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1-1975

Culture of the Bay Scallop, Argopecten irradians, in Virginia

Michael Castagna Virginia Institute of Marine Science

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Recommended Citation Castagna, Michael, "Culture of the Bay Scallop, Argopecten irradians, in Virginia" (1975). VIMS Articles. 1200. https://scholarworks.wm.edu/vimsarticles/1200

This Article is brought to you for free and open access by 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]. MFR PAPER 1113 Michael Castagna is Scientist in Ch arge, Eastern Shore Lab­ oratory, Virginia Institute of Marine Science, Wacha­ preague, VA 23480. This paper is Contribution No. 589 from Virginia Institute of Marine Culture of the Bay Sea llop, Science. It was originally pre­ sented at the symposium Aqua­ Argopecten irradians, in Virginia culture in the Americas held at the Inter-American Scientific Meeting, "Science and Man in the Americas," jointly spon­ sored by the American Asso­ ciation for the Advancement MICHAEL CASTAGNA of Science ( AAAS) and Con­ sejo Nacional de Ciencia y Te cnologia (CONACYT), Me­ xico 18, D.F., Mexico, 20 June to 4 July 1973.

INTRODUCTION In recent years there has been an in creased interest in the development of marine aqu aculture o r mariculture. Techniques fo r growing many tradi­ ti o nal species. such as oysters and quahogs. have been developed, and considerable e ffort has also been made to test the feasibility of cultur­ in g new. less traditio nal species (Loos­ anoff and Davis, 1963 : Iversen. 1968; McNeil , 1970; Price and Maurer, 197 1: and Milne, 1972). This paper reviews the natural hi sto ry of the bay scall op. Argopecren irradaians Lam­ arck, and presents a review of the V irginia Institute o f Marine Science's (VI MS) continuing research on this species whi c h began in 1968. T he bay scallop has several cha r­ acteristics well suited for mariculture. It is fast growin g, easy to condition and spawn . and is relatively ha rdy throughout a ll life hi story stages. Most import ant. it has a good market demand and commands hi gh prices. Many spcr ies are biologically amen­ able to mariculture, but el!onomics dictate the usc of gourmet species whi ch command high prices to defray hi gh costs of culture. Only adductor muscles of scall ops arc utilized. Yields vary, but approxi­ mately 1- I \4 bu of scall ops produces I gal (9 lb) of adductor muscle. The price o f shucked scall ops rose to $38 per gal (for adducto r muscles) in 1973, or over $4.20 per lb . certainly qualify­ ing scall ops as a gourmet food. Utilization of she ll and viscera Bay scallops (Argopecten lrradians), top photo, grew from 16 to 57 mm In size In pen In would not significantly change the Asaateague Channel from 9 July to 24 November 1970. Shucked, lower photo , 247 of these scallops price or the demand. A mechanical yielded approximately 1 qt adductor muscle.

19 were achieved in 1-5 em/sec, and a flow volume of 4 liters/hr/scall op the slowest current velocities tested. Scallops apparently retain their ability to form byssal attachment throughout their lives, but are seldom found at­ tached when fully grown . They are active swimmers at all sizes and ap­ parently use this abi lity to avoid pred­ ators such as starfish and crabs. Davis and Marshall ( 1961). studying the filter fe eding of bay scall ops, found an abundance of benthic and tych­ pelagic diatoms in the stomachs . They considered this an indication that much of the food is microftora, detritus, bacteria, and organic matter that is common in the water immedi­ ately adjacent to the bottom. The bay scall op has a relatively high pumping rate, proba bly corre­ lated with its rapid rate of growth. The average rate for small scallops, 38-44 mm in length, was 3.26 liters/ hr . The larger scallops, 64-65 mm in length , averaged 14 .72 liters/hr. with a maximum rate of 24.4 liters/ Scallop, showing developing gonad. hr (Ch ipman and Hopkins, 1954). The average lifespan is about 12- 16 shucking and eviscerating machine usua ll y release sperm first, fo llowed mo with a few individuals surviving developed for the calico scallop fi shery by eggs (Loosanoff and Davis, 1963 ), to 18 mo and rarely even to 24 mo along th e southeast coast of the United which encourages cross-fe rtilizatio n. (Belding, 1910). The scall op, typical States could be used on bay scall ops Fertilized eggs develop into st raight­ of animals with short life cycles, (We bb and Thomas, 1971). This hinge veli gers in a few hours, and the ex hibits great fluctuations in abun­ would markedly reduce manpower larvae are planktonic for about 5-8 dance. and cost problems associated with hand clays. Longer larval periods are com­ MATERIALS AND METHODS shuc king. mo n when environmental conditions Bay scall ops retain the ability to are less than optimum. The total The procedures used by YIMS swim at all sizes, making it necessary length of the straight-hinge stage scientists for conditioning and spawn­ to confine them in suitable enclosures. ranges fro m 85 11 minimum to 140 ing scall ops and handling larvae were A lthough th is necessity in c reases ex­ 11 maximum (C ha nley and Andrews, similar to those used by Loosanofl penses, it is parti a ll y compensated by 1971). and Davis ( 1963). Stocks of spawners reducing the cost of harvesting ex­ Juveniles attach by byssal threads were coll ected from the seaside of penses . to eelgrass or othe r epibenthic sup­ Eastern Sho re and fr om North C aro­ lin a. Scall ops were grown in pens and NATURAL HISTORY port. They usually maintain attach­ ment until 20-30 mm size is reached, floats bui lt of plastic screen stretched The natural hi story of the species after which most scall ops drop to the over wooden frames. Measurements has been described by Belding ( 1910), botto m. Marine plants or other suit­ of scall ops were from hinge to lip. Wells ( 1927), G utsell ( 1930), Loos­ able cover is quite important to scal­ Seawater used in the laboratory anoff and Davis ( 1963), Sastry ( 1965), lops. Small scall ops (under I 0 mm) was pumped from an adjacent creek and Castagna and Duggan ( 197 I). do not survive well when exposed by cast-iron pumps. All pipes and Bay scall ops in the mid-A tlantic area to silt. By attaching to the leaves or containers were plastic or glass. The spawn fr om mid-A pri l through early stems of submerged plants, they grow seawater .used for larvae and early September (C ha nl ey and Andrews, large enough to survive the more juveniles was clarified by centri fuga­ 197 I). Spawning in New E ngl and rigorous existence and greater expo­ lion in a Sharples ' clarifier, T ype AS- occurs when water temperatu res reach sure to silt o n the botto m. Further, 14 , or a Westfalia separator, Model 22-26°C (B elding, 19 10). Altho ugh grass beds reduce current ve lociti es. KDD 605. T he average sa linity for the scall ops arc hermaphroditic. self­ Work by Kirby-Smith ( 1972) indi­ ferti lizatio n is uncommon in natu re cates that scallops grow fa ster in slow 'Reference to trade names docs not imply endorseme nt or commercial products by the (B elding, l l) IO ; G utscll . 1930). They current s. Maximum growth rates National Marine Fisheries Service, NOAA.

20 the ex pe ri mental area was 29.5 °/00 side the adductor muscl e. When ripe, to 24 °C. Spawning usually took place with seasonal tempe ratures ra nging it is usua ll y a red-orange color (often at 28-26°C. from 3 to 28°C. covered by a black epithelium). The A sperm suspensio n (either stripped testi s comprises the white anterior CONDITIONING or spawned) was added to further border of the gonad (Castagna and stimulate scall ops to spawn . Various FOR SPAWNING Duggan, 197 1). chemical stimulants have been tested The scall ops were conditioned by with little o r no success. Both sex placing them in aerated standing sea­ products are o ft en released by the water at tempe ratures of from 18 to SPAWNING same scall op but usually not simul­ 22 °C for 3-6 wk depending on food . Spawning was accomplished by taneously. temperatures. and the initi al gonadal pl acing one o r two adult scall ops in A ft er spawning the scall op was cond iti o n of the scall ops (Castagna a !-liter Pyrex container fill ed with removed fr om th e di sh and the egg and Duggan, 197 1). The condi ti oning filt ered seawater. A number of these suspension was poured through a was usua ll y do ne o n scall ops taken containers were placed in a water screen, to remove d irt and fecal ma­ from ambi ent-temperature seawater, ta bl e. By fl ooding the water table teri al ejected by the spawner, into a w hi ch dropped as low as 3°C in with hot or cold water, the scall ops cali brated container of filtered sea­ winter. Wh il e held in standing water. were subjected to temperature changes water. Eggs were counted by stirring the scall ops were fed mixed algal suffici ent to induce spawning . Tem­ the contents of the container and sub­ cultures. T he maturation o f the gonads peratures of 24-26°C induced maxi ­ sampling several 1-ml sampl es . An could be seen by holding the valves mum pumping activit y. Temperatures estimate of the number of eggs was sli ghtly open . The gonad is a tri­ were usuall y raised to 30°C fo r a made by averaging the counts and angu lar bulbi sh o rgan lying alo ng- few minutes and then dropped back multiplying by the total volume . FERTILIZATION Fertilizati o n was initiated by add­ ing approximately 6 ml of sperm sus­ pension per liter of egg suspension. Fertilization was nearl y 100 percent successful even when sperm and eggs from the same individual were used. T he addition of too much sperm suspension can cause larval defo rm­ iti es, probably due to polyspermy.

DEVELOPMENT Survival and development were usually enhanced by holding develop­ ing eggs above 20°C. O ptimum tem­ perature for development appeared to be 26-28 °C. A minimum salini ty of

22.5 °/00 was necessary for develop­ ment to straight -hinge stage. At nca r­ optimum temperature in 28-30 °/oo sa­ linity, the blastula stage was reached in about 4 hr. trochopho re stage in 8- 12 hr. and straight -h in ge stage in 16-24 hr. T he embryonic stages pre­ ceding th e straight-hinge stage were most vu ln erable to environ mental conditio ns. but with proper mainte­ nance approximately 60 percent sur­ vival can be expected. Larvae from self-fertilized eggs usuall y appeared

normal in the F 1 ge neration. Sub­ sequent generati o ns oft en had larval deformit ies and poor survival. T he larvae were grown in 60-lit.:r plastic cont ainers . Three times a week the water was siphoned fr om th ese Scallop In foreground (left) Is spawning . containers through a line nylon screen

21 to retain larvae. These were concen­ and holding seawater in aerated vats trated in calibrated containers of fil­ in sunlight in a solarium or green­ tered seawater, subsampl ed, and count­ house. The stored water develops a ed by th e same procedures previously bloom of diatoms and flagell ates which described. Measurements of a small can be used as food. sample were taken using an ocular The greenhouse method was used mi c rometer, and the general condition successfull y at YIMS. Seawater was of the larvae was ascertained . The run through an AS- 14 Sharples clari­ larvae were then redistributed to fi e r, whi ch spins the water at 15 ,000 containers of clean filt ered seawater rpm in an 8-in diameter tube exerting containing food and, if necessary, 13,200 X N· Essentially a clarifier antibi ot ics. separates heavier particles by centri­ fugal force instead of gravity. The LARVAL DENSITY AND clarified seaw ater was then stored in LARVAL ENVIRONMENT 4 X 8 X 4-ft fib erglassed plywood Larval densit y, although not critical, tanks in a solarium and was continu­ influenced the success of a group of ously gently aerated. The clarified larvae. Since labor and space were seawater retains small diatoms, flag­ often in short supply, it was tempting ellates, and protozoans. Heavier and to crowd as many Ia rvae into as few larger forms, including zooplankters containers as· possible. T hi s practice and diato ms with dense or heavy tests, increased the number of failures, per­ are left on the wall of the clarifi er ha ps by increasing chances of di sease tube. When stored in a solarium, the transmi ssio n or because of competition water temperature in the large aerated for food or space. To avoid th ese ranks rises, and the small diatoms problems, cultures were started at and naked flagellates reproduce in a max imum densities of 40 eggs per mi. bloom that eventually colors the As the larvae grew, their densiti es water. Seawater treated in this manner were reduced with each water change was referred to as cultured water and until densiti es of 5 per ml were reached was used as a medium in which to when la rvae were ready to set. grow larvae and early juvenile stages. Aerati on was not necessary for sur­ No additional food was required. The vival at th e densities stated above. cultured water was normally held 24 Gentle aerati on enh anced growth rate hr before use. This was sufficient and survival of late larval stages but time for a bloom to occur . If stored made little or no difference in small water was not used in 48 hr, it was or earl y larvae. Since scallop larvae usually di scarded, since new cultured set at a relativel y small size, aerat ion water resulted in fa ster growth and was not used routinely. better survival of the larvae. Fertiliza­ M64 · p: tion or in oculati on was not necessary FOOD to attain dense blooms of useful Several unicellul ar cultures of ma­ food organi sms. rine fl agellates or diatoms were tried M44 J Mixed wild algal cultures th at grow as larval fo od with va rying degrees in this system (Glancy method) were of success. In all trials, mixtures of better foods than any combination of two or more species worked bett er N". 3 s unicellular algae tested . Growth and than one species . No artificial food survi val were usually better than 1n mi xt ure was found that gave com­ larvae fed unicellular cultures. parabl e results . In top photo, a technician waahea acallop Some successful species used were larvae into container lor counting and mea­ LARVAL DISEASES, Monochrysis lu theri , /sochrysis !:lli­ suring. A technician grades scallop larvae in the lower photo. hana , Plweodacty lu111 TricornuTu nl , PREDATORS, Dunaliella Terliolecla, and Nanoch­ fici ent unicellular algae become a AND COMPETITORS loris oculma. Even though food was seri ous problem. An excell ent method Di seases, predators, and competi­ added, the water was changed peri odi­ of growing quantities of food is th e tors were controll ed by maintaining call y to cl eanse cultures of metabolic solarium method, often referred to cl ean conditions. No physical , chemi­ wastes and dead larvae . as th e Glancy method. (Joseph G lancy, cal, or prophylaxis treatment was When raising large numbers of Sayvill e, N .Y . was the biologist re­ used routinely except when water scall ops (or any other cultured filt er sponsible for introducin g this method.) temperatures were over 28 °C. Then, feeder) , the logisti cs of growing suf- This method consists of cl arifying water was subjected to ultraviolet

22 Scallops in growing container.

fen·ed vertical surfaces and most were found clinging to the sides o f th e containers or th e panels. As food re­ quirements increased , fl owing raw seawater was introduced. A screen of suitable size was placed at th e overll ow to retain scall ops th at were sucked into the ove r!~ ow pipe while swimming. Juvenil es were held in this manner until they reached 10- 13 mm size. large enough to stay in 11-J­ in plastic screen. W hen the juvenile scall ops were moved into the field , they required confinement to prevent them from swimming away. A vari ety o f enclo­ sures were used. Floats anchored at the surface had severe fouling prob­ lems which reduced the fl ow of water. Additional problems of boat wakes and wave acti on. washing the scall ops li ght treatment. This treatment is re­ genetic factors. The most obvious about in the fl oats and often causin g viewed by Loosanoff and Davis, indication of spat stage was attach­ a concentration in a corner with some ( 1963). ment by byssal threads to th e culture loss due to smothering. were also The most common di sease prob­ container. The early juvenil es have encount ered. Floats placed on th e lem was bacillary necrosis. This was a well-developed foot with a heel­ bottom had fewer problems but the treated with streptomycin (50 mg per li ke byssal gland. T he shell measures scall ops did not grow well. liter) o r with a wide spectrum anti ­ 17 5-200 J1 at metamorphosis (Chan­ The most successful growth and biotic such as chl oromycetin or poly­ ley and Andrews, 1971). This period, survival was in pens constructed of ci llin. Care was taken in estimating when the scall ops were undergoin g poles placed int o the bottom with 1/2 - dosage since ant ibi otics often caused metamorphosis, was probably the most in mesh plast ic screen tacked a round the larvae to stop fe eding for several critical. and o ft en heavy morta li ties the outside o f the poles. The pens days. and overdoses caused mortal­ occurred. were 10 ft square and 7 ft hi gh. They ities. Through earl y metamorphosis or were constructed in shall ow subtidal A rthropods o ften appeared in the setting, the sca ll ops were kept in areas. larval cultures. These were controlled clarified water or in slowly fl owing Bay scall ops grown in pens were with tetraethyl pyrophosphate. Four raw seawater. At this time verti cal brought to market size in 5-7 mo. drops in 60 liters of culture would surfaces for attachment were pre­ F urther. the adductor muscle was usually kill a ll arthropods in less than sent ed to the setting scall ops. These considerabl y larger th an in scall ops an hour. Obviously this is a potent were panels o f wood. mylar, or fiber­ grown in lloats. This may be due to chemical and silould not be used in ­ glass that the juveniles fastened to by di scriminately. Arthropods were also their byssus. Juveniles apparent ly pre- Juvenile scallops tagged and ready to be released. removed by screening. This method was preferred over chemical control. Protozoans o ften appeared as a sy mptom of bacterial contamination. They were controll ed by reducing the number o f bacteria w ith a n antibiotic. As always. labor a nd space were considered as in a commerciall y­ ori ented culture practice. T herefore. it was usu all y more expedient to discard poor or sick cultures and start over rather than attempting treatment. SETTING Setting took place in 5-7 days. depending on food, temperature, and probably other enviro nmental and the opportunity of scall ops in pens feeding of the bay scall op, Aeqllipec ten ACKNOWLEDGMENT irradiam. Proc. Nat!. Shellfish . Assoc. to make vertical swimming excursions. 52:25-29. The size of the adductor muscle is Grateful thanks are due to Nancy Duggan, W. P. 1973 . Growth and survival of the bay scallop, An.:opecten irradians, important since it is the only part of Lewis, Sharon Schneider, Mike Peir­ at various locations in the water column the scallop which is sold. son, and Rick Karney for their assis­ and at various densities. Proc. Nat!. Shellfish. Assoc . 63:68-71 . A series of tests were completed to tance in carrying out these experi­ G utsell, J . S. 1930. Natural hi story of the assess the best depth to grow scallops. ments. My special thanks to W. P. bay scallop. Bull. U.S. Bur. Fish. 46:569- 632. Little difference was found between Duggan for his colla boration and help Iversen, E . S. 1968. Farming the edge of the sea. Fishing News (Books) Ltd., Lond., depths if fouling, silting, and washing in much of this work and for carrying 304 p. could be controlled. Experiments were out most of the work on enclosures, Kirby-Smith, W. W. 1972 . Growth of the bay scallop: The influence of experi­ also run to find the maximum opti­ densities, and depth experiments . I mental water currents. J. Exp. Mar. Bioi. mum number of scallops per unit also wish to thank J. D. Andrews Eco1.8:7- 18. LoosanoiT, Y. L., and H . C. Davis. 1963. area that can survive and grow. Op­ whose suggestions and review were Rearing of bivalve mollusks. Adv. Mar. timum growth and sur vi val were found greatly appreciated. Bioi. 1: 2- 130. McNeil, W. J. (editor). 1970. Marine aqui­ at 25 per sq ft of bottom area. How­ culture. Ore. State U niv. Press, Corvallis, ever, the data suggest that 60-65 LITERATURE CITED 172 Milne pP.. H. 1972. Fts~ · I1 an d s I1 e II ti' s h lanmn. . g scallops per sq ft would be optimal Belding, D. L. 1910. A report upon the in ~oastal waters. Fishing News (Books) scall op fishery of Mas sa~ huse tts, including Ltd., Lond., 208 p. economically, even though growth th e habits, life history or Pecten irradiaHS , Price, K. S., and D. L. Maurer (editors). rates were less than optimum (Dug­ its rate of growth and other !'actors of 1971. Artificial propagation of commer­ ec onomic value. Mass. Comm . Fish. Game, ciall y valuable shellfish. U niv. Del., 2 12 p. gan, 197 3) . Spec. Rep., I SOp. Sastry, A. N . 1965. The development and Castagna, M .. and W. Duggan. 1971. Rear­ external morphology of pelagic larval PREDATORS in g the bay scallop, Aeqllipecten irradians. and post-larval stages of the bay scallop, Proc. Nat!. Shellfish. Assoc. 61:80-85. Aequipecten irradians concentricus Say, Although smothering is definitely C ha nl ey, P., and J. D. Andrews. 1971. Aids reared in th e laboratory . Bull. Mar. Sci. for id entification of bivalve larvae of 15:4 17 -435. the main cause of death, there are Virginia. (Germ. and Fr. summ.) Mala­ Webb, N. B., and F. B. Thomas. 197 1. ln­ some seri ous predators. The rough cologia 11:45- 11 8. lluence of mechanical processing on the Chipman, W. A., a nd J. G. Hopkins. 1954 . quality and yield of bay scallop meats. oyster drill Eup/e ura, start1sh, crabs Water filtration by th e bay sca llop, Pecten U .S. Dep. Commer., Nat!. Mar. Fish. irradians, as observed with the· use of Serv., Spec. Sci. Rep. Fish. 624, II p. (especiall y the blue crab, Cal/inec tes radioactive plankton. Bioi. Bull. (Woods Wells, W . F. 1927. Report of the experi­ .wpiflus) and vari ous fi sh species are Hole) I 07:80-91. mental shelllish station. N.Y. StateConserv . Davis, R. L., and N. Marshall. 1961. The Dep., 16th Annu. Rep., p. 11 3- 130. known predators of this species . No predator control methods were used in these experiments, but they should MFR Paper 1113. From Marine Fisheries Review, Vol. 37, No. 1, January 1975. Copies of this paper, in limited numbers, are available be considered in any commercial from D83 , Tec hnica l Information Division, Environmental Science venture. Information Center, NOAA, Wa shington, DC 20235.

MFR PAPER 1114

Crustacean Aquaculture in Middle America

HAROLD H. WEBBER

INTRODUCTION in the expanding world markets MARKETS demands that new sources of sup­ This paper is designed to inform There exists a market for high­ ply be developed. the reader regarding the technical value crustacean aquafoods, includ­ and economic feasibility o f establi sh­ 2) A n aquacultural production ing marine and freshwater shrimps, ing a profitabl e aquaculture ve nture technology is maturing which wil l lobsters. and crabs, which is now un­ in certain specifi c locations o n the enable us to generate large volumes satisfied and is likely to rema in west coast of Central A meri ca. of shrimps at favorable cost. supply-constrained for the remainder The recommendations made here 3) The ri sks and rewards o f a of the century. This is a consequence arc predicated on the following basic verticall y integrated aquafood en­ in part of an increasing affluence in premises: terprise have been evaluated, and the highly developed industrial so­ I) The continuing paucity o f the business project io ns reveal an cieties in the north temperate !ali­ hi gh-value crust acean aquafoods advantageous return on investment. tudes. This elevated economic status

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