Spy aaa aS = IX VIII TO THE REPORT OF THE U. S. COMMISSIONER OF FISHERIES FOR 1919) Uyishee DEPARTMENT OF COMMERCE BUREAU OF FISHERIES HUGH M. SMITH, Commissioner THE OYSTER AND THE OYSTER INDUSTRY OF THE ATLANTIC AND GULF COASTS By E. P. CHURCHILL, Jr. Assistant, U. S. Bureau of Fisheries APPENDIX VIII TO THE REPORT OF THE U. S. COMMISSIONER OF FISHERIES FOR 1919 Bureau of Fisheries Document No. 890 PRICE, 20 CENTS Sold only by the Superintendent of Documents, Government Printing Office Washington, D.C. WASHINGTON H GOVERNMENT PRINTING OFFICE 1920 p; ef ws oct 2i 4999: CONTENTS. TEs aUtPEROG LUNCH ONS al es I ae A aus CA cc CCI AS Ae A CcosrapmicaladistralpiMiome 255 Ss se a ee ky ee a eee ee ots) IIS Sa CHAUISE tS so see ee eet teeta la CENT OE I Vea RL SSN AG Oe pe MNS uO dewlisl ames eee eas OW OM aaa eR ee aN dee eaees rN atl (COMMeO CH CUEHE eS: OURAN BN NA RO ec SAG ea da te carla SAS AINE Savas XGOoT Kes soe eS Nise SERS Ais li Saree LAS ic EDS A Me Rieu eS Lan See apne ea OE ING WEES CIV ( Sere recente tcc sd A Senor) GG ry eee ae AB) SLAW Ae penn area LDN Ie Us RCO LI Uru MO Ue cee) evacuees Mie hein Are ere Saya) 0D Memes sas OG en eu Seer Un vee A RNs a Siale ia Re gaan AGREES Ae sees tN Ma a Vee Meanie Sater Monn ea gals es Our a WEA Caren esa. North Carolina SES RUNES ise Le eesilee N casoate ORCA IC Oe ea a eae Cae x IM GTSSTISSIY OF ODL Ee SO ae MO Sn GG ANC ARUN aie er a Me tL ALE CO UDAT SL ca 1 hee este es ees Onan et CO IA ae UNO MeN ea AO Ae US ICU pacaee en Output ob Vvaniousecioms 7 yes ey aor eas ee en aug el Ore Wescripuomand amatoniye mee see Me Ue ee a Ne ay oe. CIASSHCA TOMA eee ee AA eee Nm ie CU a ON aac a ychernalbapPearanCeenea a man wen ee te a Le a ATTA LOMMICa bea LUTES Enron. Umea ecrna md yO LEM a Vea So! oo Ru oe ithe IstOryssce 2 SiGe tL ea ie Ve aya ae i Saat Rs ee Ua ere imme FOP SpA WANING tre vere Me Ee ee Sacks Reproduce tome: Vo. zea Ri OG ek en Nr ee Sate aes Anes Goro wil Seen Cte ni Bae Ce ek emiperatUrehOnWaberer. mus eNO ke eo) ne oe IDEristTyMOlRWateT ee ye imc Utes MUNa EUS CA WRT ERGs es Oey malas ea ae Mud aliand suspendedsmatter news See ee eee Midesamducurremtyr i esta Minne a GRO ea ak eis Me pEnNolewatence weenie tr emma A ee ia ale ie resets mstOnmawandCet eae sey ie | Nee Se eee HOOMEGE CeO VS LCR see iam Aa ie CU Cees i Ea Rhoda ay ee De All fy iNeieumala bed merce yee err iM eat Val) eck ae OO ae Developmentandideseription. 664 ee ee Ne) Mele tome ee yee Agee ae CL ONE EC ea ies a nah ca ae CHUN EIOTO is fk I dees Set esti ee at baa EG ae pet Ae oa ee ea Artificial propagation Wegalecommideravlomset ue ecm NaN Sn Ge ee 8 Procuring ground [Vaisala Seeds tere ieee eens adi MIN SE Sky OE Methodsohoyeremeultuneta ge cme ea ei mien yest oc ck ok Catching of spat, or ‘‘set””’ Cultch.. Pesta ses ie 2 se Is CUS eae ie Character and pr eparation 0 onbottorn a es Time for planting cultch.. ocattontoneulichipedatawes 2 ene ee on Roca tion otspammine bhedsuys ot: wave a ie eh General desirability of planting cultch Planting seed oysters Sowing the seed Care of beds 4 CONTENTS. Cultivation—Continued. Page. Protechion againstienemies: 2. ~ 222)52-2..25. Sees see was Se a ee eee 36 GAMISHe fe tset 328 is SS ee Be cw eS ee eee aoe Oto ee ee 36 Drills. cee behets k Dac se oo See ne eel ee =, Moore, H. F. (1897, p. 266.) 10 THE OYSTER AND THE OYSTER INDUSTRY. Each valve or shell is lined with a thin membrane called the mantle, fringed on the edge and attached to the shell over nearly all its ex- panse, but free along the margin. The right mantle has been re- moved with the shell in Plate i In about the center of the body is the large adductor muscle, by the contraction of which the oyster closes its shell. As stated above, when this muscle is relaxed or cut, the ligament in the hinge forces the valves apart. The main body of the oyster lies between the right and left sides of the mantle and is attached to it and the adductor muscle. It will thus be seen that the oyster is held to the shell by the mantle and the muscle. In Plate IT part of the body wall is represented as having been re- moved with the right side of the mantle, thus exposing to view the liver or digestive gland and the cesophagus or gullet leading from the mouth to the stomach, which opens into the intestine. This extends downward and backward beneath the muscle, then curves sharply and runs forward on the left of the stomach to the cesophagus, where it again turns to the rear and extends backward to the vent or anus above the muscle. In a thin-walled sac, the pericardium, immediately in front of the muscle, lies the real heart of the oyster. (The adductor muscle is often erroneously referred to as the ‘‘heart,’’ smmce when it is cut the oyster eventually dies from mablility to close its valves.) The circulatory system of the oyster is of the ‘‘open”’ type; that is, the arteries do not terminate in capillaries ich lead to the veins, as in man, but deliver the blood, which is colorless, into large spaces, or lacune, between the tissues. The blood, as it spreads through these lacune, bathes the various cells of the body and is then gathered up by the veins and collected in the auricle or lower chamber of the heart. It then passes into the ventricle, or upper chamber, which contracts and forces the blood through arteries to the different parts of the body. A hinged valve between the two chambers of the Boag prevents the blood being driven back into the auricle. The nervous system of the oyster (not shown in the figures) is very simple, consistimg of two ganglia or knots of nervous matter, lying just over the gullet and two nerves passing back from them, one on each side, to another pair of ganglia beneath the adductor muscle. Smaller nerves extend from these two pairs of ganglia to the various parts of the body. ‘ At the anterior end of the body four thin lips or palps hang free in the mantle cavity and extend backward from beneath the mouth for about one-third the length of the body, the posterior ends lapping. under the ends of the gills. The latter, four in number, are somewhat similar to the palps in appearance, and extend backward and upward in crescent fashion, as shown in Plate II. Microscopic examination shows that the gills are covered on both sides with very fine hairs or cilia, arranged in rows. These beat back and forth and, when the oyster is lying with the valves open, cause a current of sea water to pass on to the gills. The water is forced through fine openings on the surfaces of the gills into water tubes inside the gills and thence into the cavity above them. As the water passes through the gills the blood is aerated as in the case of a fish. i Plate Il the openings of the tubes can be seen on the inner edge of the gills. The right mantle having been removed, the cavity into which the water passes is exposed. 1t lies in the space just above the inner edge ot the gills. THE OYSTER AND THE OYSTER INDUSTRY. 11 From this cavity the water passes behind the adductor muscle and out between the edges of the valves of the shell around the rear end of the gills, at a point in the upper left of the figure. The food of the oyster consists entirely of minute animal and vegetable organisms and small particles of organized matter. Ordinary sea water contains an abundance of this sort of food, which is drawn into the gills with the water, but as the water strains through the pores into the water tubes, the food particles are caught on the surface of the gills by a layer of adhesive slime wich covers all the soft parts of the body. As soon as they are entangled the cilia strike against them in such a way as to roll or slide them along the gills toward the mouth. When they reach the anterior ends of the gills they are pushed off and fall between the lips, and these again are covered with cilia, which carry the particles forward until they slide into the mouth, which is always wide open and ciliated, so as to draw the food through the csophagus into the stomach. Whenever the shell is open these cilia are in action, and as long as the oyster is breathing a current of food is sliding into its mouth.¢ The food then passes to the stomach, is acted on by the fluids from t':. liver, and moves along the intestine. The nutritive portion is yy z { i : c “i , a , [hy oe ; Ce yt ie SLANG Fic. 1.—Diagram of dissection of oyster to show reproductive organ, consisting of the branching tubules spread over the dotted portion. aw, auricle of heart; d, external opening of reproductive organ; 9, gills; M, adductor muscle; m, mouth; p, palps; ve, ventricle of heart; y, posterior end of gills. About naturalsize. (After Moore.) absorbed and the feces are thrown out the vent in long, ribbonlike form and carried outside the shell with the stream of water passing out from the chamber over the gills. The position, form, and general appearance of the reproductive organs of the oyster are the same for both sexes. Really there is but one reproductive organ, which consists of a mass made up of micro- scopic tubules and connective tissue lying between the folds of the intestine and investing it and the stomach and liver in such a manner as to cover the vcard organs when the opened oyster is viewed from either side. In Plate IL most of the reproductive organ has been removed, a small portion being shown about the tolds of the intestine. Text figure 1 represents an oyster with the left valve and mantle removed, showing the reproductive organ as it appears from the left side, covering the visceral mass and partially surrounding the heart and adductor muscle. Numerous ducts arise from the organ, unite into one and open at point d below the adductor muscle. A view a Brooks, W. K. (1880. p. 9.) 12 THE OYSTER AND THE OYSTER INDUSTRY. of the right side of the organ would present practically the same appearance, there being a similar system of ducts opening on that side beneath the muscle. Through these two openings the genital products are discharged into the water at spawning time. LIFE HISTORY. TIME OF SPAWNING. The oyster may spawn when the water reaches a temperature of 68° F., but spawning proceeds at normal speed only when the water is 70° or above. For this reason the spawning period varies in different regions, depending on the temperature of the water, which is regulated by the Aapth of the water and the general meteorological conditions. Shallow bodies of water, even though in more northern latitudes, often become warm as early or earlier than deeper waters farther south. In the north, where the season 1s shorter, the spawn- ing period is relatively short, often lasting only two or three weeks, Phils in the south oysters may be found in a spawning condition - from early spring until fall. In Long Island Sound, the bulk of the oysters spawn about the last of July; in Great South Bay, spawning occurs from about June 5 until after the Fourth of July. In New Jersey waters spawn- ing begins about June 1. Spawning extends in Chesapeake Bay from May until September. On the Gulf coast, spawning begins in March and spawning oysters may be found as late as November. REPRODUCTION. In spite of the fact that the sex of the oyster can not be distinguished by the external appearance of the shell, of the body, or of the repro- ductive organs, the sexes are separate. Some oysters are male, the reproductive organs developing spermatozoa or milt; other oysters are female and produce ova or eggs. While it has at times been stated that the sex might change from year to year, an oyster being perhaps male one year and female the next, or the reverse, there is no evidence on which to base this belief, except some inconclusive researches made nearly 50 years ago and not borne out by sub- sequent investigations. It can be almost conclusively stated that the sex of the eastern oyster is permanent and does not change during the life of the individual. . The sexes can be distinguished only by an examination of the products discharged by the reproductive organs. The spermatozoa and eggs are so extremely small that a lens must be employed to distinguish one from the other. The eggs (PI. III, fig. 2) vary from roughly pear-shaped to oval or nearly spherical and measure about sty of an inch in diameter. It is estimated that.a female oyster will produce over 16,000,000 eggs. The male genital products, or sperma- tozoa, are many times smaller than the eggs. seach Spermatozoon. (Pl. III, fig. 1) is made up of a head about yz5-4yo5 of an inch in diameter, pointed at one end and flattened at the other. To this flat base is attached a very slender threadlike tail about 20 times the length of the head. This tail lashes about and moves the spermatozoon around in the water after it has been discharged by the male oyster. THE OYSTER AND THE OYSTER INDUSTRY. £3 Fertilization of the eggs occurs in the water. The oysters, male and female, lying about over the bottom, at spawning time discharge the reproductive elements into the water where they mingle as chance may bring about. The more numerous the oysters on a particular bed, the greater the chance of the actively moving spermatozoa meeting the eggs. The spermatozoa swarm around the eggs, many about each one, until a spermatozoon penetrates the egg membrane, the head only of the spermatozoon passing on in, the tail dropping off. The material of the head unites with that of the egg, and important changes in the latter are thereby initiated. The single cell of the ege begins to divide into many cells and to change its form and in the course of from 5 to 10 hours develops into a small oyster larva, which swims by means of fine hairs or cilia on the outside of its body. A shell then begins to develop and soon covers the entire body, so that the larva resembles a tiny hard clam. A definite organ of locomotion also appears, consisting of a disk, known as the velum, borne on the end of a thick stalk which is pro- truded from between the valves of the shell in front. The disk bears cilia which by their movement enable the larva to swim about rapidly (Pl. Ill, fig. 4). When the velum is retracted the larva settles to the bottom. The larva is now about two days old and measures about 0.08 mm. in length. As it increases in size certain elevations, the umbones, can be noted on the upper part of the hinge, one on eachside. Shortly one valve becomes much deeper than the other, and the umbo on it much more prominent than that on the right side, and by this characteristic the oyster larva may be readily distinguished under the microscope from the larval form of any other bivalve. The deeper valve is the left one and that by which the oyster later becomes attached. During the advanced stages of the larval form, the left umbo is very conspicuous, juttmg back in aimost the form of a hook (PI. ITI, fig. 3). The period passed through by the oyster larva from the develop- ment of the cilia, a few hours after fertilization, until it ‘‘sets’’ or “strikes” is known as the free-swimming stage. Although the larva swims about freely in the water, being so small, its move- ments and location at any particular time are largely subject to the tides and currents. The free-swimming period lasts from about 14 to 18 days in the more northern waters and a somewhat shorter time in the southern. The warmer the water the more rapidly go eeu occurs and consequently the shorter the free-swimming period. At the close of the free-swimming period, when the oyster is about one-third of a millimeter (one seventy-fifth of an inch) long, it ‘“‘sets”’ if the proper conditions are present. It attaches itself by the left valve to some surface in the water, a rock, shell, stake, in fact almost any object (Pl. IV). The first essential is that the surface should be clean and that it should remain so a sufficient length of time.to enable the young oyster to firmly establish itself. So long as this condition obtains, the nature of the material seems to matter but little. In most bodies of water the spat fixes itself at all levels from the surface to the bottom _ butin certain parts of the coast its place of attachment is confined to the zone between high and low water, the midtide mark being the place of maximum fixation. @Moore, H. F. (1897, p. 274.) 14 THE OYSTER AND THE OYSTER INDUSTRY. Once secured, the swimming organ disappears and the oyster never wanders again of its own volition. ! GROWTH. The shell is secreted by the mantle, the membrane lining the shell. Horny material is first deposited over the outer surface of the mantle - and to this is added lime, forming the familiar hard shell. As the mantle increases in size with the general growth of the rest of the body, and as it can be extended somewhat from between the edges of the valves, new shell material is added to the inner surface of the valve and to the outer edge. This makes each valve thick in the central portion, sloping to a condition of extreme thinness at the edges. The outer edges of the valves of a rapidly growing oyster are so thin and knifelike that care must be exercised in handling them to avoid cutting the fingers. The rate of growth of oysters varies widely, depending on tem- perature, density and food content of the water, season of the year, and other factors. Its growth is more rapid in the warmer southern waters than in the colder northern. In Long Island Sound about four years are required for an oyster to reach a length of 4 to 5 inches, or marketable size. In southern waters that size is reached in two years. Oysters if left undisturbed may attain a length of 8 to 10 inches or more. While the exact age which an oyster may reach can not be definitely stated, oysters have been found which appeared from the number of layers in the shell to be at least 15 years of age. Oysters which have unrestricted space for growth acquire the normal shape shown in Plates I, XX, and XXI. When crowded together, the shape becomes modified, even greatly distorted at times. Often numerous set will fasten upon a relatively small piece of cultch, and as growth proceeds a crowded cluster of oysters will result. If broken apart by pressure of growth or by artificial means, their shape will improve. The crowding of oysters reaches its climax upon the ‘‘raccoon” oyster beds. Rac- coon oysters are usually found in localities where the bottom is soft and the only firm place which offers itself for the attachment of the spat is upon the shells of its ancestors. Temperature and other conditions are favorable, growth is rapid, the young oysters are crowded into the most irregular shapes, the shells are long, thin, and sharp- edged, and eventually the mass of young is so dense that it crowds out and smothers the preceding generations which produced it and offered means for its attachment. Oysters crowded in this excessive manner are poor-flavored, as well as ill-shaped, but both defects are corrected if they be broken apart, as may be readily done, and planted elsewhere.@ FACTORS OF ENVIRONMENT.? TEMPERATURE OF WATER. The fact that the oyster is found from Cape Cod to Mexico shows that it can become adapted to living in waters of considerable differ- ence of temperature and in certain regions may withstand wide changes during the course of the seasons. In. Long Island Sound @Moore, H. F. (1897, p. 275. + The outline of this section, “‘ Factors of Environment,” and of the one following, ‘‘ Natural Beds,” and the details of certain topics therein, specifically stated in each such case, are substantially as prepared by Dr. H. F. Moore, Deputy Commissioner of Fisheries, for an uncompleted revision of his ‘‘Oysters and Methods of Oyster Culture’’ (1897). THE OYSTER AND THE OYSTER INDUSTRY. 15 the temperature over the oyster beds falls in winter nearly to 32° F., the freezing point, and in summer rises to 72° in deep water and 75 to 78° over the inshore beds. In Chesapeake Bay oysters in certain shallow water beds withstand variation from the freezing point, below 32 to 90° F.¢ In the Gulf of Mexico the usual range of temperature over the oyster beds is from 50 to 90° F. The rela- tion between temperature and the spawning of oysters has been discussed on page 12. DENSITY OF WATER. The higher the proportion of salt contained in sea water the greater the density. Therefore, it is common practice to estimate the proportion of salt by measuring the density of the water with the salinometer. This consists of a glass bulb with a narrow stem at one end on which are gradings reading from 1.000 to 1.031. The bulb is weighted at the end opposite the stem, so that it will smk some- what below the surface, leaving the stem projecting from the water. The less salt in the water the less the density and the lower the salinometer will sink. Fresh water is arbitrarily considered as 1.000 and the poimt on the stem of the salinometer to which the water reaches when the instrument is placed in fresh water is so marked. Grades are marked below that on the stem, the bulb rising higher in the water the greater the density. The highest grade is usually 1.031. For convenience three bulbs are usually used, one reading from 1.000 to 1.011, one from 1.010 to 1.021, and one from 1.020 to 1.031. Common sea water usually reads from 1.025 to 1.026 on the salinometer. Oysters are found in water ranging in density from ‘1.002 to 1.025, but can not withstand densities lower than 1.007 for indefinite periods. In general they seem to thrive best in densities between 1.011 and 1.022. Oysters are not usually found out in the main body of the sea- water, away from the influence of the fresh water from the streams, where the density is 1.025 or more. It will thus be apparent that oysters have become adapted to a certain range of densities, and natural beds have grown up at points fairly close to shore or in inclosed bays where the salinity of the seawater is modified by the inflowing of fresh water. MUD, SILT, AND SUSPENDED MATTER? A bottom composed of slightly shifting sands or of very soft mud imto which the adult oysters will sink and on which the minute spat can gain no firm support is alike unfavorable to oyster culture and to the development of natural beds. If, however, hard objects be distributed on or above such bottoms they will become collectors of spat so long as they remain clean and free from slime or sediment, and if it be desired to produce permanent beds or to catch the float- ing spat for the purpose of seeding other beds it is manifest that, the scourmg action of the currents being equal, waters containing a minimum of sedimentary matter are to be preferred to those more or less laden with mud. @ Moore, H. F. (1897, p. 280. >’ Moore, H. F. Proposed revision of ‘Oysters and Methods of Oyster Culture?’ (1897). 16 THE OYSTER AND THE OYSTER INDUSTRY. In this connection a distinction must be drawn between beds used for seed production and those employed in growing and fattening stock for the market. Oysters will frequently grow more rapidly in silt-laden waters, on muddy bottoms, or in their vicinity, than they will elsewhere, as such places are usually more productive of food organisms, owing to the larger amount of dissolved material available for the sustenance of the minute plants which constitute a considerable part of the food of the oyster. Even adult oysters may be destroyed, however, by heavy deposits of silt such as often result from freshets and crevasses. For the purposes of seed culture or the establishment of self-perpetuating beds the most desirable waters are those which contain an abundance of microscopic vegetation with a minimum of suspended imorganic particles, although an organic slime such as rapidly forms on sub- merged surfaces in some localities is as effective m preventing the fixation of spat as is inorganic sediment. In many places in Chesa- peake Bay and in the bays on the New Jersey coast the sediment, as well as the bottom mud, is largely composed of finely comminuted fragments of seaweeds and other vegetable matter the rapid deposit of which soon covers with a flocculent film the surfaces of all objects exposed to it, excepting when the currents are sufficiently strong to exert a scouring influence. During warm weather this organic deposit is likely to undergo rapid decomposition, the toxic products of which sicken and kill ihe oysters. The more or less constant dribbling of fine material upon the bottom has comparatively little effect upon adult oysters, operating mainly to cover the shells and prevent the attachment of spat or to stifle the young oysters after attachment. This rain of fine material occurs almost everywhere but especially where the currents are weak, and it is generally in the latter localities that it is of sufficient volume to be obnoxious, TIDES AND CURRENTS. The effects of tides and currents upon the development and growth of oysters are quite important. The genital products, cast directly - into the water as previously stated, are moved about so that more opportunity is afforded for the contact of the spermatozoa of the male with the eggs of the female. The free-swimming larve are carried to. and fro by the tides and currents, and thus when large enough to set are often some distance from where they were spawned. ‘The importance of this fact in the method of oyster culture by planting cultch is very great and the matter is discussed under a separate section on page 31. Tides and currents tend to prevent the fouling of material upon which the larve set by washing away silt and débris. In still water, as in an inclosed bay, the suspended débris has an opportunity to settle upon the cultch and form a slime and film which prevents the attachment of the larve. If the larve have attached, the deposit is often sufficient to smother them. _ Since the food of oysters consists of microscopic materials found in the water (see p. 19), it follows that currents affect the distribu- tion of the food of the oyster. In still water, nearly all the organ- isms might settle to the bottom or those in the neighborhood of the THE OYSTER AND THE OYSTER INDUSTRY. 17 oyster might become exhausted. Currents keep the material agi- tated and cause a fresh supply to sweep across the oyster beds. Movement of the water also brings a fresh supply of oxygen to the oyster which aerates the blood by oxygen derived from the water passed through its gills. -DEPTH OF WATER.® The known vertical range of oysters under natural conditions is from or near high-water mark to a depth of about 130 feet, the latter extreme occurring over densely stocked and productive beds in Patuxent River, Md. In a large part of the oyster region of South Carolina the natural beds occur almost exclusively between high and low water marks, and some of the beds of Florida are similarly situated, the oysters growing on the aerial roots of man- groves, as they frequently or generally do in Porto Rico and others of the West Indies. In places on the Gulf coast oysters set and grow in limited numbers in the grass on the edges of the marsh prairies above the level reached by many high tides, but in such situations they are frequently killed by freezing. In the Mississippi delta region a good set is often obtained on cultch planted at or near high-water mark, but the young oysters are removed to deeper water before cold weather arrives. Elsewhere oysters are rarely planted in this country on bottoms exposed at low water. In most places comparatively shallow depths ranging from 2 to 12 or 15 feet are utilized in oyster culture, but in Long Island Sound the practice has been successfully extended to depths of 60 feet or more. FRESHETS, STORMS, AND ICH.? Freshets occur with more or less frequency in the rivers discharg- ing near the oyster beds of many of the South Atlantic and Gulf Coast States, and with them are to be classed the crevasses or breaks in the levees which sometimes accompany high water in the coastal streams of Louisiana. The effects of a freshet are twofold. The most immediate effect is that, owing to the vastly increased volume of fresh water dis- charged, the salinity of the water over the oyster beds is reduced far below the normal and in many cases becomes fresh or practically so for considerable periods. As already stated in another connec- tion, this is often fatal to the oysters already on the beds, and, even when this is not the case, the production of a set is inhibited during the prevalence of the abnormal conditions. Freshets also carry large quantities of mud and débris scoured from old channels and washed from the land, and as the currents slacken in the bays and estuaries, where the oyster abounds, their carrying power diminishes, and the materials are dropped on the beds. If the deposits so made be deep, the old oysters may be killed, while even a light deposit is sufficient to prevent the attachment of spat until it be again gradually scoured from the shells and other hard bodies on the bottom. 4 Moore, H. F. Proposed revision of “Oysters and Methods of Oyster Culture’? (1897). 181698°—20-——_2 a ee aE ey eee Neen 18 THE OYSTER AND THE OYSTER INDUSTRY. It sometimes happens that a freshet of unusual severity, while disastrous in its immediate effects, results eventually in an increased productiveness of the beds. If the disaster be due to a prolonged freshening of the water without an undue deposit of silt, the shells are often left in a much-improved condition. This is apparently due in part to the more active scouring action of currents of more than usual velocity, but mainly to the destruction of the organic slime, which often covers the shells in sea water, and the cultch is thereby left in a more favorable condition for the attachment of spat carried from more or less distant beds. The fresh water also exterminates the drills which feed on the little oysters, and, as Dr. Moore’s observations of improved sets under the conditions described indicate that sets usually occur in waters of rather high normal salinity, where the drill ordinarily thrives, it is probable that this action of the fresh water is no unimportant beneficial factor. The oysters, from the nature of their reproductive and developmental characteristics, are able to reestablish themselves much more rapidly than their enemies. Gales, to have an effect on adult oysters in moderately deep water, must be of extraordinary severity, but they frequently do great damage or exterminate beds in shoal water. The waves sometimes pick up the oysters and throw them on the beach, but more fre- quently they are destroyed by being buried in situ by sand, sea- weeds, and débris piled up by the sea. Cases are known of where well-established beds have been overwhelmed by such deposits and others in which thick strata of sand between layers of old shells indi- cate a succession of such disasters in the more or less remote history of the beds. Sometimes the eroding effect of currents and waves will uncover the buried oysters and shells, and the beds will again reestablish themselves through the attachment of young; but in other cases the beds are permanently destroyed. The former is the usual result when the reefs rise rather abruptly from the surrounding bottom, and the latter is frequent when they are but little elevated above the general floor of the sea. Planted beds, which usually lie at the general level of the bottom, are usually permanently covered. Gales are sometimes agents in the establishment of new beds, carrying oysters and shells to surrounding barren bottoms, where they form a nucleus that gradually develops into economic impor- tance. Certain productive beds at the eastern end of Mississippi eet by character and by repute, appear to have been so estab- ished. The free-swimming larye are more susceptible to the weather conditions than are the adults, and cold rain storms, which would have no effect on the latter, undoubtedly kill large numbers of the swimming young. This was first noticed by Ryder and has been amply corroborated.¢ Ice is occasionally destructive to oyster beds quite independently of the factor of temperature. When heavy ice grounds at extremely low tides, it sometimes crushes the oysters or presses them into a The author and J. S. Gutsell, during the study of the occurrence of free-swimming oyster larve in Great South Bay, 1919, found that the average number in 50 gallons of water was 8,339 on July 8. A vio- lent squall and rain followed, together with a drop in temperature of 5° F. On July 11, as soon as collec- tions could he made, the average number had dropped to 3,558 larvee per 50 gallons of water. THE OYSTER AND THE OYSTER INDUSTRY. 19 the bottom, and occasionally they freeze fast to the underside of the ice and are carried away when it floats. FOOD OF THE OYSTER. The food of the oyster consists of microscopic plants and animals and organic detritus growing or found in the water on and above the bottoms on which the oysters lie, or carried to such waters by currents. ; A large proportion of the oyster’s food is made up of the plant forms which are known as diatoms. There are many species of diatoms, typical forms being shown in text figure 2. Diatoms are found in more or less abundance in almost all waters, varying greatly Fia. 2.—T ypical diatoms, which make up a large part of the food of the oyster. Magnified about 500 times. (Aiter Moore ) in numbers in different places and at different seasons in the same place or in the same season of different years. Diatoms derive their sustenance from the various organic mate- rials washed down from the land and held in solution in the water. These organic fertilizers consist of decayed and decaying vegetable and animal matter gathered up from the land by the water result- ing from rains and carried down streams and rivers to the sea. The food supply of oysters is thus directly affected by the character of the soil adjoining the tributaries leading to the water over the beds, by the kind and amount of forest or other vegetation and animal life on that soil, by the industries carried on there, and by the amount and seasons of rainfall. While a large portion of the food of the oyster is made up of diatoms, considerable numbers of microscopic animal forms are eS Se se OE FU A ae a i 20 THE OYSTER AND THE ‘OYSTER INDUSTRY. also eaten. The recent work of Dr. T. C. Nelson“® shows that a larger proportion of the oyster’s food is of this nature than was formerly supposed. Copepods, or ‘‘water-fleas,” the free-swimming larve of snails and bivalves (including the oyster), worms, rotifers, and protozoa have been found in the stomach of the oyster. These animals, like the plants, are found in greater or less abundance in all waters. A systematic effort to ascertain the food content avail- able for oysters in any particular water should include the determi- nation of the quantities of the suitable animal as well as plant forms resent. ‘ Dr. Nelson kept under observation a number of oysters in water shallow enough for a system of wires and levers to be connected with the shells in such a way that the opening and closing of the valves were recorded on a revolving smoked drum or chimograph in the floating laboratory above. It was found that, during the summer months at least, the oysters remained open, and conse- uently feeding, for 19 to 20 hours out of 24. Feeding is thus evi- Ge a fairly continuous process during the warmer months. Organic detritus or débris resulting from the decay and disintegra- tion of plant and animal life undoubtedly contributes to the food of the oyster. As the diatoms-and other plant forms become broken up some of their fragments are ingested by the oyster, and a certain amount of nutriment is derived therefrom. After death, animal forms disintegrate and release fats, albumens, etc., into the water. it has been found that the fresh-water mussel may make use of such products, and probably the same is true in the case of the oyster. NATURAL BEDS. ® DEVELOPMENT AND DESCRIPTION. A natural oyster bed is an area of the bottom on which oysters have become established without the voluntary and intentional agency of man. In law, the term is usually held to include only such bottoms as bear oysters in sufficient quantities to make fishing for them ‘by legitimate methods a means of reasonable livelihood or areas which have formerly been such and whose present char- acter indicates a reasonable likelihood that they may again become productive. The only difference between natural and _ artificial beds lies in the fact that the latter originate by the intentional act of man, whereas the former arise from natural conditions purely, from accident, or from unintentional human agency incidental to other works and purposes. In most cases the natural beds, and especially the larger ones, have been produced by the operation of factors in which man has no part, and we know nothing of their origin. In a few instances, small beds have been caused by ship- wrecks and other accidents; but on the other hand there are many beds, some of them very productive, which have grown on ashes and similar material thrown overboard from vessels and upon shells culled from the live oysters by oystermen and strewn at random over the bottom. Whatever their origins, all oyster beds, if left to a Nelson, T.C. Forthcoming report, N. J. Agricultural College Experiment Station. b Moore, H. F. Proposed revision of ‘Oysters and Methods of Oyster Culture” (1897). THE OYSTER AND THE OYSTER INDUSTRY. Dy themselves will assume the same general physical and biological characters:in so far as their environments permit. The natural beds of the Atlantic and Gulf coast practically all lie like islands in a sea of mud more or less soft. In some places the oysters are in clusters rooted in the mud, in others the substratum is hard to a greater or less depth, but examination will show that this hardness is in most cases superficial, and below it lies mud of a con- sistency corresponding to that which surrounds the bed. There are a few beds which have grown on rocky bottom, and there is a larger | number lying on firm, unshifting sand; but there are few rocky out- crops on the coast south of New England, and most sandy areas tend to shift more or less and engulf such oysters and shells as may be lying on them. The oyster is an inhabitant, par excellence, of the muddy bays, sounds, and lagoons, and in them attains its best development. In tracing the history of any oyster bed, reference must be made to the nature and characteristics of the young oyster as it develops from the egg. As has been explained on page 13 the embryo oyster is a minute organism endowed with certain feeble powers of locomo- tion, which are sufficient for awhile to keep it suspended in thé water and permit its being carried by the currents. In some cases it may be carried several miles from its parents before the setting stage is attained. The chances are many that when this happens it will lodge on mud and end its story, for so small is the larva at this stage that a mere film of ooze suffices to stifle it. If, however, by rare good fortune it, at this time or just before, comes into contact with a shell, pebble, twig, rocky ridge, or other clean body, whether at the bottom or not, it speedily attaches itself and continues its growth. So abundant is the supply of larve in any prolific oyster region that ordinarily several or many will attach to each square inch of clean surface, and a shell may furnish attachment for a hundred or more. Under such circumstances there soon begins a struggle for existence that is none the less rigorous for being purely passive. As the young oysters grow there is not room for all, and the more vigor- ous ones, themselves distorted by the crowding, overgrow, stifle, starve, and eventually kill those of slower growth or less advanta- geously situated. At the end of the first year there has developed a cluster of perhaps from two to a dozen young oysters growing on the original shell, all projecting upward and crowding one another into long, narrow shapes. Upon the projecting mouths of these shells there is another set of spat on the succeeding year, and as this grows some of the survivors of the earlier generation are in their turn crowded and killed. The result of this is that in the course of a few years there is formed a cluster like an inverted pyramid with its apex being gradually driven into the mud by the increasing weight above, while its broad base is made up of several generations of living oysters attached to the dead shells which constitute the middle parts. The oysters around the edge where they have room to grow are often of fair shape and quality, while those more centrally located are irreg- ular, long, narrow, and usually poor, owing to their crowded condition and difficulty in obtaining food. From the decay of the hinge ligaments of the dead valves, the cor- toding effect of boring animals, and the solvent action of seawater on the limy shells, these top-heavy clusters tend to break up under their RE SS CPL ee ie eee: i i i 22, THE OYSTER AND THE OYSTER INDUSTRY. own weight and under the force of the waves. On hard bottom the disintegrated parts are rolled about and more or less evenly distrib- uted, resulting eventually in the production of other similar clusters scattered at intervals. On soft mud the shells can not roll so readily, and they fall and remain close to the base of the original cluster, where, if not completely engulfed, they form places of attachment for new generations. If the mud be very soft they sink for a short dis- tance and accumulate until they harden the bottom and form a firm support for the shells which fall later, and which in turn are covered with a growth of young. As these phenomena recur year after year the original single cluster gradually extends around its edges now more or less at the top until it becomes converted into a little bed composed of a dense mass of clusters, with its boundaries sharply defined and limited by the soft mud surrounding it. A number of other clusters have probably been growing simultaneously on the same muddy bottom, and, the areas between becoming narrowed and obliterated, there results a great flat bed made up of a number of smaller patches separated by a muddy network. Where a deep, muddy channel occurs the oyster growth usually stops near the edge of the slope, the shells which would else serve as Teh sinking down into the deep soft ooze. Opposite the mouths of smaller streams, even where there is no such deep chan- nel, the oyster growth is also inhibited, partly by the freshness of the water, but principally and often entirely by the deposit of silt which soon spreads its thin coating over everything lying on the bottom. In some cases the beds may be completely interrupted, but in others they are continuous in their offshore part, passing by and inclosing ~ the unfavorable area as an oval or subtriangular barren, muddy patch surrounded, excepting on its shoreward side, by productive oyster bottom. It is difficult to say what may have been the condition of the nat- ural beds in Chesapeake Bay before they were disturbed by man, but at the present time they are essentially in the condition so far de- scribed, though with their boundaries often ill-defined and the clusters usually smaller and less dense as a result of tonging and dredging. They usually exhibit no great depth of shells, though the bottom is more or less hardened by their accumulation in the underlying mud. They usually extend alongshore, their greatest length in the direction of the currents and their width extending from a couple of feet below low water toward, and often to, the edge of the deep, muddy channels. In South Carolina and adjacent regions the beds are of essentially the same type, excepting that they are smaller and narrower, and particularly that they are crowded closer to the shores and almost entirely confined to the area between high and low water, a situation impossible in Chesapeake Bay and more northern regions, owing to the killing cold of winter. Further development in the history of natural oyster beds beyond the stage which has been described results in a gradual thickening of the deposit of shells and the production of a short reef or lump, with a more or less distinct shoaling of water over its top. The living oysters standing vertically in the dense mass, with their growing tips directed upward and kept clean by the currents, present the onl available place for spat fixation. Each year the set occurs on reopade THE OYSTER AND THE OYSTER INDUSTRY. 23 ing generations, raising the living parts of the bed higher above the bottom, while the interstices beneath become filled with old shells, fragments, sand, and mud to form a compact mass. Hventually, in shallow water, the living oysters pieces low-water mark or in some parts of the coast rise above it, where their progress is arrested by cold or long periods of exposure to the air. Each year a set may occur only to be killed in winter, the dead shells, fragments, sand, and mud piling up under wave action, until the crest may become raised to a level several feet above high water, pueducing a shell island usually surrounded by a more or less dense owth of live oysters. Such islands are not uncommon in the South tlantic and Gulf States, and they frequently accumulate in time a erowth of grass and brush, which more or less obscures their true character. Sometimes the material is thrown up around their edges atoll-like, leaving a depression in the middle in which muddy deposits collect and support a growth of brush. In places where the bottom is composed M7 very soft mud the sides of these lumps are compara- tively steep and soundings will change 1 or 2 feet within a few yards, the difference being due to the depth of shells and oysters. In open waters, not especially subject to freshets, where the cur- rents are moderate and the silt carried not excessive, such lumps tend to maintain a round or oval outline, with no great difference between the long and short diameters; but where the currents are rapid or the bodies of water constricted, there, as soon as they rear themselves well above the bottom, they show a strong tendency to grow transversely to the tides, especially if the water be silt-laden. Such long, narrow reefs are common in the rivers of North Carolina and in the bays and rivers of Florida, Alabama, Louisiana, and Texas. In James River, Va., and probably in other rivers of the Chesapeake region, the beds, while often showing their greatest extent in the direction of the current, usually have their shoalest parts trans- versely to it or are made up of a series of transverse shoals and ridges porepored of a dense mass of shells and fragments. The reasons for this transverse development are as follows: The upgrowing reefs form partial dams or obstructions to the flow of the currents, and, in accordance with well-known laws, cause eddies or backwaters on both the side presented to the current and on that sheltered from it, in tidal waters the two being periodically reversed with the reversal of the tide. When the velocity of asilt-laden stream ~ 1s checked, it deposits part of its load in the slack water, and, under the conditions stated above, mud falls on the upper and lower sides of the reef, while the somewhat accelerated flow around the ends scours the shells and keeps them clean and fit to receive fresh sets of young oysters. These factors operate more energetically the more eavily silt-laden the water, and they would become nonoperative in perfectly clear water. Not only does heavily silt-laden water deposit more mud when its velocity is checked, but it scours more energet- ieally when its velocity is accelerated, the particles of sand and other materials carried in suspension, acting as so many small brushes to rub off such materials as may have previously lodged. The greater volume of water passing the ends of the reef has. still two other effects—it brings a large number of swimming larvee in contact with the shells and it carries more food to the oysters living there. Clean cultch, abundant larve, and ample food, three principal factors in 24 THE OYSTER AND THE OYSTER INDUSTRY. heavy production and rapid growth of oysters, are, therefore, found better Pulfilled at the ends of the reef than at the sides lying across the currents. This tendency to transverse growth once established is increased with every increase in the length of the reef, the jetty effect, retarding the flow of water in one place and accelerating it nm another, becoming more pronounced. It frequently happens that reefs similar in general character to those just described begin their development from or close to the shore, usually at projecting points. They grow, of course, principally at their outer ends and extend outward from the shore at right angles to the current, maintaining a nearly uniform width throughout their length. In the foregoing description of natural beds consideration has been given solely to the oyster itself, but the conditions are always com- plicated by the presence of other organisms between which and the oyster there are more or less complex biological relations. Some of the minute forms, especially the plants, constitute the oyster food, while many of the larger anes either prey ace, on the oyster or its young or compete with it in the struggle for food, oxygen, and space in which to grow. . DEPLETION. Until the last 40 years the majority of the oysters taken from Cape Cod to Mexico came from natural oyster beds which covered an area of such great extent that they were regarded as inexhaustible. That this belief is quite erroneous is shown by the fact that on the northern parts of the coast, where the temperature is about the minimum for the support of oysters, the natural beds have disappeared or have become sadly depleted. Those of Massachusetts are greatly ex- hausted, and few are found in Narragansett Bay. On the Connecticut coast only two beds of importance remain—one in the mouth of New Haven Harbor and one west of Stratford Lighthouse, near Bridgeport. There are very few in New York waters. Many of the beds of Chesapeake Bay are seriously or quite depleted, although many still remain. From that point southward the depletion has not been nearly so great, as the oyster fishery has not been pursued as vig- orously and the environment has been such that the oyster repro- duced much more abundantly than in the north, where a failure to obtain set is only too common. In some cases the depletion or destruction of natural beds is the result of natural causes, such as the cutting off of the inlet to a bay or sound and the reduction of the salinity of the water; the covering of the beds with silt, débris, and fresh water during a freshet; the shifting of sand or mud by storms; or the inroads of living enemies. The greatest enemy to the oyster, however, isman. Most of the depleted condition of the natural oyster beds is the result of careless overfishing by oystermen. The beds are stripped down so completely that not enough adult oysters are left to furnish sufficient spawn to insure a subsequent crop. Although millions of eggs and sperma- tozoa are produced; those products are thrown into the water, where many of the eggs fail of fertilization; many eggs and larvee die or are eaten by enemies; and many fall at setting time on soft bottoms and are smothered. The percentage that finally reaches the adult THE OYSTER AND THE OYSTER INDUSTRY. D5) stage is relatively small. For that reason too complete removal of the adult oysters from a bed destroys hope for an ensuing generation. During the past 40 years certain methods of oyster culture have been developed, especially in certain regions, whereby new beds have been built up and a constructive system of increasing the oyster supply has been initiated in addition to the negative one of restric- tions on fishing, such as close seasons and the hike. Biologists have become concerned in this work, and efforts have been made to pro- mote, by experimentation, methods for the improvement of oyster culture. CULTIVATION. From the table on page 5 it will be seen that about half the oysters produced in the United States are taken from private or lanted beds, the rest coming from natural or uncultivated areas. t will also be noted that in New England over 90 per cent of the oysters are produced on planted beds, that in the Middle Atlantic States the natural beds are considerably in excess, and that in the South Atlantic and Gulf States the proportion of natural beds is much higher yet. The table shows, however, that the value of the oysters from the planted beds is nearly twice that of those from the natural. This is due largely to the better quality and shape of the oysters produced by cultivation. Tt is intended maily to set forth here the methods of oyster culture which so far have proved to be commercially successful: on the Atlantic and Gulf coasts, together with such suggestions concerning | their improvement as biological science has to offer. Since there yet He occasionally arise false hopes that the so-called artificial propaga- tion, or the hatching and rearing of oysters in tanks or ponds, as is done in the case of fish, is on the verge of practical accomplishment, it may be well to dispose of this matter before proceeding to the treatment of the successful methods mentioned above. ARTIFICIAL PROPAGATION. This attempted method. of oyster culture can be treated most | simply by stating that its perfection and practical application are substantially no nearer solution than when the problem was opened up by Brooks (1880, pp. 10 to 18). He succeeded im artificially fertilizing the oyster eggs with spermatozoa of the male oyster and in rearing some free-swimming larve to the age of four or five days. Brooks’s methods are in themselves not difficult, and the experiment has been repeated time and again both by biologists and laymen. Owing, however, to the immense practical difficulties of restraining the microscopic larve in receptacles or tanks and at the same time Brodin for a pee of water and the introduction of the proper ood and removal of waste, no one has succeeded in rearing many of the larvee until they attach to cultch. It would seem, moreover, impossible to do this on a scale sufficiently large to be of practical application in the oyster industry. i The same statements are true regarding the adaptation of this method, in which attempts were made to substitute for the tanks ponds connected by narrow inlets or ditches with tidewater. While eran ll 26 THE OYSTER AND THE OYSTER INDUSTRY. elaborate designs have been constructed for the manipulation of such ponds and the catching of set on cultch placed in the ponds or the connecting ditches, none has proved to be of any practical value whatever. The principal difficulty seems to have been that, in the effort to confine the set to the pond, too scanty an inlet was provided for the entrance and exit of the tide, and the oysters suffered in consequence. In the cases where efforts were made to catch the set on cultch placed along the connecting canal, if the latter were broad enough to allow sufficient rush of water to keep the cultch clean, most of the set passed out to sea. Oysters, on the other hand, will reproduce, grow, and fatten in ponds or inlets to which the tide has access in sufficient volume to render the water properly saline, provide the requisite food, and remove the débris. The set from such oysters is at the mercy of the tide; some may be caught in the pond or inlet, and some will be carried outside. In France ponds or ‘‘claires” are profitably maintained for the growth and fattening of oysters. The seed oysters placed therein consist of set from outside oyster beds which has been caught on collectors placed in the water along the beach. While it can not be said that the problem of so-called artificial propagation may not be solved at some future time, for the present it must be emphasized that oyster culturists should base no false hopes on the practical application of this method. n view of the barren results of 40 years’ experiments in this line, it is best to devote attention to the amplification and perfection of methods which have proved to have a certain measure of success and which are applicable to the industry as carried out on such a vast scale in the United States. LEGAL CONSIDERATIONS. PROCURING GROUND. Tn order to carry on oyster culture either by catching set or plant- ing seed oysters, it must first be ascertained whether ground for that purpose can be leased or otherwise obtained from the State and, if so leased, whether public sentiment is such that the laws will be respected and enforced. In some States ample provision is made for the rental of oyster grounds and the lessee is protected. Oysters are not taken from his beds any more than corn is taken from a man’s cornfield. In other States conditions have been in the past such that protection of leased ground, if attempted at all, was an- absolute failure. Considerable improvement is noted, however, in this respect within recent years. - In selection of ground for locating oyster beds care must be exer- cised to avoid waters into which trade wastes are discharged in quantities sufficient to kill either the free-swimming larve or the oyster after it has set. It has been found that certain trade wastes from factories are injurious to oysters if present above certain con- centrations. Further, the Federal and State health laws must be borne in mind in order to avoid grounds condemned by health authorities because of pollution by sewage. Stringent laws forbid the use of such grounds for raising or fattening oysters. THE OYSTER AND THE OYSTER INDUSTRY. 27 MARKING BEDS. Some States employ competent surveyors, and oyster beds are | laid out with the aid of ranges, such as important natural objects or special signals set for the purpose. The planters then place stakes or buoys along these lines in such a way that each man knows exactly where his boundary line lies. Such practice is to be highly recom- mended as tending to avoid disputes and litigation. METHODS OF OYSTER CULTURE. Owing to the great size of the oyster beds, to the large number of oysters handled, and to the high price of labor and the relatively low price of the product, it is not practicable in the United States to use the intensive methods of oyster culture employed in European countries, such as France, or in Japan. In those countries, special devices are used for catching the oyster spat and the individual oysters are removed by hand from the collectors and placed on specially prepared bottoms or in ponds for growth and fattening. In the United States, oyster cultivation, in general, is limited to operations which can be carried on by mechanical means on a fairly large scale over areas of considerable size, thousands of bushels of oysters being involved. Oyster culture in the United States involves two main methods, the catching of spat, or ‘“set,’’ on artificially placed cultch and the planting of ‘‘seed’’ oysters. Where oyster culture is practiced one or the other or both of these processes is carried on, depending on the region and the desires of the planter. ¢e ) CATCHING OF SPAT, OR ‘‘SET.’ As stated previously, for some days after hatching the young or larval oyster is free-swimming. At the close of that period, it becomes attached to some fairly smooth, hard surface in the water, usually rocks, shells, etc., on the bottom. Once fixed, it is there for if and never wanders but proceeds to develop and grow. Failing to make such an attachment, it dies. Both while free-swimming and for a time after fixation the oyster larve are referred to by oystermen as “‘set.”’ Advantage is taken of this habit of the oyster larve, and artificial means are employed to increase the area of suitable surface upon which to “catch a set’”’ of young oysters. Various sorts of material are put down to provide a suitable surface upon which the set may become attached. The material used for such a purpose is known as cultch. The most commonly used cultch is oyster shells, although the light thin shells of other bivalves, especially the ‘‘jingle”’ shells, are sometimes employed. Oyster shells, being available in great quantities from the opened oysters, may be returned easily to the bottoms, thus providing the cheapest, most abundant, and most suitable form of cultch for the large beds cultivated by American oyster planters. : After a set is thus obtained on the shells it may be left there to mature into oysters of marketable size, or the shells with the attached set may be taken up and shifted to other beds. This is commonly eee 28 THE OYSTER AND THE OYSTER INDUSTRY. done in the fall after setting occurs, but sometimes set is allowed to grow for a year or two and then treated as ‘‘seed,’’ which is discussed - on page 33. This method of oyster culture is more extensively practiced in Long Island Sound, Narragansett Bay, on the southern side of Long Island, in New Jersey waters, and in Louisiana than elsewhere. The bottoms are cleaned up by dredging from them the old shells, débris, etc. This is done in May, after the close of the season. The shells are put down during the last half of June or the month of July. In Long Island Sound the old rule was to begin “shelling” the day after the Fourth of July. In Louisiana the shells are put down in June, since the oysters spawn earlier there because of the higher temperature of the water. For shelling purposes in northern waters, the shells are usually loaded upon large scows (PI. V, fig.1) and towed out to the grounds by steamers or gasoline boats. Then while the scow is towed slowly back and forth over the beds, the shells are shoveled overboard by men on the scow (PI. V, fig. 2). If the ground is new and somewhat soft, sufficient shells are put down to form a firm coating such that the upper layers remain clean and exposed above the mud. In any case, enough shells are put down to form a fairly level continuous layer over the bottom. In northern waters, examination is made about September 1 to 15 to see whether a set has been obtained. Since many factors—such as time of spawning, condition of the cultch, temperature of the water, storms, currents, etc.—enter in to affect the setting, this is the most critical point in the cultivation of oysters by this method and is the one at which the most failures occur. If no set of consequence has fixed on the shells, sometimes they are left until the following season and ‘‘harrowed”’ just before setting time by dragging over them an oyster dredge with the bag removed. This stirs them up and cleans them somewhat, so that often a fairly suitable surface is provided for the attachment of set. Often, however, they are dredged up and heaped upon the ground beside the oyster house. Here they dry, any oyster enemies upon them dying in the meantime, and may be used over again next season. In case aset (by which the oysterman Means a sufficient quantity to be of commercial import- ance) is found upon the shells, they are either left, in order that oysters may develop on that bed, or are shifted to other beds. The shifting is accomplished by dredging up the shells, set and all, with ordinary oyster dredges or, rarely, by lifting them with tongs. Sometimes the oysters are moved after attaining the age of one or two years, since growth and fattening proceed more rapidly on some beds than on others, due to differences in food content of the water, etc. In certain places oysters become green, and their sale is hin- dered by the unsightly appearance. When shifted to certain other beds, this color is thrown off in the course of a few months and the oysters are marketed. The planting of cultch to catch set is mainly performed on “bar- ren” ground, that is, bottoms practically free from oysters. Such ground is leased from the State or purchased outright by the planters. Some States make ample provisions for such procedure, and the lessee or owner has complete protection for his oysters. In other States public sentiment has not supported efforts to provide for leas- U. S. B. F.—Doc. 890. PLATE IV. OYSTER SPAT OR SET TWO OR THREE WEEKS OLD ON INSIDE OF OVSTERES FIBEE: Natural size. (After Moore.) PLATE V. U. S. B. F.—Doc. 890. FIG. 1.—LOADING SHELLS ON BOAT FOR PLANTING. Pea ee a FIG, 2.—PLANTING OYSTER SHELLS IN LONG ISLAND SOUND IN ORDER TO CATCH “SIEM, The large scow loads of shells are towed by a gasoline boat or steamer. THE OYSTER AND THE OYSTER INDUSTRY. . 29 ing of ground for this purpose and dependence is placed largely on natural beds for the supply of oysters. In some few cases a State plants a limited amount of cultch upon certain partially depleted natural beds for public benefit. In gen- eral, however, the natural beds are staked off and reserved for general public use by the “natural growther” subject to certain restrictions, mentioned elsewhere. The principal considerations involved in this method of oyster cul- ture are character of the cultch, character and preparation of the bottom, time for planting cultch, the proper location of cultch beds with respect to tides and currents and the spawning oysters, and the location of beds of spawning oysters. Cultch.—While formerly limited use was made in the United States of various forms of cultch—such as tin cans, bits of pottery, brush, pebbles, ‘‘jingle”’ shells, and oyster shells—only the last three mate- rials have proved to be of practical value, and at the present time the cultch used consists almost entirely of oyster shells. A few “jingle” shells are known to be employed at one point in Long Island Sound. Oyster shells are large and afford surface for the attachment of quan- tities of spat (PL. IV). As this grows, overcrowding is apt to result, since the shells are too heavy to be broken apart by the pressure of the developing set. This is overcome by breaking apart and culling the clusters thus formed. The advantages of oyster shells as cultch consist largely in their general adaptability, presenting a smooth surface for the attachment of the set, and their abundance and convenience, since an oyster- shucking house has only to turn about and convert its shell pile into spat collectors by the use of its own boats. At the same time the gradual disintegration of the shells provides lime for the succeeding generations. “Jingle” shells, or silver shells, belonging to the species of Anomia, - and scallop shells are thinner and more fragile than oyster shells. Consequently, they make a superior form of cultch, smce the pressure of the growing young oysters breaks them apart and the formation of clusters is prevented. Unfortunately, the supply of such shells is so limited that very few are now used. Character and preparation of bottom.—lf the bottom at the pomt where it is desired to plant cultch is sufficiently hard to support It a layer of shells is spread upon it broadcast, as previously described. In case the bottom is soft, it may be prepared by putting down sand or gravel in sufficient quantities to support the shells. Often, how- ever, the bottom is stiffened merely by the use of shells. Sufficient quantities are put down and allowed to sink, until a substratum is formed firm enough to support a layer of cultch several inches or a foot thick above the ground. 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