NOAA TR NMFS SSRF-648 A UNITED STATES DEPARTMENT OF COMMERCE PUBLICATION NOAA Technical Report NMFS SSRF-648 U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Marine Fisheries Service SEATTLE, WA. December 1971 Weight Loss of Pond-Raised Channel Catfish {Ictalurus punctatus) During Holding in Processing Plant Vats DONALD C. GREENLAND and ROBERT L. GILL Mirifte Biological Laboratory LIBRARY SEP13»72 Woods Hole, iviass. NOAA TECHNICAL REPORTS National Marine Fisheries Service, Special Scientific Report-Fisheries Series The major responsibilities of the National Marine Fisheries Service (NMFS) are to monitor and assess the abundance and geographic distribution of fishery resources, to understand and predict fluctuations in the quantity and distribution of these resources, and to establish levels for optimum use of the resources. NMFS is also charged with the development and implementation of policies for managing national fishing grounds, develop- ment and enforcement of domestic fisheries regulations, surveillance of foreign fishing off United States coastal waters, and the development and enforcement of international fishery agreements and policies. NMFS also as- sists the fishing industry through marketing service and economic analysis programs, and mortgage insurance and vessel construction subsidies. It collects, analyzes, and publishes statistics on various phases of the industry. The Special Scientific Report — Fisheries series was established in 1949. The series carries reports on scien- tific investigations that document long-term continuing programs of NMFS, or intensive scientific reports on studies of restricted scope. The reports may deal with applied fishery problems. The series is also used as a medium for the publication of bibliographies of a specialized scientific nature. NOAA Technical Reports NMFS SSRF are available fi-ee in limited numbers to governmental agencies, both Federal and State. They are also available in exchange for other scientific and technical publications in the marine sciences. Individual copies may be obtained (unless otherwise noted) from NOAA Publications Section, Rockville, Md. 20852. Recent SSRF's are: 604. The flora and fauna of a basin in central Florida Bay. By J. Harold Hud.son, Uonak! M. Allen, and T. J. Costello. May 1970, iii + 14 pp., 2 figs., 1 table. 605. Contributions to the life histories of several penaeid shrimps (Penaeiilae) along the south Atlantic Coast of the United States. By William W. Anderson. May 1970, iii + 24 pp., 15 figs., 12 tables. 606. Annotated references on the Pacific saury, Colol- ahis saira. By Steven E. Hughes. June 1970, iii -f 12 pp. 607. Studies on continuous transmission frequency modulated sonar. Edited by Frank J. Hester. June 1970, iii + 2G pp. 1st paper, Sonar target classification experiments with a continuous- transmission noppler sonar, by Frank J. Hester, pp. 1-20, 14 figs., 4 tables; 2d paper. Acoustic target strength of several species of fish, by H. W. Volberg, pp. 21-26, 10 figs. 608. Preliminary designs of traveling screens to col- lect juvenile fish. July 1970, v + 15 pp. 1st paper. Traveling screens for collection of juvenile salmon (models I and II), by Daniel W. Bates and John G. Vanderwalker, pp. 1-5, 6 figs., 1 table; 2d paper, Design and operation of a canti- levered traveling fish screen (model V), by Dan- iel W. Bates, Ernest W. Murphey, and Earl F. Prentice, 10 figs., 1 table. 609. Annotated bibliography of zooplankton sampling devices. By Jack W. Jossi. July 1970, iii + 90 pp. 610. Limnological study of lower Colrunbia River, 1967-68. By Shirley M. Clark and George R. Snyder. July 1970, iii + 14 pp., 15 figs., 11 tables. 611. Laboratory tests of an electrical barrier for con- trolling predation by northern squawfish. By Galen H. Maxfield, Robert H. Lander, and Charles D. Volz. July 1970, iii + 8 pp., 4 figs., 5 tables. 612. The Trade Wind Zone Oceanography Pilot Study. Part VIII: Sea-level meteorological properties and heat exchange processes, Julv 1963 to June 1965. By CJunter R. Seckel. June 1970, iv + 129 pp., 6 figs., 8 tables. 613. Sea-bottom photographs and macrobenthos col- lections from the Continental Shelf ofl" Massa- chusetts. By Roland L. Wigley and Roger B. Theroux. August 1970, iii + 12 pp., 8 figs., 2 tables. 614. A sled-mounted suction sampler for benthic or- ganisms. By Donald M. Allen and J. Harold Hudson. August 1970, iii -|- 5 pp., 5 figs., 1 table. 615. Distribution of fishing efl'ort and catches of skip- jack tuna, Katsuwonus pelainis, in Hawaiian waters, by quarters of the year, 1948-65. By Richard N. Uchida. June 1970, iv + 37 pp., 6 figs., 22 tables. 616. Effect of quality of the spawning bed on growth and development of pink salmon embryos and alevins. By Ralph A. Wells and William J. Mc- Neil. August 1970, iii + 6 pp., 4 tables. 617. Fur seal investigations, 1968. By NMFS, Ma- rine IMammal Biological Laboratory. December 1970, iii + 69 pp., 68 tables. 618. Spawning areas and abundance of steelhead trout and coho, sockeye, and chum salmon in the Columbia River Basin - past and present. By Leonard A. Fulton. December 1970, iii + 37 pp., 6 figs., 11 maps, 9 tables. 619. Macrozooplankton and small nekton in the coastal waters off Vancouver Island (Canada) and Wasliingtcn, spring and fall of 1963. By Donald S. Day, January 1971, iii + 94 pp., 19 figs., 13 tables. 620. The Trade Wind Zone Oceanography Pilot Study. Part IX : The sea-level wind field and wind stress values, July 1963 to June 1965. By Gunter R. Seckel. June 1970, iii -|- 66 pp., 5 figs. Continued on inside back cover. ^O MMOsp^^ ■'"H.I^T^f ^^''~ U.S. DEPARTMENT OF COMMERCE Maurice H. Stans, Secretary NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Robert M. White, Administrator NATIONAL MARINE FISHERIES SERVICE Philip M. Roedel, Director NOAA Technical Report NMFS SSRF-648 Weight Loss of Pond-Raised Channel Catfish (Ictalurus punctatus) During Holding in Processing Plant Vats DONALD C. GREENLAND and ROBERT L. GILL Marine Biological Laborjtory LIBRARY SEP 1 3 1972 Woods Hole, Mass. SEAHLE, WA. December 1971 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C., 20402 - Price 25 cents The National Marine Fisheries Service (NMFS) does not approve, rec- ommend or endorse any proprietary product or proprietary material mentioned in this publication. No reference shall be made to NMFS, or to this publication furnished by NMFS, in any advertising or sales pro- motion which would indicate or imply that NMFS approves, recommends or endorses any proprietary product or proprietary material mentioned herein, or which has as its purpose an intent to cause directly or indirectly the advertised product to be used or purchased because of this NMFS publication. CONTENTS Page Introduction 1 Test procedures 2 Test results 4 Discussion 6 Conclusions 7 in Weight Loss of Pond-Raised Channel Catfish {Icfalurus punctatus) During Holding in Processing Plant Vats By DONALD C. GREENLAND, Fishery Biologist and ROBERT L. GILL, Fishery Methods and Equipment Specialist National Marine Fisheries Service P.O. Box 711 Rohwer, Arkansas 71666 ABSTRACT Information on weight loss and mortality was obtained for samples of channel cat- fish (Ictahirus punctatus) held for processing at a catfish processing plant located at Dumas, Ark. Weight losses were determined for several different holding situations by daily weighings of samples held in wire containers. Mortality was recorded at 24-hr intervals. Test results showed peak weight loss during the test period for all holding situations averaged 55 kg per metric ton (5.5 lb. per cwt), 82.0';r of which occurred during the first 48 hr of holding. There was no difference in weight loss of fish held at densities of 320.3 kg per cubic meter (20.0 lb. per cu ft) and 640.6 kg per cubic meter (40.0 lb. per cu ft) of water ranging from 21.1° to 22.2° C (70.0° to 72.0° F). However, at the heavier loading there was twice the mortality, 8.0% compared to 4.5%. Fish held in a pond with temperatures from 8.9° to 15.0° C (48.0° to 59.0° F) fared the best of any of the test groups. These fish had a peak weight loss of 2.0% and suffered no mortality. Similar groups of fish held in vats at 21.1° C (71.0° F) aerated with agi- tators and compressed air had peak weight losses of 4.2% and 6.9% and suffered mor- talities of 34.0% and 15.0% respectively. INTRODUCTION Most of the catfish processing plants located in Alabama, Arkansas, and Mississippi utilize live fish delivered to their plants to insure a high-quality finished product. These catfish are held in large concrete vats at the plants. As needed, fish are removed from the vats, killed, and run directly onto the processing line. Processors have often mentioned to us that the weight of fish being held for processing "shrinks" from pond-side weighings and that weight deductions for scrap fish and removal of dead catfish account for only a portion of the diflPerence. These weight discrepancies have caused misunderstandings between farm- ers and processors. Without accurate "shrink" data, processors have been reluctant to con- sider changing plant facilities to try to reduce weight loss. Our assistance was requested to obtain data that would be helpful to processing plant managers in deciding whether fish weight losses were indeed a problem. During the win- ter of 1970-71, a study to determine this was conducted at the Southern Catfish Processors, Inc. in Dumas, Ark., by National Marine Fish- eries Service personnel. TEST PROCEDURES Samples of channel catfish {Ictalunis punc- tahis) coming- into the processing plant lo- cated at Dumas, Ark., were weighed and placed in wire-mesh containers located in the plant holding vats. These containers were weighed at approximately 24-hr intervals (Fig. 1 and 2) and the weight change was determined by com- paring the daily reading with that of the pre- vious day. If mortality had occurred in the interim, the dead fish were removed and weighed, and these data were used to establish the beginning weight for the following day. The fish used in this study came from several farms. All were harvested by seining and had been held in the net for periods ranging from a couple of hours to 2 days. These fish were delivered to the plant in Dumas, Ark., in haul trucks equipped with agitators and had spent from 2 to 4 hr in transit. Three series of tests were conducted over a 3-month period. During this time, water tem- peratures in the holding vats ranged from 21.0° to 22.0° C (70.0° to 72.0° F). The ponds from which the test populations came had water temperatures of 8.9° C (48.0° F), 10.0° C (50.0° F), and 13.9° C (57.0° F) for Tests "A", "B", and "C". Test "A" consisted of measuring weight changes in four pots: the first two contained 90.7 kg (200.0 lb.) of channel catfish each, and the second two, 181.4 kg (400.0 lb.) of fish each. Fish densities were 320.3 kg (20.0 lb.) and 640.6 kg (40.0 lb.) per cubic meter (cu ft) of water. These pots were set in line near the Figure 1. — Weighing container of channel catfish held in pond to determine weight change. -^- '.. -a^8E^Jt-=»,*; Figure 2.— Weighing container of channel catfish held in vats to determine weight change. head of a holding vat being aerated by com- pressed air delivered through three perforated plastic hoses fastened to the vat bottom. A clearance of about 0.46 m (1.5 ft) was allowed between pots. Fish being held for the plant were present in this vat and circulated freely around the pots. Test "B" was similar to "A" except that two additional pots were used as controls to de- termine if the daily disturbance of weighing caused undue weight loss or mortality. These two pots, one containing 90.7 kg (200.0 lb.) of fish and the other 181.4 kg (400.0 lb.) were weighed only at the start and at the termination of Test "B". After the results of Tests "A" and "B" were examined, additional tests were run to deter- mine if different holding conditions would alter experimental results. Six pots, each contain- ing 136.1 kg (300.0 lb.) of catfish, were used. Two were placed in a vat which was aerated with agitators, two were positioned in vats aerated with compressed air, and the last two were put in a small, dirt, holding pond located adjacent to the plant. Water temperatures were 21.1° C (71° F) in both vats and ranged from 8.9° to 15.0° C (48.0° to 59.0° F) in the pond during testing. As in the previous ex- periments, all the pots were weighed at approx- imately 24-hr intervals, using the same set of scales and the same procedures. TEST RESULTS All groups of test fish lost weight during the 7-day holding period (Table 1). In all tests the bulk of this weight loss occurred dur- ing the first 3 days. Figure 3 shows the results 72 96 120 144 168 192 216 HOURS Figure 3. — Cumulative weight loss in percent for chan- nel catfish held at different concentrations and in different water conditions. of tests comparing concentrations of 320.3 and 640.6 kg of fish per cubic meter (20.0 and 40.0 lb. of fish per cu ft) of water, for fish held in vats having difl'erent aeration systems, and for fish held in cooler pond water. In all cases, the most rapid rate of weight loss occurred during the first 48 hr. Surprisingly, the weights were static for almost all of the test groups between the third and fourth weighings (48 to 72 hr) . After passing this plateau, the Table 1. — Weight change in percent for individual samples. Test 'A" Test ' 'B" Test "C" Day Pot Pot Pot: 1 2 3 4 1 2 3 4 5 6 1 2 3 4 5 6 1-2 -4.9 -2.9 -3.2 -4.2 -1.9 -2.2 -1.9 C -3.9 C -1.7 -2.0 -2.4 -2.1 -0.3 -0.3 2-3 -1.0 -3.0 -1.8 -1.0 -3.3 -3.2 -2.2 O -2.0 O -2.6 -2.0 -1,4 -2.2 -1.3 -2.0 3-4 -1.0 +0.5 -2.1 -2.1 +0.8 -0.1 -0.1 N -1.4 N -0.6 0.0 + 0.1 0.0 + 0.3 + 0.3 4.5 0.0 -1.5 -0.5 -1.1 -2.6 -1.5 -1.0 T -0.5 T + 0.6 -2.5 + 0.1 + 0.8 + 1.0 + 1.3 5-6 -1.7 -1.5 -0.6 R + 0.2 R -0.6 -0.1 -0.4 -1.0 -0.0 + 0.3 6-7 -0.5 -0.3 -0.9 O + 0.3 O -1.7 -0.3 +2.4 + 1.4 + 1.6 +0.7 7-8 0.0 0.0 -0.3 -0.3 +0.1 -0.8 0.0 L -0.5 L + 3.0 + 1.4 +2.5 +3.0 -1.6 -0.7 Total -6.9 -6.9 -7.9 -8.7 -9.1 -9.6 -6.7 - -9.4 -7.8 -9.2 -3.6 -5.5 +0.9 -0.1 -0.3 -0.4 Table 2. — Mortality in kilograms for individual samples. Test "A" Test ■B" Test "C" Hours Po Pot Pot: 1 2 3 4 1 2 3 4 5 6 1 2 3 4 5 6 24 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.4 12.3 0.0 0.0 6.8 0.0 0.0 48 0.0 0.0 0.5 0.0 5.3 8.0 18.4 0.0 0.8 0.0 0.2 0.0 0.5 0.0 0.0 0.0 72 0.0 0.0 0.4 0.0 0.0 0.0 3.9 0.0 0.0 0.0 2.0 1.5 1.1 1.0 0.0 0.0 96 0.5 0.4 2.1 1.3 0.8 0.0 0.0 0.0 1.0 0.0 3.9 2.1 2.2 5.1 0.0 0.0 120 _. __ 0.0 0.6 0.0 0.0 3.7 0.9 2.3 3.2 6.9 6.5 0.0 0.0 144 _. _. .. 1.0 1.1 0.0 0.0 3.8 0.0 2.2 1.3 15.5 8.5 0.0 0.0 168 1.2 1.8 12.3 16.1 1.4 0.0 2.5 0.0 3.3 0.3 5.5 4.2 19.1 19.8 0.0 0.0 Total 1.7 2.2 15.3 17.4 8.5 9.7 24.8 0.0 12.6 1.6 28.4 12.3 44.9 47.7 0.0 0.0 curves showing weight loss for Tests "A" and "B" continued at a much reduced level for the last 96 hr. The Test "C" curves started a sim- ilar trend, but during the final days of the test period these curves started downward, in- dicating the fish were possibly regaining some weight. Daily mortality was tabulated in kilograms (Table 2) . The greatest mortality, 34.0%, oc- curred to Test "C" fish held in the vats aerated by agitators. Test "C" catfish held in the vats supplied with compressed air suffered 15.0% mortality. Mortality for the 320.3 and 640.6 kg (20.0 and 40.0 lb.) loadings of fish in Tests "A" and "B" averaged 4.5% and 8.0%, respectively. Almost no mortality occurred to fish held in the two control pots in Test "B" and none occurred to the Test "C" fish held in the cool pond water. The effect of the daily handling on weight loss and mortality was checked with two control groups in Test "B". These two containers, one with a fish density of 320.3 kg per cubic meter (20.0 lb. per cu ft) of water and the other with a fish density of 640 kg (40.0 lb.), were weighed every 24 hr. The weight loss for the controls averaged 9.3%; for the pots weighed every 24 hr, the loss was 8.4% . It appears that daily weighing did not contribute to weight loss. The daily handling during weighing did cause mortality. In the containers handled every 24 hr, 8.0% of the fish held at the higher den- sity died and 4.5% of the fish held at the lower density succumbed. None of the 320.3 kg (20.0 lb.) control group died and only 0.9% of the fish expired at the heavier loading of 640.6 kg (40.0 1b.). The test results comparing weight losses of fish held at concentrations of 320.3 kg and 640.6 kg per cubic meter (20.0 and 40.0 lb. per cu ft) of water indicated that at these loadings density had little effect. At the end of 168 hr, con- tainers with 320.3 kg (20.0 lb.) of fish incurred an average weight loss of 8.4% and those with 640.6 kg (40.0 lb.) of fish lost 8.1%. Even though density did not appear to affect weight loss, it did contribute to higher mortality. At the end of the test period, containers with the heavier loadings sustained twice the mortality of those with 320.3 kg (20.0 lb.) of fish: 8.0% compared to 4.5%. The results of the tests comparing weight losses in vats aerated by compressed air and by agitators indicated the peak weight loss was slightly greater in the compressed air situation than with agitators (6.9% compared to 4.2%). However, a substantially greater mortality oc- curred in the vat with agitators (34.0% com- pared to 15.0%). The two containers of fish held in the cool pond water fared the best of any of the test groups. The peak weight loss for those fish averaged 2.0%. No mortality was recorded. The test results for all groups of fish held in the plant vats indicated weight losses were fairly similar at the end of 48 hr (Fig. 3) . The average loss during this period of 45 kg per metric ton (4.5 lb. per cwt) constitutes 82.0% of the peak weight loss of 55 kg per metric ton (5.5 lb. per cwt) for these groups. The max- imum weight losses for each test situation show the containers with 329.3 and 640.6 kg (20 and 40 lb.) of fish lost 84.0 and 81.0 kg per metric ton (8.4 and 8.1 lb. per cwt). Fish held in vats aerated by compressed air and by agitators lost 69.0 and 42.0 kg per metric ton (6.9 and 4.2 lb. per cwt) , respectively; those in the cool- er pond water incurred a 20.0 kg per metric ton (2.0 lb. per cwt) loss. DISCUSSION All groups lost weight during the test period. However, during the last few days of the test some positive weight change readings were ob- tained, indicating some of the groups, partic- ularly those in Test "C", were regaining weight. This seemed highly unlikely as none of the fish were being fed and all were under stress be- cause of the holding situation. We surmised that these positive weight changes were caused either by the test gear or procedure and were not the result of fish growth. Perhaps some of these positive observations could be attributed to misreading the weighing scales; and, as the scale was calibrated prior to each day's weighing, there could have been some misadjustment. Another possibility was that the scale itself was inaccurate. However, this unit had been sent to the manufacturer prior to the beginning of these tests for clean- ing and reconditioning. It has since been checked against other scales and found to be accurate. It is doubtful any of these factors would account for the large percentage (23.0%) of positive daily observations ob- served. We speculated that wind blowing on certain days might have affected the suspended scale. The weighing operations were conducted in an open shed, and perhaps wind pressure on the lift cable might be biasing the test results. However, examination of meteorological obser- vations for the general area does not support this. One of the most reasonable explanations for the positive weight gains was the possibility that the fish became infected with hemorrhagic septicemia, a bacterial infection which can im- pair kidney function and cause water retention and which would result in a weight gain. As each test progressed, the condition of the test population deteriorated and some of the fish in all the test groups exhibited outward signs of bacterial infection. However, none of these fish was examined by anyone qualified to make a positive diagnosis of hemorrhagic septicemia, nor was it determined that kidney damage oc- curred. One other consideration that lends support to a disease-caused weight increase was that positive weights did not occur until the third day of holding in any of the tests, in- dicating a build-up time was required, as would be expected in a bacterial disease. One known factor that biased our figures was the presence of dead fish in the containers at the time of weighing. We determined that dead fish held in the plant's holding vats gained weight. Samples of fish that averaged 764.0 g (26.9 oz) were sacrificed, and, over a 24-hr period, gained an average of 62.5 g (2.2 oz). This weight increase amounted to 8.2% of the beginning weight. A complication in utilizing this information to adjust data when dead fish were present was the fact that it was not known when individual fish succumbed nor how long they had been dead. Without this information, appropriate weight adjustments for mortality could not be allocated. Two additional factors that could aflTect weight changes have been suggested for our consideration; the time of last feeding and the state of sexual maturity. During the period the weight loss study was conducted, mid-De- cember to late March, the influence of both these factors would be minimal. However, at other seasons of the year, particularly in late spring, both these variables would have to be accounted for in studying weight changes dur- ing holding. Regardless of the cause, weight losses, par- ticularly in the last days of Test "C", were masked by unknown factors and losses would probably have been greater than shown. We are suspicious of the figures showing slightly more weight loss in vats with compressed air than those having agitators, and would like further verification of this before accepting this as fact. This study did not determine whether the weight losses that occurred during holding were evident in the finished product, the dressed fish. This point and other factors encountered, such as the eff"ect of fish density on mortality, the damage caused by handling, and the possi- bility of using cool water to reduce mortality and weight loss would be worthwhile research projects for future programs. CONCLUSIONS Based on the test results, the following con- clusions were made concernino: catfish weight loss and mortality during holding: 1. Channel catfish lose weight during hold- ing. Most of the loss occurs during the first 48 hr and the test results showed 82.0% of the maximum average weight loss of 55 kg per metric ton (5.5 lb. per cwt) occurred during this period. 2. Weight loss was similar for fish held at densities of 320.3 and 640.6 kg per cubic meter (20.0 and 40.0 lb. per cu ft) of water but mor- tality was twice as much, 8.0''^ , for the higher concentrations of fish. 3. Handling the fish every 24 hr to weigh them did not contribute to weight loss but did cause mortalities of 4.5 '^r and 8.0% to occur in containers with loadings of 320.3 and 640.6 kg of fish per cubic meter (20 and 40 lb. per cu ft) of water. 4. Our data showed fish held in vats with agitators suffered slightly less weight loss than those held in vats supplied with compressed air. Mortalities, however, were 34.0% with agi- tators and 15.0% with compressed air. Be- cause of this large mortality, and a number of positive weight readings during the final days of this test, we are hesitant of accepting these results. Additional studies should be conducted before judging the merits of aerating vats with agitators or compressed air. 5. Fish held best in cool pond water of 8.9° to 15.0° C (48.0° to 59.0° F) : they suffered no mortality and had a maximum weight loss of 2.0' Similar fish held in vats with 21.7° C (71° F) water incurred twice the weight loss and had mortalities averaging 15.0% and 34.0%. GPO 999-665 %-.-». MBL WHOl V^IflX.nii^fi'i'nlnil WHSE 01828 621. Predation by sculpins on fall chinook salmon, Oncorhynclniii tshawjiisclia, fry of hatchery or- igin. By Benjamin G. Patten. February 1971, iii + 14 pp., 6 figs., 9 tables. 622. Number and lengths, by season, of fishes caught with an otter trawl near Woods Hole, Massa- chusetts, September 1961 to December 1962. By F. E. Lux and F. E. Nichy. February 1971, iii 4- 15 pp., 3 figs., 19 tables. 623. Apparent abundance, distribution, and migra- tions of albacore, Tltiinyiiis alalunga, on the North Pacific longline grounds. By Brian J. Rothschild and Marian Y. Y. Yong. September 1970, v -|- 37 pp., 19 figs., 5 tables. 624. Influence of mechanical processing on the quality and yield of bay .scallop meats. Bv N. B. Webb and F. B. Thomas. April 1971, ii'i + 11 pp., 9 figs., 3 tables. 625. Distribution of salmon and related oceanographic features in tlie North Pacific Ocean, spring 1968. By Robert R. French, Richard G. Bakkala, Ma- sanao Osako, and Jun Ito. March 1971, iii -f 22 pp., 19 figs., 3 tables. 626. Commercial fi.shery and biology of the fresh- water shrimp, Maci-obrachiiim, in the Lower St. Paul River, Liberia, 1952-53. By George C. Mil- ler. February 1971, iii -f 13 pp., 8 figs., 7 tables. 627. Calico scallops of the Southeastern United States, 1959-69. By Robert Cummins, Jr. June 1971, iii + 22 pp., 23 figs., 3 tables. 628. Fur Seal Investigations, 1969. By NMFS, Ma- rine Mammal Biological Laboratory. August 1971, 82 pp., 20 figs., 44 tables, 23 appendix A tables, 10 appendix B tables. 629. Analysis of the operations of seven Hawaiian skipjack tuna fishing vessels, June-August 1967. By Richard N. Uchida and Ray F. Sumida. March 1971, v + 25 pp., 14 figs., 21 tables. For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - 35 cents. 630. Blue crab meat. I. Preservation by freezing. July 1971, iii + 13 pp., 5 figs., 2 tables. II. Effect of chemical treatments on acceptability. By Jurgen H. Strasser, Jean S. Lennon, and Fred- erick J. King. July 1971, iii + 12 pp., 1 fig., 9 tables. 631. Occurrence of thiaminase in some common aquat- ic animals of the United States and Canada. By R. A. Greig and R. H. Gnaedinger. July 1971, iii -f- 7 pp., 2 tables. 632. An annotated bibliography of attempts to rear the larvae of marine fishes in the laboratory. By Robert C. May. August 1971, iii -1- 24 pp., 1 ap- pendix I table, 1 appendix II table. For sale by the Superintendent of Documents, U.S. Ciovern- ment Printing Office. Washington, D.C. 20402 - 35 cents. 633. Blueing of processed crab meat. II. Identification of some factors involved in the blue discoloration of canned crab meat Callinectes sapidus. By Melvin E. Waters. May 1971, iii + 7 pp., 1 fig!, 3 tables. 634. Age composition, weight, length, and .sex of her- ring, Clupra pallasii, used for reduction in Alas- ka, 1929-66. By Gerald M. Reid. July 1971, iii -f 25 pp., 4 figs., 18 tables. 635. A bibliography of the blackfin tuna, Thumnis nthintici(S (Ijes.son). By Grant L. Beardsley and David C. Simmons. .August 1971, 10 pp. For sale by the Superintendent of Documents, U.S. Government Printing Ofl^ce, Washington, D.C. 20402 - 25 cents. 636. Oil pollution on Wake Island from the tanker ;?. C. Stoiier. By Reginald M. Gooding. May 1971, iii -I- 12 pp., 8 figs., 2 tables. For sale by the Superintendent of Documents, U.S. Govern- ment Printing Office, Wa.shington, D.C. 20402 - Price 25 cents. 637. Occurrence of larval, juvenile, and mature crabs in the vicinity of Beaufort Inlet, North Carolina. By Donnie L. Dudley and Mayo H. Judy. August 1971, iii + 10 pj)., 1 fig., 5 "tables. For sale bv the Superintendent of Documents, U.S. Govern- ment Printing Office, Washington, D.C. 20402 - Price 25 cents. 638. Length-weight relations of haddock from com- mercial landings in New England, 1931-55. By Bradford E. Brown and Richard C. Hennemuth. August 1971, V + 13 pp., 16 fig., 6 tables, 10 appendix A tables. For sale by the .Supei'intend- ent of Documents, LI.S. Government Printing Office, Wa.shington, D.C. 20402 - Price 25 cents. 639. A hvdrographic survey of the Galveston Bay system, Texas 1963-66. By E. J. Pullen, W. L. Trent, and G. B. Atiams. October 1971, v -f 13 pp., 15 figs., 12 tables. For sale by the Super- intendent of Documents, U.S. Government Print- ing Office, Washington, D.C. 20402 - Price 30 cents. 640. Annotated bibliography on the fishing industry and biology of the blue crab, Callinectes sapidus. By Marlin E. Tagatz and .\nn Bowman Hall. August 1971, 94 pp. For sale by the Superinten- dent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price $1.00. 641. Use of threadfin shad, Dorosoma petenense, as live bait during experimental pole-and-line fish- ing for skipjack tuna, Katsnwovus pelamis, in Hawaii. By Robert T. B. Iversen. August 1971, iii -f 10 pp., 3 figs., 7 tables. For sale by the Superintendent of Documents, U..S. Government Printing Office, Washington, D.C. 20402 - Price 25 cents. 642. Atlantic menhaden Brevoortia tyrannus resource and fishery — analysis of decline. By Kenneth A. Henry. August 1971, v -f 32 pp., 40 figs., 5 appendix figs., 3 tables, 2 appendix tables. For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price 45 cents. 646. Dissolved nitrogen concentrations in the Colum- bia and Snake Rivers in 1970 and their eff'ect on chinook salmon and steelhead trout. By Wesley J. Ebel. August 1971, iii PP-, figs., 6 tables. For sale by the Superintendent of Doc- uments, U.S. Government Printing Office, Wash- ington, D.C. 20402 - Price 20 cents. UNITED STATES DEPARTMENT OF COAAMERCE NATIONAL OCEANIC & ATMOSPHERIC ADMINISTRATION NATIONAL MARINE FISHERIES SERVICE SCIENTIFIC PUBLICATIONS STAFF BLDG. 67, NAVAL SUPPORT ACTIVITY SEAHLE, WASHINGTON 98115 OFFICIAL BUSINESS POSTAGE AND FEES PAID U.S. DEPARTMENT OF COMMERCE