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1980

A Review Of Introductions Of Exotic Oysters And Biological Planning For New Importations

Jay D. Andrews Virginia Institute of Marine Science

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Recommended Citation Andrews, Jay D., A Review Of Introductions Of Exotic Oysters And Biological Planning For New Importations (1980). Marine Fisheries Review, 42(12), 1-11. https://scholarworks.wm.edu/vimsarticles/1250

This Article is brought to you for free and open access by the Virginia Institute of Marine Science at W&M ScholarWorks. It has been accepted for inclusion in VIMS Articles by an authorized administrator of W&M ScholarWorks. For more information, please contact [email protected]. A Review of Introductions of Exotic Oysters and Biological Planning for New Importations

JAY D. ANDREWS

Introduction ber of coastal communities around the seed from acclimated broodstocks pre­ world. In the temperate zone of the cariously established in Boothbay Har­ Oysters have been transported by Northern Hemisphere only the Atlantic bor, Maine (Welch, 1966). mankind since Roman times because coast of North America does not now Extensive transplantation of native they are superbly adapted to with­ depend on this species for oyster pro­ oysters along major coasts has long stand long journeys out of water. In duction. Crassostrea gigas was suc­ been used to sustain fisheries without this paper, the consequences of man's cessfully introduced to western North regard for adaptations of local races to movement of oysters and the biological America, western European, and Aus­ new environments. Transplantation of requirements for future introductions of tralasian coasts. Most introductions be­ flat oysters from one country to another oysters are reviewed. gan as casual unplanned events that in Europe has a long history. It was Only one species of oyster, Crass­ were soon followed by deliberate ones instigated primarily because of failure ostrea gigas, the Pacific oyster, has on a larger scale. With the aid of man, of reproduction in the cold waters been introduced as a successful mem- the oysters spread on the coasts to the of northern countries such as France, limit of their tolerances of climates Great Britain, the Netherlands, and and salinities. Denmark (ICES, 1972). Crises such as Some scientists desire to culture C. continent-wide unexplained mortalities ABSTRACT-Importation and trans­ gigas in New England. A major prob­ in 1920-21 and recent (1967-76) mortal­ plantation of exotic oysters has probably resulted in the introduction into new areas lem is keeping it confined to New ities from diseases also caused exten­ of more marine invertebrate species than England and away from large oyster sive importations from the Adriatic Sea any other ofman's activities. Unintentional fisheries of C. virginica to the south. and Greece as well as Spain and Portu­ imroductions have resulted from careless Crassostrea gigas is a vigorous, fast­ gal. No consideration was given to movements of oysters without planning or growing oyster that could compete ad­ racial traits of these diverse stocks for consideration of consequences. Diseases and parasites of marine invertebrates are vantageously with the native oyster, adaptation to various local climates poorly known and oysters cannot be ade­ and possibly replace it, in the warm (Andrews, 1979b). However, the Neth­ quatelv diagnosed or inspected for prob­ waters of Chesapeake Bay and Dela­ erlands is trying to build up stocks of lems by biologists. The vigorous Pacific ware Bay. isolated native oysters which exhibit oyster. Crassostrea gigas. was introduced to the Atlamic coast of western Europe in The famous European flat oyster, greater winter hardiness than imported the past decade with serious effects on OSlrea edulis, has been tried on both French seed oysters now sustaining the native oyster species. Some scientists pro­ coasts of North America and in Japa­ industry (Drinkwaard, 1978). Trans­ pose to introduce it to the Atlamic coast of nese waters with Iittle success as a plantation between regions on a coast North America. primarily for culture in self-sustaining species. It is frequently New England. If imroduClion is carried out is a short-term marketing expedient properly, diseases and parasites mav be grown in hatcheries in North America that is not expected to contribute to excluded bv breeding selected brood oysters for experimental plantings. This favor­ rehabilitation of native stocks. How­ in hatcheries under quarantine conditions. ite raw-bar oyster sustains a small ever, it may result in genetic mixing The progeny mav then be tested in con­ industry in Maine by use of hatchery and the spread of pests and diseases. trolled natural environments for growth rates and reaction to native diseases and The impact of exotic marine species parasiles. Selection of races. strains. and Jay D. Andrews is Senior Marine Scientist, on endemic communities is difficult to hybrids may be pursued in hatcheries to fit Virginia Institute of Marine Science and College predict until they are widespread in the of William and Mary, Gloucester Point, VA exotic oysters to new ecosystems. Intro­ new area and irrevocably established. duction -of an exotic species is a serious 23062. This paper is Contribution No. 968 from the Virginia Institute of Marine Science and Introductions of marine exotics are irreversible evel1t which merits careful con­ College of William and Mary. Views or opin­ more difficult to isolate and to co~­ sideration of the reasons for culture of ions expressed or implied are those of the author a new shellfish and Ihe consequences to and do not necessarily reflect the position of the trol than terrestrial ones because of native biOla Gnd coastal ecosystems. National Marine Fisheries Service. NOAA. rapid dispersion of larvae by currents.

December 1980 Inadequate monitoring and limited be considered accidental. The risks and trast, organisms acclimated to mild knowledge of identity, abundance, and consequences are the same as for strict­ oceanic cI imates are usually not able distribution of native species may leave ly accidental importations, i.e., inad­ to survive either summer or winter ex­ exotic species obscured for long peri­ vertent introductions. Most large-scale tremes in severe climates of continen­ ods. Often diseases of marine inverte­ importat:ons of oysters were preceded tal-type coasts. These adaptations to brates become known only after mass by accidental ones on a small scale. climates explain in large measure the mortalities of the host species (Sinder­ These accidental importations may pre­ numerous invasions of exotic species in mann, 1976). Seldom can such diseases pare the way sociologically for sub­ the temperate zones on the western be proven to be introduced. The strong­ sequent large-scale deliberate ones. coasts of continents (Hanna, 1966) est circumstantial evidence is that of Importee oysters may exhibit excellent whereas introduced species are rare on timing when stocks were transplanted growth and survival while native spe­ eastern coasts. Tropical coasts are more or imported immediately before an cies are destroyed by exotic diseases easily invaded (Courtenay and Robins, epizootic mortal ity. associated with the importation. This 1973). series of events occurred recently in In general, Ostrea species are adapt­ Categories of Importations France following importation of C. ed to oceanic climates and Crassostrea The transport of endemic oysters of gigas in 1966 (Marteil, 1976). to continental ones, although excep­ the same species along a coast is de­ tions occur as waters along a coast fined as transplantation (Mann, 1979). Adaptations of Marine Organisms become more tropical. Consequently, This is not the primary concern of this to Oceanic and Continental Climates Ostrea species breed at lower summer discussion. After hundreds of years of Continental air masses cro sing large temperatures (usually < 20° C) and are transplantation the potential for further land masses exhibit the rapid heating more sensiti ve to low salinities and low damage may be minimal. However, and cool ing attri butes of the land with winter temperatures. They will not care should be exercised in moving strong warming during summers and withstand intertidal exposure to heat or endemic oysters from regions of a coast prolonged cooling from back-radiation cold. Ostrea edulis and O. lurida are that have been isolated by land barriers, in winters. Coastal waters on the east­ the endemic species of western Europe ocean currents, or even temperature ern shores of continents share these and western North America, respec­ differences for many centuries. Ex­ extremes of atmospheric temperature tively; Crassostrea virginica and C. changes between such areas on a coast with cold winter and warm summer gigas are respective endemic com­ carry the same dangers from diseases temperatures. In contrast, coastal wa­ mercial oysters of eastern shores of and pests as from importation of exotic ters on western shores of continents, North America and Asia. These adap­ oysters of a different species. Examples bathed by moderated oceanic air mass­ tations to respective climates should be of isolated regions in North America es, receive mi Id weather, therefore, considered before irreversible conse­ include the Gulf of Mexico and the exhibit cool summers and mild winters. quences of importations are incurred. Gulf of St. Lawrence from which trans­ Hydrocl imographs for estuaries on the Examples of serious alterations of bi­ plantings to and from the Middle Atlan­ eastern coast of North America show otic communities by importations of tic coast have been rare. The Mediter­ annual temperature ranges of 20°C or exotic oysters with their associated ranean Sea and the Atlantic coast of more inshore, whereas those for the faunas are found on the maritime coasts Europe could also be hazardous regions western coast exhibit only about 10°C of western Europe and western North for exchanges of oysters. range (Andrews, 1971). These differ­ America (Quayle, 1964; Hanna, 1966; Importations of exotic species of ences in maximal and minimal mean Dundee, 1969; ICES, 1972). oysters that result in establishment of temperatures affect adaptations for new populations are called introduc­ summer breeding and winter survival Brief History of Major tions to distinguish them from trans­ of endemic species on the respective Introductions of Oysters plantations along a coast. Introductions coasts. Crassostrea angulata From from one continental coast to another The temperature effects on imported Portugal and Spain to France are nearly al ways through the acti vities exotic species are most dramatic on and agencies of man because wide land maritime coasts which receive ocean­ Crassostrea angulata, the Portu­ or ocean barriers precl ude natural dis­ tempered air masses and currents that guese oyster, is known to have thrived persal. These importations may be de­ induce summer upwelling of deep, cold in southwestern Portugal and southern Iiberate or accidental depending upon waters. The resulting moderated water Spain for several hundred years (Kor­ the roleofman. They can be subdivided temperatures and nutrient enrichment ringa, 1970). The Sado and Tejo Rivers into several categories according to the from upwell ing ensure rapid growth in and the Gulf of Cadiz provide waters purpose of the importation, agent of a continuous growing season for most warm enough (>20°C) for reproduc­ dispersal, and stage of the organism organisms. Marine species native to tion of this subtropical oyster. The utilized (ICES, 1972). For purposes of continental-type climates with wide oysters were little used locally. When discussion, casual im portations ofsmall distributions and northern ranges are the natural public beds of O. edulis in lots of oysters without planning, super­ most likely to establ ish populations on southwest France and northern Spain vision, or subsequent monitoring may coasts with oceanic climates. In con- were depleted about 1850, a famous

2 Marine Fisheries Review report by Coste (1861) to Napoleon decl ine in production of the Portuguese oyster, C. virginica, began about 1869 III initiated private culture. With a oyster from mortalities caused by the to San Francisco Bay with completion scarcity of O. edulis seed stocks, C. gill disease resulted in a decision to of transcontinental railroads (Hanna, angulata was soon imported from Por­ import C. gigas in commercial quanti­ 1966). Shipments of oysters from New tugal's Sado River to stock private ties in the early 1970's. In southwestern England continued to various rail beds. The initial introduction of C. France, C. gigas reproduced prolifical­ points along the coast until about 1935. angulata to the French coast was at­ ly permitting the cessation of commer­ Growth was excellent in the early years tributed to the dumping of a shipload cial importations after 1975. but failure of reproduction from low of spoiling oysters in the Gironde Another disease appeared in O. summer temperatures required regular River in 1868 (Marteil, 1976). Crass­ edulis in Brittany in Aber Wrach in importations from the east coast. oslrea angulata proliferated in the 1968 where some Pacific oysters were Crassoslrea virginica is now rare on Gironde and other areas of southwest being held. Aber Disease, caused by the Pacific Coast with one small per­ France providing seed stocks for a a protozoan, Marteilia refringens, sistent population in Boundary Bay, hundred years. Eventually, in the caused extensive mortalities of flat B.C. (Bourne, 1979). Importations over 1960's, it produced five times as many oysters in Brittany. Crassoslrea gigas a period of 60 years failed to establ ish oysters in France as O. edulis (Marteil, was not appreciably affected by either the species. The cool California cur­ 1970). Cold summer temperatures pre­ of the new diseases. A shell malady of rent and accompanying upwelling kept vented the Portuguese oyster from C. gigas has affected marketing some­ coastal waters too cold for regular reproducing in Brittany and more what (Marteil, 1976). Crassostrea reproduction. Nevertheless, Califor­ northern countries; therefore it was gigas has completely replaced C. nia permitted regular importation and transplanted annually to Great Britain angulala in French waters south of planting of market-sized oysters from for growth and marketing. Brittany and it has tended to breed Long Island for raw-bar trade in the Although C. angulala was consid­ farther north in Brittany and in the 1960's and 1970's. During this period, ered to have a less desirable taste than Netherlands in warm summers such risks were high of introduction of new the European flat oyster, it provided in as 1976 (23°C). Intensive spatfalls diseases prevalent on the east coast. abundance relatively inexpensive oys­ through 1976 in southern France re­ CrassOSlrea gigas has supported a ters for Europe. It was a useful intro­ duced the growth rate by crowding. growing industry along wide reaches of duction to supplement production of the Pacific Coast. The earl iest importa­ the more temperature-sensitive O. Crassostrea virginica (1869) tions were made by oriental residents edulis which is slower and more diffi­ and C. gigas (1902) to about 1902 (Kincaid, 1951). Beginning cult to grow. The Portuguese oyster Pacific Coast of North America in the late 1920's thousands of cases of often sets and grows intertidally which The native Olympia oyster, Ostrea spat on shells were shipped from Japan offers cultural advantages of pest con­ lurida, of this coast is small, slow­ on decks of ships (Quayle, 1964). High trol and intensive visual farming at growing, and difficult to culture (Kor­ prices and competition with air ship­ low tides. It is difficult to judge the ringa, 1976). Overfishing of natural ments to France greatly reduced Pacific extent of biological competition in beds caused depletion of most areas in Coast importations from Japan in the France because O. edulis was grown the last half of the 19th century. A early 1970's. Fortunately, the industry primarily in Brittany and was over­ further decline occurred in the mid­ has developed its own seed supply over fished and depleted in southwest France 1920's despite adoption of European the years. Two areas of regular spat­ before C. angulata was introduced. cultural methods of diked parks to falls, Pendrell Sound, B.C. , and Dabob The Portuguese oyster certainly re­ protect the cold- and heat-sensitive Bay, Wash., supplement seed supplies placed the flat oyster in the warm Olympia oysters from exposure to air for growing areas with irregular or no waters of southern France where the temperatures. From 1928 to 1945, pulp­ sets (Quayle, 1969; Bourne, 1979). latter was native. mill wastes were blamed for the decline Crassostrea gigas From in southern Puget Sound (McKernan et Crassostrea gigas From Japan to Australasia (1947-52) Japan to France (1966) aI., 1949). The species did not recover production appreciably after the pulp­ Crassoslrea gigas became estab­ A small importation of 900 kg of mill was closed. Oyster planters turned lished in Tasmania about 25 years ago. seed of the Pacific oyster was intro­ their attention to C. gigas in the late Five shipments from Japan to Australia duced to the Marennes area of France in 1920's. This species grew to market­ were made between 1947 and 1952 March 1966 (ICES, 1972). The follow­ able size in 2 years from imported (Thomson, 1952, 1959; Bourne, 1979). ing fall (November 1966), a new dis­ Japanese seed whereas the Olympia Three races of Pacific oysters (Mi­ ease was found in the gills of C. oyster required about 4 years to attain yagi, Kumamoto, and Hiroshima) were angulata by Trochon (Marteil, 1969, its maximum size of 2 inches. Ostrea shipped as spat on shells and planted at 1976). The disease spread widely in lurida did not fulfill the needs of a two sites. Oysters planted at Pittwater France and in the fall of 1967 an region with rich waters suitable for on the southern shore of Tasmania embargo was placed on further impor­ extensive oyster culture. survived well. Those exposed on the tations from Japan. However, the rapid The first importations of the eastern shores of southern West Australia died.

December 1980 3 One recent shipment (1970) from Japan and marketing (lCES, 1972). Among The importation of tropical C. rhizo­ concluded the importations (Medcof the exotic species introduced with oys­ phorae, the mangrove oyster, from and Wolf, 1975). Transplantations from ters from North America was the pred­ French Guyana to France defies expla­ Pittwater were made to Pt. Sorell on the atory oyster drill, Urosalpinx cinerea, nation. Why this oyster should be northern shore of Tasmania where the found in England in 1920. It is now well expected to survive in the cold waters species is now firmly established. Rela­ established on the southeastern and of the French Atlantic coast is not ti ve isolation at Pittwater provided a southern coasts. A gastropod com­ evident and its use in French oyster period for observation of growth and petitor, Crepidula fornicata, which at­ culture is obscure. Continued importa­ mortalities before native oysters were taches to oysters in chains, exhibited tions present the threat of introducing exposed. Unfortunately, all three races fantastic populations in England on oyster diseases and parasites of the were planted in the same area and the derelict beds called "mud and lim­ western Atlantic (Maurin and Gras, surviving race of accl imated oysters is pets" after its introduction about 1880 1979). not known-probably Miyagi or Hiro­ (Orton, 1937). [t spread to the conti­ shima oysters or a mixture. nent and is now distributed widely Exotic Mollusks on the Scattered individuals of C. gigas from Sweden to France. It has pelagic Pacific Coast of North America appeared in New South Wales in the larvae but was probably spread mostly 1970's where an important commercial by man while attached to mussels and A long list of exotic biota introduced fishery for C. commercialis is pursued oysters. Other American species prob­ from New England and Japan has been (Medcof and Wolf, 1975). Some speci­ ably introduced with oysters, but compiled by Hanna (1966) and Dundee mens were found on cultch sticks used exhibiting more subtle, noneconomic (1969). The long periods of repeated to collect native oysters, implying that effects, include the bi valves Petricola oyster importations offered many op­ they were derived from larvae origi­ pholadiformis, Mya arenaria, and a portunities for establishment of exotic nating in the locality. The Pacific oys­ mud crab, Rithropanopeus harrisi, all species in this mild oceanic-type cli­ ter outgrew the native oyster on these now with wide distributions in northern mate. Species capable of breeding sticks suggesting that environmental Europe (ICES, 1972). at temperatures of 20°C or less, or conditions are favorable for growth. The introduction of C. gigas to finding warm niches, were successful The location and source of brood oys­ France has added some oriental spe­ colonizers. The introduced mollusks ters for spat found in New South Wales cies to the fauna but their eventual exemplify the opportunities provided are unknown but probably they were status after importations ceased in immigrant species by man's importa­ derived from small accidental or illegal 1975 remains to be determined (Gruet tions. In the early years, no care was importations from Tasmania. Dispersal et aI., 1976). The parasitic copepod exercised in cleaning shipments of has been slow in Australasia providing Mytilicola orientalis may be the most oysters from New England or Japan of opportunities to monitor population in­ destructive species introduced because unwanted aliens. Bonnot found 22 spe­ creases, and permitting industry adap­ it attacks both oysters and mussels. cies of marine shells in 20 boxes of tations if C. gigas replaces the native Sargassum muticum, an asiatic phaeo­ Japanese seed in 1930 (Hanna, 1966). rock oysters. Four Australian states per­ phyte introduced with Pacific oysters, All three commercially important mit transplantings of C. gigas whereas is establ ished on the coasts of France bivalves on the Atlantic coast of North New South Wales, with a valuable and England (Maurin and LeDantec, America were imported early to the fishery based on C. commercialis, does 1979). [t is spreading and interferes West Coast. Mya arenaria, appar­ not. Crassostrea gigas appeared sud­ with the commercial species Chondrus ently introduced accidentally with oys­ denly in New Zealand in 1970 from crispus. Two other algal species have ter transplantations, was immediately unknown sources (Dinamani, 1974) and been introduced: Undaria pinnafida in successful because of its adaptation is increasing rapidly in abundance. the Mediterranean Sea and Laminaria for breeding at low temperatures. It Further spread of C. gigas in temperate japonica on the Atlantic coast of is now distributed from Alaska to San zones of Australasia is to be expected. France. Fi ve additional in vertebrate Diego. The American oyster, C. vir­ species from the Orient have been ginica, and the hard clam, Mercenaria Introduction of Exotic Invertebrate collected in Brittany, including an mercenaria, did not reproduce suc­ Species Associated With Oysters annel id, a bi val ve mollusk, an antho­ cessfully which necessitated continued Exotic Invertebrate Species zoan, and two barnacle species (Gruet importations to produce crops. Both in Western European Waters et ai., 1976). The two oyster patho­ species can be grown commercially on gens that appeared immediately after the West Coast using hatchery seed. The most serious introductions of the first introductions of C. gigas are Several western Atlantic mollusks foreign species accompanied importa­ probably exotics from Japan also. The closely associated with oysters for tion of American oysters, C. virginica, elimination of the Portuguese oyster food or substrate achieved distribu­ to Great Britain. Reproduction did not from France and the serious reduction tions on the West Coast in localized occur in the cold waters, therefore they of production of the flat oyster are niches where oysters are grown. The were relaid in British waters annually the most dramatic consequences of oyster predator, Urosalpinx cinerea, is from the late 1800's to 1939 for growth im portation of C. gigas. often found on oyster beds but not in all

4 Marine Fisheries Rel'ie\\' areas where salinities are favorable. Parasites and diseases have the ad­ Delaware Bay All three species of Crepidula (c. vantage of often being able to attack Disease On Mid-Atlantic fornieata, C. eonvexa, and C. plana) new hosts when introduced to a new Coast of North were introduced but only C. fornieata ecosystem, and they survive transpor­ America (1957) became established with a preference tation easily in mollusk hosts. for the warm diked waters used for O. The oyster industry of the Mid-Atlan­ lurida culture. Many imported exotics tic Coast was crippled by the sporozoan The Role of Importations in were first observed with oysters in pathogen Minchinia nelsoni which Spreading Diseases and Parasites local seafood markets (Hanna, 1966). appeared in Delaware Bay in 1957 Modiolus (Guekensia) demissus was Along any given continental coast (Haskin et aI., 1966), and in Chesa­ very common on the warm intertidal there are marine communities, iso­ peake Bay in 1959 (Andrews and Wood, shores of San Francisco Bay during the lated for thousands of years by phys­ 1967). More than 90 percent of oysters years of oyster imports and was some­ ical barriers, that had no opportunity growing in the two bays in waters times marketed. The common east­ to exchange fauna with neighboring > 15%0 salinity were killed within 2 ern mud snail, Nassarius (Ilyanassa) areas until modern man and his trans­ years. obsoletus, is now localized in warm portation arrived. Many races of C. The origin of this disease is un­ bays where C. virginiea was imported. virginiea occur along the North Atlantic known but imported oysters is a likely Several small mollusks such as Gem­ coast of America (Stauber, 1950) and explanation (Rosenfield and Kern, ma gemma from the East Coast and they appear to have retained their 1979). Many small lots of exotic oys­ Batillaria zonalis from Japan are genetic traits despite much transplant­ ters have been planted along the East widely established in Puget Sound and ing between regions. By transplanting Coast from Louisiana to Maine (Dean, California. Some mollusks, e.g., Area oysters across these natural barriers, 1979). Often mature oysters were transversa and Busyeon eanalieulatus, man has provided many opportunities brought in secretly so that no records were present only as long as imports for parasites and diseases to find of the origins or the histories of im­ continued because they did not breed. susceptible hosts. portations exist. A few examples will The most spectacular accidental in­ illustrate the pattern of these careless vasion of West Coast ecosystems was importations. Malpeque Bay Disease made by the Japanese clam Venerupis Recently, C. gigas from the West in Canada (1914) japoniea. It has a wide distribution and Coast of North America was planted in great abundance in Japan. It has been The most infamous mortality of oys­ Maryland waters by a seafood dealer highly successful on the West Coast ters in North America was caused by which resulted in a specific law in that and has filled a warm intertidal niche Malpeque Bay Disease in the east­ State prohibiting the species. The oys­ not occupied by native clams (Quayle, ern Canadian provinces (Needler and ters were recovered as completely as 1964). It is widely accepted both eco­ Logie, 1947). Oysters from New En­ possible by scuba diving. An oyster­ logically and as a convenient shellfish gland were imported into MaJpeque man from Delaware saw impressive for human food. Several species of Bay, Prince Edward Island, in 1914. specimens of C. gigas at the Seattle Venerupis endemic to western Europe This was to supplement reproduction World's Fair in 1962 and he had some are also used for food, and are cultured which had become inadequate from sent to his home state for planting. The there in hatcheries for commercial overfishing and depletion of stocks oysters were confiscated by a biologist plantings. The Japanese oyster drill, (Needler, 1931). A severe mortal ity who held them in trays in open waters Oeenebra japoniea, is common on first occurred in 1915-16 and the in Rehoboth Bay, Del., for several West Coast oyster beds from acci­ epizootic continued until about 1930. years without serious mortality or ap­ dental importations. The native oysters achieved resis­ parent successful reproduction. Crass­ Two nonmolluscan species intro­ tance in a few generations, but over a oslrea gigas was apparently resis­ duced to the West Coast from Japan long period due to infrequent spatfalls tant to Delaware Bay disease which are serious parasites of oysters and (Logie, 1956). The disease spread at that time killed C. virginica in mussels. The flatworm predator Pseu­ slowly around the bays of the Island Rehoboth Bay. dostyloehus ostreophagus kills oyster and in 1952-55 it spread to tributaries A bushel of C. gigas was planted in spat in Puget Sound and is difficult to of mainland New Brunswick in the Gulf Barnegat Bay, N.J., in the early 1930's. control. A macroscopic red copepod, of St. Lawrence. The causative orga­ These oysters failed to grow, which is Mytilieola orientalis , infests intestinal nism has not been demonstrated al­ unusual for this species, and they died tracts of mollusks which affects their though exposure of susceptible oysters over a 2-year period. A shipment of C. glycogen condition and saleability from Bras d'Or Lakes shows that the cucullala (= C. commercialis) failed to (Glude, 1975). This copepod genus is pathogen is still present. Curiously, survive air travel from Australia to New more serious as a parasite of mussels the disease has not been associated Jersey in the care of T. C. Roughley than of oysters. An extensive literature with mortalities in the New England (Nelson, 1946). Two eminent scien­ exists on M. inteslinalis, the west­ area from which it was supposed to tists were invol ved which reflects the ern European species (Marteil, 1976). have originated. attitude toward importations at that

December 1980 5 time. None of these known incidents by Perkinsus marinus (formerly Der­ the Pacific oyster would spread rap­ fits precisely the timing of arrival mocystidium marinum) was introduced idly in Europe. The economic and of the pathogen M. nelsoni in Dela­ to Chesapeake Bay with seed oysters political decision to hasten the replace­ ware Bay. from South Carolina or the Gulf of ment of C. angulata by C. gigas For about 6 years prior to the ap­ Mexico prior to 1940 (Andrews and involved additional risks, but sustained pearance of Delaware Bay disease, Hewatt, 1957). the French industry without serious seed oysters from the James River and reductions in total production (Maurin Seaside of Eastern Shore, Virginia, Biological Planning for New Importations and LeDantec, 1979). The Atlantic had been transplanted to Delaware coast of France was the major source of Bay in large quantities. It is now The rationale for introducing new seed of O. edulis for Holland and known that Seaside oysters are infected species of commercial organisms is some C. angulata for Great Britain. with an endemic pathogen, Minchinia usually economic and political, and not The cutoff of seed oysters encouraged costalis , which is closely related to based on biological need. It could be development of hatcheries in Great M. nelsoni (Andrews, 1979a). Possibly argued that survival of the fittest is the Britain to produce C. gigas spat for by hybridization or mutation, a new most rational way to handle exotic England, Germany, and France. Crass­ virulent race of pathogens arose in oysters. Presumably, this could be jus­ ostrea gigas is now established as wild Delaware Bay waters (Andrews, 1968). tified by the success of Crassostrea stocks in Holland and also grown in However, I believe it is more likely that gigas, the Pacific oyster, on the major the Adriatic Sea and the Mediterranean the pathogen M. nelsoni was intro­ oyster-growing coasts of the temperate Sea (France). duced from Asia. zones of the world. It has succeeded The proponents of use of C. gigas biologically in western Europe, Tas­ in New England argue that land and Sacculinid Parasite mania, New Zealand, and the West cold water barriers would prevent lar­ of Mud Crabs Introduced Coast of North America as well as its vae from spreading southward (Dean, From Gulf of Mexico (1962-63) native areas on eastern Asian coasts. It 1979). But man is the problem. No laws One last example can be documented is vigorous, fast-growing, relatively or regulations will prevent the tourists of an oyster transplantation that greatly disease resistant, and increasingly ac­ in Maine from taking home to Chesa­ altered crab populations in Virginia. cepted as a raw-bar oyster due to peake Bay waters live oysters sold This event illustrates the complexity of rapidly changing economic and social for raw consumption. From Massa­ such faunal changes. Disruption of oys­ mores (Bourne, 1979). Why not accept chusetts southward the warm summers ter production in Virginia by Delaware this superior oyster as the standard for of our continental climate should per­ Bay disease caused oystermen to search temperate zone ostreid culture? Crass­ mit C. gigas to reproduce successfully. for new sources of supply. Live oysters ostrea gigas was also tried in tropical The spatfalls could be excessive and were trucked from the Gulf of Mexico regions of the South Pacific with poor cover all objects in the water as has (Louisiana, Texas, and Florida) to Vir­ results (Bourne, 1979). Fortunately, occurred in the Arcachon area of ginia for shucking at waterside plants most consultants and FAO officials are France. Crassostrea virginica already where shells and wastes were discarded recommending use of native oysters in exhibits this tendency in South Caro­ near native oyster beds. the tropics. lina, Georgia, and some areas of the A year or two after importations The French decision to introduce C. Gulf of Mexico. It is not conducive began (1962-63), two dominant species gigas has greatly altered oyster culture to production of quality oysters (Hop­ of mud crabs, Eurypanopeus depressus in Europe (Marteil, 1969,1976). French kins, 1954). and Rithropanopeus harrisi, were oyster growers are adapting the tech­ The careful introduction of C. gigas found to be infested with a castrat­ nology of culture to C. gigas with new into Maine through hatcheries and quar­ ing sacculinid (cirripede) parasite cultural methods and using new areas antine methods to avoid diseases and (Loxothylacus panopaei) (Van Engel in Brittany where C. angulata was not pests (Andrews, 1979) is most desirable et a!., 1966). These formerly dominant grown. After excessi ve spatfalls oc­ in contrast to the French approach of crab species, which were major scav­ curred in the early 1970's, culminating mass importation. Yet elimination of engers of dead oysters, soon became in the hot summer of 1976, there have many agents of biological control pro­ scarce and have remained rare for 15 been spa:fall failures. The effects of vides the exotic species with a con­ years to the present. A third crab the parasitic copepod Mytilicola orien­ trived advantage in competition with species, Neopanope texana sayi, for­ talis and introduced foul ing organisms the native oyster. Provided it does not merly rare on oyster beds in Chesa­ are yet to be determined. The rapid encounter an endemic disease to which peake Bay, became abundant and is spread of gill disease resulted in elim­ it is susceptible, the Pacific oyster now the dominant mud crab. It is not ination of C. angulata, the Portuguese should thrive on the Atlantic coast. susceptible to the parasite. oyster, from France, and Aber disease This species is an intertidal oyster Fortunately, no new oyster diseases caused a severe decrease in Ostrea whose breeding populations escape were introduced with these Gulf edulis production (Alderman, 1979). many subtidal enemies. Miyagi oysters of Mexico transplantations. It is sus­ Once introduced into southern (northern race) also tend to reproduce pected that another disease caused France, it wa probably inevitable that and grow in slightly colder waters

6 Marine Fisheries Review than comparable native races (Hickey, sensitive species that does not survive introductions of shellfish into several 1979). The argument that C. gigas in the warm summer waters of Chesa­ countries of Europe are documented by has had opportunities to establish it­ peake Bay. It does not pose a threat in ICES (1972). self through careless importations is terms of growth and competition with not persuasive because circumstances the cultured native oyster south of Competition With and conditions of importation were New England. However, careless im­ Native Species not known. portations could introduce diseases and pests. The European shell disease pre­ The most important aspect of com­ fers warm waters (Alderman and Jones, petition is the ability of exotic oyster Attitudes and Rationales 1971). If imported, it could have disas­ species to reproduce successfully in for New Introductions trous effects on native oysters along new environments. On oceanic-type It is no longer tolerable to permit the our coast. It is reported to occur in coasts in the temperate zone, C. gigas whims of individual citizens and scien­ flat oysters on Prince Edward Island is limited in its reproduction by low tists to determine the distribution of in open waters after hatchery rearing summer temperatures. However, it is exotic species in an increasingly cos­ in quarantine 1 successful to the point of severe crowd­ mopolitan manner. Courtenay and It is assumed that future importations ing in southwestern France. Tempera­ Robins (1973) described the minimal of shellfish species will be made under tures for breeding are no problem for research and public review activities quarantine conditions using hatcheries Crassostrea species on coasts with con­ that should precede intentional intro­ to produce disease-free and parasite­ tinental-type climates. However, the ductions even for the best of rationales, free progeny for testing and eventual races of C. gigas evolved in Japan with such as biological control of estab­ release in open waters. This technique salinities near oceanic level may not lished pests. It should not be necessary has proven to be feasible with oysters, tolerate the low salinities found in for each state or country to prohibit and it overcomes the most serious Chesapeake Bay and other southern each species individually by specific problems of introductions in the past. estuaries during winter and spring. laws. All marine importations should However, this method is slow and The amount of competition between be made under appropriate licensing has not been practiced in distributing exotic and native species depends upon authority after public review and with C. gigas to Europe in recent years, usage and relative adaptations of exot­ clear obligations of control of orga­ except in Great Britain (Walne and ics to the new environments. In a nisms and responsibility for negative Helm, 1979). region, such as northern Europe or New consequences. In the case of commer­ The times and quantities of recent England, that depends on hatchery-pro­ cial species such as oysters, exporta­ French importations are not readily duced seed oysters, there is no re­ tions should be subject to the same available in the literature despite the productive competition. Therefore, the controls as importations. They should large volume of papers on the new most serious problem is eliminated. In not remain private decisions of indi­ diseases. No description of C. gigas the Netherlands, C. gigas has repro­ viduals or agencies whose motives may importations is given in a comprehen­ duced naturally in two recent years and be profit or ego satisfaction. si ve review of French shellfish culture competition with O. edulis may occur The rationale or reasons for intro­ (Marteil, 1976). An uninformed reader for space and food. However, Crass­ ducing a new oyster species must offer may not realize that the Pacific oyster is ostrea species tend to set and survive more advantages than just bringing a an exotic species in France. Ranson most intensively in intertidal zones new competing species to a coastline. (1967) showed that the prodissoconchs which reduces the competition for Importations may benefit one sector of or larval shells of C. gigas and space. Crassostrea gigas grows faster a coast and endanger a commercial C. angulata are indistinguishable and than its nati ve competitors in Australia industry in another sector. It is impor­ Menzel (1974) claimed they are the (Medcof and Wolf, 1973), western tant to determine how widely the new same species. Even if the oysters are Europe (Marteil, 1976) and eastern species will spread naturally and with accepted as cospecific, isolation from North American (Hickey, 1979). man's help. Except for special niches each other for several centuries is cer­ Excessive reproduction of oysters in (e.g., Pendrell Sound), C. gigas does tain to have altered their immunities to an area results in slow growth and not reproduce regularly on the Pacific diseases. Pathogens similar to those stunting. This is characteristic of seed Coast of North America, yet it spread causing mass mortalities in eastern oyster areas. Accumulation of succes­ widely during occasional warm years North America and western Europe sive year classes of young oysters on and persists without recruitment as have been found in Asiatic and Austra­ growing stocks is particularly harmful breeding populations for many years lian oysters (Kern, 1976; Sindermann, when shellfish are intended for raw-bar (Quayle, 1969). 1976; Perkins and Wolf, 1976). Trial trade, as in Europe where appearance Ostrea edulis is now grown in Maine is important. by hatchery reproduction from a small When crowding of oysters encom­ wild population adapted to the Gulf of passes most growing areas of a region, 'Drinnan, R. E., Fisheries and Environment Maine over a 30-year period (Welch, Canada, Halifax, N.S., Canada. Personal com­ such as in Seaside Virginia, South 1966). The flat oyster is a temperature- mun., 1979. Carolina and Georgia coasts, and many

December 1980 7 Gulf of Mexico estuaries, harvesting Eastern Shore, Va., suffered severe In eastern Canada, Ostrea edulis may require steaming and shaking drill predation when introduced to Del­ introduced from Conway, Wales, in out meats for canned products. These aware Bay in the 1950's. South Carolina 1957-59 did not survive the cold win­ canned oysters involve much waste oysters showed severe winter kills and ters. A stock from Holland (Loosanoff, of small oysters and they bring the remained poor when transplanted to 1955) was found to be hardy in Prince lowest price of all shellfish prepara­ Seaside of Virginia. The Malpeque Edward Island (Medcof, 1961) after tions (Lunz, 1954). Excessive repro­ Bay disease in Canada followed trans­ nearly three decades of selection in the duction in an estuary or region inhibits plantation of New England oysters. It cold waters of the Gulf of Maine. efficient culture and is almost impos­ is the classical example of the conse­ Even vigorous C. gigas may en­ sible to alleviate. quences of mixing oyster races along counter difficulties in adaptation along The potential effect of excessive a coast. the Atlantic coast from low salinities, populations of exotic oysters on other In Virginia, at least three races of warm climates, and diseases and pred­ species in an ecosystem can only be sur­ oysters are known by growth habits, ators. Depending upon the races intro­ mised. Predators, diseases, parasites, shape, and susceptibility to diseases duced from Asia, the species could and fouling organisms are likely to and predators. Most distinctive are fast­ be limited to certain areas and hydro­ increase when excessive abundance of growing thin-shelled Seaside oysters. graphic regimes. Since numerous races an exotic occurs from an irreversible Spatfall is excessive and predation in­ of C. gigas probably occur along the introduction. The full consequences tensive. Therefore, rapid growth and Asian coast, it would be advantageous can only become apparent with time. early harvesting are necessary. One to fit each new region with a race from a The most desirable introduction would might attribute all these traits to the comparable climate on the coast of be one where reproduction of the spe­ environment, but the oysters fail to origin (Newkirk and Haley, 1977). cies is limited by temperatures or iso­ grow and survive well in low salinity Much needs to be learned about races lated by hydrography to a few favorable waters within Chesapeake Bay. In con­ with respect to diseases, climates, and seed areas. This now occurs in Dela­ trast, Potomac River oysters are accli­ genetic parameters of oysters before ware Bay and Chesapeake Bay with the mated to low salinities, but are notable this is done. To learn by trial and error native oyster C. virginica. A good for their susceptibility to diseases, par­ from hasty, unplanned imports has un­ example of a successful introduction of ticularly Minchinia nelsoni (Andrews, acceptable risks for the industry and a species with limited reproduction 1968). They, too, exhibit vigorous for the stabil ity of present ecosystems. areas is C. gigas on the West Coast of growth and achieve larger sizes than North America. Seaside oysters. The typical oyster The Role of Hatcheries in Importations of Chesapeake Bay is exemplified by James River seed oysters which Most importations of exotic oysters Importance of Races Nelson3 believed were genetically in the past have been from natural sets There are many races of C. virginica selected for slow growth by 100 years of adult oysters or spat on shells grown along the Atlantic Coast of North of tonging the largest ones for market. in open waters. This made inspections America. These were first recognized Their small mature size may be a con­ for diseases and pests difficult if not because southern oysters failed to breed sequence of early stunting in the un­ impossible. The development of com­ in New England waters (Stauber, 1950). favorable growing conditions of James mercial and experimental hatcheries Morphological traits of shell thickness River. These three races illustrate the in most major oyster-growing areas and shape persist when oysters from genetic adaptations necessary to grow of the world has made it possible to several regions are grown in trays in oysters in only one region of the At­ avoid these problems. Hatchery-reared Chesapeake Bay. Differences in sus­ lantic coast. spat of 2-5 mOl may now be obtained a ceptibility and resistance to diseases In Europe, winter hardiness of few weeks after setting without expo­ are exhibited by races not previously Ostrea edulis is a problem when seed sure to natural waters. Thousands of selected by the pathogens (Andrews, oysters are transplanted from regions tiny live spat are shipped safely by air to 1968). Isozyme characterization has with warmer climates. Since the severe distant countries at small cost. The shown regional genetic differences wi nter kill of nati ves in 1962-63, the subsequent handling of tiny spat in along the Atlantic Coast2 despite much Netherlands is dependent on seed oys­ commercial numbers to prevent preda­ transplanting. ters from Brittany. A culture of one tion and smothering is tedious and Experience has taught oystermen to warm-season is followed because the costly, however. use local seed oysters if available. French race is less hardy than natives To avoid these problems of early Some disastrous losses occurred in (Korringa, 1976). There is also the handling of cultchless spat (Andrews oysters transplanted from other regions. threat of Gill and Aber diseases from and Mason, 1969), many hatcheries Thin-shelled oysters from Seaside of importing French oysters. have returned to the technique of set­ ting on shells or shell fragments which 2Anderson, W. W. University of Georgia, 3Nelson, T. C. Rutgers University, New Bruns­ facilitates early planting on oyster beds. Athens, Ga. Personal commun. wick, N.J. (Deceased). Personal commun. These lots must soon be planted in open

8 Marine Fisheries Review waters and hence carry the same risks after severe losses to Minchinia nelsoni slower growth in warm summer tem­ as wild oysters for importations. In the in the 1960's is evidence of this capac­ peratures, and due to low salinities in decade between 1966 and 1975, the ity. Moreover, the oyster industries in seed areas. The fouling of native or French imported 500 tons of adult the south are much more productive exotic oysters on growing and fattening oysters and 7,100 tons of spat on shells. than those in the north despite much beds by heavy spatfalls of C. gigas All of these were wild oysters from lower market prices and greater prob­ would be disastrous to the Mid-Atlantic British Columbia, Canada, and Japan, lems of diseases and predators. coast industry. Hatchery production respectively. North of Long Island, the major of seed oysters in the south is not oyster crop is raw-bar oysters which economically feasible yet. Unless C. sell for high prices thus compensating virginica is replaced by C. gigas, the Preimportation Studies for relatively low production. Supply problem of separation for marketing of Needed and Controls Required of seed oysters is a constant problem two easily distinguished species grow­ The rationale for introduction of C. in the north except in occasional years ing side by side may occur. Both quality gigas is based on its vigor and fast of intensive sets. Furthermore, slow of meats (fatness and taste) and differ­ growth. It appears to grow faster and growth in cold waters prolongs the ences in appearance of meats and shells during the cold season longer than cycle of marketable crops. will probably be noticeable to con­ native C. virginica. This applies only These factors provide a division of sumers. The proximity of C. gigas to the Miyagi race which is the only one interests in use of exotic oysters and in New England would enhance the tried in most new areas. production of seed oysters in hatch­ chances of accidental introduction Crassostrea gigas presents the po­ eries. In the north, the cost of hatchery in the south. Self-appointed "experi­ tential difficulties of: I) Competition seed is not prohibitive where natural mentel's" could easily buy shell stock and hybridization with C. virginica, spatfalls do not occur, and the fast­ in Maine and transplant it to Chesa­ 2) probable susceptibility to some growing C. gigas has an added appeal. peake Bay for later "eating." Enact­ nati ve diseases, and 3) some question Drinnan ~ reported that C. gigas out­ ment and enforcement of laws to protect as to its marketability as raw oysters grew C. virginica at Ellerslie, Prince against this type of transplanting are not in competition with the native oyster. Edward Island, 4 to I by dry meat feasible. Canadian importations of both It also may be expected to spread all weights over a period of 12 months in C. gigas and O. edulis are not dis­ along the North Atlantic coast and open waters. A recent report on tray­ cussed further since additional barriers compete d irectly wi th nati ve C. vir­ grown spat of the two species in a of distance, cold waters, and a national ginica for food and space in nearly Massachusetts cove closed to a pond in boundary provide added protection. all sal inity regimes and en vironments. the warm season also found faster Introduction of C. gigas cannot One must be prepared for replacement growth in C. gigas (Hickey, 1979). strictly be said to have occurred in New of the native oyster. Another commercial operation using England until natural wild populations In the opinion of the author, C. gigas C. virginica hatchery spat in trays is occur, although some oysters are being could be a useful species in New being conducted by Cotuit Oyster Co.5 held in Maine and Massachusetts. In England where artificial reproduction because of scarcity of natural seed the south, where it is not needed, much in hatcheries can compensate for failure in Massachusetts (Matthiessen, 1979). additional information should be col­ of natural spatfalls. However, based on Biologists in Maine would like to re­ lected before releasing this species in hatchery seed, O. edulis and selected place native C. virginica with hatchery­ open waters. The necessary tests are strains of C. virginica offer equal or grown C. gigas, along with hatchery going to be difficult to conduct, con­ better opportunities for culture of raw­ seed of O. edulis already being grown trol, and interpret within quarantine bar oysters. Crassostrea gigas presents in floats (Dean, 1979). The failure of systems. Needed topics of study in­ high risks in southern waters where it C. gigas to reproduce in Massachusetts clude the following items. may be expected to reproduce naturally and Maine waters is a strong argument I) Characterization of major native and to compete strongly and possibly for use of hatchery seed in these north­ seed-source populations in eastern Asia interbreed with native oysters. These ern waters. The risk of these exotic and along the North American Atlantic advantages and disadvantages of C. species spreading is thereby minimized. coast before mixing and hybridization gigas will be discussed and contrasted In the southern sector of the North occur. This involves isozyme tests of for two large sectors of the coast, Atlantic coast, faster growth of C. large wild breeding populations in south and north of Long Island, NY gigas may be completely nullified by genetic equilibrium (Hardy-Weinburg The oyster-producing areas in the losses resulting from native diseases, law). This procedure is costly and states south of Long Island generally tedious, and depends upon how many have adequate spatfalls of C. virginica 4Drinnan, R. E. Fisheries and Environment enzyme systems need to be tested and rather regularly, or they have the poten­ Canada, Halifax, .S., Canada. Personal com­ the number of oysters required to char­ tial to yield large seed oyster crops if mun., 1973. acterize races. 5Mention of trade names or commercial firms properly managed. The resurgence of does not imply endorsement by the National 2) Testing of races of exotic and Delaware Bay seed beds in the 1970's Marine Fisheries Service, NOAA. native oysters for critical temperatures

December 1980 9 and sal inities that induce gonad matura­ peake Bay. Mar. Fish. Rev. 41(1-2):45-53. Rep. 32, 59 p. tion, spawning, and favorable growth 1979b. Scenario for introduction of Kern, F. G. 1976. Sporulation of Minchinia sp. Crassostrea gigas to the Atlantic Coast of (Haplosporida, Haplosporidiidae) in the Pa­ of larvae. Tolerances to salinity re­ North America. In R. Mann (editor), Exotic cific oyster Crassostrea gigas (Thunberg) gimes and reactions to temperature and species in mariculture, p. 225-231. The MIT from the Republic of Korea. J. Protozool. Press, Cambridge, Mass. 23:498-500. salinity parameters in terms of survival ____ , and M. Castagna. 1978. Epizootiol­ Kincaid, T. 1951. The oyster industry of Willapa and growth are needed for each species ogy of Minchinia costatis in susceptible oys­ Bay, Washington. The Tribune, Ilwaco, and its major races. ters in Seaside bays of Virginia's Eastern Wash., 45 p. Shore, 1959-1976. J Invertebr. Pathol. 32: Korringa, P. 1970. The basic principles of shell­ 3) Long-term monitoring of exotic 124-138. fish farming on the continental coast of Eu­ species in their native habitats for prev­ ____ , and W. G. Hewatt. 1957. Oyster rope. In Proceedings of the Symposium on alences and effects of oyster diseases mortality studies in Virginia. II. The fungus Mollusca. Part III, p. 818-823. Mar. BioI. disease caused by Dermocystidium marinum Assoc. India Symp. Ser. 3. and parasites; and testing of exotic in oysters of Chesapeake Bay. Ecol. Monogr. ____ . 1976. Farming the flat oysters of the oysters for susceptibility to diseases 27:1-26. genus Ostrea. Dev. Aquaculture Fish. Sci. 3, ____ , and J. L. Wood. 1967. Oyster native to proposed sites of importation. Elsevier Sci. Publ. Co., N.Y, 238 p. mortality studies in Virginia. VI. History and Logie, R. R. 1956. Oyster mortalities, old and This involves coordination of research distribution of Minchinia nelsoni, a patho­ new, in the maritimes. Fish. Res. Board Can., efforts in two widely separated regions gen of oysters, in Virginia. Chesapeake Sci. Prog. Rep. Atl. Coast Stn. 65, p. 3-11. 8:1-13. Loosanoff. Y. L. 1955. The European oyster in or countries. Testing exotic species ____ , and L. W. Mason. 1969. Cultchless American waters. Science (Wash., D.C.) 121: against native pests may prove difficult seed oysters being developed. Md. Dep. Chesa­ 119-121. without exposure in open waters. Dis­ peake Bay Aff., Commer. Fish. News 2(6). Lunz, GR. 1954. The general pattern of oyster Bourne, N. 1979. Pacific oysters, Crassostrea setting in South Carolina. Proc. Natl. Shell­ eases may be unknown for certain gigas (Thunberg), in British Columbia and the fish. Assoc. 45:47-51. regions and artificial infection tech­ South Pacific Islands. In R. Mann (editor), Mann, R. 1979. Exotic species in aquaculture: niques have not been developed for Exotic species in maricullUre, p. I-53 The An overview of when, why and how. In R. MIT Press, Cambridge, Mass. Mann (editor), Exotic species in mariculture, other pathogens and parasites. Coste, P. 1861. Voyage d'exploration sur Ie p. 331-354. The MIT Press, Cambridge, Mass. 4) Evaluation of comparative growth littoral de la France et de I·ltalie. Second Marteil, L. 1969. Donnees generales sur la ed. Paris. maladie des branchies. Rev. Trav. Inst. Peches rates under various conditions of bot­ Courtenay, W. R., Jr., and C. R. Robins. 1973. Marit. 33:145-150. tom types, intertidal exposure, depths, Exotic aquatic organisms in Florida with em­ 1970. La culture des hUltres et des and phytoplankton regimes. The meth­ phasis on fishes: a review and recommenda­ moules en France. [In Fr., Engl. abstr.] In tions. Trans. Am. Fish Soc. 102:1-12. Proceedings of the Symposium on Mollusca, od ofculture strongly influences growth Dean, D. 1979. Introduced species and the Maine Part Ill, p. 994-998. Mar. BioI. Assoc. India, rates and glycogen deposition. Oysters situation. In R. Mann (editor), Exotic species Symp. Ser. 3. in mariculture, p. 149-164 The MIT Press, grow faster when suspended in the ____ . 1976. La conchyliculture Fran~aise. Cambridge, Mass. Part 2. Biologie de I'hultre et de la moule. water, but currents, seasonal tempera­ Dinamani, P. 1974. Pacific oyster may pose Rev. Trav. Inst. Peches Marit. 40: 149-345. ture regimes, duration of spawning threat to rock oyster. Catch 74, Fish. Manage., Matthiessen, G. C. 1979. The oyster industry of Div. Minist. Agric. Fish., Wellington, N. Z. Massachusetts and the introduction of exotic season, and substrate type greatly in­ 1(6):5-9. species. In R. Mann (editor), Exotic species in fluence growth and fattening. Drinkwaard. A. C. 1978 Molluscs. Int. Counc. mariculture, p. 212-224. The MIT Press, 5) Exploration of hybrids and se­ Explor. Sea Shellfish Committee Admin Rep. Cambridge, Mass. Dundee, D. S. 1969. Introduced molluscs of the Maurin, c., and P. Gras. 1979. Experiments on lected strains for particular uses and United States. Malacologia 9:264. the growth of the Mangrove oyster, Crass­ adaptation to localities and needs. The Glude, J. B 1975 A summary report of Pacific ostrea rhizophorae, in France. In R. Mann Coast oyster mortality investigations 1965­ availability of hatcheries provides great (editor), Exotic species in mariculture, p. 123­ 1972. In ?roceedings of the third U.S.-Japan 128. The MIT Press, Cambridge, Mass. opportunities for hybridizing species meeting on aquaculture at Tokyo, Japan. ____ , and J. LeDantec. 1979. The culture and races and selection of superior October 15-16, 1974, p. 1-28. Jpn. Sea Reg. of Crassostrea gigas in France. In R. Mann Fish. Res Lab., Niigata. (editor), Exotic species in mariculture, p. 106­ strains to meet special conditions. Oys­ Gruet, Y, M. Heral, and J-M. Robert. 1976. 122 The MIT Press. Cambridge, Mass. ters resistant to sporozoan diseases Premieres observations sur I' introduction de la McKernan, D. L., Y. Tartar. and R. Tollefson. have already been selected. faune associee au naissain d 'hultres japonaises 1949 An investigation of the decline of the Crassostrea gigas (Thunberg), importe sur native oyster industry of the state of Wash­ Literature Cited la cote atlantique fran~aise. [In Fr., Engl. ington, with special reference to the effects summ.] Cah. BioI. Mar. 17:173-184. of sulfite pulp mill waste on the Olympia Alderman, D. 1. 1979. Epizootiology of Mar­ Hanna, G. D. 1966. Introduced mollusks of oyster (Ostrea I/lrida). Wash Dep. Fish teilia refringens in Europe. Mar. Fish. Rev. western North America. Occas. Pap. Calif. Bioi Rep. 49: 115-165 41(1-2):67-69. Acad. Sci 108 p. Medcof, J. C. 1961. Trial introduction of Euro­ ____ , and E. B. G. Jones. 1971. Shell Haskin, H. H., L.A. Stauber, and J. A. 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The MIT Press, Cambridge, Can. 31:453-456. and D. L. Maurer (editors), Proceedings of the Mass. Needler, A. W. H. 1931. The oysters of Mal­ conference on artificial propagation of com­ Hopkins, S. H. 1954. Oyster setting on the Gulf peque Bay. BioI. Board Can. Bull. 22, 35 p. mercially valuable shellfish-oysters-Octo­ Coast. Proc. Natl. Shellfish. Assoc. 45:52-55. ____ , and R. R. Logie. 1947. Serious ber 22-23, 1969, p. 97-108. Univ. Delaware, ICES. 1972 Report of the working group on mortalities in Prince Edward Island oysters Newark. introduction of non-indigenous marine organ­ caused by a contagious disease. Trans. R. Soc. 1979a. Oyster diseases in Chesa- isms. Int. Counc Explor. Sea. Coop. Res. Can., Ser. 3,41(5):73-89.

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