< eer, Fewest Bate NaN evar tl ture TNS webed yee ated Te Pale NATIONAL = SHELLFISHERIES ASSOCIATION a rg alee! igre = cts ear rate tape Veer ie ADDRESSES DELIVERED AT THE CONVENTION OF THE NATIONAL SHELLFISHERIES ASSOCIATION Washington, D. C. August 1) = 16, 1951 James Nelson Gowanloch James B. Engle President Vice-President A. F. Chestnut Secretary Published for the National Shellfisheries Association by the Fish and Wildlife Service, U. S. Department of the Interior Washington July 1953 aay NG ASTI | it “ Z a ree, VT, etre Pay : dy 2 eit es ae hi ell ——— he, © tk i = ~ a e = inge 7 aN 1 ‘ 1 a Pe TABLE OF CONTENTS 1951 ADDRESSES Title Page Seasonal Variations of Coliforms and Enterococci in a Closed Shellfish Area William Arcisz, Elsie Wattie, James L. Dallas it Notes on Growth of Thais haemastoma floridana and Thais (Stramonita) rustica Robert M. Ingle 12 A Method of Reducing Winter Mortalities of Venus Mercenaria in Maine Waters Robert L. Dow and Dana E. Wallace 15 Incidence of Infection of Oysters by Dermocystidium in the Barataria Bay Area of Louisiana J. G. Mackin 22 A Report on the Interrelationship Between the Growth and Mortality of Oysters H. Malcolm Owen and Lester L. Walters 36 The Effects of Predation on Soft Clams, Mya Arenaria Osgood R. Smith and Edward Chin 37 Variations in Sizes and Rate of Growth of Lamellibranch Larvae of the Same Parents Robert R. Marak Ty) The Bonnet Carré Spillway and the Oyster Beds of Mississippi Sound Gordon Gunter 6 Biological Effects of Bullraking vs. Power Dredging on a Population of Hard Shell Clams, Venus Mercenaria John B. Glude and Warren S. Landers 7 Oyster Condition Affected by Attached Mussels James B, Engle and Charles R. Chapman 70 Some Factors Influencing Steam Yields in Oysters Francis X. Lueth 79 TABLE OF OONTENTS 1951 ADDRESSES Title Page Studies of the North Carolina Clam Industry A. F. Chestnut 85 A Soft Clam Population Census in Sagadahoc Bay, Maine 1949=?50='51 Harlan S. Spear 89 SEASONAL VARIATIONS OF COLIFORMS AND ENTEROCOCCI IN A CLOSED SHELLFISH AREA William Arcisz, Elsie Wattie, James L. Dallas U. S. Public Health Service, Shellfish Sanitation Laboratory, Woods Hole, Massachusetts Many valuable shellfish resources cannot be utilized because they exist in polluted waters near seashore communities. Some of these communities have a stable population contributing a uniform yearly pollution. Others, such as summer resorts, have widely fluctuating populations, and contribute varying amounts of pollution to the receiv- ing waters. A vital question is raised concerning restriction of shell- fish gathering after the summer population has gone and the pollution is materially reduced. The purpose of this study was to determine, (1) the year-round variability of the quality of both water and shellfish from an area with such a seasonal fluctuation in population, and (2) the ratio of pollu- tional organisms present in the overlying water and in the shellfish. The study consisted of a sanitary and bacteriological survey. Sanitary Survey of Eel Pond Description Eel Pond (see Figure 1), situated in the center of Woods Hole, Massachusetts, has an area of approximately 0.025 sq. mi., and a water- shed area of approximately 0.28 sq. mi. The pond, varying in depth from about two feet at the shore to 20 feet in the center, has about 80 per- cent of the shore line well defined.by vertical stone walls. Three fresh water inlets, one on the east side, two on the north side, numerous sur- face drains, and some private sewers, discharge into the pond. The land immediately surrounding Eel Pond is fully developed. On the immediate shores are located domestic dwellings, stores, bakeries, restaurants and biological laboratories. The pond provides an excellent harborage for large and small pleasure carft, and is used as such all year round; naturally, the numbers of such craft increase greatly during the summer, Eel pond is directly connected to Great Harbor by a boat channel about 500 feet long and 75 feet wide. Current observations made at the Eel Pond outlet to this channel during a 6-hour period revealed 18 cyclic changes of current flow with a maximum velocity of about one foot per second. This fluctuation of current, coupled with the mean range of tide which is 1.8 feet, indicates that the pond seldom gets a thorough flushing. Thus, it appears that the pollution in the pond has a tendency to be maintained at a high level. | 3YNSI4 ae we wo a PROS Sanitary Survey A sanitary survey of the immediate vicinity of Eel Pond shows that there are 90 homes and establishments which contribute pollution either directly or indirectly into the pond. There is an increase in the pollution load inthe sunmer due to summer residents. It is estimated that the population in the immediate vicinity of Eel Pond increases to 2,200 during the months of June, July and August, as compared to 00 year-round residents. Although most of the homes bordering on the pond have cesspools, there are a few which discharge their sewage directly into the pond. Seepage and overflow from a number of the cesspools cause some pollution of the pond. The waters of Great Harbor near the Eel Pond boat channel receive considerable pollution from commercial establishments and dwellings along the channel. Some of this pollution probably enters Eel Pond during the flood tide. On the basis of the sanitary survey, it would appear that Eel Pond is subject to moderate pollution throughout the year with a marked increase during the months of June, July and August. Bacteriological Survey A series of six stations (Figure 1) was established in Eel Pond; one in the approximate center, one at the entrance of the boat channel, and four at approximately equidistant points along the periphery of the pond. Surface water samples were collected at these stations at least once a month from August 198 through July 1950. Additional samples were collected for salinity determinations. At one station (Captain Kidd's), in addition to the water samples, a shellfish sample consisting of six or more quahogs (Venus mercenaria) was collected for bacteriological examination. The temperature of the water was determined at each col- lection. Laboratory Methods Samples of shellfish and water were collected and prepared for analysis, except for a few minor deviations, in accordance with the methods described in "Recommended Procedure for the Bacteriological Examination of Shellfish and Shellfish Waters". Phosphate dilution water (2) was used instead of one percent salins. Shellfish were prepared for disintegration in a Waring Blendor by weigh- ing the contents of six shellfish and adding an equal amount by weight of sterile phosphate buffered diluent instead of the recommended 200 ml. of one percent saline to 200 ml. of meats and liquor. Suitable aliquot portions of samples were planted in at least three decimal dilutions using five tubes per dilution. Parallel plantings ey° made into standard lactose broth and Winter and Sandholzer enterococcus presumptive broth. The presumptive lactose broth tubes were incubated at 37° C. (air incubator) and examined for the presence of gas at 2l and 48 hours. All lactose broth tubes showing gas were confirmed by transferring a 3 mm. loop= ful to brilliant green lactose bile broth 2% (B.G.B.). The presence of gas in any amount in B.G.B. after 2h or 48 hours of incubation at 37° C. was considered a positive test for the coliform group. The enterococcus presumptive broth tubes were incubated for 2h hours in a 5* C. (water bath) and examined for turbidity and acid which indicate a positive presumptive test. Positive presumptive tubes were checked by transferring two loopfuls (3mm. loop) to con= firmatory agar-broth slants for incubation at 37° C.-for 18 to 2h hours. The confirmed test consisted of: (1) pin-point colonies on the agar slant, (2) sedimented growth in the broth portion, and (3) the demonstrations of gram positive streptococci. oe oo. were recorded in terms of the "Most Probable Number" (MPN) 3 per 100 ml. for members of the coliform and enterococcus groups. Results In Figure 2, the average MPN values for coliforms and enterococci and the average monthly temperatures for Stations 1 through 5 are presented. In general, the coliform content of the waters follows the tempera- ture fluctuations, however, this condition is not constant. The sharp rise of coliforms and enterococci in April as compared to March and May might be due to a temporary increase in population. Summer residents often come to Woods Hole in April to inspect their homes and to make the necessary preparations for reopening themin June. During June, July and August, when the population of Woods Hole is at its peak, the coliform content of the water increases. Since the recovery of enterococci, with one exception, is low (not more than 10 organisms per 100 ml.), it seems that no conclusions regarding the effect of temperature on the numbers of organisms of this group of bacteria can be made. Figure 3 shows the average coliform and enterococcus values of waters and quahogs from the Captain Kidd station. In December, January, February, March and April the coliform content of quahogs was considerably below the 200 per 100 ml.5 Public Health Service's tentative coliform standard for shellfish other than oysters. For the most part, however, the overlying water during the period is in grossly polluted range, having a coliform content of 700 or more per 100 ml. Quahogs are inactive at temperatures of 5° C. or SOVYDSIINID o JUNLWY3dNIL DO. = Jas oNW ANC OS-8r6l--SHINOW AG GNOd 133 S-! SNOILWLS Y3IWM 5O SYNLVESdDNSLY SANIWA NAW SNDDODIOYI3LNA YWHOSIINOD NVAW roe? || SINAC WW ddV BOVYSILNSD © AYNIWHAdWIL YSLYM -SNDDODOYUSALNA Y31VM - WXOYITI0D Ol ool oool “WOO! 43d SAMWA Nad W SNDD0D0N3INI ¥ WHOsIINOD FAVYSILN3SD 0 SUN IWesdWSL 3350 JON 12 © Ids 0S6| HONOYHLEVGi - SHLNOW Ad GNOd 134 dGIH Nividv5 SOOHVNO SYS1IWM Os SANIWA NdW SNDD09083 1N3 3 WeOSsITOD NVAW € SYN! 4 2, a) WV MIN SNNC AV W odvV UV (aie FOVYOSILNID o SWNIVEIdW 31 SDNOHYNOD SNDDODOY3LN3 YAIWM SNDDODOYZLNI SOOHVND WHOA 10D YH3LWM WxHOsI1059 ?QN39 Nv ie “WW OO! Yad SAN TW NdW SNDD03D083.LN3 SWeOsI 109 lower and it is interesting to note that, during the cold months, the coliform content of these shellfish was significantly low. With the advent of higher temperatures an increase in the coliform and enterococcus content of the quahog was observed. A simultaneous rise and fall of the coliform content and ube) (EAP esaEEre is noted. These data are in agreement with Loosanoff's observations. Using "shell openness" asa measure of activity he found that hibernation, for a majority of quahogs examined, began at 5.0° to 6.0° C. At tempera- tures of 3.9° to 10.0° C. he found there was a correlation with period of openness and the rise in mean temperature. He found no correlation when the temperature of the overlying water was in the range of 11° to 27.9*° C. However, he did find that the animals were open 69 to 90 percent of the times; the highest percentage of openness, 90%, occurred at tempera- tures between 21 and 22° C. These observations are borne out in Figure 3. A rise in temperature and an increase in population is reflected in the coliform and enterococcus densities of water and quahog samples. The maximum numbers of these bacteria occur in June, July and August when Woods Hole has its maximum population. Although the coliform and entero- coccus groups of organisms follow a similar pattern, no constant ratio exists between them. In Figure ), the mean monthly coliform and enterococcus content of waters from Stations 1 through 5 are compared with those from Captain Kidd's. The rise and fall of coliforms at both sampling areas show a Similar pattern. However, the above trend is not apparent in the enterococcus results. The average salinities and coliform and enterococcus numbers from Stations 1 through 5 and Captain Kidd's are presented in Table I. There is no marked variation of salinity during the course of the year. The salinity of the pond is slightly less than that of Vineyard Sound, the outer boundary of Great Harbor. The salinity of Eel Pond has no apparent effect on the bacteriological population. In Figure 5, the effect of population on the coliform and entero- coccus densities in samples from the Captain Kidd station is shown. During the summer months of June, July and August the approximate popu- lation discharging wastes in the immediate area of this station is 1,000, as compared to 75 during the remainder of the year. The popula- tion density increases in an approximate ratio of 13 to 13; the coliform and enterococcus ratios increase only three to one. Discussion and Conclusions The data indicate that when the population contributing pollutions increases, the coliform and enterococcus organisms in quahogs also increase. Quahogs (Venus mercenaria) are quiescent at temperatures of 5°C. or less. The results show that the bacterial content of the 7 258 ON 415@ bel SS oN MAD + anne WW udv UVN ; - f Ls a b : ° a} ) ad ‘ poy oh band (a4 *ABTJ JO COBJANS UO UMOP POXB4S O1TM UeHOTYO Yseou yout-euo fq pezoeqoid s,oTd wo1z pue szotd peqoogjoudun worz ‘sotduss jooj eaenbs uy ‘suelTo oATZwU Jo seTOUSNbery YyQsuUe]--"[ *2T4 g319410ud G3LI3SLOYUdNN “WWOD oe O02 Ol “WUE de Wddv 4O YSEWNAN SWV19 NUMBER OF CLAMS NOV. 18 ,1949 SIZE WHEN PLANTED MAY 11,1950 JUNE 22,1950 AUG. 9, 1950 SErt. co lado NOV. 1,1950 me) 20 30 40 50 mm. Fig. 2.--Length frequencies of planted clams proteoted by one-inch mesh chioken wire staked down on surface of flat. May 11 to November 1 histograms represent one-square-foot samples. Size at planting determined from sample at time of planting, on November 18. 43 Figure 2 illustrates the growth and survival of planted clams under the same small piece of one=inch mesh chicken wire protecting the native clams of Figure 1. The unprotected planted clams completely disappeared in May and June. As in Figure 1, it may be seen that growth was relatively rapid in the spring, but stopped in mid-summer. In fact, there was an apparent shrinkage, a phenomenon that may warrant further investigation. Both native and planted stock were taken in the same samples, hence the numbers of protected clams in Figs. 1 and 2 may be added to show the total numbers of clams per square foot under the chicken wire. The shells of the transplanted clams were more rough and chalky- looking than the relatively smooth native clams's. but thé new growth took _on the smooth appearance of the native stock. Hence they could be readily distinguished from the natives under the same screen. For the same reasons the winter or planting check and the new growth were clearly marked. Measure- ments of lengths at the annulus coincided with the length frequency at plant- ing. Conclusions beth iehed wh eat From the above observations it would seem that during periods of clam scarcity, the young clams.in the open flats will not survive the combined‘ predation of the horseshoe crabs and green crabs. Ciams can be protected from the horseshoe crabs by a fence but only the legal or nearly legal sized clams go deep enough to survive green crab predation. Some large | clams will survive inside a fence, but they will show little or no increase in volume per unit area and hence no economic gain. Under chicken wire, however, both native and transplanted clams will survive well and grow. We have yet to learn what the clam and predator relationships are during periods of clam abundance. Those experiments clearly demonstrate that clams would return in numbers to these flats if it were not for the predators, and so the present scarcity cannot be blamed entirely on overdigging and not at all on changes in climate or unfavorablesoil, except as these changes might affect the abundance of predators. REFER ENCES 1. Medcof, J. C. 199. "Puddling"--a method of feeding by herring gulls. The Auk, Vol. 66, April, 1949, pp. 204-205. 2. Turner, Harry J., Jr. 199. Report on investigations of methods of improving shellfish resources of Massachusetts. Woods Hole Oceano- graphic Inst. Contribution Wo. 510. Pub. by Comm. of Mass. Dec. 31, 199. Lh VARIATIONS IN SIZES AND RATE OF GROWTH OF LAMELLIBRANCH LARVAE OF THE SAME PARENTS Robert R. Marak U. S. Fish & Wildlife Service, Milford, Conn. Abstract The larvae obtained from the eggs of a single female of Venus mercenaria and fertilized with the sperm of a single male of the same species, and a similar culture of the larvae of Mytilus edulis, were grown to metamor- phosis. Examination and measurement of the samples collected at two-day intervals indicated that the larvae originating from the same parents and kept under identical conditions showed great variations in rate of growth, size and time of beginning of setting. hs THE BONNET CARRE SPILLWAY AND THE OYSTER BEDS OF MISSISSIPPI SOUND Gordon Gunter Institute of Marine Science, University of Texas, Port Aransas, Texas The Bonnet Carré Spillway was constructed thirty-three miles above Canal Street of New Orleans by the Crops of Engineers, U. S. Army as a part of the project to control floods in the Mississippi Valley. An Act of Congress directs the Engineers to open the spillway when the water height is 20 feet on the New Orleans flood gauge. The spillway discharges a little more than 250,000 second feet of water into a floodway leading into Lake Pontchartrain and thence out through Lake Borgne to Mississippi Sound, where the flood waters affect oyster beds of the states of Louisiana and Mississippi. Since its completion in 1932 the spillway was opened in 1937, 1945 and 1950. The periods of flow were February )=March 15, March 2h-May 17, and February 11- March 17, respectively. The respective flows in acre feet were 12,),00,000, 244,500,000 and 10,900,000. The 1937 opening was generally conceded to be beneficial and increased crops of oysters, shrimp and fish followed. The 1945 opening did considerable damage to oysters in Mississippi Sound and the Louisiana Marsh, killing them out in proportions ranging from 50 to 100 percent. The 1950 opening caused a maximum mortality of about 15 percent on the inmost beds, lying near the mouth of Lake Borgne, as shown by independent checks by the writer and biologists of the Louisiana Department of Wild Life and Fisheries. Prior to the opening of this spillway the oysters in this whole region had been subjected to low salinity from rainfall in te area and drainage fromthe Pearl River. It was noted that oysters in the low salinity areas survived the Mississippi flood waters better than those in salinities which had previously been higher. No silting on the oyster beds was observed although the muddy riverwater could be traced far out into Chandeleur Sound. As a whole, the 1950 opening was beneficial and it may be said that there is a beneficial aspect to all spill- way openings, even those which cause heavy mortality, because various oyster enemies, such as Thais, are killed out and nutrient salts are brought into the area. The effect of fresh water upon oysters and other marine organisms depend in part upontemperature, the previous salinity to which the animals were subjected, the rapidity of the onslaught of fresh water and the length of its stay. The factors are complex and each opening of the spillway will doubtless differ in certain respects. It is significant that the 195 open- ing, which caused damage, came later in the year, was longer extended, and flowed twice as mach water as the other two. At the present time the Bonnet Carré Spillway is operated purely as a flood control measure. In certain years the waters of Mississippi Sound be- come too saline for oysters and the possibility of operating the spillway so as to allow river water to flow into the floodway in high salinity years is worthy of consideration. This would utilize the spillway positively in a phase of biological engineering and such an operation would doubtless necessi- tate certain changes. The feasibility of utilizing the existing structure for increased benefits should be determined. 46 _ BIOLOGICAL EFFECTS OF BULLRAKING VS. POWER DREDGING ON A ‘ POPULATION OF HARD SHELL CLAMS, VENUS MERCENARIA John B. Glude and Warren S. Landers U. S. Fish and Wildlife Service Narragansett Bay, Rhode Island has supported an intensive commercial fishery for hard shell clams or quahaugs for many years. Hand diggers using tongs or bullrakes are allowed to fish in any unpolluted waters in the state. Power dredges have been restricted to the southern half of the Sakonnet River except for a short time during World War II when additional areas were opened to increase food production. Locations of quahaug fishing areas are shown in Figure l. Controversies continually arise between fishermen using power methods and those who harvest the clams by hand. Rakers and tongers claim that they are using the only methods which do not harm the bottom or destroy young clams. They claim the dredges tear up the bottom, breaking many of the clams which are caught as well as those which go through the bag of the dredge and are left to die. They also believe the dredges bury the small clams so deeply that they are smothered, and that the bottom is sometimes plowed to such an extent that current action causes scouring which prevents a new "set" from surviving. Dredgers claimthey are merely cultivating the bottom and preventing it from becoming too compact for the clams to live. Dredging, they state, really improves the bottom, inducing new sets and increasing the growth rate of those clams which are left. The Division of Fish and Game of the Rhode Island Department of Agri- culture and Conservation has the responsibility of enforcing laws regulat- ing areas which may be fished by dredging as well as the dredging catch limit of 30 bushels per day. Difficulties in enforcing these laws, the dredgers demands for additional areas, and controversies between power and hand diggers resulted in a request by the Division of Fish and Game that the Fish and Wildlife Service investigate the problem. Since this controversy Note.=-=-The authors wish to acknowledge the valuable assistance of Dr. Charles J. Fish in planning the experiment, and the cooperation of the Narragannsett Marine Laboratory in providing equipment and laboratory space. Louis D. Stringer, Fishery Biologist, U. S. Fish and Wildlife Service, prepared most of the illustrations for this paper. Thomas F. Kane, Fishery Aid, U. S. Fish and Wildlife Service, collected much of the field data used in this report. h7 Providence O East GreenwichO4 TEST PLOY Wickford U.S.F.W.S. LaboratoryQ Hand-fished im Power-dredged Polluted THIS Fig. l--Narragansett Bay, R. I. showing location of hard clam fishery and test plot. 48 has been encountered in other states, it was decided that the Service should undertake an experiment to determine the relative biological effect of power dredging and hand raking upon a population of quahaugs. The Division of Fish and Game agreed to close an experimental area and to patrol it to prevent illegal fishing. The Narragansett Marine Labora- tory of the University of Rhode Island agreed to furnish office and labora- tory space and to share the expenses of operating a research boat. The Fish and Wildlife Service agreed to conduct the ee analyze, and publish the results. FISHING METHODS Fishermen bullrake from flat-bottomed skiffs about 16 feet long. The rake, sometimes called a Shinnecock Rake, is about 36 inches wide and has about 30 teeth with 7/8-inch spaces between. The teeth are curved on about a )-inch radius so the rake will dig about 8 inches deep. (Figure 2). The handle or stale is in sections and may be increased to about a 36-foot length for digging in waters 25 feet deep. Although the maximum depth for raking is about O feet, most is done at less than 20 feet. The fisherman pulls the rake through the bottom in a series of short jerks, occasionally bringing it to the surface to empty the catch into the boat, About 1,00 fishermen are licensed in Rhode Island to catch quahaugs by hand digging methods, and about half of these use bullrakes. The maximum catch per day for rakers is about ten 80-pound bushels, but the average is only about four bushels. The price depends upon the size composition of the catch. Rakes will efficiently catch clams as small as 6 mm. length which is just under the legal length of 7-8 mm. (1-1/2-inch width).Therefore, their catch represents fairly well the size composition of clams above 5 mm. A few smaller clams are trapped in the mud, shells and debris brought up by the rake, but most of these pass between the teeth. Rakers prefer to catch "little necks" which range in size from 1-1/2-inch width (7-8 mm. length) to 2-inch width (60 mm. length) since the price for these averages $5.00 to $6.00 per bushel compared to $2.50 to $3.50 per bushel for larger clams. Clams over 2-inch width are known to the fishermen as "mediums", tlarge", or "chowders", although dealers establish additional size groups. Fishermen tong from flat-bottomed boats similar to those used in raking. The tongs are similar to those used for oysters but are modified to dig through the bottom to remove the clams. Stales (Handles) are usually no longer than 15 feet, which allows digging in water about 12 feet deep, although 18 to 20 foot stales are sometimes used in water 15-16 feet deep. Because this type of fishing is less strenuous than bullraking it is the method used by the older fishermen, although most men use tongs where the water is shallow. The tongs catch clams of the same size range as rakes. The maximum catch per fisherman in 80-pound bushels is about five per day, and the average is about three. 49 2.--Bullrakes are used by atout half of Rhode Island's 1,400 "hand" diggers. Fig. 50 The quahaug dredge, sometimes called the "Fall River" or "Nantucket" dredge, consists of an iron frame with a row of teeth spaced 2 inches apart which dig the clams from the bottom. The bag which holds the catch is made of 2=inch iron rings which allow clams under 2=inch width (60 mm. length) to pass through. (Figure 3.) The dredge is used primarily for catching quahaugs of the large or chowder size. Dredge boats which range from 30 to 5 feet in length require masts, booms, winches and powerful engines for dragging the dredge through the bottom. A crew of two is normally required. Boats dredge in water as deep as quahaugs occur and as shallow as the draft of the boat will permit. They can operate in weather which wuld be too rough for hand digging. The daily catch in Rhode Island is limited to 30 bushels per boat, but this amount can only be attained for a short time after the opening of the season inthe southern part of the Sakonnet River. The dredg- ing season is from December 1 to March 31. Rhode Island has about 2) licensed quahaug dredge boats, although at the maximum of the fishery in 1943-1945, 6 boats were engaged. METHODS FOR CONDUCTING THE EXPERIMENT After dredging quahaugs at stations throughout Narragansett Bay we decided that the Highbanks area between Quonset Naval Air Station and Greenwich Bay was suitable for the experiment. The depth of the plot selected is about 20 feet and the bottom is firm sandy mud. Samples dredged with a small mesh liner inside the bag showed quahaugs of all sizes to be present (Figure };). We held meetings with the dredgers and with the hand diggers to dis- cuss the proposed experiment and both groups gave their approval. The Division of Fish and Game then closed the 3-acre test area to commercial fishing. This area included three parts as shown in Figure 5, with the plots to be dredged and bull raked during two summers separated by a con- trol tract. The dredged plot was placed dowmstream in relation to the non-= tidal drift so silt would not be deposited upon the control and bullraked plots as the hand fishermen claimed that silting or scouring was one of the bad effects of dredging. The and digging method chosen for the experiment was bullraking since the depth was too great for tonging. We divided each test plot into-quarters to determine the effect of the fishing upon a new set of clams in relation to the length of time before or after setting. A different arrangement of the quarters was necessary in the two areas since dredging required a long tract, whereas a square plot was more suitable for raking. Unfished corridors 25 feet wide were left on both sides of the contro] plot to prevent overlapping. Bullraking Operations We employed two commercial bullrakers to fish Area B. Each digger sold his catch and in addition received enough remuneration to make his wages equal to those he would have received had he fished wherever he desired. This total wage was based upon catch records from commercial bull- 51 Fig. 3.--Hard clam dredges are operated from 30-45 foot power boats in the southern half of the Sakonnet River. 52 Number of Quahaugs SE ae 40 35 25 20 ° 20 25 30 35 40 45 50 55 60 65 Length of Quahaugs in Millimeters Figs 4.--Size distribution of 640 before experiment. Data 53 quahaugs from test plot May 1949-- smoothed by moving average of 3's. 70 ant 75 HLNOS *90Td 4804 ZuTyer *sa BupZperp jo uetg--°¢ *3tq e6pasg-@d josguoj-3 eyosjjng ~ g =< _———————— 1jI14¥d 1VGIL-NON LAN3Y¥YND IVOGIL 1S3M eek Gis ee as at Se ST 00Ss a a Se ee eS a eee ) 2 aan ae 7 lgz-l <+O0S> 1 +O0S> | +0S> | «0S—> | oz. | <—,00l> | G2. | + 00I— | <00!— me z=! ! 1 ! 1 ! ! ' Oe ae 1 Le) | f 5°} ' Yo 1 ' | ! eat a 1 fo) 3 —- ow ' te} 91 ee If 1 1 | ty | So ' ! to} 1 | J ' 1 1 ; ' —- 1 4 ' i] is’) ' ' a ‘ ) + 1 1 J HLYON 54 rakers in the area. The diggers raked in each quarter in 199 until their individual daily catch fell to a pre-established minimum value of $5.00; then they began a new quarter. In 1950 the catch of larger clams per day began at a lower level than in 1949. Termination of fishing in each quarter could not be based on the minimum catch value used in 199. Bullraking was therefore continued in each quarter for approximately a two-week period. Digging occurred during the periods from July 1) to September 30, 199 and July 5 to September 7, 1950. A biologist was always present to obtain records of catch, size and breakage of clams. Dredging Operations The boat ».Lil-Joy chartered by the Narragansett Marine Laboratory dredged Area D in 1909, using an 8-tooth commercial dredge. In 1950 the Fish and Wildlife Service chartered the boat Marie with a 12-tooth dredge to fish the experimental area. The size and shape of the quarters of the test plot made it impossible to dredge in circles as is done commercially. In the experiment the dredge was dropped at the border of the tract, pulled the length of the quarter, and then lifted clear of the bottom. The boat then turned to make another pass across the area. After several drags the dredge was lifted aboard, the catch removed, counted, and measured, and the breakage recorded. Dredging continued in each quarter until the sanmequantity of clams over 60 mm. in length had been obtained from the corresponding quarter of the bullrake area (Figure 5). Actually, more clams were removed from the bullrake area than from the dredge area since the rake regularly catches clams as small as 5 mm., whereas the minimum size caught efficiently by the dredge is about 60 mm. as shown in figures 9, 10, 11, and 12. The few clams below 60 mm. taken by the dredge were usually caught in the mud, shells and debris and incommercial practice would have been washed through the bag before it was brought aboard. Underwater Photography Woods Hole Oceanographic Institution took underwater photographs of the bottom after digging had been completed in 199. Seven pictures were taken in each quarter of the two test areas and fourteen in the control. The photographs included a total of 2,520 square feet of the bottom, or 2-1/2 percent of the total area of the plot. Unfortunately, due to tech- nical difficulties, many of the pictures were unsatisfactory. Enough were usable, however, to demonstrate that this method could be a practical tool for assessing bottom surface conditions if operational difficulties were overcome. Bottom Samples We obtained bottom samples with a 2-1/2-cubic foot clamshell bucket after fishing had been completed (Figure 6). This bucket samplai an area of five square feet to a great enough depth to remove all of the clams. After lifting the bucket aboard with the winch, the sample was dumped into 55 °m10490q Jo 30eF etwnbs eats seTdues 3ex0Nq 1 [TSYsUBTO--"9 *3ta Re or saaie A as a tia'8 eke sn 56 YR yA uostsvduos 4103 00 efacusts eSpeap Aq [waower sMOYsS SeUTT PTLOS P eJuTUsty BPET 199Te Bore pospoip wors 8 Asaysij abpaip hq joa~oway —— ‘Bulysiy a40jaq uoypDjndog—»s *8,¢ jo e2vtoae Zuysou fq pey_oous 646 [ 04 pesverouy setduws yeH0Nq TLSYsUBTS Bz uo peseg us pog40Pp UseeMZeq SOUeTEZ JTC Sneyenb JO uoTANgysAZsTP SZTS--"6 °3td S4asawiy/iW ul sBnoyono yo y4bua7 09 SS os Se Ov se OF S2 ‘Buiysis 6b 6! 434jO woiojndog °OT emata ol S! Se o¢e ce Ob Sb os SS 09 $9 OL GZ s6noyono j0 saquinn 57 ey ‘Asaysij ab6pasp 4q peyjoous ¥4¥q eSpei1p fq [BAoWeI smoYs SCUTT PTLOS pus pe_zop USeM40q eoUeIES ITC 06 ss 08 GZ “x. > Aq |DAcwaYy 940J9q UoljDj/Ndog *seTduws 4030Nq [leysMeTO COT UO pesey 8,9 JO e2eicAe Zutaou Ssajawisjiw ul Bnoyono yo y4ybua7 s9 09 SS os Sb Ov Se ‘Buys OG6I 4JafjD UOIZOjINdog oe ekieuBTy *SUTUSTS OS6T 10936 wore peSpeup wo1z s¥neyenb jo UOTINGTARZSTPD OZTS=-"OL °3tq Ol SI je) N S2 ° " sBnoyon® 40 saqunn » U2] Ov So 58 Number of Quahaugs 170 Fige 1ll.-- ‘Sieg a at Removal by ~ bullrake fishery Population after 1949 fishing —_——$_ So 55.60 65 70 7S 60 8 20 25 30 35 40 45 Length of Quahaugs In Miiliin..ters Size distribution of quahaugs from bullraked area after 1949 fishing. Difference Setween dotted and solid lines shows removal by bullrake fishery+ Based on 28 clamshell bucket samples increased to 100 for comparison with Figure 12. Data smoothed by moving average of 3's. 59 Population before aq : = ~ 1950 fishing. N a N oO o a o ° a on a (e) Removal by ~ bullrake fishery. Number of Quahaugs <= —_+- - > a 40 th. 5 G 718. 20. 25 30.85.40 a5 50. 55.60 65 70 Length of Quahuugs in Millimeters Fig. 12.--Size distribution of quahaugs from bullraked area after 1950 fishing. Difference between dotted and solid lines shows removal by bullrake fishery. Based on 100 clamshell bucket samples. Data smoothed by moving average of 3's. 60 a box with screen bottom, and the mud washed through with a fire pump. The quahaugs were counted and measured and returned to the water outside of the test plot. Sampling included 28 grabs in each of the three areas in 199 and 100 in each in 1950. Breakage of commercial sized quahaugs Breakage records for dredging are for clams above 60 mm. in length, whereas bullraking records include clams as small as 56 m. TABLE I - Breakage of Commercial Sized Quahaugs by Bullraking and by Dredging in Test Plot. 1949 1950 Bullraking 0.1% 0. 353 Dredging 1.2% 0.7% % Most of breakage caused by handling ## 0.02% gear breakage; balance from handling The gear caused most of the breakage in the dredging operation, whereas in raking the breakage was mostly from handling the catch. The difference in size composition of the catches probably resulted in greater breakage in handling for the hand digging operation since the smaller quahaugs are more fragile. Narragansett Marine Laboratory conducted a population survey of qua-= haugs in Narragansett Bay during the summers of 199 and 1950 using an 8=tooth commercial dredge. Records of this survey show average breakage of 1.0% of the quahaugs in bottoms without rocks and 2.9% in bottoms with rocks. The bottom in our test plot is uniformly sandy mud.without rocks, and the breakage there agrees closely with that reported by the Narragansett Marine Laboratory for similar bottoms. The maximum breakage reported in the survey of the Bay was 21.1% at one station where the bottom was mud with rocks and shells, although at tow other stations having bottoms in the same category no breakage was observed. Breakage of undersized clams We examined borken shells in bottom samples to determine the breakage of clams below the legal size of )7-l\8 mm. length. We found no evidence that this breakage was important in either test area, nor was there evidence of extensive breakage of clams below 60 mm. which had been left in the dredge area. 61 Smothering Fishermen thought that one or both types of fishing might stir up the bottom to such an extent that some clams would be buried beyond the depth at which they could survive. Observations of recently dead clams mde during the bottom sampling showed no evidence of significant mortality which might have been due to smothering. Effect of fishing upon setting and set survival Each experimental plot was divided into quarters which were fished successively during the summer to detect the effect of fishing at different times in relation to setting. Unfortunately, practically no setting of clams occurred in the test plot during 1949 or 1950 and therefore no results were obtained. Bottom sampling in 1949 obtained a total of 7 spat in the control area, 5 in the bullrake area, and 6 in the dredge area. No spat were found in 1950. Effect of fishing upon the physical characteristics of the bottom We examined bottom samples each year for evidence of silting, scouring, and mixing. Surface conditions were practically identical in the test areas and in the control one to three months after fishing. This was substantiated by the underwater photographs. The top one to two inches of soil is uniform- ly yellow mud or silt throughout the test plot. Below this is a 5-6 inch layer of black sandy mud in which the quahaugs live, and below that clay which supports no life. The general appearance of these layers was the same in all three areas in 199 but in the two test areas the clay and sandy=-mud layers were mixed more than in the control. No difference in extent of mix= ing was observed in clamshell bucket samples from the dredged and raked areas. In 1950 the control area showed more mixing of the clay and sandy-mud layers than it had in 1949, although mixing in the fished areas was still more pro- nounced than inthe control. The bullraked area seemed to be softer than the control, whereas the bottom in the dredged area varied in compactness from firm as the control, to soft as the bullraked area. The firm spots were probably places which had been missed by the dredge. The odor of decomposi- tion was greater in the control than in either test area, probably because less mixing occurred there than in the fished areas. Effect on other bottom forms Bottom samples in the control area contained the following species in addition to the quahaug, Venus mercenaria: Common name Species Remarks Amphipod Amoelisca macrocephala Abundant in places. lives in mud tubes. Tube worm Cistenides gouldi (Verrill) This Polychaete was very abundant, 62 Common name Worm Clam worm Worm Softshell clam Little surf clam Starfish Borer or drill Scallop Clam Delicate tellin Boring clam File Yoldia Species Clymenella torquata (Leidy) Nereis virens (Sars) Amphitrite sp. Mya arenaria (Linne) Mulinia lateralis (Say) Asterias forbesi (Desor) Eupleura caudata (Say) Pecten irradians (Lamarck) Nucula proxima Tellina tenera (Say) Petricola pholadiformis (Lamarck) Yoldia limatula (Say) Remarks This Polychaete was very abundant in surface layer. Infrequent. Infrequent. About two dozen up to 2" in length found in clamshell bucket samples. Some recently dead. Many shells, but few live specimens. Some shown in underwater photographs. Common. Some shown in underwater photographs. Abundant. Common. Infrequent. Common. Bottom samples and underwater photographs in the bullraked area indi- cated fewer living forms than the control. worms Cistenides was especially noted. Decrease in the number of tube Bottom samples and underwater photographs in the dredged area showed a decrease in living forms similar to that observed in the bullraked area. On the basis of these observations no difference was noted in the effect of the two fishing methods on bottom forms associated with the quahaugs. Size composition of clams left in plot Figures 9 and 10 show the size composition of the clam population left in the dredged area after fishing. The dotted line in Figure 9 shows the original pouplation in the dredged area as determined by adding those removed 63 by 199 fishing to the population shown by bottom samples after the dredging had been completed. Figures 11 and 12 show similar information for the bull- raked area, The dotted line representing those clams removed by bullraking begins slightly below 5 mm. instead of just under 60 mm. as in the dredge area. This reflects the difference in the size composition of the catch by the two methods. It would be desirable to know whether it. is better to remove only large clams as dredging does, or to remove both large and small clams as raking does. The present experiment, however, does not provide an answer to this question, nor was this an original objective. We know that a spawning stock must be left, but the magnitude of this stock and its size composition has not yet been established. Further information is needed on the annual mor- tality from causes other than man before we can decide if growth from "little neck" to "medium" size will increase the yield sufficiently to offset mortality. These factors are under investigation in Greenwich Bay where quahaugs are fished by hand methods. A similar study in the Sakonnet River could answer these questions for a dredged area. Economic considerations such as the price differential between little necks and mediums would affect a decision onthe best method of harvesting quahaugs, but these factors are beyond the scope of the present investiga- tions. Disappearance of Group "B" in control and in bullraked areas Figures 7 and 8 show the size composition of the population in autum 199 and 1950 in the control area. A great change has occurred in this area even though we removed no clams. The group of clams from 30 to 56 mm. in Figure 7, which we will designate as Group "A", decreased 19.0% by 1950 as determined from clamshell bucket samples. The larger group from 57 to 75 mm. in 1949, which will be known as Group "B", decreased 70.5% by 1950. The combined groups had a loss of 35.7%. The original presence of Group "B" is substantiated by sampling of the test plot in May 199 with a dredge equipped with a liner in the bag to retain small clams. At that time this group ranged from 52 to 70 mn. and comprised 35.3% of the total as shown in Figure 5. In the November 1, 1949 survey (Figure 7), Group "B" had grown to 57-75 mm. and included 30.3% of the total. By November 8, 1950 (Figure 8) it had grown to 6-79 mm. but contributed only 13.)% of the population. Duplicate sampling in 1950 substantiated the disappearance of Group "B". Statistical malyses of the differences in mean number of clams per sample in 1949 and 1950 showed the probability of this difference occurring by chance is only one time in 100. This means there was a real difference in the population of the control area in the two years and that this differ- ence was not due to sampling error. 6h *°8,9 JO e2ea1cav Zuzaow Aq peyjoous 248G °g eANnZTy yt uosTIBdM0O JOJ COT 04 PesBeioUT setTdues yoH0NQ [TL eYysuBe TO gz UY Ppes®g *EPET UUMANY vote [O“QUOD WOLZ sBneyenb Jo UOTANGTAQSTP OZTS-="1 °STy es0sawsi/W uJ SBnoYoONO 4o ysbue7 s6 06 se os SZ oP $9 o9 ss os Sb Ov se oe Td 02 SI ol S fo) s6noyono jo saquan se o8 *8,2 jo uo peseg G2 exeiexs ZutAow Aq peyjoous ¥4¥q *seTdues 4exoNG [[SeYsUBTO OOT *OS6T uuM4Ny Bore [O1QU00 Wors sZneyeNb Jo uoTANqTAZsIp EZTS--*¢s °*3Tq SsazawisIW ul sBnoyono yo yy6ua7q OZ s9 o9 GS os Sb Ov Se o¢ S2 02 s6noyon® 30 saqwnn 66 During this same period Group "B" had largely disappeared from the bullraked area also. Catch measurements of quahaugs bullraked from each of the four quar= ters in 1949 showed the presence of this larger group of quahaugs. Bull- raking was completed September 30, 199. The clamshell bucket census of the bullraked plot was taken December 15, 1949. Grouo "B" was not indicated by this sampling (See solid line Figure 11). Catch measurements of quahaugs bullraked from each of the four quarters during 1950 also indicated the absence of Group "B" which substantiated the results of the 199 clamshell bucket census. The 1950 clamshell bucket census taken September 6-13 also showed no peak for Group "B" (Figure 12). One explanation for the disappearance of Group "B" in both bullraked and control areas is illegal fishing. Catch measurements from quarter )-B had shown that group was present as late as September 30 in the bullraked area. Clamshell bucket sampling in the control area showed Group B was present on November 1, 199. Clamshell bucket samples December 15 in bull- raked area showed group B was absent. If illegal fishing occurred it must have been between November 1 and December 15, 19h9. Reports by shore residents confirm the theory that illegal fishing occurred in the Highbanks area during autum 199. The dotted line in Figure 11 would then indicate a lower original population than actually existed. This line would be low by the amount of clams illegally fished from the sampled area. CONCLUSIONS 1. The objective of the present experiment was to determine the relative biological effects of power dredging as compared with hand digging on a population of quahaugs. The use of the term "biological effects" should be emphasized since we made no attempt to investigate the conomic, sociological, or legal phases of this problem. Therefore, the information presented in this report must not be considered as the final answer to the power vs. hand digger controversy, but rather as information on the biological phase alone. Because of the time, effort and expense involved, it was possible to conduct this experiment in only one location. Care must be taken, therefore, in applying the results to all areas. Likewise, the fishing methods used followed a set pattern necessitated by the size of the test area. Deviation from these fishing methods might also mdify the results. 67 2. Fishing operations during the summers of 1949 and 1950 demonstrated the differences in size composition of the catch. Dredges removed only quahaugs above 60 mn. in length, whereas bullrakes regularly caught those above 5 mm. The effect of this differ- ence on the quahaug population over a long period of time is not known. Productivity studies which are now underway in Greenwich Bay may also provide information on the long range effect of removing both small and large sized quahaugs by hand-digging. 3. Underwater photographs failed to show any difference in the surface condition of the two fished sections of the plot. Both parts appeared similar to the control area. The unsatisfactory nature of many of the pictures prevents their use as a positive criterion for comparing the two fishing methods. h. Bottom samples confirmed the indications of the wderwater photo- graphs that surface appearance of the three areas was similar. Mixing of the sandy-mud layer and the underlying clay was more pronounced in both fished areas than in the control. Fished areas were also softer and had less odor of decomposition than the control. No difference in the above physical characteristics was observed between dredged and bullraked sections. 5. Breakage of commercial sized quahaugs was recorded during the experimental fishing. Bullraking operations broke about 0.1% of the clams above 5 mm. but most of this breakage was from handling. Dredging broke about 1.0% of the clams above 60 mm. in length. Even though dredging breakage was 10 times that of raking, it is still extremely low in this sandy-mud bottom, and is not considered to be important. The observations of Narragansett Marine Laboratory agree with our records for this type of bottom, but list dredge breakage of 2.9% in rocky bottoms. In one instance 21.1% breakage was observed in. a rocky=shelly bottom. 6. Breakage of undersized clams by raking and dredging is shown to be negligible in the sandy-mud of the test plot, but this might not be true in rocky or shelly ground. 7. Observations of recently dead quahaugs made during bottom sampling showed no evidence of significant mrtality which might be due to smothering in either fished area. 68 8. No setting occurred on the test plot during the summers of 19,9 and 1950. Therefore, no observations could be made on the effect of fishing upon setting and set survival. 9. Bottom samples and underwater photographs indicated fewer living bottom forms in the test areas than in the control. Decrease in number of tube worms Cistenides was especially noted. No difference was shown in the effect of dredging and raking on bottom forms associated with the quahaugs. 10. The disappearance of 35.7% of clams in the control area from 199 to 1950 is real as demonstrated by statistical analyses and is not due to sampling errors. A similar disappearance of the larger group of clams occurred in the bullraked section between September 30 and December 15, 199. Natural mortality could not have caused this loss or shells wuld have been found in bottom samples. It is therefore concluded that these clams were removed by illegal fishing. 69 OYSTER CONDITION AFFECTED BY ATTACHED MUSSELS James B. Engle and Charles R. Chapman U. S. Fish and Wildlife Service, Annapolis, Maryland Oyster production has declined materially since the turn of the cen- tury. On the basis of government statistics, the only figures of national scope available, the present yield is about one-third of what it was in the first decade of the 20th century. (Table I). Production in the years prior to 1900 undoubtedly demonstrated exploi- tation of a vast accumulation of a natural resource. Efforts to maintain the high yield pushed the capacity of the natural population beyond its ability to reproduce the stock, hence the decline. Losses, cumulative in the natural population, are more acute as the stock becomes smaller. We must attempt to control the sources of these losses, due in part to predatory and competitory animals, mortalities from changing conditions such as flooding, silting and contamination, and man-caused destruction of bottoms. To some extent we have accomplished a measure of relief in isolated instances. Efforts of the combined research team of Federal, State and private interests have not been sufficient, however, to plug all the holes draining this resource, partly because fingers are too few and we have been mable to investigate all the leaks sufficiently. At the Chesapeake Shellfish Investigations Station we have observed the condition of oysters and the causes of its variation. In Maryland and in many other areas oysters must compete with mussels (Brachiodontus recurvus in Maryland) for food and space. The question in our minds was to what extent this competition affected the condition and therefore the yield of oysters. Oysters with large clumps of mussels attached were poorer than those free : of mussels taken from the same location. Fat oysters produce more pounds of meat than lean ones. The measurement of the difference is the theme of this report. Our observations were conducted in two parts. (1) Oysters were collected at two week intervals over a period of six months from mussel infested oyster bars and divided into two groups, according to the amount of mussels attached. Those heavily covered were used as one group, and those free of mussels as the other. Comparison of these groups proceeded as follows: physical characteristics of size, shape H and cavity volume; meat condition determined by percent solids, percent glycogen on a dry basis; and the condition factor, a ratio between amount of meat and cavity volume. (2) When the preceding observations established the existence of a difference, an experiment was designed to test the permanence of the difference when the attached mussels were removed. The same methods of analysis were used as in (1). 70 Table I. Oyster Production in the United States 1/ 1888 LB 19 million pounds of meats 1892 — 183 " " 8, 18 1908 --- 23h " " oon 1929 --- 152 = " BAe 1937 -—— 95 " " es 1939 --- 93 «Oo " non 190 v= 89" " non 192 --- : a " non 19kh — Woeroc 8 " n om 195 --- 78 inc " non 19,6 -- 80 " non LAMY ci sect im oil ts) helbodd 19,8 oon 78 " " non yf Fishery Statistics of the U. S. and Alaska, Ue Se Fish and Wildlife Service, Washington, D. C. 71 The results of these observations demonstrated the extent of the differences. Physically, oysters with mussels attached were generally larger, more elongate and contained larger shell cavities. The difference in size was not great, about 1.5 centimeters; the difference in cavity volume, also small, was about 12.5 cubic centimeters. The ratio of length to width pointed out a more significant difference and indicated the elonga- tion characteristic of mussel-covered oysters. These oysters had a ratio of width over length of 0.67 while mussel-free oysters had a ratio of O.7S: Elongation was usually caused by a deformity at the bill or posterior end of the oyster away from the main cluster ¢ mussels. Irregularity in shape in itself made this oyster less desirable commercially because of added diffi- culty in shucking. Other detrimental effects of mussels attached to oysters will be discussed later in this paper. Analysis of the meats of these two groups of oysters gave more tangible evidence of the effect of mussels on oysters. Considering first the total solids produced, a difference, constant over the six months, amounted to 12.8 percent. From this we conclude that more meat is produced from mussel- free oysters. As a measure of quality we examined the total glycogen con- tent of these oyster. Glycogen determines the "fatness" of oysters, and in these two groups the difference was 11.1 percent favoring the mussel-free oysters. From this we say that mussel-covered oysters have a lower nutri- tive value. A third index of meat value, the "condition factor", is of direct interest to producers because it shows the variation in yield of meats per unit of shell stock. Mussel-free oysters on this basis were 27.5 percent better than those with mussels attached. (Table II). To indicate the effect of mussel masses on the condition of oyster meats may, at first glance, appear to be more academic than practical. We went a step further and examined oysters from which mussels were removed to see how permanent the differences were. Oysters with attached mussels were collected, the mussels removed and a series of observations made to see if the oysters thus freed of mussels could recover the advantage they lost over those originally free of mussels. The cleaned oysters were put overboard in trays with controls of mussel-free animals. The two groups were periodically checked in the same manner as those in the field study discussed earlier in this report. The results of this experiment are as follows: (1) No material change occurred in the shape, size or cavity volume of the oysters during the six week period. (2) In the condition of the meats, however, progressive changes were noted. Oysters with attached mussels at the beginning of the period had a percent solids of 13.38 and those free of mussels 14.58. At the end of two weeks there was no improvement following the removal of mussels. But at the end of four weeks the two groups of oysters showed about the same percent solids or 16.77 for oysters with mussels removed and 16.63 for oysters free of mussels. After six weeks, at the end of the experiment, 12 9L°2 VW JIOPORY UOTYTPUOH sousTeTsIq esereay LO°€ = UEs0dh4[TD qUeoteg soUeTeT JIG esereay O2°? f= SPTLOG JUedteg soUeTeTJTIG eser1eaAy 2 i AYTACD TTeusg sousresjiq eseroay TO° OL teed OL"ee eye 62 69°LT €T°St gre o°et eSeIeAY 59°65 T9°L T2° Sz 19°22 10° 02 LOT ET g°6r TS/g2/s S*6 eT"9 Ze*le Oz° TE 90° LT oL°€L g°ze Gros TS/TL/S eng S8°S GL*0€ Or°L2 gs° TL ge°eL SE g° Li ts/9t/1 S€*Or Sed. gle LE LL?Ce 2°ot 29° TL o*ge 2°8t] ts/s/€ Ort €g°g LE*SE LO EE TL? Qt TH LT 9°se 0° 6' 19/62/T Tg*Ot €o°g €o* z€ 06°22 99°6T HLT g°te ge lt 1S/2/T E0°OT 6L°9 Zeece 19°62 €S°LT Te°Tt T° 2€ 9°07 0$/TT/2t S[Tessni[ sSpessmy Tessny splessnit STessn sToessniq STessnuil spessny a4e¢ go YpEM go Ug Tan go yy Pn fo YP Tae 398a— padenod eet pezteacd Self persa0o eetz pateaod s1394sk9Q —-s.e4sh0 sieyskp_ _saaqgsko szeyshQ —s.toqsfo szeqsfo — s.aqskO Ioyoeg UoOTATpUdD uaesooAT) Juseoreg SpTLOS 4ueoreg JO uoT}TpucD Apnys pretd *it eTqeL °09 UT AQTAPD [TLeUS 73 CONDITION OF FIECD 207 STEERS 40 ol Ol oO oO PERCENT GLYCOGEN Le] oO N (e) CONDITION FACTOR PERCENT SOLIDS ely a =O Pid (Cm = _,/ PERCENT GLYCOGEN CONDITION FACTOR & FREE OF MUSSELS O MUSSEL COVERED DEG. JAN. FEBS. 74 = PERCENT SOLIDS D oysters with mussels removed showed a percent solids of 17.80 and the control 17.71. Oysters in the field during this same period showed a percent solids at the start of 13.38, after fourweeks 13.70, and at the close of the experimental period of six weeks 16.1). These figures are compared at the same time with mussel-free oysters in the field and give 14.58, 17.06 and 20.0) respectively, indicating no relative difference occurred in the field. With the experimental groups the percent glycogen also showed a trend Similar to percent solids. At the beginning of the period the percent glycogen of oysters with mussels removed was 27.10 and of oysters originally free of mussels 30.75. Two weeks later the percent glycogen was 35.9) and 1.25 respectively. At fourweeks the percent glycogen was 33.76 and 35.25, and at six weeks when the experiment was concluded the percent glycogen was 25.41 and 25.61. Oysters in the field collected and analyzed at the same intervals maintained the same difference in percent glycogen from the start to the end of the experimental period. The improvement in the condition of the meats was again demonstrated by the condition factor index. The difference existing at the start of the experimental period was 2.58; in two weeks no improvement occurred, the difference in C. F. being 3.91; at four weeks the difference was reduced to 1.36; and at the end of the sixth week it was further reduced to 1.09. In the field, condition factors for the above intervals of examination main= tained the same difference from start to finish of about 2.76 = plus or minus - 0.5 (Table III). SUMMARY These two series of observations, one on the oysters in the field exposed to a natural condition where they compete with mussels and the other on a group of oysters where this competition has been removed have been analyzed to show the effect of the competition on the oysters. The results are summarized as follows: 1. Oysters covered with mussels have poorer meats than those free of mussels. 2. When mussels are removed from these oysters they recover in four weeks to the same condition of percent solids and percent glycogen as the oysters originally free of mussels. 3. Mussel-covered oysters in the field have 27.5 percent less meat per animal than those free of mussels on the basis of condition factor. h. In the experiment this difference dropped to 10 percent in six weeks with the trend still approaching equality. 75 S9°6 T9*L T2°Sz_ — lor22 To*oz = TL°9T qth g°6t TS/92/S St°6 €t°9 2 a 202 ae D0°lt- «OL EE g°ze S°0S TS/tT/S Eteg S9°S SOG Sod QS*tt = QE° ET TSE grLn TS/9T/N SsTessau, spessniy S[TessnylT stTessny STessny spessnif STessnyl sTessni{ s7eq go UqTa go UTM go UTM go qqcm. eety pazeaod eeIf pezeaod Geely pezeasoco Self pereaod s104sfo $.104S£0 s§.167.sf9 sreysko s.10ysf9 s104Sf0 $.107.sf09 sireysfo 10498 UOTYTpUOD uaesooATD) quedreg SPTTOS qusd1ed *o90 ut AAtTAed TLeus Si10yskO JO uoTyTpu0g Apr4S PTeta TE° OL 19 T Og* ZT He*or <=. 16% Gece = 9 LEE €9°9T ~—s LL 9T S°6€ ot TS/*t/S 95°93 soe Seth = 6"SE OO°9T 3 =—s«O EP HIT. €°6E O°€S TS/0€/11 eng 59° BISOE OL" Le gst = GEV ET (°SE€ get 1S/9T/" sTessnyy peaouer STessn] peaouet sTessny, peAaocues s[Tessny, peaouer o1eC jO eety sTessnit jo seIy sTessni{ jo eelg spessni jo deif sTessniq ATTeuUTETIO U4tm STTeutst10 UTM ATTeUTSTIO ugTM ATL EULSTIO UdtM s194sfo sz0eysfQ szeayisip sueqsk szeysfp saeysfkO steqyskp sueqsko IOPORT UOTATPUOD UasookT) juaeoteg SPTLOS queozeg *90 uT AQTaed [TTeUS STessnj] JO peueetTD sueyshO UTM JuoUTIe UOT YTpUuoD III elaeL 76 CONDITION OF EXPERIMENTAL OYSTERS PERCENT GLYCOGEN CONDITION PERCENT SOLIDS FACTOR 45 40 35 re ci if PERCENT GLYCOGEN 25 ie) 2 past _27” CONDITION "> --o FACTOR 18 17 16 PERCENT rs SOLIDS 15 / / 7 / Yo 14 ’ OQ ORIGINALLY FREE OF MUSSELS 13 O MUSSELS REMOVED 16 30 19 28 APRIL MAY 17 5. Mussel-covered oysters tend to be irregular in shape and there- fore more difficult to shuck. All investigators should have the prerogative of speculation based on the results of experiments and observations. We feel that the yield in pounds or pints of oyster meats may be increased in a region like Maryland, where many acres of oyster bottom are heavily infested with mussels. This increase is possible without increasing the number of oysters present if the mussels are destroyed in time on the beds. We demonstrated this in our experi- ments. Methods and equipment for accomplishing the destruction of mussels are in our plans and on our drawing boards at the present time, and the attempt to demonstrate the economic feasibility in the field is on our pro- gram of research for the near future. 78 SOME FACTORS INFLUENCING STEAM YIELDS IN OYSTERS Francis X. Lueth Alabama Marine Laboratory, Coden, Alabama Not all oysters taken from the waters of our coasts are eaten raw at some osyter bar or served in some exclusive rest: urant "a la Rocker- feller". There are many oysters that are steamed and canned for use - usually at some inland point where few persons have ever tasted the delightful flavor of a really fresh oyster. Some recent figures of the U. S. Fish and Wildlife Service reveal that over 3,000,000 pounds of steamed oyster-meats were canned on the Gulf Coast during the 1950-51 canning season. Alabama factories took more than twice as many barrels of oysters than the forty-odd raw shucking houses during the past season. Any factory or factories that handle as high a percentage of a harvest of a natural resource as do the oyster factories of Alabama certainly have a great influence on that harvest. Too, the harvest, in this case the oyster, affects greatly the profits of the factories and thus the economics of the localities in which the factories are located. A study this past winter and early spring was devoted to the kind, size and value of steam oysters in Alabama. The three factories that operated in our state this past season assisted in the study by giving oysters and confidential reports on daily or load yields. Assistance from McPhillips Packing Cooperation, Graham's Seafood, and Mexican-Gulf Seafoods are gratefully acknowledged by this biologist. It was evident from observations made in 1950 that the steam yield varied in the number of cans of meat per barrel of oysters. It was hoped that the study now being reported might throw some light on the causes of variance. In all, thirty samples (usually of one-tenth barrel) were taken from the factories and tested. These samples were weighed, all or most of the oysters measured, and either shucked raw or steamed in a pressure cooker where the pressure was raised to fifteen pounds and then left for five or more minutes. (The factories usually steam their oysters at fif- teen pounds for five minutes.) Notes were made as to the amount of loose shell in each sample and some samples were culled until the oysters were singles and then the amount of culled waste was weighed. Computations were later made using a barrel weight of 225 pounds. When it was necessary to convert raw weights to steam weights the conversion factor .56 was used. Dry solids were obtained by drying either the raw meat cr the steamed meat in a constant temperature oven for three days at a temperature of 80° C. 19 Dry solids were based on only five or ten oysters from the original sample. Laboratory yields were checked against the factory yield for the same day, and if possible for the same load from which the sample came. Laboratory samples yielded from 5.7 pounds to 10.) pounds of steamed meats per barrel of shell stock. The later yield was that of a selected sample of single medium sized oysters. The average yield of non-selected samples was 7.6 pounds of steamed meats per barrel of shell stock. The factory yields on loads or even days are considered as confiden- tial information. However, these yields varied from just below 5.7 pounds to a little better than 8.2 pounds of steamed meats per barrel of shell stock. The yields of only a few loads ever exceeded, or ever approached, eight pounds. Factory yields, as an average, were from 8% to 15% less than laboratory yields. There were considerable differences in the weights of the barrels of shell stock that were purchased by the factories. Purchased at identical prices were oysters that weighed as little as 186 pounds to as much as 2)8 pounds per barrel. The factory buying the larger barrel got 32% more for its money than when it purchased the smaller barrel. This however, is not so important as it might at first appear. Buying in large quantities the factories averaged out the daily differences. The average barrel of shell stock, this past season weighed 228 pounds. Over 50% of the purchases were of shell stock that weighed within ten pounds of this figure. There was a definite tendency this past season for the weight of the average barrel of shell stock to increase slightly as the season progressed. The following is based on observation only; but it is believed to be of some significance. The lighter barrel of shell stock contained oysters that were "bunchy" with from five to many oysters in a cluster. The heavier samples contained a high percentage of singles. The percentage of Single oysters increased as the season progressed. Laboratory yields, when corrected to a 225 pound barrel of shell stock, still varied from 6.) to 9.l, pounds of steamed meats per barrel of shell stock. The average was again 7.6 pounds per barrel. Records were kept on twenty of the samples on how much of the original weight was loose shell (or boxes) and of no value to the factory. Surpris- ingly to the biologist, this varied from only 5% to 9% of the weight of the shell stock. The amount of waste in loose shell was relatively constant throughout the season and apparently was a minor factor in differences in yields. Only five samples were inspected for "attached waste" a name given to the dead shells, mussels, and other waste directly attached to the oyster. To obtain this, all oysters were culled to singles and the waste weighed. 80 The varience was from 6% to 17% of the original weight. This could, and probably did, affect factory yields. There were indications that the "bunchy" oysters ahd the greatest amount of attached waste. As previously mentioned, laboratory yields were consistently better than those of the factory. In the laboratory, at first all oysters were shucked out. Later only those over forty millimeters from hinge across the greatest distance of shell were shucked out. On two samples the smaller oysters were shucked separately and the increase in weight was only 2%. In order to determine, if possible, where the differences in the laboratory and factory yields might be, the shell piles of the factories were examined on six different occasions. From 10% to 20% of the oysters were being discarded with the meats still attached to the shell. These oysters, however, were of such size that only % to 12% of the weight of the oyster meats were being discarded. It was quite evident that when- ever the oysters were of a regular size there was less waste thanwhen the oysters were of many sizes. This held true even if the oysters were quite small. Where the oysters were in bunches, the number of discarded meats was also higher. Shuckers used a few oysters from the 1-50 millimeter sisze group, over 75% of the oysters from the 51-60 millimeter size group and only a few oysters that measured over 61 millimeters were discarded. One factory operator informed the biologist, and it was checked on one occasion, that there was a difference in the mount of wasted meats according to the time of day the oysters were shucked. On the day in question about l% of the weight of meats was being discarded in the early morning hours, but just before closing time 10% of the weight of meats was discarded. The factory yields on separate loads brought in the same day varied from less than one-half vound to over one pound of meats per barrel of steam stock. These variances are the ones that can be explained by the preceding information. These differences are the ones that can be partially overcome and the lower yields increased by closer supervision of the buy- ing and shucking of the shell stock. The differences in pounds of steam meats per barrel of shell stock that occur over a period of time, particularly when there is a definite tendency for an increase in yield as the season progresses are not so easily explained. The average barrel weight increased slightly and there was apparently less attached waste as the number of single oysters increased; but the average yield in March was still somewhat better than the yield in January if these were the only factors involved. It is this difference that was next tested = and tested rather unsuccessfully. Although the factories steam their oysters at nearly the same inter- 81 val throughout the season, it was decided to first see what effect steam- ing had on yield. Three samples were tested by placing ten pounds of shell stock into pressure cookers and cooking for five, ten and fifteen minutes each at fifteen pounds pressure. There was little or no difference inthe hield providing the full eye was shucked from each oyster. This was defi- nitely harder to do if the oyster had been overcooked = as it had been when steamed the longer period. Measurement of a high percentage of the oysters in the samples revealed that a large number of small oysters were being purchased and shucked out. In fact, when measured from the hinge across the greatest distance of the shell, over 75% of the oysters purchased were less than three inches long. The average length varied only a small amount during the season with more uniform sizes being taken in March and April (due apparently to a depletion of the larger oysters) than in late January and February. In order to determine the differences in yield due to the size of the oyster, a number of oysters were collected, culled into singles, placed in a tank at the laboratory from five to ten days, and then, after conditioning, they were measured and placed into ten millimeter size groups. They were then measured in a 1/0 barrel container, weighed to the nearest el pound and then opened as raw stock. The shucked oysters were then drained and weighed. Five oysters from each group were then dried at 80° C. for three days. The following tabulations are based on the bulk and not upon the weight of the shell stock. Total sample equaled only one- fourth barrel. TABLE 1 OYSTER SIZE = YIELD EXPERIMENT Size of Weight of Number of Weight of Weight of Oysters Barrel Oysters in Shucked Dry Solid MM Pounds Barrel Oyster Pounds Pounds ho-h9 26h 3600 19.3 3a 50-59 26) 2560 20 3.2 60-69 256 1600 20.8 3.0 70-79 2hh 1320 pe | 30h 80-89 20 12)0 21.8 3.8 90-99 228 80 Ppa Biel 100-109 252 80 P38 Be7 From this, even though the sample was small, it appears that there is a little difference in yield, within the limits examined, that is caused by size. This perhaps needs further study for despite the heavier weight of 82 the shell stock of the smaller oysters, the yield (in dry solids at least) was no greater than from larger oysters. It is possible that whatever gain in yield made by the smaller oysters due to an increase in the weight of the shell stock is lost because of the better quality of the larger oyster. It is the=problem of "quality" that still remains a mystery. Trying to find a constant on which to determine this quality for steam stock is still a major problem. Volume or weight of raw shucked oysters did not vary in proportion to the weight of steamed meats. Early in the season the weight of the steamed meats averaged .56 the weight of the raw meats. This was used for a con= version factor; but late in the season was found to be erroneous when the average of the steamed meats weighed .6) times the weight of the raw meats. The ratio of the weight of the dry solids to the weight of drained raw meats varied considerably. The weight of the dry solids was from 11.9% to 18.8% (average 15.0%) of the weight of the drained raw meats. Even the ratio of the weight of the dry solids to the weight of steamed meats varied from 22.0% to 28.)% with an average of 25.2%. Factory men explained the latter by stating that during a portion of the year (which corresponded to the time when the percentage of dry solids is high) that they do not put the full measure of steamed meats into the can. The oysters, during this part of the season, absorb water after being placed in the can and being further processed. When opened these cans con- tain oysters whose drained meats weigh the number of ounces marked on the can. Late in the season the factories must put in the full measure so that they will "cut" the required weight the following morning. It is en- tirely possible, and even probable, that the factories are packing a pro- duct where the dry solids remain constant, and that the laboratory yields varied because the processing was not continued. There appeared to be a direct correlation between the salinity of the raw oyster liquor and the percentage of dry solids in the steamed meats. The lower the salinity, the higher the percentage of dry solids. The roles of glycogen content, ratio of cavity volume to dry solids, and the amount of sex products in the oyster were not studied. Certainly in these factors are some fertile fields for study. Conclusions : It was possible to evaluate the roles of the size of the barrel, per- centage of waste in a barrel, and percentage of wasted meats in shucking as factors that influence the yield in steam oysters. Time of steaming plays a minor role in the yield of steamed oysters, except that overcooking may increase waste. 83 Size of the shell stock apparently plays a minor role in yield of steam stock. Whatever gains there might be because of increased shell stock weight per barrel in small oysters is apparently overcome by an increased quality of the larger oysters. The role of quality as it affects steam yields could not be evaluated because no constant was found. 8h, STUDIES OF THE NORTH CAROLINA CLAM INDUSTRY A. F. Chestnut Institute of Fisheries Research, University of North Carolina Morehead City, North Carolina Clams have been harvested in commercial quantities from North Carolina since about 1880. A review of the available catch statistics for North Carolina shows an unusually high production of 1,175,000 pounds of clams as early as 1902. This production is attriouted to the activities of a clam plant established at Ocracoke, on the outer banks, in 1898 by Mr. J. H. Doxsee who came to North Carolina from Islip, Long Island, New York. Several older residents of Ocracoke Island who worked in the plant report that the clams were packed as clam chowder, whole clams and clam juice. The shipments were labeled as "quahaugs" with the origin as Islip, Long Island, New York. Later, the plant was moved to the mainland at SeaLevel, North Carolina and finally was moved to the west coast of Florida in the vicinity of Marco, Florida. Statistics are not available during the period that the Doxsee plant was in operation in North Carolina, except for the year 1902, but this is reputed to be the period of greatest clam production in North Carolina. There is little information pertaining to clams in North Carolina. In 19h9, the Institute of Fisheries Research began studies on the biology of clams, the operations of the industry, population studies and collec- tions of catch statistics. This information is to be used in developing a sound program of management. This discussion is limited primarily to the activities of the industry. Production of clams has fluctuated considerably through the years as indicated by the statistics in Table I. From the available informa- tion, the fluctuations in production reflect the lack of development of a steady market rather than a decrease in supply of clams. The clam industry at present is concentrated im Core Sound between Harkers Island and the vicinity of Drum Inlet. Commercial quantities of clams are gathered from Bogue Sound, Ocracoke Inlet, Brunswick County and from the sounds of Pender and Onslow counties. The clams are found in the sounds with the greatest concentrations found along the outer banks and in the areas coming under the influence of the numerous inlets. The bulk of the clam population is composed of the species Venus mercenaria and the variety Venus mercenaria notata. Some Venus campechiensis are found in the catches from the immediate areas of Drum and Barden inlets of Core Sound. Clams are gathered by hand with rakes in the shallow waters and, to a limited extent, with tongs in the deeper waters up to fifteen feet. Since December 199, the bulk of the commercial clams has been dredged in Core Sound, utilizing a method developed by some local clammers, 85 TABLE I HARD CLAM PRODUCTION, NORTH CAROLINA, 1880 to 1950 Year Pounds# Value 1880 310,000 $ --- 1887 78,000 ea ic oe 1888 148,000 6,150 1889 155,000 8,265 1890 226,000 12,090 1897 938,000 53,703 1902 1,175,000 86,662 1908 726,000 82,000 1918 197 ,000 46,598 1923 263,000 6h,,06) 1927 315,000 70,90 1928 32,000 61,168 1929 380,000 59, 83h 1930 317 ,000 0, 680 1931 332,000 30,775 1932 261,000 17,278 193k 338 ,000 33, 6h7 1936 839,000 75, 326 1937 430,000 3h, 343 1938 358,000 27,756 1939 628,000 50,360 190 530, 000 5,067 191 1,011, 613# --- 192 897 , 612# “es 1943 519, 381# i94 19h) 320,757# --- 1945 502,000 151,47 196 208 , 730# ce) 197 297 , 2034 ne: 19,8 203, 2834 iit 19h9 163, 802# ig 1950 1,83, 863# ings *Production figures of edible portions from Federal statistics except as noted. #Production figures based on tax receipts to N. C. Division of Commercial Fisheries, bushels converted to U. S. Standard Bushels and converted to pounds by factor of 7.65 pounds per bushel. 66 The dredging method employes a principle of loosening and washing the sand from around the clams with the propellor wash of the boat. Ex- tensive sand shoals are found in this sound. Small boats are anchored by the bow with a length of cable to an iron stake driven into the bottom. A swivel is used at the end of the line secured to the iron stake to avoid fouling the line. As the boat circles about the stake, the engine is turned up to the maximum revolutions to create a strong current of water with the propellor. A set of shrimp trawl doors, tied together with a short length of chain, are towed from the stern to slow the boat to a proper dredging speed. The stern of the boat is weighted with sand bags or water barrels to direct the propellor wash toward the bottom. An ordinary oyster dredge with a four or five foot tooth bar is used to gather the clams. As the clams are removed, the radius of the circle is increased by lengthening the cable from the bow to the stake. Dredging by this method is limited to shallow depths up to five or six feet, depending upon the draft of the boat. The action of the propellor cuts a furrow in the bottom from eighteen to wenty-four inches wide and from eight to ten inches deep. Dredge hauls of fifteen or twenty=minute intervals yield about a hundred pounds of clams, or approximately one bushel, from areas where clams are concentrated. Daily catches by small boats vary from 1,500 to more than 10,000 pounds, with an average catch of about 3,500 or ),000 pounds. Raking by hand yields from 300 to 1,000 pounds per day per individual. However, the dredging method involves an initial capital outlay for a boat and equipment which is sub-= jected to rigorous treatment. Between forty and fifty gallons of gasoline are consumed during a day of dredging. The number of clammers using the dredging method has increased from about thirty-five during the 199-50 season to approximately 85 during the 1950-51 season. Although clamming is permitted through the year, the clammers generally prefer to engage in shrimping, long-haul seining and oyster dredging and resort to clamming when the other fishing activities are at a minimum. Thus, clamming activi- ties are a peak from December to May. Hand raking for clams occurs through- out the year, but the greatest number of rakers work during the months when water temperatures permit wading. Weather conditions limit the number of days that dredgers work. During January, February and March, 1951 the dredgers averaged ten working days per month, In December, 1950 and April, 1951 the average number of working days was fifteen days per month. The composition of the catches by the dredgers showed that the bulk of the clams were of chowder size. The percentage of different size groups varies with the locality, but on the average a daily catch of ),000 pounds contained five percent cherry=-stone and little=neck clams. Examinations of catches aboard the dredge boats showed that breakage varied from two to six percent. A greater percent of breakage was found in some isolated cases when dredgers attempted to conserve on gasoline consumption by decreasing the speed of the engine. The result was that the bottom was not loosened sufficiently and the clams not exposed to facilitate gatherirg with the short teeth of the oyster dredge. 27 The price received by the clammers for their catch has increased over the past two years. In June, 1949 the clammers received orecent per pound, By January, 1950 the price had increased to one and one-half cents per pound and by January, 1951 the price was two cents per pound. The catch is sold as caught with no attempt made by the clammers to grade their clams. The dealers usually sort the clams into two or three sizes; chowders, cherry-stones and/or little-necks. Since about 190, the bulk of the clams from Core Sound has been shipped as frozen, fresh-shucked clams destined for the manufacture of clam chowder. A substantial quantity of small clams, cherry=stones and little-neck grades, are shipped to mid-western markets in the shell. Dur- ing the past two years an increased quantity of mixed sizes of clams has been shipped in the shell to dealers in Virginia, Maryland and further north. There have been no attempts made to cultivate clams in North Carolina. A few dealers have leased small areas where clams are stored until a favorable market develops. This is generally limited to holding the smaller sizes of clams. The potentialities for the development of a substantial clam industry appear to be promising in North Carolina. Perhaps the most pressing need is the development of harvesting methods to insure a steady supply of clams. (eo) [Se) A SOFT CLAM POPULATION CENSUS IN SAGADAHOC BAY, MAINE 19h9-'50-'51 Harlan S. Spear, Fishery Biologist U. S. Fish and Wildlife Service, Boothbay Harbor, Me. INTRODUCTION The Clam Investigations started population studies of the soft clan, Mya arenaria, in 199. The objective of these studies is to determine the productivity of a flat in terms of the number of bushels of clams which can be removed each year without endangering the supply. Preliminary estimates of total population, growth rate and ultimate size, which mst be made to establish productivity, are discussed in this paper. Sagadahoc Bay is located on the southern tip of Georgetown Island, Maine facing the open ocean. This bay was chosen because the center has a sand soil and the edge a muddy soil with a small amount of sand mixed with mud, the two types of flats common along the coast of Maine. At low tide Sagadahoc Bay has exposed flats three-quarters of a mile long and one-half mile wide which are dug commercially for soft clams. Methods (Census) To determine the population of clams in the bay, we dug two-foot- square sample plots which were distributed over the entire area. For each year's census we dug the first sample at a random spot in the bay and established a grid of lines from the location of the first sample. With the aid of a hand compass, we ran the grid lines approximately north to south and east to west, and located sample plots at the intersections of the grid lines over the entire area. Distances in the grid system were paced. In 199 the sample plots were dug and the clams picked out and counted. However, we suspected that many of the 0-25 mm. clams were overlooked in some of the plots. In 1950 the sampling method was expanded by the washing out of a 6" x 6" x 2" sub-sample with a fine mesh screen. This gave us a more accurate count of the actual number of clams in the sample. This method Notes=-- Field work fus this papers was done by John B. Glude, Richard E. Tiller, Walter R. Welch, Gareth W. Coffin and the writer. The outline of Sagadahoc Bay in Figures l- is based on a survey by Jr. W. H. Bradley, Chief Geologist of the U. S. Department of the Interior Geological Survey. 89 is now being carried out. In the laboratory, we measured and recorded lengths of all clams found in the sample plots, Estimates of total populations were calcu- lated from the mean number of clams per square foot and the size of the area surveyed. Volumes in bushels were estimated for the 26=50mm. size group and the over=50 mm. size group.— At the beginning of the study the entire bay was sampled to determine the productive areas. Small unproductive sections are outside the workable areas but are sampled for the annual census. To make workable sections of the productive flats, we divided the bay into three areas based on soil types (see Figure 1). Area A and Area B, widely separated, have mad soils; Area C, in the center of the bay, a sand soil. A survey of the three areas shows the size of each: Area A has 2,)59,000 square feet; Area B, 825,000, and Area C, ),484,000. Results (Census) The 1949 census was started in January and completed in March. We established north to south grid lines 150 feet apart, and east to west grid lines 300 feet apart. Plots are located at the intersections of the grid lines (see Figure 2). Area A had a total of 9) square feet sampled and a mean number of 12.7 clams per square foot; Area B, 3) square feet sampled and 11.7 clams per square foots Area C, 150 square feet sampled and 1.1 clams per square foot. Population estimates for the three areas were 31,336,000, 10,220,000 and ,962,000 clams respectively, or a total of 46,518,000 clams in 199. Estimated number of bushels in the over-50mm. size group were: 2,599 bushels in Area A, 858 in Area B, and 6,020 in Area C, or a total of 9,477 bushels of clams over=50mm. (see Table I and Figure 7). The 1950 census was started in April and completed in May. Grid lines in this census varied from area to area because analysis of the first census indicated that more samples than necessary had been taken in Area A and Area B, and too few had been taken in Area C. We located plots at the inter-sections of the grid lines (see Figure 3). Area A had a total of 48 square feet sampled and a mean number of 13.5 clams per square foot; Area B, 6 square feet sampled and 17.9 clams per square foot; Area C, 46 square feet sampled and 1.0 clams per square foot. Population estimates for the three areas were 33,19),000, 15,677,000 and 4,483,000 clams respectively, or a total of 53,354,000 clams in 1950. Estimated number of bushels in the over-50mm. size group were: 2,803 bushels in Area A, 1,111 in Area B and ,006 in Area C, or a total of 7,920 bushels of clams over-50 mm. (See Table II and Figure 7). aly For the table of clam volume, see Belling (1930). 90 SAGADAHOC BAY TIDAL FLAT GEORGETOWN MAINE Oo 0 200 400 FIGURE |: POPULATION CENSUS AREAS BASED ON SOIL TYPES. AREA °c® (SAND) AREA °B° (MUD) 91 SAGADAHOC BAY TIDAL FLAT GEORGETOWN, MAINE p 9 190 290 400 _s90___ 690 rr = uN 0 47 © ws rs i O 26 \) O 28) = 46) 236 Oe \ UO) pecs \ 67 SO) = — Oo 80 Ye} FIGURE 2: LOCATION OF PLOTS 7 2 re) FOR 1949 CENSUS. ; © 2a 6 Bi (oe) 26) O 420 AREA °A* nO 0 i> Oe 6) "© S26) 226 205 326) : 1 @) 74 ee O LG) 07, O WS) oO) MIO) re) AREA “C° nop 109 toe, '%D 1238 WG: o) 12 Ds) 92 LL7*6 L60°L 91S *947 TrL§s szesse 677*e | sTeqOL 0z0*9 9¢7 296 4 e7ee $97 T 6471 ETE 19) 8S3 ege*e Ooze ‘OT 6ce*tT slL‘s €OT U Bad Oe q 665 °Z 686 “7 9€€e°TE 4G60°7 $30°Sz EA bo haat v dnoty) ezts anoty) azts spuesnoyy *41 *bS dog Poly "WU OS—~1eA0 °uUll OS—-97 Te30L sueTO ON *ng °oN eng °on spuesnoy}) sueTO *ON TeqoL ueeyl , sdnowt) ezts 61€ 64€ ‘T €6 818 °L Ble =: STeFOL ett 64 S TY OST pues A) es THE q Sle TE pay a SST 656 "8 657°Z 46 POT v i *wu °4d *bS QOOOT UT peTawes L Body OS—12A0 0$-9z Sz=0 peseAmg 49°47 azenbs TEOS SoTdues Ut sueTD °ON eoly TeqoL dno) ezts eee ooo EEESE—EEEEEEEEE—_——ES 6%76T eg ooyepeses SNVIO La0S AO SLVALLSH NOLLVINdOd - I WIdVL 93 SAGADAHOC BAY TIDAL FLAT GEORGETOWN, MAINE 0 100 200 400 600 @00 FT VSS SS SSS FIGURE 3: LOCATION OF PLOTS FOR 1950 CENSUS. iG AREA “A° 94 026 *L B slee-& NGES ES T6556 096*L2 €T8*ST sTeqod ST fae ee ee OS SD ee Fa eS eee FF a Oe Py 900° 7 9cE est’? Tho. 6 240° T 46 O°T 3 Te “T 940 *z LL9* ST. 69L°T GTS *L €6€'9 6°LT q 608 ‘z 616 *47 HOTS EE 80s *47 €9E°6T €26°6 S°€T ¥ NotI azts dnor) 32TtS spuesnoyy *uml Q¢ 1eA0 *ul OS-9Z Te490L sueTO *ON eng °ON *ng °OoN sueTO *ON TeqOL west sdnoty oezts $Tz 43h 61S gts‘. CEL STeqIOL si US TL yi ret" 4 ge pues r0) €6 GS6E 9€€ SL3 94 Put d 33 SLE 2ST 657s 87 PUT Vv *44a °DS OOOT UT petdures 0S-1eA0 0S-9z SZ-0 pesea.ms 4e°q erenbs Tros seTdueg ur sueTO °ON eety TeqOL sdnor) oezTs OS6T eg osoyepeses SNVTIO LAOS dO SLVAILSH NOLLVINdOd — IT TIdvd 95 The 1951 census was started in April and finished in May. Grid lines established for the 1951 census are similar in spacing to the grid lines used in the 1950 census. We located plots at the intersec- tions of the grid lines (see Figure }). Area A had a total of 8 square feet sampled and a mean number of 11.8 clams per square foot; Area B, ho square feet sampled and 1.8 clams per square foot; Area C, hh square feet sampled and 1.8 clams per square foot. Population estimates for the three areas were: 29,0),000, 12,953,000 and 7,847,000 respectively, or 49,844,000 clams in 1951. Estima ed number of bushels in the over-50 mm. size group were: 2,51) in Area A, 911 in Area B, and ,9)7 in Area C, or a total of 8,372 bushels of commercial size clams (see Table III and Figure qT) Population estimate for the 0-25mm. size group in 199 is low because no sub-samples were screened in that year. The low population of the 0-25 mm. size group in Area C for all years is believed to be caused by tidal currents which prevent many seed clams for establishing themselves. There is a large number of clams in the 26-50mm. size group, and a relatively small number of clams in the over=-50 mm. size group in Area A and Area B. The possible cause for this is slow growth and small ultimate size. Fluc- tuations in volume of clams from year to year are probably partially caused by commercial digging. Methods (Growth) Shells of clams found in sample plots located in Areas A, B and C were "read" for growth. Growth "readings" are based on shell rings made by interruptions of growth during the winter. We combined growth read-= ings for 1949, 1950, and 1951 to have a more adequate number of readings for each age (see Table IV). Results (Growth) The growth curves plotted from the shell readings indicate slow growth in Area A and Area B, and fast growth in Area C (See Figure 5). Methods (Ultimate Length) Ultimate length of soft clams in Sagadahoc Bay was determined by a new method described by L. A. Walford in his paper of 196, "A New Graphic Method of Describing the Growth of Animals". The body length of the animal is represented along both the x axis and the y axis on graph paper. Length at age n cn the x axis is plotted against length at age n+ 1on the y axis. For several animals, the points plotted for lengths at several ages will fall in a straight line. This line may be regarded as a sort of transformatim of the usual growth curve. By extending this line, ultimate length ot the animal can be located at the point where the length at age n equals the length at age n +1. 96 SAGADAHOC BAY TIDAL FLAT GEORGETOWN, MAINE Q 100 200 490 $90 8go0 FT. 120) BS 6 wn bang \\ "0 WY ! 1 @) mS SF / ibe eS / 40 ae es FIGURE 4; LOCATION OF PLOTS / 5a, 100 FOR 1951 CENSUS. po as al i eee RAC? AREA "A O A ie 400 i | \ ule) tel es yeh Oo rte) 58E) a o | () oa 580 40 ©) ore PO 80 2 / joa ine nyo) iy oor AREA “C* 40 "© . a a 40 _AREA “B" 24S) a | 220 | \ | Lie) 4@) ene) ¥ fen 11@) | ’ 5 (@) 370 | ES S 36) g/ j ; | | q 97 ZLe’s T80‘9 718° 64 9616 9179 *72 000S9T SsTeqoL ——— ————————SvxVs——e—e————rrooe eo Te”... CL >”»”S”CO=NWBG *>OC~™S LG 7 €97 L473" Lh T9S?"E 8£0°?% 87S °c 8°T 0) T16 96 °E €56°Z1 Ze *T srt <¢ EL6°S 3° a 415 °% cee S47 7062 cov S47 O9T LT 6L7*L 8°TL Vv nods) eZTS *T Ul e414 *pSs Jed eoly "ull OG aad *uwm 0S-92 TeqoOL sueTO °ON *ng °ONn ng °ON ueayl a i a ee 88T 4709 rh gT8*L ZET STEROL a cE 0% Ge uti aal 77 pues i) oL 67Z €lLe GL3 ov Eni q 93 Gee 9vT 657% cu pay ¥ Wu Ul *TmI “aq *bS OOOT Ut peTdures addy, eoly 0S—12840 0S$-92 62-0 peferAms qoe0 etenbs Tres Setdues ur sueTD ‘°oN eoly TeqOL sdnoiy) eZts eee oooeoeoeooqqQu<“RlNaSSSaSOaaeae=SS—“—wwomss TS6T seg osoyepeses SWVIO LHOS JO GLVNILSaA NOLLVIndOd - III TIavL 98 *TS6L pue OS6T *646T TOF peuTquiog [Tr TEES ot €°TS SE 9 S°389 T3 6°87 LOT 8°L" 97c S S°9S TIT €° 7 16€ G°ey BLL uf T° et 002 o°S€ TT9 6°7€ TEE T € 0°8z Lez 8°72 6S, 6° 689 T z €°OT TEz O°TT ETB A 069 *T T U4sSuUeT soTdures Y4sueT sotdues YUyusyT OSeIOAY *ON Ose IOAY eViy ese Ieay "ON O VauV q Yau Vo vauy SS Aeg oouepeses Ve SONTQVEY HIMOUD — AT FIVE 99 AVS JOHVAVIOVS S3AUND HLiMOUD >§ 3yuNndis viauv v3iauv Je Viauv Ol ler. o¢ fo} vr °o wo NI HLONSIT 2) o WW ol 08 06 190 WW NI HLONIT oc! O02! Ol) oko} 06 os OL 09 os Ov O€ OZ io} 06 Ob Ss Zz = 001 osy 5 z (ww zZ9) oo oll aa vauv = (wwg9) 2a, “Va oy 02) (oy O€! (ww j¢1) os Aap v3auv “AVS DJOHVAGVOVS Or! SWV19 3O 3Z1S JLVWILIN 739 3yuNndl4 WW OS Y¥3A0 OS-92 S2-0 SdNOUY9 3Z\S 2) viauv WW OS Y3AO0 0S-92 SZ2-0 SdN0¥d —e 3Z!S V3auV AVS JOHVOVSOVS S3LVWILS3 NOILVINdOd 1°SZ WW OSUY3A0 0S-92 SZ2-0 SdnOU9d aZIs a vauv :2 3yNndld4 SNOITTIN = = rr (2) 75 no SNOITIIW o 102 Among theexamples given by Walford are the fresh water mussel and the Pacific razor clam. As ultimate length is a factor in estab- lishing productivity, we are using this method for indicating the ultimate length for the soft clam. Results (Ultimate Length) The ultimate lengths of clams in Sagadahoc Bay (see Figure 6) located by the new graphic method are 62 mm. in Area A, 65 mm. in Area B, and 131 mm. in Area C. These lengths are in close agreement with the lengths of the largest clams found in the census plots. The point plotted for the length at age 5 (n), against the length at age 6 (n +1), is omitted because of an inadequate number of samples in the 6-year clams. Discussion The center of Sagadahoc Bay has a good stock of large clams and a low stock of small clams. The mud areas on the edge of the bay have a large stock of small clams and a small stock of large clams. Fast growth occures in the center of the bay; slow growth occurs along the edge. The ultimate lengths of clams as plotted by areas indicates that clams in Area C have two times the possible ultimate size of clams in Area A and Area B. REFERENCES 1. Belding, D. L. 163). The soft-shelled clam fishery of Massachusetts. Mass. Dept. Consv. Mar. Fish., Series No. 1 2. Walford, L. A. 19h6.. A new graphic method of describing the growth of animals. Biol. Bull. 90(2): (April 196), pp. 141-147. 103 oe Rae fox) oid eis enbeapEhs: =F 4 f Acre exagX see } 2eFclo ares Sis aw Qo taGars ig yee VOLS at e- we ® , arr at .me } deeans 136 pegaa #2, vie orl Met edt Sentese (cr) 2 on ataupsiiss i prot fey ye mets of aos Tue SIZ ight Eeiey ote. tw prrerrier ies cA tei Tone OEE -" DY he ae pa] st mee Mow suf aver> bo edema d etn Bbip oat ats bextisn, otdqang Hen ante