the sea. At the beginning of the 19th century there were only natural oyster beds in the basin, and these produced 75 million oysters per annum. But in the See also:middle of the century the natural beds had been almost exhausted and the system of government control, letting " parks " to private tenants, and artificial cultivation was instituted. Certain beds in the basin are reserved and kept under government control. Cultch is placed upon them every year, and gathering of oysters upon them is allowed only at intervals of two or more years, when the authority thinks they are sufficiently stocked to permit of it. These beds supply spat for the private cultivators. The latter collect the spat on tiles: these are made of earthenware and See also:concave on one side. One of the most important points in the system is the coating of the tiles with See also:lime. It is necessary to detach the young oysters from the tiles when they are nearly a year old (detroquage) : this could not be done without destroying the oysters if they were attached directly to the surface of the See also:tile. The coating of lime or See also:mortar is soft and brittle, and consequently the young oysters can easily be detached with a stout See also:knife. The method of liming the tiles (chaulage) consists in dipping them into a liquid mixture of lime and water. Sometimes lime only is used, sometimes equal quantities of lime and sand, or lime and mud. Often it is necessary to repeat the dipping, and for the second coat See also:hydraulic lime may be employed. The tiles coated with lime are set out on the shore near the low-water See also:mark of See also:spring tides, at the beginning of the spatting season. This is earlier in the See also:south of France than in England : at Arcachon the collectors are put in position about the middle of See also:June. Various methods are adopted for keeping the tiles in place and for arranging them in the position most favourable to the collection of spat. At Arcachon they are arranged in piles each layer being transverse to the one below, so that the space formed by the concavity of the tile is kept open. A wooden See also:frame-See also:work often surrounds the heap of tiles to prevent them being scattered by the waves. In the following season, about See also:April, the young oysters, then from 1 to 1 in. in diameter, are separated or detroques. They may then be placed in oyster cases (misses ostreophiles) or in shallow ponds (claires) made on the fore-shore. The cases are about 8 in. deep, made with a wooden frame-work, and galvanized See also:wire netting See also:top and bottom, the lid being hinged. These cases about 8 ft. by 4 ft. in dimensions are fixed on the fore-shore by means of See also:short posts driven into the ground, so that they are raised about 9 in. or ft. from the latter. The young oysters grow rapidly in thesecases, and have to be thinned out as they grow larger. When they have been in the boxes a year they are large enough to be placed in the claires or simply scattered along the fore-shore. In Brittany the chief seat of oyster production is the gulf of See also:Morbihan, where the estuaries of numerous small See also:rivers furnish fore-shores suitable to the industry. Here the prevalence of mud is one of the chief obstacles, and for this See also:reason the tile-collectors are usually fastened together by wire and suspended to posts (tuiles en bouquets). The collectors are not set out before the middle of See also:July. The natural beds from which the supply of spat is derived are reserved, but apparently are insufficiently protected, so that much poaching goes on. These two regions of production, Arcachon and Morbihan supply young oysters for " relaying," i.e. rearing, not only to numerous places on the coast of France, but also to England, Ireland and elsewhere. Among rearing districts Marennes and La Tremblade are specially celebrated on See also:account of the extensive system of claires or oyster ponds, in which the See also:green oysters so much prized in See also:Paris are produced. The See also:irrigation of the claires is entirely under control, and the claires undergo a See also:special preparation for the production of the green oysters, whose See also:colour seems to be derived from a species of Diatom which abounds in the claires. In Holland the French system of oyster-culture is followed in the estuary of the See also:Scheldt, with some modifications in detail. The tiles used are See also:flat and heavy, and are placed on the foreshores in an oblique position resting on their edges and against each other. The tiles with the young oysters on them are placed in enclosures during the See also:winter, and detroquage is carried out in the following summer. In England the use of tiles has been tried on various occasions, in See also:Cornwall on the river Fal, at Hayling Island and in See also:Essex, but has nowhere become permanently established. The reasons for this are that the fall of spat is not usually very abundant, and the kind of labour required cannot be obtained at a sufficiently cheap rate. In many places oysters are simply imported from France and Holland and laid down to grow, or are obtained by dredging from open grounds. At Whitstable most of the stock is thus obtained, but cultch (i.e. dead shells) is here and elsewhere scattered over the ground to serve for the attachment of spat. The use of cultch as See also:collector is a very See also:ancient practice in England, and is still almost universally maintained. In the estuaries of Essex there are many private or semi-private oyster fisheries, where the method of culture is to dredge up the oysters in autumn and place them in, pits, where they are sorted out, and the suitable ones are selected for the market. Just before the close season the young oysters and all the rest that remain are scattered over the beds again, with quantities of cultch, and in many cases the fishery is maintained by the See also:local fall of spat, without importation.. In some places where the ground is suitable cultch is spread over the foreshores also to collect spat. The genuine English " native " is produced in its greatest perfection in the Essex fisheries, and is probably the highest priced oyster in the world. In addition to the literature quoted see also the following: See also:Rap-See also:port sur See also:les recherches concernant l'huitre et l'ostreiculture publie See also:par la See also:Commission de la Societe Neerlandaise de Zoologie (See also:Leiden, 1883—'884); P. See also:Brocchi, Traite de l'ostreiculture (Paris, 1883) ; Bashford See also:Dean, European Oyster Culture, Bulletin U.S. See also:Fish Commission, vol. x. for 189o, vol. xi. for 1891; J. T. See also:Cunningham, See also:Report of the Lecturer on Fishery Subjects, in Report of Technical Instruction See also:Committee of Cornwall (1899, 1900). . (G. B. G.; J. T. Additional information and CommentsThere are no comments yet for this article.
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