tt*i!!IS^. CONVENTION ADDK^ES Gr/EN AT THE IjIEETING OF iVIarine Biological Laboratofy X. I B R .A. i» '^ir OCT^ 6 1953 WOODS HOLE MASS THE NATION/vL SHELLFISHERIES JSQOCUiTIOm. ' '^^- NE'j? YORK CITY JUNE 5-7, 1946 Richard Messer, President Edwin Ifarfield, Jr., Vice-President Dr. Victor L. Loosanofl", Secretary J* Richards Nelson, Treasurer TABLE OF CONTENTS TITLE P-'^G-E On the need for developine nevj streins of oysters through selective breeding of domestic stock, cross breedin.^ with other species and the introduction of species frora other eress - Dr. Thurlow C Nelson 1 Observations of Japanese oyster culture in the State of Washington - Dr. ii» E. Hopkins 8 Growth of oysters of different aces in Milford Harbor - Dr. Victor L. Loosanoff • 12 Some observations on the feeding of oysters with especial reference to the tide - A. F. Chestnut 22 A brief critical survey of the evidence for the horizontal movements of oyster larvae - Dr. Melbourne R. Carriker 28 Louisiana's oyster management program - James N. McConnell 33 Effect of Susquehanna River stream flow on Chesapeake Bey salinities and history of past oyster mortalities on upper Bay bars - G. Francis Beaven 38 Commercial aspects of the upper Chesapeake Bay oyster bars in lif-ht of the recent oyster mortalities - Janes B. Enr-le 42 How fcan we profit by the U. S. Food and Drug Administration hearings - Dr. Curtis L» Newcombe 47 Bacteriolojxiftal observations on oyster frrounds of the Hampton Roads area - Dr. P* ^ne Hansen 50 ON UKR NF.ED FOR DWELCtPJUd NEW STRAINS OF OYSTERS THROUf^H S^JJiT.T'VrE BREED INO OF DOMESTIC STOCK, CROSS BRE-RDTNOr WITH OTHER SPECIES AKD THE lOTRODUCTION OF SPECIES FROM OTHER AREAS Thurlow C. Nelson, Rutgers University and New Jersey Oyster Research Laboratory It is a basic biological law that each animal and plant reproduces "after its kind". Within certain definite limits of variation each species produces generation after generation of offspring which vje readily recognize because of their close approximation to parental types. During the twentieth century, together with the rediscovery of Mendel's principles of heredity and a vast amount of brilliant research, we have made greater progress in the im- provement of agricultural crops and in farm animals in four decades than was made in all historic time prior to 1900. The dominant position of America in the world's food picture of today is no accident. V/e stand where we do primarily for tvro reasons: hard v;ork end the application of the results of scientific research. Oysters are a farm crop raised under water, and like the land farmer the oyster farmer is thoroughly familiar with hard work. He knows long hours, hard back breaking labor, most of it performed in freezing and subfreezing weather. But in the application of science to his industry the oyster grower is a good half cen- tury behind his brother on the land. Aside from the ic^roved sanitary condi- tions in our shucking houses which have grown out of our knov;ledge of bac- teriology, oyster growers today are making use of but one scientific finding; the prediction of time and probably intensity of setting based upon; (1) the microscopic examination of water for oyster larvae; and (S) the condition of spawning of adult oysters. The pioneer work in this field was done by my father, the late Dr. Julius Nelson, between 1900 and 1915 in New Jersey and at Prince Edv;ard Island, Canada. The work was developed practically by us at the New Jersey Oyster Research Laboratory, and by Churchill and Outsell, jnd by Prytherch of the Fish and Wildlife Service, between 1917 and 1931. Application of these methods, together with much more accurate observations of the onset of spawning carried on chiefly at Milford, Connecticut, by scientists of the Fish and Wildlife Service, have been the most important factors in the recovery of the Long Island and New England oyster industry since the mid nineteen twenties. Restoration of the inshore spawning beds of Connecticut under the able direction of Dr. Prytherch, followed by the accurate setting predictions of Dr. Loosanoff and J. B. Engle, and by Dr. Loosanoff alone, have yielded financial returns to the oyster growers many times greater than the cost of all the research which made these results possible. - 2 - ■ But why stop her«? Tli«- land farmer many years ago abendoned the scrub chickens, the scrawny cattle and other nondescript stock of their grand- fathers, and developed flocks and herds of vastly improved animals. Through the results of research in genetics the farmer learned that a high milk pro- ducing heifer can transmit that quality only through her son to her grand- daughters, she cannot pass this directly on to her daughters. Likev;ise we honor the hen v;hose son v;ill never set, yet we know that the 300-egg-a-year bird car, pass on this character only througla this never-setting son to ap- pear then in her granddaughters, not in her daughters. V/hat do vje know about inheritance in oysters? The answer is - virtually nothing. ?;e do knov; that throughout the world over fifty different species are recognized and that these species breed true. To date I know of no clearly pi-oven case of hybrids among these shellfish. Within each species exist fairly clear cut regional varieties. Thus, for example, any experi- enced oyster grov;er vjill quickly pick a southern oyster from among a group of Long Island oynters. Conversely when eastern or Long Island oysters were being transplanted in large numbers to Delaware Bay during the early nineteen thirties, even a relatively inexperienced observer could separate the new- comers from the native stock. It is important to note, however, that although these eastern oysters spawned extensively they have left no observable per- manent effect on the oysters of Delav/are Bay. We cannot pick out a spat here and there and state definitely that its parents were from Long Island. Vie know in some instances that these eastern oysters spawned at least two weeks prior to the first spavming of natives. Early sets v;ere obtained but in their later growth these oysters have taken on at least the shell character- istics of the Delaware Bay oyster, not those of their Long Island parents. Oyster growers in New Jersey, at least within my memory, have alviays stressed the value of introducing oysters from other areas. They insist that crossing must occur since the intensity of setting and the vigor of the stock seem to rise after such importations. Scientific proof does not exist either of crossing nor of increased vigor following the importation of oysters from outside. But, as a scientist who has been in life long con- tact with oyster growers, I would be among the first to pay tribute to their keen powers of observation^ It costs money to bring in oysters from a dis- tant point, hence I doubt if such importations would be continued unless there were pretty clear evidence of its beneficial results. The improvements v^hich follow crossing in other lines of plants and animals are well known. Outstanding are the results with hybrid corn and the superior strength and endurance of the mule. This the biologist attri- butes to so-called hybrid vigor or heterosis which has now been demonstrated among so many animals and plants that it may be considered a biological law. America's position in the vrorld today is chiefly because of this very hybrid vigor: we humans are mostly hybrids and to this largely we owe the energy which so astonishes the rest of the world. Rate of growth and ultimate size are hereditary factors which in other animals and plants have been shown to be handed on according to definite patterns of inheritance. Through selection of superior animals and by in- dividual matings Mr. Charles 0. Hayford of the New Jersey trout hatchery at Hac.kettstown was able by the third generation to double the rate of - 3 - growth in ■tr'^^xt. Ry Mc'v^rn^'^v of t.hoiv f-.R^ond yf^gy he iipd same) fish up to fourteen, inches in length as against a maximum of seven for the unseleoted general stocks. Dr. Carriker, later to appear on this program, together with co-workers in Wisconsin, developed a race of the common fresh-;vater snail, Lymnea , which was approximately one-fourth larger at maturity than the wild type from which the original parents came. G. If. Martin working in our own laboratories showed twenty years ago that of oyster spat which attach at the same time on glass plates whery they are able to grow without obstruction from other spat, some may grow as much as three times more rapidly than others nearby. Confirming this ere these two oysters of the same age from Nyatt Point, Naragansett Bay, Riiode Island, which I am now showing you. These oysters were on the same bed, subject to the same conditions. The smaller one repre- sents a good average for the oysters as a whole v:hich were remarkably uniform as to size and shape. The most probable explanation for the much greater size of the larger oyster is that it was due to internal factors of inheri- tance. Looking closely at these oysters we see that in two of the years growth was greater than in the others. In these better years, however, the larger oyster made relatively a larger growth than did its neighbors. In other v^rords it made better use of the more favorable growing conditions than did the other oysters nearby. V/hat do we know about the factors of size and rate of growth in the oyster? In the European oyster, Ostrea edulis , Professor J. H. Orton of Liverpool, showed in 1925 that in the Fal Estuary in England 42^ of the oysters on the beds were of a type recognized as "dumpy". In these the growth rings are much closer together, the shell is rough, frequently mis- shapen and the thiclcness is appreciably greater due to greater thickness of the shells, not to a larger meat. He states that in general such oysters are from two to three years older than normal oysters of the same size. Because of the prohibition against removing oysters of less than two and one half inches from the beds Orton found a higher percentage of dumpy oysters among the small oysters under two and one half inches than among those above this size. I have recently suggested that one contributing cause to the decline in oyster production in the Chesapeake Bay has been the "three inch law" in accord with which all small oysters must be returned. Iftiere dwarfed oysters are present it follov;s that their number v/ill steadily increase since their slower growth will keep them below three inches longer than required for normal oysters. In many cases the d'omipy oysters may never exceed three inches in length. Ovang to the slov/er growth of the "dumps*' a larger pro- portion of these was being thrown back on the beds than of normal oysters, resulting in almost one half of the oysters being "dumps" at the time of his investigation. Remembering that the European oyster carries its larvae upon the gills, let me quote from a paper by Professor Orton in 1926. "Although the dumps are now seen to be not so good as the others for spawning purposes, yet they are only slightly inferior. There can remain no doubt, therefore, that dumps are valuable for breeding inasmuch as a high proportion yield larvae like normal individuals. We have no means at present of ascertaining the survival value of the larvae of the tv;o types - 4 - of oysters, and on the othpr hand no substantial reason to doubt that the larvae of l.oth types are healthy and will produce sDst equslly well under favorable ccndlt ions." May I emphasize that Dr, Orton judrjed the spavming ability of the dumps solely upon the nu nto crs of J.arvae on gills vjhich were only slightly less than in normal oysters. His conclusion that vie have "no substantial reason to doubt" that the larvae of the dumps are as healthy and will produce spat equally with normal oysters is contrary to everything we know in other animals. In the European oyster we have the great advantage in that prior to being shed into the water the larvae can all be traced back to at least one parent, the mother, on whose gills they lie. The fathers are unlaiown since oysters are not self impregnating, but the eggs on the gills are fertilized by sperm carried in with the incurrent stream of watero In Orton' s observa- tions there was an equal chance therefore of sperm from normal and of diimpy males fertilizing the eggs of the dumpy mothers. Assuming that Orton is correct in his assumption that dumps produce as vigorous larvae as normal oysters, it it, probable that at least one quarter of the larvae on these beds came from parents both of which vjere dumpy while one half of them had either a dumpy father or a dumpy mother. It is most unfortunate that Orton did not examine these oyster lar^/ae microscopically. In Barnegat Day, where most of my own larval oyster studies were carried on, a thriving industry practically disappeared in fifteen years. During this period the proportion of slov; growing dwarfed oysters, which I class with the English dumps, steadily and rapidly increased. Coincidentally I began to find many swimming larvae in my collections in which the shell showed numerous wrinkles and was greyish rather than transparent. Unfortu- nately I did not photograph any of these larvae since at that time I did not suspect their possible significance. I have no proof that such larvae came from diimpy parents; I can only report their presence correlated with a rapid increase in the percentage of dumpy parents on the beds. The larval broods which contained large numbers of these wrinkled shelled larvae decreased very rapidly in numbers with but a small proportion of them reaching setting size. In other animals as vrell as in plants tallness and dwarfness are in- herited as definite characters as are also vigor and rapidity of grovrth. We are justified therefore, in assuming similar inheritance of these factors in oysters until definite scientific proof is obtained. The rate of growth and the size attained by the Japanese oyster in the Pacific northwest is loiovm to all of you. The shells on exhibit shov; oysters eighteen months after their importation as spat to Olympia, "Jashington. The meats of these sarrie oysters, some of which I shucked immediately upon arrival from the west coast, ran eight to the pint, sixteen to the quart, or at the rate of sixty-four to the gallon. Dr. Pryth&rch has called my attention to a note by Dr. Bashford Dean, in 1903 that hs found in Japan, oysters weighing with shell four to five pounds not infrequently. Although inferior to the best of our own virginica when eaten ravj, I em informed that in at least tv;o respects they are superior. If canned when in their prime in May they - 5 - are reported to be free from the oily rancid taste which often develops in our eastern canned oyster. When rolled in dry bread crumbs, sprayed with olive oil and baked for five minutes in an oven of 450*F. they emerge brovm as chestnuts and cooked to a delicious turn in their own steam. For such baking, I am informed, the home economics department of the University of British Columbia prefers the large Japanese oyster. If it were possible to obtain in our eastern oyster the rapid growth of the Japanese oyster it would revolutionize our industry. The cattleman takes three years to grow a fifteen hundred pound steer for market. The oysterman requires six years, or just twice as long, to grow a one ounce oyster. It just doesn't make sense, and the time has come when oyster growers and scientists should combine to remedy the situation. V/e know from our studies in Delaware Bay that the survivors from the intense sets on the Cape May shore rapidly outgrow oysters from elsewhere in Maurice River Cove. Samples on exhibit cleerly support this. During studies of water pumping it was found that two-year-old Cape Shore oysters could outpump eight and ten year old Bamegat Bay oysters by two or three to one, thus giving evidence of their much greater vigor. Frequently the survivors each represent the one oyster out of 630 spat per square inch which reached the end of the first year. The others were crowded out and smothered by their fellows. As yet no one has bred exclu- sively from such fast growers and proved that they will pass on this capacity for rapid growth to their offspring. May I suggest, however, that the im- provement of New Jersey stock over the years following the introduction of southern oysters may be due to this very vigor. The imported stock which I have seen is mostly bunched with many long "cat tongue" oysters among them. As such they are of little value as market oysters, but being the survivors of heavy sets they may have passed along to their offspring the vigor which they themselves v^rere prevented by crowding from exhibiting. My only first hand experience with the Japanese oyster vras in the early nineteen thirties when a bushel of them were tried out in Barnegat Bay in the hope of reviving the dying industry there. During the first tv/o weeks in the bay they grew nearly three quarters of an inch. Then they stopped growing and gradually died over the next two years without showing any further signs of growth. It must be noted that salinities here ranged from approximately twelve to twenty as against salinities of over thirty or oceanic saltness on the beds of Japan where Dr. Dean studied them. In addi- tion to these low salinities these gigas oysters in Barnegat Bay had to contend with the very factors of stagnation and low oxygen v;hich were hasten- ing the destruction of the native virginicas. It was, therefore, by no means a fair test of their ability to survive in iltlantic waters. Another oyster in which I am deeply interested is the Australian oyster, Gryphaea cucullata . My good friend, Mr. T. C. Roughley, undertook to fly some to us in New Jersey last October but his plane was delayed in v;arm weather at Hawaii, so the oysters having been out of water for nine days without refrigeration were eaten and enjoyed by newspaper men and others in California. Mr. Roughley tells me that all /jnericans with whom he has talked in Australia claim the superiority of cucullata over our own virgin- ica in flavor. - 6 - Whert the industry nftfids at this time is a thorough end unbiased study of" fchfi moi-o prrMnir.ing tOT'='.i<7n rrystprs together with efforts to hybridize them with each other and with our own eastern oyster. A hybrid with xts increasRd viRor should grow to full market size in two years thus enabling the oyeter planter to turn his money over three times where novi he turns it over once. All such work must be conducted vjith the greatest care in enclosed basins in a laboratory whence no enemies nor infurior hybrid oyster, if produced, mi^,ht escape to en oyster bearing region. Vill waste water from tanks holding any fcrr;ign oysters must be run into a sand pit v..benoQ it will enter the natural waters only through the sand, or the waste vrater musu be ^^reated to kill any life therein. Our industry is far too valuable to take any chances or to trust to luck. The virtual wiping out of the superior European oyster, Ostrea edul_is, in ^France by the accidental introdviotion of the inferior Portuguese oyster into the Gironde Kiver about 1870 furnishes a vivid lesson to all of us. The gigas oyster has already proved its value in the Pacific Northvrest. Dr. Prytherch points out thnt Fisheries Statistics of the Fish and Wildlife Service for 1941 shows that from V/ashington, Oregon and California over twelve million pounds of these oysters were harvested in that year wi^.h a value of seventy-five cents per pound as comparad with sixty-three cents for the small native lurida and forty-one cents for virginica raised out there. Such figures do not support the claim of inferi'.or:; by. There are undoubtedly areas of hig,h salinity along our Atlantic seaboard where the gigas oyster would do well but ;vhere the lack of fresh- -water reteids the growth and fattening of eastern oysters. \"e ere taking a short sighted view of the potential development of our coastal waters if we do not at least consider the possibility of introducing into such areas an oyster which will thrive there. A Sug gested Pro gra m 1. In all areas dependent upon seed oysters produced under the care of the state it is urged that spav;ning sanctuaries be established in proxim- ity to the areas to be she]-led. To these sanctuaries should go the largest ana most vigorous oysters available. I am recommending in New Jersey that the funds available for spawners be spent to buy back from the tongcrs and dredgers the largest and the best of the oysters as taken. A simple gage such as that illustrated at the side table should suffice for obtaining these. As these sanctuaries are developed their value will be demonstrated and year by year the population of superior breeders will be built up. 2. Where all seed oysters are obtained from private seed beds it is urged that when these are at some distance from the planted grounds small sanctuaries be established experimentally in close proximity to the shells. To these sanctuaries should go the largest end most thrifty of the oysters produced. 3. I concur fully v;ith the recommendations which Dr. Prytherch has already made with respect to the Pacific or gigas oyster. - 7 - (e) That we c-ea&e calling them Jap oysters end thus get away from our present natural aversion to everything "made in Japan". The term Pacific oyster is a good ono since the little native of our west coa^t is called the Olympia oyster. This would give us in the Pacific oyster the natural counterpart of the Atlantic oyster for the species virginioa. (b) That seed and adult Pacific oysters be promptly shipped to our Atlantic and Gulf shellfish laboratories for scientific studies of their suitability and adaptability for commercial use on those coasts. (c) That test plantings be made on a small commercial scale under natural conditions where control or elimination of the imported species can be exercised if necessary. (d) That a conference be arranged v;ith the leaders in the oyster industry and state conservation officials, for a critical discussion of this issue with a view to permitting importation of Pacific oysters under control. To the above conference I would ask that there be invited Dr. Radcliffe, Mr. Vifayne Heydecker of the Atlantic Coast Fisheries Commission and those scientists who are in a position to throw light upon the discussion. I should like to include also Dr. C. Roy Elsey of British Columbia who combines technical scientific knowledge v/ith extensive experience in handling the Pacific oyster. I ask also that consideration be given to other foreign species especially the European oyster, Ostree edu lis, and the Australian oyster, C-rypheea cucullsta . V/ith its spavming temperature S^C. belov; that of the Atlantic oyster, edulis might well be the answer to our need of an oyster for the northern coastline. To those who rightly fear uncontrolled importation of foreign shellfish I commend our New Jersey law which for thirteen years has given us complete protection but which gives the xvidsst possible latitude for importation of foreign shellfish for scientific study under license of the Division of Shellf isheries of the State Department of Conservation. In conclusion, oysters are a delicious, nutritious, health-giving food but their cost interferes with their becoming a conmon article of diet. Every year that can be cut off from the time required to raise them will materially reduce that cost. Science has given the oyster grower a depend- able source of seed. The next two most important problems - fa^'. fcen.ng and more rapid growth await scientific study and solution. I have fait;- that -both will yield to attack by research and that newer, better and fatter oysters await us in the not-too-far-distant future. 'Whatever the outgrowth of our deliberations here today the crying need of the v;orld today for food leaves no room for less then the maximum development of our coastal waters for the production of seafood. To that task v;e dedicate ourselves. OBSERVATIOKS OF JAPANESE OYSTER CULTURE IN THE STATE OF WASHINGTON A. E. Hopkins, Aquatic Biologist U. S. Fish and V.'ildlife Service For about seven years I was rather closely associated with the oyster industry in Puget Sound, Grays Harbor, and Willapa Bay, and had an oppor- tunity to observe the repidly developing Japanese oyster industry on the Pacific Coast. It has been about ten years since I left that region, but I was able to see this new species in its relatively early stage of impor- tance as a conmercial fishery venture. A group of Japanese first introduced Japanese seed oysters into Samish Bay, a portion of Puget Sound, in about 1905. At that time there was no control over importation, or inspection of the seeds, which had been caught on either shells or brush. This company operated for a number of years on bottoms which had formerly been used for the production of Olympie oysters and for the bedding and fattening of eastern seeds brought in from Long Island Sound and adjacent areas. In the early 1920 's the Japanese company was taken over by an American company, and for several years small annual importations of seeds were made. I do not believe that, on the market, any distinction was made betvfeen the oysters grown from Japanese seeds and eastern oysters fresh ship^oed from the East Coast, or those grown from the seeds brought from the East. However, it was well demonstrated that the Japanese species thrived, and certain business men in Japan recognized the possibility of raising seeds for export to the United States. In about 1928 various j'^merican companies in association with Japanese seed oyster producers started a rather tremendous seed planting program, particularly in Puget Sound, Sfillapa Bay, and Grays Harbor. It may be imagined that various promoters sold, at fabulous prices, large areas of previously non-productive bottom to the public. Such ventiires, although they may have been designed to make profits from investors rather than from oysters, resulted in importations of seeds from Japan amounting to about 75,000 boxes of seeds per year during the early 1930' s. During the time of which I speak, the seed oysters were shipped in boxes containing about two cubic feet of shells on v;hich the young oysters were growing. The spat ranged from about one-eighth to one-half inch in diameter, and I believe the Japanese producers were conservative when they guaranteed a minimum of 10,000 seeds per box. The price at that time ranged from $2.50 to $3.00 per box. - 9 - The Japanese method of stringing shells on wires and suspending them from racks to catch the seeds is probably vjell known to you. It is ciairied ..toy the seed producers that this method prevents the inclusion of predators, although one may be sure that there is no certain method of eliminating completely the, possibility of importing a few such organisms. It was very surprising to me to see how well those small spat lived through two or three weeks of travel, on the deck of freight ships across the Pacific, and also how rapidly the young oysters grew after being planted on virgin ground. They were planted on all types of bottom, from extremely soft mud to hard sand, but in almost all cases, they thrived to such an ex- tent as to make increased importations at this low price economically feasible. It must be borne in mind that our Pacific Coast previously had not pro- duced oysters in any significant quantity with respect to the total oyster production of the Atlantic and Gulf Coasts. Our East Coast oyster had been tried for many years in various places and had not propagated on a commercial scale, except in one or two very small places, such as the mouth of the Naselle River, which empties into Willapa Bay. For that reason the fishery industry on the Pacific Coast had little to lose by importing a foreign species. In fact, it had much to gain as shown by the fact that in 1942 the pack of steam-canned oysters on the Pacific Coast amounted to approximately one-fourth the total steam-canned pack of the United States. itt first, with limited planting of seeds, the Japenese oysters grevj at a tremendous rate so that within one year after the seeds were planted the oysters would produce meats at the rate of about one gallon to the bushel. During the second winter those same oysters would measure from six to fifteen inches in length* having a very deeply cupped shell holding a large-sized meat. In almost all cases the Japanese oyster is rather thin-shelled and deeply cupped. However, on hard bottom, it was often noted that the shells were muGh thicker and harder. It was consistently noted by oyster growers that with increased quan- tities of seeds planted, growth and fattening became much slov/er. I miglit cite the case of a company operating in Padilla Bay, a portion of Puget Sound, which planted about 400 boxes of seeds on virgin bottoms in 1S30. Within two years these seeds had grown to a very large size and the meats were rich and fat. Then the company started an intensive promotion by selling ground to the public to be planted by the company and harvested as a unit. During the next three years approximately 100,000 boxes of seeds were planted and arrangements made with a canner to handle the product. So far as I knov;, this company was never able to put any canned oyster products on the market except oyster soup, because the oysters not only grew very slowly but they failed to fatten like the original samples. This would sug- gest that there is a limitation on the number of oysters which any piece of ground or body of water may nourish and support. _ ID _ The above, instance may not be significant, for it was claimed that a pulp mill in the vicinity may have been responsible for the poor oystars due to discharge of waste materials. However, the sariie has been found to be true in the VJillapa Bay area vjhere it has been definitely noted by every- one that oysters more recently planted, since the bay has become we.ll popu- lated, do not grow at the rate of the original sample plantings. This may not be considered a disadvantage in every respect, since the early experience of many of the growers was that if they could not harvest the oysters vAen they reached the right size, the oysters would be too large for market during the following season. Culture of the Japanese oyster on the Pacific Coast is in a transition stage, for it is attempting to become independent of the necessity for im- porting seeds from Japan. This species has apparently become adapted to environmental conditions in this country and, in at least a fev; places, has been propagating for several years on a commercial scale, particularly in certain portions of Puget Sound and VJillapa Bay. In 1935 and 1936 the shores of parts of Puget Sound, such as Quilcene Bay, were completely covered with young Japanese oysters. In that region the shore line consists of peb- bles which are exposed at low tide. Japanese oysters are very resistent to climatic conditions and are able to withstand exposure for long periods, both to drying in the sunshine and to freezing in the v;inter. That there has been a considerable amount of propagation is demonstrated by the fact that the war and the cessation of seed importation only slowed oyster pro- duction on the Pacific Coast. In one portion of Willapa Bay there is still a small population of Eastern oysters vjhich are the off -spring of stock originally imported from this coast. Frequently oyster grovrers have shovm me oysters which they considered to be hybrids of the Japanese end i\merican species. However, I was never able to be sure that such was the case, although I well recog- nize this possibility. In view of Dr. Galtsoff 's findings that the two species will cross-fertilize, I should not be surprised if a hybrid would eventually be produced. According to available biological information, in the laboratory experiments the Japanese oyster required a higher temperature than the Eastern oyster in order to spawn. I found that at some times Japanese female oysters will spawn at temperatures as low as about eight degrees centigrade, or about fifty degrees I. With this in mind, I think we should be well aware of the probability that, if the tv;o species ere reasonably close together, cross-fertilization may take place, aad that we do not know what the resulting oyster might be. Two varieties of the Japanese oyster, although presumably the same species, have been used on the Pacific Coast. The variety of which I have been speaking grows in Northern Japan and the seeds are caught in the Matsushima region where the water is relatively cold. The seeds are caught during the summer, and by the following spring when they are shipped to this country, they are not more than one-half inch in diametero The other variety is grown in the region near Hiroshima in Southern Japan, in warn water, so that the seeds caught during the summer are already an inch-and- a-half or more in diameter by the following spring v;hen they are shipped. - 11 - These Hiroshima oysters look very different fron the others. They are round and very deeply cupped so that many seeraed to be alnost spherica.l , like a walnut, for example. The uortality during shipment has been found to be much greater than that of the sraaller MatEUshima seeds. It has also been noted that growth is very much slower and that they never achieve tho large size of the other variety. I mention this Hiroshima oyster because I be- lieve if experiments are to be made on the importation of the Japanese oyster to the East Coast, special attention should be paid to this variety. During my experience on the Pacific Coast I noticed only one enemy which had been imported v/ith the seeds. This is the Japanese oyster drill, Tritonalie japonic^.. This drill is definitely very violent and dangerous, for, psruif^uipi'ly :.n Samish Bay, I found a tremendous mortality due defi- nitely to drilling by this snail. I have also found this seine snail in southern Fuget Sou'id on Ol^rmpia oyster grounds where soiae Japanese seeds had been planted. At the time I 3.eft the State of Washington, very fev/ were to be found in 'Jillepa Bay, and it may be that salinity in that bay is low enough to prevent them thriving. If experiments are to be carried out on the possibilities cOid potenti- alities of the Japanese oyster on our Atlantic and Gulf Coast, I should recommend that the work be done in such a manner that the overflow water in which they are kept be sterilized, or filtered, before entering any of our natural waters. If fertilized eggs, or developing larvae, should escape and attach end grow in such a manner as to endanger the great east- ern oyster industry, which we have had for many years, it would be about as impossible to control them as it is now to control the ship v;onn, star- fish, drill, and other similar pests. By importing those foreign species, the Pacific Coast had little to lose and everything to gain. By contrast, the East Coast may gain, but it could lose one of the greatest fishery in- dustries in the v/orld. Small plantings of Japanese seeds on the Gulf Coast have not resulted successfully enough to warrant optimism, although it may well be possible that in the colder waters of the North Atlantic Coast the results might be different. The Japanese oyster is biologically similar to the j\nerican oyster, and hybrids might presumably be obtained. One may be an optimist and assume that the hybrid oysters would combine the better qualities of the two species, but should this hybrid merely blend the unfavorable. quali- ties of the two species, a very severe damage to the oyster industry vrould be produced. Several years ago Dr. Galtsoff very definitely warned the industry to avoid importing this species, and my experiences lead me to state that I think his warning was very opportune and very correct. GROWTH OF OYSTERS OF DIFFEEENT AGES IN MIIFORD H.'JffiOR Victor L. Loosanoff , Director Fish and V/ildlife Service Biological Laboratory Milford, Connecticut The success of oyster farming, so widely practiced in the waters of New England and New York, depends chiefly upon growing small "seed" oysters to narkctsble size. This size is usually reached four or five years after the oyster larvae attach themselves to the cultr.h and metaiaorphose into juvenile oysters which the oystermen call "set"» So far little has been done to ascertain the increase in size and volume of oysters du^in^, each year of their oxictenoe from the ti.'ie of set- ting until tho age ci 5 yea.vs or more is reached. In vevjev/ing the litera- ture on this subject one is jjnprossed with the fact thot th.e majority ^_' the attempts to study the grov/th of oysters was of vew short durei.iorx, u-ua31y of a few months, and of a rether lir.iited scope. The longest period dt voted to such observations was approxiniately one year, iis a ru.le, the studr'e.s were confined to groups of T.he same age, end no distinction between the rate of growth of different age-classes v/as attempted. Thus, although the field offers a very large number of unansv;ered prob- lems the solution of which may be of considem.ble praot.i'^.al in'iierest, ve"/ limited progress has been made in studjang the grovrtL of cysiiers to obtain necessary knovjledge on grov.''th, certain phases of wr Lch wov vide a sound basis for estimation of the increase in size and volume from year to year, extensive studies have been carried on ^t Milford 'j&ho:c?.x-o.rj since 1940. Because of linibed time only certain aspt^ct ~ of -,he studie:; are discussed in this article. A more comprehensive description will be pub- lished later in a scientific journal. I am taking this opportunity to express my thanks to Mr. James B. Engle, who until his transfer to another assignment assisted in the ear.-ly stages of this investigation, and to Mr. Charles Nomejko, who for the last few years has been extremely helpful in conducting a number of grov/th experiments and in tabulating the data obtained during the entire course of this work. The experiments were conducted in Milford Harbor, Connecticut^ Five groups of oysters of different ages were collected from the beds of Long Island Sound and brought in for initial examination and measurement in early April 1940 (Table 1). Each group consisted of at least 125 individuals- The youngest group was composed of sinall oysters which set during the s'^mmer of 1939, therefore having grown only one season before having been used in the experiments. The oysters of the 1938, 1937 and 1936 year-clasces had lived through two, three and four growing periods respect ivelyc The g-'oup which was designated as the 1935* year-class consisted of oysters which had 12 'T'htrefore, Id px-o- 13 •-3 cr O fD cr M ^ ca CD vo \oJ ;v) M ^ VjJ --J M VjJ O v^ 4:- VjJ NJ M >0 ^ CX) Vn M OJ M H 00 -J CN O O 4^ -J VjJ VO Ni M 03 4^ (VJ O 03 ^ O ^Ji M M M I-" VjO M I— ' O vD O VO VjO M ^J 00 -o ~o -a o M -J o ro o ^ -P- VjJ U3 vo ^ o ~o '-ri o •-< p^ en W CO 1 > Cr-i fD CO nj t-' M 5-- O > OP Co a > OP > o a OP t-' > '-a c -p- a O! vO > CO t-' 14 lived at least tiirou^JS grcwing periods. Their age varied froa 5 to 10 years. The majority of these individuals was 6 years or older. Such a heterogeneous age-group was fomed to study the growth of a nixed population of old oysters, which are usually used for stocking spawning beds. In these studies the age of the oysters is based upon the number of growing periods completed. In Connecticut waters the period extends from the latter part of April to early November. Since in Milford Harbor and Long Island Sound a nev; generation of oysters usually appears in the middle of summer, its first growing period, confined betv/een the date of setting and the beginning of hibernation, is shorter than subsequent ones, v;hen growth continues from spring until autumn. Nevertheless, the first growing season, even if it is of short duration, will be regarded here as a complete one. Therefore, the oysters which have completed their first growing season will be considered here as one year old; those that have completed two grow- ing seasons, two years old, etc. This method of age classification may be different from that employed by some oyster growers who consider the oysters which have completed their first growing period as "set^', those which have completed their first and second growing periods as only one year old, etc. In such instances the age estimates of the oystermen will be one year behind ours. This discrepancy can be siiripJy adjusted for the convenience of the oystermen by subtracting one year from our age figures. In preparing the oysters for the experiments their shells were cleaned of all foreign growth and then the greatest length, width and depth of each individual viere measured with the aid of calipers. Measurements were ex- pressed in millimeters. Later, the volume was ascertained by using the dis- placement chamber method. After the oysters had been measured they were placed in large wire baskets, which were suspended from a float anchored in the harbor. Each year-class v;as kept in a separate basket. Annual determinations of the increase in size were made each autumn when the growing period was over end the oysters were entering the hibernation stage. The initial measurements made at the beginning of the experiment, in April 1940, showed that the most significant difference in sizes existed between the youngest year-class (1939) and the class composed of animals one year older (Table 1) . The difference diminished when the older groups were compared. In the two youngest groups the difference was especially pronounced in the case of depth, or thickness. The mean depth of the 1939 class was only approximately 3 millimeters, as compared with 20 millimeters shown by the group only one year older. Thus, the mean depth of the older (1938) age-class vras almost seven times greater, vjhile the mean length and width of the same year-class were only about three times as great as those of the younger group. Obviously, during the first growing period the increase in length and width progressed at a much more rapid rate than the increase in 15 •<3apth. During the second period, however, the increase in depth proceeded at a corrparBtiv^Iy fc'.reeteo: rate than that of the length or width (Tables 1 and 2). TiSLE 2 PERCENT INCRE^^^E IN MEJM LENGTH, 17IDTH ^^KD DEPTH OF OYSTERS OF FIVE DIFFERENT YELi.R-GI^vSSE3 DURKG GRO'TING PERIODS OF 1940, 1941 and 1942 MILFORD IL.RB0R INCREi'^E S^CPE/i^E .INCRE4IS.E YEAR- AGE iiPRIL 1940 DURING 1940 DUREMG 1941 DURIIJG 1942 CL^-^S Jige ..L. W. D. i'.ge L. '.v.. D. /*gs L. H. D. 1939 1 year 2 205 221 557 3 45 38 30 4 10 6 15 1938 2 years 3 37 33 33 4 16 13 14 5 9 6 9 1937 3 years 4 18 14 11 5 12 9 13 6 10 6 9 1936 4 years 5 9 8 6 6 7 3 9 7 8 8 5 1935+ 5*years 6* 7 8 3 7+ 2 1 5 &fr 5 4 5 During the first season of observation the greatest percentage increase in size was shown by the youngest (1939) year-class which was then conpleting the second grovjing period of its life. This increase was 205, 221 and 567 percent for the length, width and depth respectively (Taole 2) . It was sev- eral times greater than the percentage of increase recorded for the 1938 class. In the latter case the increase in length, vjidth and depth vras only 37, 33 and 33 percent respectively. In comparing these two groups it is interesting to note once more that the increase in depth of the younger year- class proceeded raore rapidly than that of the length or width. The three older year-classes, including the 1935* group, also showed an increase in all three dimensions. However, the percen'tage of increase became progressively srualler as the age of the oysters increased. At the end of the second vear of observation, 194-1, the most outstand- ing fact noticed was a pronounced decrease in the rate o± growth of the 1939 year-class which had just finished tho third growing seasono (Jhlle during the preceding season the increase in length of thi-i gr:oup was 205 percent, it was now only 45 percent (Table 2) . A similar decrease was also noted in the case of the width, while in the case of the depth it was even 16 more sharply defined. C»>viously, during the second year the rate of growth was much more rapid than in the third growing season. The oysters of the classes older than the 1939 group also showed a continued growth during the second season of observation. However, in all cases their relative rate of growth was slower than that of the younger animals. As observed during the preceding year, the percent increase in size decreased with the advancing age of the oysters (Table 2). During the third and last period of observation, which included the spring, Eunner and autumn of 1942, euLl the year-cle.sses shovjed a further increase in size (Tables 1 and 2). However, in the case of the tvrc youngest groups the relative rate of growth was much slovjer than in the preceding years. ^t the end of the experiment the age of the oysters constituting the oldest age-class ranged from 8 to 13 years. Examination of the largest in- dividuals of this group shov/ed that they, too, had formed a new shell growth during the last summer of observation. Evident.ly, even those old oysters, which were completing the 13th year of life, still continued to grov;. In reviewing the experimental data attention may be called to a simi- larity of the mean dimensions reached by the different groups of oysters upon attaining the same age, For example, during this study four different groups were at some time four years of age (Table l). The mean length of all these groups at the age of four vjes very close to 90 mm- ; the mean vjidth varied between 64 and 68 mm, , whereas the mean depth was from 30 to 33 mm. In the case of the groups reaching the age of 2, 3, 5 or 6 years similar conclusions could be formed. It was also noted that the oysters of the 1936 year-class, upon reaching the age of seven closely resembled in their dimen- sions the measurements of the 19'55* class made at the beginning of the ex- periments, when the average age of the latter group was also approximately 7 years. Perhaps the most significant part of our studies v;as that devoted to observations on the increase in the volume of the oysters from year to year. Both Milford Harbor and Long Island Sound oysters were used. The Sound oysters were supplied through the courtesy of Mr, Charles ITheeler, Manager of the Connecticut Oyster Farnis, from the beds where oysters of known ages were kept, in comparing the mean volumes of Milford lyszeTs with those of others of the same age a very close similarity was noted. By volume determinations it was ascertained that the youngest year-class showed a relatively greater increase in volume than any other group (Table 3) . The average volume of the animals representative of that class increased from. 0.4 cc. to 19.5 cc. during the secvjnd growing period of their existence. This represented an increase of 4775 percent, indicating that during the second year of their lives the oysters may increase in voliime almost 48 times. Thus, if they were grown under such hypothetical conditions where no mortality among them would occur, a bushel of culled single oysters planted at tho end 17 of their first growing I>«riod would yield more than 47 bushels one yeer later. By the end of the fourth growing, period their volume according to our estinetes would show an increase of 16,500 percent. As shown In Table 3 a coraparatively large relative increase in volume was also shown during the third year of life. This increase averaged ap- proximately 130 percent over the initial one recorded at the age of 2 years. «n increase in volume was also noted in the case of all the other year- classes, but the proportional or percentage gain became smaller as the aga of the oysters increased (Table 3). TifflLE 3 AVER(\GE PERCENT mCRE/iSE IN VOLUME OF OYSTERS OF DIFFERENT i.GS-GROUPS IN ON'E IM) IN THREE GRO:'JIKG 3Ei.S0NS AVERAGES BJSED ON DLTA FOR MILFORD ILJIBOR OYSTERS GRO;'/ING SE.;^ONS PERCENT INCRE*'\SE GROWING SE^ISONS PERCENT INCREif^E (Age in Years) IN ONE SEASON (Age in Years) IN THREE SK/.30NS Between 1 end 2 4775 n 2 n 3 130 n 3 n 4 44 w 4 M 5 39 w 5 n 6 25 tt 6 It 7 21 2, 3, 4 3, 4, 5 4, 5, 6 5, 6, 7 16150 300 185 ].08 The figures given in Table 3 are based upon the data obtained during certain phases of the growth studies of Milford Harbor oysters. These fig- ures, of course, should not be considered as fully applicable to evsry locality where the oysters pre grown. It also should be remembered that during some years the rate of growth may be somewhat slower or faster than during others. Finally, it may be pointed out thet the percent of increase in volume between the ends of the first and fourth growing seasons will be greatly influenced by the time of the year the oysters first sot. If the setting occurred early in the summer and the set grew well, the percent of increase in volume between the end of the first growing period and the end of the fourth may be substantially smaller than shown in our table. On 18 the other hand, if the oysters of the late September set are taken as e group to beein with, their increase in volurie during the next three growing seasons nay even be greater than shown in Figure 3 for the youngest age- group. Nevertheless, regardless of possible wide variations the fact re- mains that the increase in volume during the second year of existence is proportionally far greater than during the following years of life. It is obvious that under natural conditions it would be impossible to achieve such high yields as have been indicated in our experiments, where it was shown theoretically that the volume of oysters, planted after the end of their first season of growth and gathered at the end of the fourth, may increase 16,150 percent. Nevertheless, we must admit that the present yields are extremely lovj. The experience of the oyster growers shows that only under very favorable conditions may one expect to gather 4 bushels of 4-year-olds for each bushel of l-ycsr-olds. It is more common, hov;ever, that the yield is only £ or even 1 bushel of marketable oysters per each bushel of seed planted. Thus, instead of the theoretically possible 161 bushels or more the oyster farmers get only from 1 to 4 bushels. The above given figures indicate very emphatically that the cultivation of oysters as it is now practiced is far from reaching its ultimate goal, and that considerable improvements in the methods of cultivation are de- sirable. Obviously, the industry which produces only a small fraction of what it may produce should attempt to ascertain and, if possible, eliminate various factors which so effectively keep the yield et a very low level. The question that naturally arises is what are those factors. The answer can be given only after systematic prolonged studies are made by combining the efforts of the biologists and the oyster growers. At this time we are well aware of the fact that in some areas starfish and drills kill a large percentage of oysters. However, in many other instances the heavy mortality rate cannot be attributed to these tv/o enemies. Yet, be- cause of the lack of direct observations and studies, we may only speculate as to the enemies or conditions vjhich so profoundly affect the survival of the oysters. Obviously future studies are necessary to clarify many aspects of this interesting and extremely important problem. Kov/ever, because of the complexity of the problem it cannct be solved if we give it only casual attention by examining a few samples on infrequent occasions. The study should begin as soon as the oysters set and steadily continue through a period of four or five years until the oysters ere ready to be marketed. Detrimental effects of and mortality caused by dredging, mopping and shifting are to be determined, while ecological conditions should be studied in as much detail as possible. A program of this type will require the efforts of several investigators and the full cooperation of oyster grovrers, but it vail undoubtedly provide very valuable information which should result in a significant increase in the production of oysters. 19 Cases of unusually high yields, nevertheless, are known in the history of oyster cultivation. For exanple, one incident of this nature vras described in a letter to the author by the manager of one of the New England coinp&nies. It was stated that in 1906 an oyster cocipany located at 'lickford, R- I- planted 200 bushels of three-nonth-old oy-ters gathered from lot 607 near Milford, Connecticut in Long Island Sound. Four years later when the planted oysters were dredged their volume amounted to 2,200 bushels. Thus the yield of 1.1. bushels for each bushel of set nlanted appears to be possible if con- ditions are favorable. In the course of these studies it was determined, by ascertaining the actual volume of the oysters filling s bushel, that only approximately from 48 to 54 percent cf the space in the container was taken up by the oysters, whereas the other part consisted of voids formed between thorn. Groups of oysters aged from 1 to 5 years were used in these determinations but no cor- relation between the age-groups and the percent of actual space occupied could be found. Therefore, if the capacity of a bushel is equal to 35,238 cubic centimeters, only approximately one half of its volume, or 17,619 cc, would actually contain oysters. Using the figures for the average volume of oysters of different ages, as determined by the studies in Milford Harbor, it was possible to calculate the approximate numbers of oysters of a given age per bushel. These numbers appear to be 44,047; 801; 383; 271 and 198 for oysters of the 1, 2, 3, 4 and 5 year-classes respectively. In the case of deep water oysters, where the rate of growth is slower, larger numbers of Individuals of corresponding ages would be needed to fill a bushel. In connection with the discussion it should be remembered that all ref- erences to bushels or any other units of volume are made here on the basis that only single culled oysters were used in these detenainations. The presence of shells and other foreign material would, of course, decrease the number of oysters per bushel. Returning again to the growth studies of oysters we may discuss the possibilities of applying some of the results to practical use. Of consid- erable importance is the observation that during their second year of life the oysters increase in volume proportionally much more rapidly than during later years (Table 3). Obviously it is of more advantage to oyster growers to purchase and plant this age-class in preference to any older group, even if the mortality is relatively higher. The planting of oysters that are two years old also appears practical because during the next growing season they may more than double their volume, and at the age of five years yield approximately 3 bushels per each bushel planted provided, of course, that the mortality rate is kept at a low level. In practice, however, it may not be often achieved. Oysters 3 years and older also continue to increase in Volume, but such an increase proceeds at a comparatively slow rate. Therefore, the growers, who intend to plant older oysters should carefully evaluate whether the 20 inoreasa in volume would conpensate for the losses due to nstural mortality, and the nortality which is caused by injuries sustained during the dredging and planting operations. Finally our figures may serve as a criterion for coniparing the yields fron different beds with theoretically possible naxinum production. Th:' s will enable the oyster growers to appraise critically the relative efficiency of their methods of cultivation. /mother aspect of our studies that may be of interest to the oystemen engaged in the shucking of oysters is that devoted to the detsrraination of the average total weight, weight of shells and weight of meats of the oysters of different groups the age of which ranged from 3 to 8* years. The results of the study showed that the average total weight of the oysters at the end of the third growing period was only 73 gram.-?, vxhere'ss at the age of seven it vras about 215 grams. The average total weight of the oysters constituting the age-class designated as 8^ years and including specimens between 8 and 13 years of age, was slightly over 280 grams. The average weight of shells for 3 and 7-year-olds was 50 end 167 graris respec- tively. The average weight of meats varied from 10.1 graias for the 3-year-old animals to 22,1 grams for the 7-year-old group. It should be remembered that since the oysters were examined in November, the time of the year when large quantities of glycogen v;ere already accumulated and stored in their bodies, the meats were larger and heavier than at some other period of the annual cycle, for example, soon after the completion of spawning when the meats are usually very poor. With the increase in age, the weight of meats became proportionally smaller, whereas the weight of shells gradually increased. In the youngest year-class especially kept for this study and v/hich at the time of examination had completed their third growing season, the meats constituted 13.7 percent and the shells 67.6 percent of the total weight. In the case of the year- class composed of oysters from 8 to 13 years old, the vjeight of meats con- stituted only 10.1 percent of the total weight, while the weight of shells rose to 80.3 percent. Examination of the data for the intermediate year- classes showed a general trend toward a decrease in the percentage weight of meats and increase in the percentage weight of shells vjith advancing age. The data offered here represent the results of observations on the growth of oysters (_0. vi rgin ica) of different ages in Mi:..ford Harbor and to some extent in Long Island .Sound. Since our obsorvations were ccn:Cined to a limited locality only, the conclusions fonried cannot bo considered as applicable to the oyster populations of all other areas where those animals exist. It is thought nevertheless, that the results of our experiments may be used as a criterion for the growth of oysters of a rather largo geograph- ical district, including the shore waters of the State of Kew Y:rk and of 21 New England. iUthough it is quit© probable that the absolute growth in the different sections of this district may show certain variations, the relative grovrth. -'epresenting proirartional or percentage gains at each age, wo'jld probably closely resemble that observed in our experiaents. SOME OBSERVATIONS ON THE FEEDING OF OYSTERS l-JITH ESPT5CIAL REFERENCE TO THE TIDE A. F. Chestnut New Jersey Oyster Resea'^ch Laboratory Eutgers Universi'^.y Growth and fattening of oysters can be said to depend priinariDv upon many factors in the environment, all of which have a part in reguleting the feeding mechanism (Nelson, Martin, Galtsoff, Hopkins, Berkely and others). The quantity and quality of the food in the surrounding v/aters pro;; ace the desired results after active feeding coramenceso Feeding has been shovm by Nelson to be closely correlated with tidal cycles, witr. active feeding taking place on the fD.ood and ceasing during the ebb tide. Loosanoff and Nomejko, however, concluded recently that under favorable conditions in Long Island Sound, tidal changes do not affect the rate of feeding- Their results, then, do net lend support to the theory that oysters are relatively inactive during the ebb tide. Random examinations of oysters in Delavmre Bay showed some discrepan- cies when attempts 'vere made to correlate feeding activities of the o./nter with tidal cycles. Such variations were found as oysters with full stomach contents during the ebb tide and oysters v/ith empty stomach contents during the flood. The contents of the stomachs were withjrav.'n with a pipette as described by Nelson then examined with the aid of a microscope. Compari- sons of numbers of stomach contents examined by this method showed a decided difference between the oysters dredged during the late flood and chos3 dredged during the late ebb, although to the naked eye some of these samples appeared the same rich brown color. The typical stomach contents of an oyster dredged during the late flood tide consist of a fairly large amount of dark, opaque matter su^h as sand grains, plant cells and detritus. The diatoms usually contain chloroplasts and from all appearances are undigested. The typical stomach conten/'.s of an oyster dredged during the early ebb tide contain fewer sand grains and evidence that a sorting of material has taken place in a few hours tijae. The diatoms are nearly all digested and the cell contents have p-^ob'ibly gone into solution thus giving the stomach contents their brown color. In studying the problem from a different approach it v/as found that oysters when kept out of water from tv/o to six days in a cool place upon examination, instead of finding the animals starved as was anticipated, the stomach contents v;ere dark in color. One such oyster was found with its digestive crypts full of oil globules, presumably of diatom origin; which stained readily with Sudan IV. Occasionally an oyster was opened which when cut through the stomach, the contents gushed out freely as some oysters do when opened immediately after dredging. Many of the diatoms in these stomach contents were unchanged end had not been digested. The contents of oysters 22 S3 kept out of water for as long as nine days at air temperatures of from 50* to 60* F. differed only in becoming very viscid. It would not be wise to draw any definite conclusions since these studies are still in their prelim- inary stage but at present it appears that when an oyster which is actively feeding and with full stomach contents, is removed from the water, digestion ceases upon the dissolution of the style. The data from such oysters kept out of water and from actively feeding oysters dredged at all stages of the tide indicate that digestion continues at a fairly rapid rate in oysters which, are passing water through their gills. Some of the stations in Delaware Bay and its tributaries used in the routine collections of samples were selected as locations for further studies of feeding activities. At hourly intervals, approximately fifty oysters were dredged and examined through portions of the tidal cycle, with emphasis on the ebb tide. The oysters v^hen opened were seuarated into one of six groups, based on the color and condition of the style or its absence and a rough estimation of the quantity of stomach contents. Since Nelson has shovm that the style is built up when the animal begins active feeding, and Martin stated "that the style is of very considerable value as an indication of feeding, not only on the basis of its presence or absence, but also on., its varying color and consistency" the presence of the style as a criterion of feeding is justified. The results from three different areas are presented in the fol3.owing tables (#11, #6iJ), i/lZ) . The three columns on the left indicate the liydro- graphical conditions. In the right hand column, the dark brown f 'rm style and full stomach contents indicate active feeding. The pale brown firra style and presence of food are interpreted as the beginning of feeding during the flood or the first signs of cessation of feeding at the first of the ebb. The pale brown soft style is a further indication of cessation of feeding on the ebb and probably the first sign of active feeding during the flood, (see table #11, 4 hours flood). Some overlapping may occur between the pale brown styles for some cases are not clear cut. The Vi/hite style and the ab- sence of styles are interpreted as complete cessation of feeding an hour or more previous. Station #11 is at the mouth of Maurice River, an area where oysters rarely grow to market size because of the prevailing lovj salinities- The oysters are typical low salinity oysters characterized by their thin, vjhite shells and stunted growth. These oysters ere tonged and sold for seed. The results at this station show that active feeding ceases at low water, with the greatest percentage of oysters with no styles and no food occuring soon after Iot; water. Salinity is, no doubt, the factor influencing feeding in this area. Station #6AD is located in the third reach of Dennis Creek, an area re- served for the tonging of market oysters. Large, well-shaped oysters are found here usually in a good condition and sold by the tongers to the 24 shucking houses. In this area we also find that as low water is approached there is a uniform response to the decrease in salinity with the complete c.^psstion of fecdinr, act^.-rixteE. Station #13 is in the privately leased area of Delaware Bay, located offshore In one of the best grovring and fattening regions. In this t:ible the discrepancios mentioned at the bef^inning bsccrce e-ident v;hen large ni:jn- bers of oyster': are opened in a series ra'^hor than random samplings. Here tiie salinity and teiiiper-ture he-^ changed -very 3.ittie yet a decidt;.! differ- ence is noted betv/een tlie percentage of oysters feeding at high v;ater and those feeding during the ebb ti.de. In view of the light that Nelson's work was carried on in a tidal creek where the salinities approach the ninimum for oysters, the results in the first two tables (^=11 and ffo^] are in accord and support his findings as well as his conclusions, tuat in New Jersey oysters are relatively inactive during the ebb tide. Studies have not been made in the higher salinity ranges but on the basis of the findings at station fflZ more diverse results would be expected. It is porsible, therefore, that the difference between the findings of Nelson in Nevj Jersey and those of Loosanoff and Nomejko in Long Island may be due to the difference in salinity of the two areas. Nelson's observations were in waters of optimum salinity and below, whereas in Long Island the salinity is at the optimum and above. 25 I-' I-' (-' t-' 1^ M t-3 J> J^ 1 4:^ J> Ui o n • • • • • • o 3 \J1 - 1— ' U1 ■ • ■^^- VjJ M t-' • ^Jll-' ^'" •-a l-'J ^-3 •-^ 2S^ fD (D D- 1— ' M M • u' cr (D O- Q- a w cr 2; s O O M M 4>- fO N3 1 ^a 1 ^ a ?a ►^ CO O rt- o I ^ ^ 4>- W1 ^ ■6^ ro 4^- VjJ UJ 4> >A ^ ■p- ;u o '<; o o s a- o •X) CO -s c+ ro ^ 0) CD a c+ 3 H- (t> •^ CO •n H o O 0) o a o CO S! tr' CO Ti O H- Hj (l; c+ c+ M n 0) CO tx) o ^ . o o o CL CO c? ri- ^-■<; •-i M CD CD CO CD (r<- cr) 3 a p Co H- C+- 1-S 03 P OD n d- 3"^ •t) o o 1-3 CO o t^ •H ul^ cc ^ o O "^ o o i M O 02 t?i ^ W t-l ^ a: \* ^ S 5^ s >-< Q ^T-" ro X > M T) vO O •F- ?d CM-3 M O 2! O •^ > It" o CO I-" 26 +-' M M H-- h- ' M M vO -£i vO 00 oa CO 00 • • • • • • « Jr- O o oa oa vn o M H' M M O o ^ M oa O O « • • • • • • vn v^ oa oa M H" o^ M Ul ■)^- VjJ M M t^ wii- HjH ^:- AiH Wl>- >-^ • H ^ ro C) 0) CD (D a • cr cr cr cr cr cr cr cr cr cr uj M oa 6-\ r^ ^ M ^^ ^^ §; o M -N M ^ ^^ ■feSi. ^'i M O CN ■60. VjJ O^ •P- M O -p- Vi ■&«. V< ■&a O M -F- -!>• 4^ CN ^■«i. •£■5, JA ^S ■P- O VJ CO ro Q Q cr^ "an §5. 'yj. ^--i. 1-1 o ro o B • •n • Xi 0-. v p B h-^ • ■ t-^ H- a. (B a 3 o O ■n CO o .+ o ^ a M ^_i CO *~^ C+ o ■^ CO M re (B p c+ i? s o ►^ o o H- (!) CT ■^ CO M O CD c+ CO =<; CD tr^ GO T) ri- ri- h-' CD O • CD rn W O P O I— ' O- CO d- T) ^i to ■^ M T 0) CD • CD '"d CS H- C+- <-i B a ^ p Co hJ- P CO O rt- ::r'<; M CD -d o BJ H > Q LTi o '-^ -^ rn M O S3 i- C/: o 3: ^ >- M 1-3 a re g^ 3 h9 M > 03 ra t-i > M W g hr] g K > r^ CO " 11 r"' t-" &-; W l-< C/3 M H .^g M C xO CJ i>- i- o^ 5^ w g txi 1-3 M M 27 M M M }-> (-' [--' M M CO -O ~0 -0 ! o o^ c^- C> « • • • 1 • • • • o CO VjJ M cr- o^ o o t-l M H W V-" M M M -0 O O -O 1 ro CO Oi 00 • • • • 1 • • • • o CO vO M o o l-J o vn 4> VjJ U1 70|M MH f-- Toli^ 1 Ml-' dl: M" VJ1 (D 1 1 1 fC ■^ 1-^ Ms cr D" cr D- cr • (-■ t-' cr cr cr cr cr a O- 1 M 1 M M ' a 5P ^ ^ M M ^ O o CT^ 1 ^ 1 ■&^ m ^ §1 H" 1 M & 1 0^ a 00 5^ M M M M I O- O^ t^ 4:^- 1 f^^ ^^ -s^i -B^ ^ 6 V>0 VjO XJl O^ o^ O CT^ VjJ W -0 •&^ D-^ ^ cA ■641. ^ h9 O iD O 3 • t) xs G-2 (u ^ H • • 1-3 H- a (t) S S o o >D CO O c+ D ^ O- H 0) •-r) O o a p. o ■n 03 >s r-i- (D Q; M H n CD D c+ O ^ CO Ct' o o D^ O O :72 (D S t-' CO "I5 O H- Hj P5 ci- c+ H' "Ti C M O re CO tx) O = o o t^ CO ch M H i-H s; CO S?3 '.^ o a a txi > ?' s rs Cl H CX) CO > s:^ td t-" H■ vO -P- ^i CJ- o S3 ^ \-\ o s o ^ A BRIEF CRTTir.AL. STJRVEY OF THE EVIDENCE FOH THF. HORTZOKTAL MOVEMENTS OF OYSTER Iw^JJVAE Melbourne R. Carriker Department of Zoology Rutgers University Over the years evidence has accuraulated indicating that the larvae of the eastern ijnerican oyster display certain horizontal movements, inde- pendent of, but aided by, the flow and ebb of the tides. This phenomenon was first mentioned by Dr. Julius Nelson in 1911 and in 1913. In recent years Dr. Thurlow Nelson has investigated this behavior in more detail, and describes their movements as follows: oyster larvae are herded horizontally into swarms of uneven distribution. These occur in definite lanes up and down stream from spawning oysters and are so distributed by the tidal cur- rents. Heaviest sets occur in these lanes. Larvae do not seem to be dis- tributed laterally to the current to any extent = They m.'^.y move upstream during the later larval stages, further than can be accoojited for by passive tidal conveyance, by remaining in the fastest currents on the flood and sink- ing on the ebb. Larvae are thought to be stimulated to rise on the flood by the saltier flood vjater and by the increased current velocity. They tend to remain in the strata of greatest salinity change (the heliciine) if such be present. o''», "mature", and "eyed". Eyed larvae are relatively more powerful swimi.iers than younger larvae, and although they are unable to mat 3 much headway against a current, may rise in less than an hour xrom the bottom to the surface of shallov; oyster bays. Eyed larvae measure about 0.3 mm. A£teT careful selection of the proper attachment site, in or during relatively still water, they cement themselves to surfaces on the bottom, and are then called spat. In laboratory experiments, T. Nolson found that older lar-zae became more active when a higlier salinity was introduced, and less active when less saline water was added. Currents passing over the larvae stimu- lated them to rise. In still water they came to rest umbo-downv;ard on the bottom in one to 20 minutes at sunrner temperatures. The Nelsons advance the following points in support of their theory on the movements of oyster larvae: (l) Most larvae were found on the flood tide in estuaries of strong tidal currents (Little Egg Harbor) and in about equal numbers on the flood and ebb in those of less currents (Barnegat Bay) . They do not state whether this decrease in the number of larvae on the ebb in certain bays is not due in part to destruction of larvae by enemies. (2) Distinct variations in the number of larvae occurred at different depths on the ebb and on the flow respectively; the youngest larvae showed no marked differences in vertical distribution, but the older larvae stayed in the lower strata or on the bottom on the ebb, and in the upper strata on the flood. Stauber, in a singular instance, once pumped 700 eyed larvae per 100 liters of water from close to the bottom at low slack water in Delavjare Bey. (3) In the horizontal plane they found the earlier larval stages farther down- stream, and the older larvae most numerous upbey. (4) Setting occurs far upstream from spawnsrs, farther than would be acco-unted for by passive trans- port on tidal currents alone. Also, larvae suddenly return to set on beds over which previously no younger larvae were found, as in Long I=;land Sound. T. Nelson, however, gives no actual figures to indicate how far larvae might be moved passively by the tides. (5) And finally, since in local ectuaries the tide usually runs for a longer time on the ebb than en the flood, tjure is produced in combination with the current caused by fresh v/ater coming down 30 from the streams above, a general tidal drift which tends to carry all freely moving objects oceanward. The fact that some larvae, ever, though carried into the ocean on the ebb, return to set in the bays, would indicsta some independent movement ererted by them. The Nelsons do not indicate hovrever, out of the billions of potential spat in larval swarms, the posslbi?. Ity that great nomters of larvae may be lost at sea during normal vjee ther conditions, and still leave encut;h larvae for the usual sets occurring in oyster regions. An analysis of such factors as salinity, current, temperafr.ire, light, turbidity and pH in larvae-bearing waters has been attempted by various investigators in order to determine the fundamental biological principles which govern larval behavior .^ T. Nelson in an extensive study of the effect of salinity, principally :In Barnegat Bay, finds that relatively greater ag- gregations of larvae occur in the halicline. T'hen no halicline is present the larvae are found in greatest nujtnbsrs on or near the bottom. Korringa writes that accorcing to Nelson's data the larvae in many instances remain uniformly distributed in the absence of a halicline., A re-view of Kelson's data does indicate this. Perkins, also working in Barnegat Bay, came to the conclusion that salinity is not as important in determining vertical distribution as T. Nelson believes; and K-orringa, after a review of the work of both of these investigators, concludes that salinity plays a greater part than Perkins is inclined to admit. T. Nelson reports that the records of seven years show significant numbers of larvae only at the halicline in Barnegat Bay, and that if such stratification were permanent few if any larvae would set in the deeper parts of the bay, but would be swept on the flats where no significant salinity gradients are evident. This has been shown to occur. Salinity gradients may, in part, explain larval movements in bays of slight tidal currents such as those of Barnegat Baj'', but would not seem to play as important a role in estuaries of strong tidal currents, Perkins, after a study of the effect of current on the vertical dis- tribution of oyster larvae in Barnegat Bay, concluded that in strong cur- rents larvae are distributed vertically according to the water currents, that when current velocities are lovj and salinity gradients relatively great, larvae congregate above the halicline, and that if the current is negligible and there is no halicline, the larvae are found near the bottom, ivorringa in an analysis of this vjork, showed conclusively, however, that in some of Perkins' data a relatively strong current has no effect in con- centrating larvae in a stratum v;hen a halicline is present and that in other instances a relatively weaker current, which according to Perkins should play a part in concentrating the larvae, eveniin the absence of a halicline does not do so. Korringa further believes that v;ater currents are not great enough to bring about the effect observed by Perkins. In the strong tidal currents of the Oosterschelde Korringa says he noted no correlation betv/een current velocity and larval distribution and yet his data show instances where more larvae occur in the surface samples than in the lower samples, .-aid further, he collected his greatest number of larvae (2,000 per 50 1.) at half flood in a surface sample? A serious objection to Perkins' larval work, as well as to much of that of others, 31 is that •consecutive vertical series of samplings have not been collected throughout the cycle of the tide. As to the influence of litiht on larval distribution, Korringa, along vjith other European workers, found no correlation. T. Nelson finds that in the presence of light, eyed larvae continue to move un'-.il they come -into shade. J. Nelson thought that larvae tend to stay near the bottom a'^ night end to rise during the day. The effect of temperature on larval movements also deserves greater study. Korringa, thou.y'h noting no correlation between temperature and dis- tribution in the field, thinks that vertical distribution of l&r7ae is not the same at lcv;er temperatures as at higher temperatures. J. Nc='Lson believed that higher water temperatures caused larvae to rise to the surface. He counted more larvae on vjsriTier than on colder days, and observed that in the laboratory embryos swim in schools in ascending and descending coluans. European vjorkeis observing tks same movements in the European oyster larvae, think they resemble convection stream movements. Perkins found no obvious correlation between pH and larval distribution in his Barnegst studies. Such factors as the effect of food and of turbidi- ties on larval distribution have received but scant attention, and merit further investigation. In the summers of 1938, 1939 and 1940, I studied the vertical distri- bution of larvae in Barnegat and in Great Bay, N. J. Series of successive vertical samplings vjere taken through the cycle of the tides, with salinity, temperature and turbidity observations. Unfortunately, current veloc-ities were not determirod. Most obvious result in this study vjas the extreme variation in both the horizontal and in the vertical distribution of the larvae. Roughly speaking more larvae were found in the flood than in the ebb in both Barnegat and Great Bpj. In general, a tendency v;a£ noted for the younger larvae to remain more uniforrdy distributed vertically than the older ones. Strata of maximum concentration of younger larvae ju::iped over the vertical picture somewhat, but tended to rise in the early flood, to sink around high water and to rise again during the middle of the ebb. Older larvae were never found in sufficient numbers to obtain a r>iear picture of their movements. Eyed larvae, however, showed definite tenden- cies: out of some 620,100 liter sa^nplings made in the three summers (about half on the ebb and half on the flood) a total of 82 eyed lar;-ae were found in 15 flood samplings, and only 15 larvae in 5 ebb saiip."! :'ngr;. In Barnegat Bay no eyed larvae were ever found in the water on the eDb \.io samples were taken off the bottom). It is realized that these are snell numlers of larvae, but then this stage is never as abundant as the earlier stages, mortality apparently proceeding at a high rate during the pelagic existence. No influence of temperature, light end turbidity on larvdl d.ls"'.;rib-j-tion vjas observed. In some instances in Barnegat haliclines eppo.-jrBa to influence distribution, at others not tOe In summary, it is possiile, at least, to agree with previous workers that the larvae, especially the older stages, 3S appear to rise on the flood end sink on the ebb tide. However, much more exhaustive vrork must be done both in the laboratory and in the field before this ecological problem is solved. Hypothetically it may help in a study of this kind to consider that differences in larval behavior are being dealt with which have arisen through natural selection over the centuries in the response of oysters in their edjustijent to the varying conditions in the different estuaries. For, it is doubtful that much, if any, intermixing has occurred in recent times betv;een the larvae of the various geographically distinct estuaries. Thus, rather than an identical reaction of oyster larvae from different regions to the various combinations of the environmental influences there, it should be expected that a few fundamental biological responses underlie this behavior, and that the identity of these responses is confused in each instance by the interplay of the changing proportions of the local influences. LOUISIANA'S OYSTER MANAGEMENT PROGRAM James N. McConnell Director, Oyster Division Mr. Gtiairraan, Ladies and Gentlemen of the 1946 annual joint oyster convention: Since the oyster interests of Louisiana have only recently become asso- ciated with your efficient end most important organization, we felt that it might be appropriate at this time to endeavor to acquaint you with our pro- gram of oyster management in Louisiana. By legislative act, the State of Louisiana has declared, and I quote from the act: "That all beds and bottoms of rivers, streams, bayous, lagoons, lakes, bays, sounds, and inlets bordering on or connecting with the Gulf of Mexico, within the ter- ritorial jurisdiction of the State of Louisiana, in- cluding all oysters and other shell fish and parts thereof, grovm thereon, either naturally or cultivated, and all oysters in the shells after the same shall have been caught or taken therefrom shall be, continue and remain the property of the State of Louisiana, until the title thereto shall be divested in the manner and form herein authorized; and shall be under the exclu- sive control of the Department of Wildlife and Fisher- ies of the State of Louisiana until the right of pri- vate ownership shall -ttest therein, as herein provided." On numerous occasions during the twenty years that I have personally directed our Oyster Division, attempts have been made by unscrupulous in- dividuals to exploit improperly the vast oyster production possibilities of our State. This type of promotion has never been allowed in Louisiana. We welcome, however, and will assist in every way possible, any legitimate oyster interests that might care to avail themselves of opportunities for oyster cultivation and production which our State affords. We in Louisiana firmly believe that at present less than ten per cent of our oyster pro- ducing area is being utilized. This opinion is concurred in by several oyster experts from other sections of the country, after surveys made of oyster producing territory in this area. It has always been felt that it is necessary to lease State-owned water bottoms to private individuals in order that the State may give proper protection and encourage individual cultivation of oyster areas. The State of Mississippi, by contrast, does not allow private leasing of water bottoms for oyster cultivation, end I believe that our other sister state, Texas, has only in recent years allowed the leasing of its water bot- toms for oyster purposes and this only under limiting conditions. 33 34 Bor.eusr.^ of a continuous high head of water back of the dans gives them little if any flood control effect. Stream flow records at Harrisburp. thus furnish a reliable index of the water discharged into the upper Bay by the Susquehanna River. Publications of various agencies in Maryland dealing with oysters have been searched for records of general mortalities occurring at the Head-of-the- Bay. It is found that such losses when occurring in spring or summer vjere sometimes unreported until the rocks were visited after Christmas so that records of such loss may be given in the follov;ing year. There is also evi- dence that oysters weakened by spring floods nay succumb the folloxving v/inter when environmental conditions are unfavorable. The following major mortali- ties and no others were found to have occurred during the period for which records are available: 1908-1909, estimated at 55^ on the Tea Tables and 6Zfo on Man 0' War Shoals; 1916, only an occasional living oyster could be found above Swan Point and the Patapsco River; 1928, an 80^ mortality of up- Bay oysters; 1936, a heavy mortality from freshets down to Swan Point and Sandy Point; 1943, 975!s loss on Tea Tables ranging to little loss at Swan Point and Sandy Point; 1945-46, to be reported in detail by Mr. Engle. The six-month progressive average daily flov/ of the Susquehanna River at Harrisburg for the period of recorded mortalities has been plotted together with the existing monthly average salinity records from Baltimore. Mortality years are marked on the graph by an "M". These six mortality periods corres- pond with the six highest sustained periods of cumulative run-off from the Susquehanna. The five laortality periods reported since Baltimore salinities were available correspond with five of the seven recorded periods when salin- ities remained below five for three months or longer. These records thus afford excellent evidence that the oyster mortalities at the Head-of-the-Bay have all been associated with and probably are the direct result of low salinities caused by periods of high run-off from the Susquehanna River. CQMMKPCIAL ASPECTS OF THE UPPER CHESAPE/JCE BAY OYSTER Bi^Jffi TN LICHT QE THK RECENT OYSTER MORT:.LITIES James B. Engle, ilquatic Biologist U. S. Fish and Wildlife Service The conditions existing on the upper Chesapeake Bay oyster bars during the last two oyster seasons present an exciting and deeply challenging situa- tion to the biologist, but a sad and depressing picture to the industry depending on the supply oi" oysters. I appreciate both viewpoints and take this opportunity to discuss the significance of our observations from both sides. The Fish and Wildlife Service in cooperation v/ith Maryland Conservation agencies has been studying the biology and factors relating to the cultiva- tion of oysters in Chesapeake Bay since 1944, and the value of the biological observations has already benefitted the oyster industry to a certain extent through advice based on information gathered in the course of these invest- igations. A major portion of the study was centered on the area known as the "Head of the Bay" located north of a line from the Chester River and Sandy Point. The reason for this critical interest is founded on the fact that vifide fluctuations of salinity occur in this area from year to year and within the year. The cause of these salinity changes is in the araoimt of the fresh vrater run-off of the Susquehanna River. The drainage area of this River is located largely outside the State of Maryland in Pennsylvania and New York, but in Maryland, however, the greater part of this drainage is im- pounded by a large dan at Conowingo situated above Havre de Grace. During years vjhen rainfall, snowfall and spring thaws are responsible for high river stages, large quantities of the fresh water escape over the dam or are re- leased through flood gates and flow into the head of Chesapeake Bay. The salinity depression caused by the influx of the overflov/ varies in its ex- tent and amount from year to year. Fortunately, coincidence during the last two years has permitted us to observe the effect on salinity of a reasonably dry season with a light flood from the Susquehanna River, and a year of heavy spring run-off following a quick and heavy thaw augmented further by excessive rainfall in the drainage basin, and in the immediate vicinity of the Bay. The contrast of these tvjo years represents the difference between the existence and the destruction of oysters found on some of these bars of the ♦•Head of the Bay". J*, more detailed discussion of our observations during each of these years v/ill disclose the effect of the changes on oysters. In 1944, the year the investigation was started, the salinity picture was as follows: From February to May 10 there was a drop from 10 parts of salt per thousand parts of water to fresh water. The fresh water lasted about two weeks, and then a steady increase in the salts occurred throughout the rest of the year reaching 15 parts per thousand in October. Oysters during this year were not materially harmed by the short period of fresh water with the exception of a slight retarding of the gonad development and 42 43 the absence of setting. Spawning did occur later in the seoson, and oysters grew normally and "fattened". In fact, the growth was better than usual and brought a large nuaiber of undersized oysters into the legal class for marketing. On the basis of the large number of market size oysters in good •^fat" condition present on the "Head of the Bay" bars, the Maryland Depart- ment of Tidewater Fisheries on the advice of the oyster biologists of the Fish and "-midlife Ssr^-ice opened about 600 acres of oyster bottom '-■o har- vesting. Detvveen 75,000 and 100,000 bushels of oystors ■mre marl:e-&d and netted a substantial profit to the industry. This move also provic''ed an additional supply of food at a critiCcil period during the meat shcr"iage. The whole operation w^.s under the control of the State and Federal agencies, and the harvesting was stopped before any serious reduction was made in the population on the bars. In view of what happened before the 1945 year was over, it might have been v/ell if all the oysters had been removed either to the market or transplanted to other bars. I'Je are not gifted with the ability to foresee whet the weatherman had in store for the area, so the bars were left with an adequate number of oysters to furnish brood stock for rebuild- ing the population for the future. Vfe followed an acceptable conservation procedure in both cases, namely in harvesting some of these oysters and in leaving a portion of the population on the bars. Now let us follow the sequence of events during 1945. From the salin- ity of 15 which was maintained through the fall and winter of 1944-5, it suddenly dropped to fresh water during the latter part of March. The fresh water remained over the bars for about three weeks. The heavy run-off was caused by an unusually early thav; in the whole Susquehanna River drainage basin that melted the heavy snovjs in New York and Pennsylvania and created flood stages on the river. When the floods had subsided, the salinity rose in the upper Chesapeake Bay to about 7 during the latter part of April. This rise was false assurance, for the spring rains came early in May and again dropped the salinity to zero. This condition was maintained until the end of May when once more the salinity started upward. The rise, hov;ever, was stopped by the rains of a very wet summer. Salinity hovered between 3 and 6 parts per thousand until the end of August; rose to about 9 during September; and dropped to 5-7 for the rest of the year. Studies by oyster scientists have shown that oysters are not able to grow, "fatten" and re- produce under these salinity conditions. Oysters in this part of Chesapeake Bay demonstrated this fact during 1945. Sex products in the majority of oysters did not ripen until j'.ugust, spawning was meager, and no setting oc- curred. Meats were puffed up and transparent with water at the time when oysters normally accumulate large amounts of glycogen, which usually accounts for their creamy "fatness" and desirable firmness. These oysters, when shucked, began losing the absorbed water immediately and soon became shrivel- led and dark and contained only one-fifth of the solid matter usually ex- pected in a good market grade oyster. By November they began to die and before the v/inter was over the mortality had reached from 50 to 98 percent of the population. Those animals that had not died were in such poor condi- tion that their survival was doubtful. For the moment it is sufficient to say that none of these oysters were fit to be marketed and the loss to the industry was great. 44 The extent of the affected area went beyond the ♦•Head of the Bay" bars, and included many of the oysters in the Chester River, most of the bars on the Bay side of Kent Island, and a major portion of the bars in J^ne jlrvndel County on the western shore of the Bay. The mortalities were not as severe belov; the "Head of the Bay" bars, but the condition of the oysters was so poor that they could not be marketed. The parts of the Bay and the tribu- taries below the above mentioned sections did produce many oysters, and made it possible for the Stste of Maryland to maintain production figures approx- imately equal to the 1944-5 season. The sad pert of this season's losses is more profound than appears at the first glance, itoong the areas effected were bars being developed as part of a program by the Maryland Department of Tidevrater fisheries for re- building the grounds of low yield and the partially depleted areas. Most of these planted and cultivated areas are in the Bay proper, but several others are located in the Chester River. During 1943 a set of oysters caught on shells planted at Love Point, Kent Shore and the bars in ilrme Arundel County. This set was supplemented by seed of the same year setting transplanted from prepared seed areas, ilany of these oysters had reached marketable size and were part of the projected crop expected for the 1945-6 production. V.'hen the past season opened in September 1945, the condition of the meats vras below the quality required for marketing on the basis of appearance and yield in pints per bushel, so the areas were not opened for harvesting. It was at first expected that the oysters would improve as the season progressed and the aniaa.ls had more time to "fatten" after spavming had ceased. They could th^^n be harvested later in the fall. This did not happen, and instead, many died. The survivors became progressively poorer as the season advanced, and entirely unfit for marketing. The fact that these oysters did not reach the market is no reflection on the State program, for the conditions occurring on these bars are unusual and they happen in- frequently. On the basis of unmarketability and loss through the heavy mortality, the State of Maryland oyster production for the season of 1945-6 was de- prived of over one million bushels, ilpproximately 40 percent of these oysters would have come from the reserved areas cultivated by the State of Maryland Oyster Management Plan. In the following table the detail upon Vifhich these figures are based is given. The losses from the "Head of the Bay" bars are not included because that area cannot be rightly classed as a dependable source of oysters for the Maryland market* The losses on these latter bars, however, v;ere heavy and represent considerably nor-s than half of the population left there after the mortalities follov.ing the freshet of 1943 end the marketing during the fall of 1944. I believe I am justified in expressing a word of encouragement to close this otherwise depressing discussion. Some of the loss during the present season was due to unraarketebility, and this may be recovered when the water conditions improve, and the subsequent improvement of the poor oysters. 45 Table 1. Mortali-ties end production losses from the bars in the upper part of Chesapeake Bay, 1945-6, end marketable residue. Bushels NsBie of Bar' Love Point Broad Creek Gum Thicket Bloody Point Chester River i\nne Arundel Expected crop 1945-6 Mortality loss Marketable r&.'idue 100,000 200,000 60,000 50,000 25,000 15,000 92,000 100,000 15,000 10,000 10,000 5,000 8,000 1/ 100,000 1/ 45,000 1/ 40,000 1/ 15,000 i/ 10,000 1/ Totals 450,000 232,000 218,000 Sv;an Point Anne /a7\mdel 500,000 500,000 300,000 150,000 200,000 350,000 2/ 2/ Totals 1,000,000 450,000 550,000 Combined Totals 1,450,000 682,000 768,000 !_/ Bars cultivated State of Maryland Oyster Management Plan 2/ Natural bars with oysters too poor to harvest 46 The lo63 through the heavy mortality on some of the bars is irreparable of course, but the cultch bought at this high price may be a small but useful element on the credit side in the rehabilitation. At the present tine, hydrographical conditions are favorable for a drier season which should improve the salinity. The blame for the losses during the 1945-6 season may be put directly on the low salinity maintained throughout the whole of 1945 and early 1946. In the effort to explore all possible causes for the poor condition and high mortalities, an independent study of the distribu- tion of the sporozoan parasite, Nematopsis , in the oysters from most of the bars in upper Chesapeake Bay was made by Miss Helen Landau, Biologist- in the Fish and Wildlife Service. No correlation could be found between the distribution and the intensity of infestation of the parasite in the oysters with the poor condition and mortality. The period just past, usually the time when the upper part of Chesa- peake Bay is under the bad influence of the spring freshets from the Sus- quehanna River show by the records that it is the driest experienced since the Conowingo dam has been in operation. The overflow has been cut off ex- cept for power manufacture, and even this has been curtailed in order to maintain sufficient head to run the turbines. The salinity at the head of the bay has reflected this meager discharge of water from the dam and is now 10 parts per thousand higher than it was in 1945, and approximately 5 parts higher than it was in 1944. I7e still may get precipitation heavy enough to cause heavy run-off vjhich would depress the salinity, but some ground has been gained by having a dry early spring, i.. short term depres- sion will not seriously harm the oysters provided a reasonably dry sunnier and fall permits the steady rise in salinity. I offer hope to Maryland in particular and to the oyster industry on the whole, for a substantial in- crease in oyster production from this area during the coming season. '?ith higher salinities one may also expect s better possibility of norriial gonad development and a subsequent set to replace some of the losses just suffered by the oyster population in the upper Chesapeake Bay. On the evidence of our observations of the "Head of the Bay" conditions it seems appropriate to mention here that it viould be more profitable to expand oyster cultivation in a southerly direction in the Maryland portion of the Chesapeake Bay and avoid trying to answer the question "is the head of the Bay a nursery or a death trap for oysters?" There is no doubt that a potential value exists in the head of the Bay and oysters will occur from time to time, ''lien they do occur it would profit the State to remove them to safer areas to grow. A better oyster is produced where salinity remains higher and with less fluctuation than is found in the above area. HOW Cj^ W. PBOFIT m THB U. S. FOOD ^JS!D DRUG ^iDMETISTP^TION HEARINGS Curtis L. Newconibe, Director Virginia Fislio.ries Laboratory Yorktowa The extent to v/hich oyster packers may profit from the recent hearings of the U. S. Food and Drug .Idinini stration depends firf^'^ly on v;hat added sig- nificance they have been led to attach to hp.nd:.3ng and packing procerli'.res, I think that many have cone to realize more in -n erer before the bad e-Cfocts on oysters and oyster markets of excessive contact with fresh water or too great variability in counts or excessive amouni. s of shell fragments. The need for a standard of sone kind is probably evident now to nany that before the hearing considered standards unnecessaiy. Hence, it is likely tbat the Hearings have resulted in giving added significance to Standards in this industry. The extent to which the Hearings have been profitable depends, secondly, on new inforuiation that has been provided by the various Federal, State, and private agencies, ditev listening to carefully prepared testimony offered by the Food and Drug Administration and by the several other agencies, I became impressed with the need for Standards of some kind, the need of the oyster industry for the backing of the established Federal agency for promul- gating standards - namely the U.S.F.D.A.- and especially the net-d for more fac ts to serve as a basis for Standards. The oystermen of the different states do not yet have the needed records to define the type of standards that best suit the country as a whole (if indeed such can be found) or thet are applicable to even one general section. It is true that the various etate agencies in cooperation with the U. S. Fish and V/ildlife Service did a great deal in a short time but the job is too big to be completed in a few months. Likewise, the testimony of the U. S. Food and Drug Administration impressed me as lacking technical facts on essential aspects of the regula- tions, and, too, the evidence seemed to reveal a lack of appreciation of the practical problems which every oysterman encounters. I may cite an example of variations in oystors from two different parts of Virginia which clearly show that there is no royal road to generalizations as far as behavior of oysters is concerned. The two localities where our observations were made were near the mouth of Chesapeake Bay - salinity about 20 parts per thousand - and on the seaside of the Eastern Shore - salr'.nity about 30 parts per tnousand. Gallon samples were used. Bayside oystors shucked in a drj' container had a drainage loss immediately after shucrlng of 25o2 percent as compared with 8-.2 percent of Seaside oysters* Kiene same oysters were drained and weighed six more times in succession to see how much liquid they continued to lose on continued draining. As a result of being drained and weighed seven times in succession, Baysido oysters had a total drainage loss of 44.4 percent whereas Seaside oysters showed a corres- ponding loss of only 18.1 percent. 47 48 These findings were supported by other experiments in which oysters were shucked into containers containing 25 percent of fresh water and 75 percent of fresh water by voluae. The data show clearly the difficulties that are likely to arise in an effort to establish Standards that will apply equally v;ell in both regions. In any attempt to proaulgate uniform handling procedures for different areas, such differences as those given above cannot bh ignored. Pertinent data on how oysters respond to different handling procedures, and, too, on what constitutes the best practical procedures for the different sections should be made known to the oyster packers and to the regulating authorities. Both groups stand to benefit from strict adherence to such regulations. The oyster growers can benefit from the Food and Drug Administration Hearings by taking steps to get a factual basis for needed regulatory measures. The subject of uniform count has been discussed at some length. Our observations have not been comprehensive enougli to permit generalizations. It seems clear, however, that the counts are more uniform in some houses than in others and that concerted effort by the industry will result in sig- nificant improvements. I^reliminary observations were made on the number and vreight of shell fragments in individual gallon samples of "Select" and "Standard"** oysters. Standards, as expected, v;ere found to contain far more bits of shell than Selects. In one instance a gallon sample of Standards contained 139 shell fragments which weigl:ied 24 grams, the largest fragment being one and one-half inches in length. The remaining samples vjere lower, one gallon of selects containing only 1 fragment which weighed 0.5 gram. These extremes are cited to Indicate that there is a large variation between different plants and be- tween different days in the same plant depending on the experience of the workers and the oyster stock. A3 in the case of the problem of getting reasonably uniform packs, the oyster packer could, seemingly, accomplish much through constant effort to reduce the amount of shell fragments. Doubtless, the Hearings have resulted in improvements in more than one plant by making the operators increasingly aware of the effect on the quality of the oyster pack of excessive contact with fresh water, excessive blowing, and excessive quantities of shell frag- ments. It would appear that such a step should help improve the demand for oysters. Furthermore, without effective regulations the progressive packer is likely to be penalized by the careless packer who is relatively indifferent to the quality of his product. The importance of quality and not just size as a basis for grading has been stressed and deserves still more emphasis. 49 I suggest that the Oyster Grower's Institute keep this whoJe subject of Standards alive by designating a coirmittee to work on the proj'e'r;:. A fuc-jtion of the Goriiai-cee ^Tiight be to stimulate sud cocraina^-o the Invest i- gat:;onF needed to provide tbe ne-.^escnry facts and to cocrerate with the governnxent aganciee in assuring adherence to the desired sv.ar.dards of hand- ling and packing oyatovs. Ey keeping the packers mors consr^lous of the ill effects of lon;^ con-Jact with fresh water, of excessive "r^.ovnng and of large numbers of sheJ.l fragrnen-^.s, a tester oysi'er pack can oe assi.:L-ed. BACTERIOLOGICAL OBSERVATIONS ON OYSTER GROUNDS OF THE HAAIPTON ROADS AREA P. Arne Hansen, Bacteriologist, U. S. Fish and V/ildlife Service Every oysterman is confronted with a great many problems in securing the best possible product for his market. One of the many obstacles which he is facing is the difficulty in finding adequate planting groiinds in a locality where the oysters will fatten quickly and vjhere sea vrater is suf- ficiently clean to meet the requirements of the U. S. Public Health Service. It may be added that the oyster grounds should be, of course, at a convenient distance from both shucking house and seed beds. The massive increase in population in the Hanpton Roads area, especially during the war years, has been responsible for adding more acres to the already extensive restricted shellfish producing area with the result that the oyster growers have been practically forced out of the lower Bay betv;een I'jilloughby Spit and Little Creek, an area of 3:847 acres. The monetary loss in production of market oysters is difficult to estimate exactly, but for the entire Hampton Roads area, it may well exceed 2 million dollars. Besides the actual decrease in the production of marketable oysters, there is an additional loss in the value of oyster bottoms which have been carefully improved for years by shell planting and which represent a considerable investment. The loss of oyster producing bottoms has caused deep concern to the oystering industry of Virginia. The Fish and Wildlife Service during the last 18 months has carried out studies on the trend of the pollution in the lower Chesapeake Bay with the object of finding areas free from objectionable contamination. Foods consumed in a raw condition, especially such which are of nitro- genous, non-acid nature, are of particular concern to public health officials. Since shellfish belong in that category, much has been done to safeguard the public and to dissociate the shellfish trade from the slightest suspicion by excluding from the market any shellfish which might possibly harbor potential danger. State officials, in cooperation with the U. S. Public Health Service, are continuously surveying shellfish waters to ascertain their suitability from the Public Health point of view. The degree of safety of shellfish waters is evaluated in terms of "Most Probable Numbers" of coliform bacteria, abbreviated M.P.N. This group of organisms in itself is not dangerous to human health, but it is universally associated with the excreta of humans and warm blooded animals which nay carry organisms that are dangerous. Coliform bacteria are not present, at least not in significant numbers, in localities which have not been exposed to recent pollution. By planting definite amounts of sea water in suitable culture media, the number of coliform organisms can bo fairly closely estimated. This quantitative method has become very widely used because it affords a fairly direct way to determine pollution. The most direct approach; namely, 50 51 the counting of dangerous pathogenic bacteria, ie not practical. Instead of testing for these, we have chosen to discriminate simply against all intestinal bacteria. According to the standard established by the Public Health Service, an M.P.N, of colifom bacteria in excess of 70 per 100 ml. should place a water as a moderately polluted, and such water areas should be considered as pol- luted and restricted for shellfish production. If the value of M.P.N, would remain more or less constant at the same sampling station, the work involved in testing would be of relatively simple nature. The task of the investigator, unfortunately, is made quite complicated by the fact that numerous factors, such as temperature of water, state of tide, recency and amount of precipi- tation, wind direction, presence of nutrients or inhibitors in the water, and still other influences, govern to a very considerable degree the number of bacteria present. Due regard must be given to occasional occurrences of very high nuiabers, hence it is prescribed that the median (the middle value) of a large set of data be used for expressing the just figure. The varia- tions from one sampling trip to another are particularly pronounced in the . Lower .Chesapeake Bay where sound judgement can be arrived at only after pro- longed and all-year-round sampling. The field laboratory at Hampton has been studying the progress of retreat of the sewage front in the lower Bay, ex- pressed in terms of M.P.K. The restricted area studied, between Fort vjool, Willoughby Spit, and Ocean View, slopes very gradually from the northwest boundary where the depth is 12-15 feet to 22-87 feet at the eastern border, the main part having a depth of about 20-24 feet. North of this region, at a distance of about 2000 yards, is a deep water channel, an important shipping lane, varying in depth, but mostly around 40-50 feet. Naturally enough, the pollution from the Hampton Roads area follows in some measures, as experiments have shown, this deep water channel being washed back and forth by the tidal wave. A certain amount reaches, as our data indicate, the oyster growing area, mostly from the west and northwest. Before the pollution reaches the extensive and al- most uniform flat regions north of V/illoughby Spit and Ocean View, it is almost uniformly mixed and somewhat diluted. The pollution of this area decreases when one passes from Fort ?fool eastward. During the war, when there was extensive activity near Little Creek, an increase of M.P.N, of coliform bacteria was noticed toward the eastern border of the area. The numbers rise, as a rule, in an off-shore direction approaching the deep water channel, except in the most western part near Fort Wool and Willoughby Spit where discharges from Norfolk leave the deeper water and pass over the Willoughby. Bank. The shallowness In this part is favorable for higher numbers, because of lesser dilution. As a whole, M.P.N, are higher on ebb than on flood tide. Excepted, however, are certain off-shore points approaching the deep water channel where the flow of sewage may be pushed out sideways with the incoming tidal water. 52 The influence of aeeson has been found to be extremely important, iifter relatively low values during parts of the winter, and into March 1945, the number of coliforms increased to high values late in April. Very high numbers were reached during July and September 1945. Not before Febnrary 1946 did the pollution subside in most of the field studied. In the region most closely situated to Fort Wool the figure remains relatively high. The pollution seems to bear s certain relationship to rainfall. Some cllmatological extremes occurred in 1945. It is worth noting that July 1945 v;as the wettest July of record for Virginia. Tidewater Virginia averaged In this month 13.45 inches of rainfall, or 8.40 above normal, September was next to the wettest September of record and Tidewater Virginia averaged 5.6 inches of reinfall, 2o22 above nomsl. This rainfall may have had some rela- tionship to the high M.P.N, of the two months. Not only did a number of stations show considerable pollution, but it was also observed over an ex- tended area. I'Jhether the seasonal variation will be repeated in 1946 is impossible to ansiver, but the first part of the year has shovm some slight hope for improvement. It may be related to the cold spring, to the decrease in wartime population, or, possibly, to a change of sewage. The future of the oyster grounds in the Lower Chesapeake Bay will de- pend very closely on the progress of the plans for the treatment of sewage effluents scheduled by the Kaupton Roads Sanitation District Coniiissionc Since 1927 an increasing effort to provide for improved sanitation of the Hampton Roads area found its expression in the fcmation of various important commissions, culminating in the creation of the liampton Roads Sanitation District and the Acts of 1940, which were approved in November 1940, The District includes territories on both sides of Hampton Roads and considerable advance has been made in the extensive engineering projects for suitable sewage disposal. So far, the main accomplishments are the following, till main sewers on the Hampton side have been coiiipleted. Sewage west of Sunset Creek since «^^pril 1st, 1946, has been discharged into tne outfall nesv the Small Boat Harbor at Newport News. The south side of the Hampton Roado area is now almost completely being served by lateral sewers, and the outfall at the Jlrmy Base has been in operation since early in 1945, The Portsmouth sewers are completed and the plant at Pinners Point is under construction. At the present moment, no sewage treatment plant in the Hampton Roeds Sani- tation District is in operation but several are under construction. The Small Boat Harbor plant is expected to start operating in November 1947 and the Army Base Outfall late in the summer or fall of 1947. The entire plan is expected to be completed at sometime in 1948. The Fish and V/ildlife Service is looking forward to following these changes closely insofar as they will reflect themselves in the b:'3teriologicel findings in the oyster producing waters of the region. It i?. hoped that the "clearing up" of a region and the consequent lifting of rest:.:'.ctions on shell- fish production will be reached in the not too distent fuvj.rp.. The importance attached to the pollution problem in the Lower Chesapeake Bay should not in any way be so construed as to be reflecting any stigma on oyster production 53 ■business in the Hanpton Roads region. On the other hand, the extremely rigid res-frictions on shellfish product ion areas, vn.th which the nierket has been prctocitod. h«s placaa the qu-.ility of the oysters beyond reproach.- Mm "IIOI I lUHAUV UH lACH 3 m 'i-crrfVr...,, ^t&i 1^ ^i''tJWiS2W' Hi ?«s^- i a(?i:s^ EWfft\; >.i^*f**>-» ^«