HE OFT­ iHELL 'LAM

UNITED STATES DEPARTMENT 8F THE INTERIOR

FISH AND WILDLIFE SERVICE BUREAU OF COMMERCIAL FISHERIES

Circular 162 CONTENTS Page

1 Intr oduc tion. • • • ...... 2 Natural history • ...... ~ ...... 2 Distribution...... 3 Taxonomy. . . . · . . . . Anatomy. • • • •• . . . · . . . . . 3 4 Life cycle. • • • • • . • •• Predators, diseases, and parasites . . . . . 7 Fishery - methods and management .•••.••• • 9 New England area. • • • • • . • • • • • . .. . 9 Chesapeake area ...... 1 1 Special problem s of paralytic shellfish poisoning and pollution ...... 13 Summary ...... 14 Acknowledgment s •••• · ...... 14 Selected bibliography •••••• 15

ABSTRACT Describes the soft- shell cla.1n industry of the Atlantic

coast; reviewing past and present economic importance,

fishery methods, fishery management programs, and special

problems associated with shellfish culture and marketing.

Provides a summary of soft- shell clam natural history in-

eluding distribution, taxonomy, anatomy, and life cycle.

l THE SOFT -SHELL CLAM

by

Robert W. Hanks Bureau of Commercial Fisheries Biological Labor ator y U.S. Fish and Wildlife Serv i c e Boothbay Harbor, Maine

INTRODUCTION for s a lted c l a m s used as bait by cod fishermen on t he G r and Bank. For the next The soft-shell clam, Myaarenaria L., has 2 5 years this was the most important outlet played an important role in the history and for cla ms a nd was a sour ce of wealth to economy of the eastern coast of our country . some coastal communities . Many of the Long before the first explorers reached digg ers e a rne d up t o $10 per day in this our shores, clams were important in the busin ess during October to March, when diet of some American Indian tribes. Early other o c cupat ions wer e difficult to find . colonists relied on the abundant cla m A b out 18 75 a new demand for soft- shell stocks during periods of privation, although c lam s a r o s e as clam bakes and shore they rarely used clams as a regular food dinner s b ecame inc r ea singly popular durmg item. In the mid-1800's an important bai t the summer. Clams became important a s a clam fishery, supplying trawl bait for c od cons umer i t em for t he fir st time, and this fishermen, was established by some N e w demand f o r clams is still important to the England coastal communities. Later, w ith nort h e r n f isher y . Around 1900, canned the decline in demand for bait clams, c l a ms became incr easingly important, and consumer interest developed in canned for the next 40 year s most clam s went clams- -maintaining the fishery at a high to the canner ies . During thlS period clam­ level up to the early 1940's. The modern m ing was p r ohibit ed in some areas dUrIng trend is toward the marketing of fresh o r the summer by State law, thereby concen­ frozen clam meats that are generally tra t i n g p r oduction in the winter when there served as fried clams in most areas, but wa s little competition from other industries fresh clams, steamed in the shell, a re f o r lab o r , and clam prices were low. still popular in coastal regions. Since the l ate 1930's most clams have In recent year s, clam supplies from the been used i'1 the fresh shucked trade and New England area have declined, primaril y recently cooked and uncooked frozen due to the activity of a voracious predator. p roducts have become popular . Clams are With the introduction of mechanical digging p rima r ily used in the fried clam retail methods, a new source of clam produc tion m a r k e t and, with the lncrease in population, has been developed in the Chesapeake B ay better p reserving and marketing methods, region, and the soft- shell clam continues a nd extensive pubbcity by large restaurant to occupy a prominent position in our chains, t he demand for clams is gradually coastal shellfisheries. inc reasing . New England has traditionally been the Ear ly p r oduction records are not easlly center of soft- shell clam production, though obtaine d, b ut the first figutes given In the no commercial interest in c lam s w as Federal statistics indicate a fairly hI h evidenced before the middle 1 8 00' s. C l a ms, leve l of production had been estabhshed by of course, had been dug extensively before 1880 (fig . 1) . The! Tew England fi shery has this period, but since they were ever y ­ b e e n mar ked by a consistently high, b t where available and demand for t h em as var iable, level of productIon untll recent food and bait was probably on an i n dividual year s . The actual dollar val e of he basis, they were not a market i tem. In fishe r y r eached the 2 million mark d rm the period around 1850 the fir st real the 10 years from 1945 to 1 55 even tho h commercial fishery began w ith the demand this per iod marked a drastic decl n m 13 12 j\ r-\ 2000 II . ~ \ 10 /. \ III 1500 9 . ! .,; ... III o .. III ... 8 o 0 Z / \l c( III III 7 ~ Z -' o ~ \.'" ./ % .. / ~ 6 1000 I= ... "'",;Jib, S / \ ~ z 5 I / .. c( ~ ~ > U 4 Now E".,.... / ~ ~ I / 0 0 ./ III "'-. ~:\/ 500 A. 3 Chesapeake Bay ,\-.

. : 2 ·~bs ~ . i _ ~Ibs ) Middle Atlantic ~/ )/i.__ --. i ·· / .-.... 1880 IBM 1890 legs 1900 19O5 1910 191' 1920 1925 19~O 19M 19 40 19 45 195-0 19" 1960 (J 1884 1889 1894 1899 1904 1909 1914 1919 1924 1929 1934 1939 1944 1949 19!54 1~9

YEAR INTERVAL

Figure 1.--Pounds of meat production and value of soft-shell clams from three major areas of the Atlantic coast.

production of almost 6 million pounds. New NA TURAL HISTORY England clams have a decidedly favored price differential and are valued at almost Distribution twice the price of their southern counter­ part. New England production figures for The soft- shell clam is found from the recent years are the lowest (between 2 and coast of Laborador to the region of Cape 3 million pounds) on record for nearly a century. Hatteras, N.C. On the European coast it has been recorded from northern Norway Following World War II, particularly to the Bay of Biscay, France. Aroun4 1879, after 1950 when the "Maryland" escalator young clams were a ccidentally introduced dredge was invented and introduced, the into San Francisco Bay, Calif., with ship­ soft- shell clam fishery in Chesapeake Bay ments of seed oysters from the Atlantic rose to dominate production. Production coast. Since then they have spread from was almost double the New England output Monterey, Calif., to Alaska. The soft- shell in 1960 although the total value of clam s clam is also found along the western Pacific from the two areas was nearly identical. coast from the Kamchatka Peninsula to the The southern fishery is now limited only southern regions of the Japanese islands. by market demand as great quantities of This species, therefore, lives on every virtually virgin stocks are available. Almost coastline in the northern hemisphere, but all southern clams are shipped to the New it is only in the United States, particularly England area, for the market demand is on our eastern coast, that these clams still centered in the north. have become commercially important.

2 Taxonomy shell, which lives in deeper northern water s, and is of no commercial interest. The soft-shell clam belongs to that group Anatomy in the animal kingdom known as the phylum Mollusca. They are further arranged, to­ A discus sion of clam anatomy requires gether with other bivalves, into the class the establishment of certain directional PeZecypoda and because of certain character­ landmarks. The siphon (neck) is considered istics of gill structure are placed in the to be posterior while the opposite (head or order EuZamellibranchia. All of the structurally mouth) end is anterior. The hinge area is similar clams are then grouped in the family the back or dorsal region while the front, Myacidae. On the western Atlantic coast there with the exposed mantle edge (rim) is are only two recorded species of clams in ventral. These terms are in underlined the genus Mya; they are Mya arenaria, our com­ bold type in figure 2. It follows that having mercially important clam, and Mya truncata, a front, back, and head, the clam will also characterized by a short, square-ended have a right and left side.

Posterior

excurrent siphon incurrent siphon

onal

pallial cavity posterior adductor muscle

epibranchial cavity

kidney mass

Dorsa I cut mantle edge heart (intestine passes through) crystalline style sheath (style within) brown or Keber's gland

intestine digestive gland

stomach Ventral mout

anterior visceral outline

foot Cllt mantle edge

opening

Anterior

Figure 2.--Soft-shell clam internal anatomy

3 The external appearance of the soft- shell The interior of the visceral mass can be clam is an irregular ellipsoid with the two exposed by tearIng away the outer wall, valves, or shells, about equal in size. The uncovering the large brown liver and t he right shell is usually slightly larger than gonad (a tissue spread throughout the body). the left. When closed the two valves may Embedded in this gonad and surrounding touch along the ventral edge but gape widely connective material lie the long, coiled in front, allowing passage of the foot, and intestine, the crystalline style within its in back, allowing extrusion of the siphons. sheath, and the stomach situated almost The outer surface of the shell is covered between the halves of the liver. The mouth with rough striations, some more pro­ opens on the anterIOr surface of the visceral nounced than others. These are the annular mass just between the two pairs of palps, marks or "rings" resulting from different which gather and pass food to the mouth . growth rates during the year and, since cold The intestine leaves the stomach, COlIs winter temperatures restrict growth, these within the ~onad, then passes dorsally rings can indicate clam age. The interior along the hinge line and through the heart. of the shell is relatively smooth with certain Finally, it passes around the base of the areas scarred at the points where major posterIor adductor muscle and ends in an muscles are attached. Along the dorsal anal papilla suspended in the epibranchial edge of each shell are the prominent hInge chamber close to the junctIOn of the ex­ teeth: one valve carries a large, projecting current SIphon where all fecal material can spoon- shaped structure, while the other be discharged. Very closely assOCIated valve has an inverted "bowl." The "bowl" with the intestine in the mid-dorsal region lies directly over the "spoon." Between are the two brown Keber glands, which these two structures a tough, rubberlike perform excretory functions. The kidney resilium acts to keep the shells apart by mass, wrapped tightly around the ventrIcle opposing the closing action of the ad­ of the heart, is located just forward of the du ctor muscles, much as a rubber eraser posterior adductor muscle. squeezed in a door hinge would force the door open. Water is taken in through the incurrent siphon, both by the actIon of ciliated cells A valve can be removed by inserting a lining the siphon and by dehmte respIratory knife along the margin of the shell and movements of the clam . Water In the body severing the attachment of the two large chamber (pallial chamber) is circulated adductor muscles. If this is done carefully past the palps, the gIlls, and through the and the valve removed, the entire animal gill septum into the epibranchial chamber, is seen to be enclosed ina thin membranous where excretory products are collected. tissue, the mantle, adhering very closely The water IS finally passed out the ex­ to the shell. It is this tissue that secretes current SIphon. Two alternate water paths and shapes the shell. If the mantle tissue from this circulation pattern may be ob ­ the upper pair of gills, the upper palps, and served. To aid in digging, the clam may the upper half of the siphons, are removed, force water out of the foot opening by the clam will appear as infigure 2. Some of closing the siphons and contracting the t~e. most obvious structures immediately valves; or toriditselfofunwantedmaterials vISIble are the large central visceral mass gathered in feeding activities, the entire (belly) with the small foot projecting from flow of water may be rever sed by muscular the anterior end, the open canals of the contraction. two siphons (each opening into a separate body chamber), and the large posterior and Unlike higher animals, the clam has blood anterior adductor muscles whose contrac­ circulating in an open system. The two­ tions cause the shell to close. Lying under chambered heart pumps blood through a these structures are the two lower folds of system of arteries which eventually empty the fragile gills. The juncture of all the into large, open lacunae. The blood is re­ gill folds provides a septum dividing the turned to the heart by a loose network of entire body (pallial) chamber within the veips. mantle into two parts: a dorsal epibranchial chamber opening into the excurrent siphon, Life Cycle and a ventral infrabranchial chamber opening into the incurrent siphon and the Life, for a soft- shell clam, begins as foot opening. sperm and egg join in the coastal waters.

4 In cold lew England w t r h can b gg d velops into a Vlmmln p .Tiod larva (fig . 3) In abou 12 ho Ir , probably from sooner In warmer, south rn wat rs. Th mu la rva mov s by hairlike pro] ction (cih ) m 11 arrang d in distInct b nds ro nd th body. d P nd on The larva also ha a mo th and minut whIch m shell gland which "ill giv ris, durlng the next 24 to 36 hours, to th tvo, alciii d Upon valves that will envelop nd prot ct th ach clam body throughout life. The formation ma· of the shell results in a new larval tag (early veliger) that is typIcal of most bivalves. Early vellger larvae (flg. 4) are characteriz.ed by a straIght hinge line and a SWImming organ, the velum, formed by the modification of the trochophores' ciliated bands into a circular pad. This s "immlng wh r organ keeps the animal suspended in th de irabl water mass where currents can carry the clam for great distances. Gradually the hinge line becomes stronger and humped w as in the adult. The velum IS reduced In stIm lat size and function, and a muscular foot a tlV 1y develops. The clam has, at thIS pOint, Clam b reached the late veliger or "setting stage" son th when metamorphosis is pas SIble and the new habit final adaptlOn to sedentary bottom existence This pow siz and a b found 0 by torm or tid .

Th Coy It hv 5 In

is 1 and th

Fl~r n

5 Figure 4.--Early veliger (upper section) and late veliger (lower section) larvae of clams. The animals are just visible to the naked eye.

6 clam can produce million of eg or billions of sperm. During spawmng, 5 x cells are extruded from the gonad in 0 he epibranchial chamber and out the excurrent siphon in successive puffs. Spa vmng 15 Predator . D1S • and related to wat r temperature and occur from early June to mid-August in northern Probably areas. The summer spawning period be­ da or comes progressively later the further outh h a clam population is located. Clams north of Cape Cod have only one reproductive cycle each year, but clam s south of Cape Cod may spawn twice in the same year. Growth rates depend primarily upon tem­ perature although many other factor s may be involved. Southern clam s may reach a shell length of 2 inches, an acceptable COTn­ tremendo mercial size, within 1 ~ or 2 years in intenslfled Chesapeake Bay, but Maine clams may resulted in a require 5 to 6 years to attain this length. catch from Food abundance, water circulation patterns, pound _ In th

f'l ure 5.--The reen r b. ) 7 2 to 3 million pounds in the early 1960' s. feeding fish such as flounders, skates, and The development of several control meth­ rays. ods, particularly fencing and pesticide bar­ Mass mortalities of some clam popula­ riers (figs. 6 and 7), have helped to reduce tions have been recorded, but there is crab predation in local areas, but these practically nothing known of the causative measures have not been used extensively agents. The incidence of observed clam enough to be significant in total clam diseases is low and probably does not production. Cold winter s apparently have an affect clam production, nor do any of these important effect in reducing crab abundance, diseases affect man. A condition known and a reversal of the previous warming as "water belly" is prevalent in some cycle could solve the crab problem in areas of New England, and clams with New England. the watery, thin meats typical of this con­ dition are not acceptable for market. "Water Other soft- shell clam predator s, not belly" may be caused by nutritional de­ comparable to green crabs but often ficiencies, but some biologists believe that of local importance, are moon snails, other factors such as parasitic infection, oyster drills, other crabs, ducks, gulls, enzyme deficiencies, and disease can be horseshoe "crabs," starfish, and bottom involved.

Figure 6.--Green crab fence. developed by Bureau of Commercial Fisheries biologists to protect clams from predation. This low. wire fence with a metal flange prevents crabs from entering bays and coves. Note large number of siphon holes visible mslde fenced area and absence of Siphon holes outside fence.

8 )

Figure 7.--Bureau-developed pesticide barrier protects other coastal areas from green crabs. Pesticide-soaked fish are sup­ ported Gn long trawl lines placed across mouth of creeks, bays, or coves. Crabs, entering the area, feed on bait and die before reaching clam stocks. ) Incidence of parasites appears to be low considered an average catch (fig. 9). and probably does not influence the abund­ At the present time the digger can ance of clam stocks. Several trematodes expect to receive about $6 for each bushel inhabit Mya arenaria during some period of sold to the clam buyer, who, in turn, their life cycle, and a parasitic ciliate, will receive a commission from the Trichodina myicola, has been recorded. processing plant. At the processing plant the clams are cleaned, graded, and shipped directly to retail markets or FISHERY--METHODSAND MANAGEMENT may be shucked, washed, and canned (fig. 10). New England Area Although it is believed that a great potential exists for shellfish farming and Armed with clam hoe and hod the New responsible management, only sporadic at­ England clam digger waits for the tide to tempts have been made during the history expose his prey. As the water drains from of the fishery. In New England, the failure the clam flats, he begins to dig, sometimes to establish reasonable management tech­ in long trenches or pits, when clams are niques is the result of a continued demand abundant, or he may search for the indi­ that the fishery be free and publicly owned. vidual depr e s s ions on the surfac e that There is only a modest inv.estment, clam indicate clams in the soil below (fig. 8). In hoe and boots, required by an individual either case, he will have about 4 hours to to enter the fishery. Very few diggers work gather his catch. F01"merly, during the on a year-round basis; most are engaged periods of great abundance, the fishermen in various seasonal work requiring un­ could expect to dig a barrel or more of skilled labor, and clamming is a part-time clams, but now 1 to 2 bushels per tide is source of income. Diggers rarely work for

) 9 Figure 8.- Methods of digging clams in New England have hardly changed since the commercial fishery began. Upper photo, taken on the Maine coast around 1891, is nearly identical to similar scenes on clam flats today (lower photo).

10 Figure 9.--New England clam fishery: Clam digger (upper left) removes clams from sandy mud with clam hoe or fork. His daily catch (upper right) is taken to central buying area (lower left) together with catch of other diggers in region. Buyer loads clams from one region on truck (lower right) for shipment to processing plant. the maximum catch obtainable at each low Chesapeake Area tide, but rather aim for a daily income determined by the individual's need. Hand About 1951 the escalator dredge (fig. 11) digging is inefficient and wastes the clam was introduced into the Chesapeake Bay resource. Research workers estimate that region to harvest subtidal soft- shell clams. 70 percent of the clams left in the flats will The dredge is attached to a boat, which die from the effects of hand digging. slowly pushes it through the bottom sedi­ ments. Clams, loosened from the sediments Recent management efforts in Maine and by the high-pressure spray of water, are Massachus~tts have been directed toward washed or scooped onto the chain-mesh predator control, clam flat improvement, belt. This belt then carries the clams to the and protection of juvenile clams. In some crew where commercial clams are re­ areas, intensive management programs moved, and all debris and small clam s fall utilize frequent population surveys to estab­ .back into the water (fig. 12). The method is lish digging periods, forecast production, efficient; it takes almost all commercial and to plan rotation of harvest areas. Un­ clams and does little damage to others, and fortunately, these techniques are not in does not appear to have detrimental effects general practice and are not typical of the on bottom sediments. Each boat takes about fishery. 30 bushels a day. Fishing is restricted to

11 ...... N

Figure 10. --New England clam fishery: Clams delJvered to processing plant (upper left), arc washed and graded (upper right). Some clams are shipped directly [0 market as whole clams, but most are shucked, washed, and packed In cans (lc1\oier left to right). Figure ll.--Typical Chesapeake Bay dredge-boat with escalator dredge raised out of water. The large hose that car ries water from a pump 00 the boat to high-pressure jets 00 the dredge haogs from the forward part of the dredge. certain parts of a sma ll number of open g r eat abundance, clams become potentially areas. The supply is greater than the present lethal organisms for man. Fortunately, the demand, and most dredg es are restricted to species of Gonyaulax involved in paralytic a daily quota. shellfish poison are restricted to northern climates. U.S. and Canadian public health Although an e x panded m a rket is needed, sci entists continuously survey the toxicity the Chesapeake fishery i s thought t o be in of edible shellfish. Whenever shellfish from good condition at this time, and no cultiva­ p r oducing areas begin to show an increase tion or ex tensive management of the f i s hery in toxin toward scientifically established resource is being underta ken. minimum levels, these areas are immedi­ ately closed to the clam fishery. Special Problems of Paralytic Shellfish Poison and Pollution Vast supplies of clams are unavailable to the fishery because of- domestic and Occasional outbreaks of paraly tic shell­ industrial pollution. Pollution problems are fish poison are of serious concern to those unfortunately increasing as our population responsible for the pub lic w elfare. The grows, and each year additional shellfish toxic agent is concent rated in clams and a r eas are closed. Bacterial pollutIon is other bivalves when t h e y feed on a small probably of primary concern to man, since marine organism, Gonyaulax sp., that pro ­ clams t end to concentrate pathogenic or­ duces the poison and is noted for erratic ganisms from domestic pollution and may population ex plosions. When Gonyaulax i s In be involved in the transmission of serious

13 Figure 12.--Boat crew removes clams from the chain escalator belt. The small air-cooled motor (upper left) provides power for the belt. diseases. Chemical pollution, such as fuel many animals other than man. Although the and industrial effluents, may kill shellfish clam fishery is beset by many problems, or may flavor the meats so that they are none are insurmountable and it is possible unacceptable to the market. Physical pollu­ that continued research, responsible man­ tion, such as the dumping of sawdust, agement of the resource, and improved masonry, and other industrial wastes, may marketing will bring the fishery to new kill clam populations by smothering and levels of economic importance. may remove producing areas from further To those who have enjoyed the rare treat production by changing physical character­ ll istics of the shore. of a real "Down- Ea st clambake or have savored the special flavor of fried clams, the need for the continued success of the soft­ SU:MMARY shell clam industry will be apparent.

The soft- shell clam is one of our most ACKNOWLEDGMENTS delicious marine bivalves. It occurs on all of the major coastlines of the northern Photographs were suppliecl by Gareth W. hemisphere, but is commercially important Coffin and Robert K. Brigham, Bureau of only on the Atlantic coast of NorthAmerica. Commercial Fisheries Biological Labora­ The clam has an interesting and hazardous ratory, Boothbay Harbor, Maine, and Woods life history, and is a source of food for Hole, Mass.

14 ) S ELECTED BIBLIOGRAPHY 1954. The effects of temperature and predators on the abundance of the Anonymous. soft- shell clam, Mya arenaria, in New 1949. A modern clam processing plant. England. T ran sac t ion s of the Fishing Gazette, vol. 66, no. 2, p. 50, American Fisheries Society, vol. 84, 52. p. 13-26.

Ayers, John C. Hanks, Robert W. 1956. Population dynamic s of the marine 1963. Chemical control of the green clam, Mya arenaria. Lim n 0 log y and crab, Carcinus maen(})s (L.). 1961 Pro­ Oceanography, vol. 1, no. 1, p. 26-34. ceedings National Shellfisheries As­ sociation, vol. 52, p. 75-86. Belding, David L. 1914. Conditions regulating the growth Inger soll, Ernest. of the clam Mya arenana. Transactions 1887. 3. The clam fisheries. In G. Brown of the American Fisheries Society, Goode, The Fisheries and fishing 43rd Annual Meeting, Boston, Mass., industries of the United States, vol. 2, p.121-130. part 20, The oyster, scallop, clam, mussel, and abalone industries, 1930. The soft- shelled clam fishery of p. 581-615. United States Commis­ Massachusetts. Commonwealth of sion of Fish and Fisheries, Section V, Massachusetts, Marine Fisheries History and Methods of the Fisheries. Series I, 65 p. Johnson, C. W. 1934. List of marine mollusca of the Dow, Robert L. Atlantic coast from Labrador to 1953. An experimental program in shell­ Texas. Proceedings of the Boston fish management. Maine Department Society of Natural History, vol. 40, of Sea and Shore Fisheries, Fisheries no. 1, p. 1-204. Circular No. 10, 11 p. Kellogg, J. L. Dow, Robert L., and Dana E. Wallace. 1901. Observations on the life history of 1957. The Maine clam (Mya arenaria).Maine the common clam, Mya arenaria. Bulle­ Department of Sea and Shore Fish­ tin of the U.S. Fish Commission, vol. eries, Bulletin, Augusta, Maine, 35 p. 19, for 1899, p. 193-202.

1961. The soft-shell clam industry of Lotsy, J. P. Maine. U.S. Fish and Wildlife Serv­ 1895. The food of the oyster, clam and ice, Circular 1l0, p. 1-36. ribbed mussel. U.S. Commission of Fish and Fisheries, Part 19, Report of the Commissioner for the year Dow, Robert L., Dana E. Wallace, and ending June 30, 1893 (1895), p. 375- Louis N. Taxiarchis. 386. 1954. Clam (Mya arenaria) b rea k age in Maine. Maine Department of Sea and Manning, Joseph H. Shore Fisheries, Research Bulletin 1957. The Maryland soft- shell clam in­ No. 15, 4 p. dustry and its effects on tidewater resources. Maryland Department Foster, R. w. Research and Education, Chesapeake 1946. The genus Mya in the western Biological Laboratory, Resource Atlantic. Johnsonia, vol. 2, no. 20, Study Report 11, 25 p: p. 32- 35. Manning, Joseph H. , and Hayes T. Pfitzen­ Glude, John B. meyer. 1954. Survival of soft- shell clams, 1957. The Maryland soft- shell clam in­ Mya arenaria, buried at various depths. dustry: its potentials and problems. Maine Department of Sea and Shore Proceedings of the National Shell­ Fisheries, Research Bulletin No. 22, fisheries Association, vol. 48, p. 110- 26 p. 114.

15 McFarren, E. F., M . L . Schafer, J. E. Smith, Osgood R., and Edward Chin. Campbell, and K. H. Lewis.. .. 1951. The effects of predation on soft 1956. Public Health s lgmflcance . of clam s, Mya arenaria. Na tional Shellfi sh­ paralytic shellfish p o i s on:. a reVIew eries Association, Convention Ad­ of literature and unpubl1s h ed re­ dress, p. 37-44. search. Proceedings National Shell­ Spear, Harlan S., and John B. Glude. fi s h eries Association, vol. 47, p . 11 4 - 1957. Effects of environment and he­ 141. r idity on growth of the soft clam (Mya arenaria). U.S. Fish and Wildlife M e d co f , J • C ., A. H. Leim, A. B. Needler , Service, F i shery Bulletin 114, vol. A. W. H. Needler, J. Gibbard, a nd 57, p. 279-292. J. Naubert. Swan, Emery F. 1947. Paralytic shellfish poisoning on 19 52. The growth of the clam Mya arenaria the C anadian A tlantic coast. Fish­ a s a ffected by the substratum. Ecol­ eries Research Board of Canada, o gy, v ol. 33, no. 4, p. 530- 534. Bulletin 75, 32 p. Turner , H a rry J., Jr. . 1949. The soft- shell clam industry of Pfitzenmeyer, Hayes T. the E a st Coast of the United States. 1962. Periods of s p a wning and setting of Appendix 1. Report on Investigations the s oft- shelled clam, Mya arenaria, at of the propagation of the soft- shell Solomons, M a r y land. Chesapeake c l a m , Mya arenaria. Woods Hole Ocean­ Science, vol. 3, no. 2 , p. 114-120. ographic Institution, Collected Re­ prints 1948, Contribution 462, p~ 11- Pfitzenmeyer, Hayes T., and Carl N. 42. Shuster. 1960. A partial bibliog raph y of the soft Turner, Harry J. , Jr. shell clam, Mya arenaria, L . Maryland 1953. A r e v iew of the biology of some Department of Resea rch and E duca­ commercial molluscs of the east tion, Chesapeake Biolog i cal L abo r a ­ coast of North America. Sixth Report tory, Contr ibution No. 123, 29 p. on Investigations of Shellfisheries of Massachusetts. Woods Hole Oceano­ graphic Institution, Collected Re­ Scattergood, Leslie W. prints 1954, Contribution 715, p. 39- 1952. The distribution of thegreencrab, 74. Carcinides maenas (L .), in the n orthwest­ ern Atlantic. Maine Department of U.S. Fish and Wildlife Service. Sea and Shore Fisheries, Fisheries Fishery s tatistics of the United Circular No.8, p. 1-10. Stat es . Department of Interior, Sta­ tist ical Digests. Annual. Wash., D.C.

Smith, Osgood R., John P . Baptist, and VIes, Fred. Edward Chin. 1909 . M onographie sommaire de la Mye 1955. Experimental farming of the soft­ (Mya arenaria Linne 1767) (1) Memoires shell clam, Mya arenaria, in Massa­ d e la Soci ete Z oologique de France, chusetts, 1949-1953. U .S . Fish and tome 22, p. 9 0-142. [English trans­ Wildlife Service, C ommercial Fish­ lation b y U.S. Fish and Wildlife Serv­ eries Review, vol. 17, no. 6, p. 1-6. ice, 1954 .]

16 MS # 1272

Gf'O 944 · 46 5 Created in 1849, the U.S. Department of the Interior is concerned with the management, conservation, and develop­ ment of the Nation's water, fish, wildlife, mineral, forest, and park and recreational resources. It also has major responsibilities for Indian and Territorial affairs. As the Nation's principal conservation agency, the De­ partment works to assure that nonrenewable resources are developed and used wisely, that park and recreational resources are conserved for the future, and that renewable resources make their full contribution to the progress, prosperity, and security of the United States--now and in the future.

)

UNITED STATES DEPARTMENT OF THE INTERIOR Stewart L. Udall, Secretary James K. Cllrr, Undf.1· Secretary Frank P. Briggs, Assistant Secretary for Fish and Wildlife FISH AND WILDLIFE SERVICE, Clarence F. Pautzke, Commissioner BUREAU OF COMMERCIAL FISHERIES, Donald L. McKernan, Director

Washington, D.C. 20240 December 1963