FISHERY RESEARCH BIOLOGICAL LABORATORY , GALVESTON FISCAL YEAR 1962 UNITED STATES DEPARTMENT OF THE INTERIOR FISH AND WILDLIFE SERVICE BUREAU OF COMMERCIAL FISHERIES OCT CIRCULAR 161 UNITED STATES DEPARTMENT OF THE INTERIOR, Stewart L. Udall, Secretary FISH AND WILDLIFE SERVICE, Clarence F. Pautzke, Commissioner Bureau of Commercial Fisheries, Donald L. McKernan, Director BIOLOGICAL LABORATORY, GALVESTON, TEX. FISHERY RESEARCH for the year ending June 30, 1962 George A. Rounsefell, Director Joseph H. Kutkuhn, Assistant Director Contribution No. 168, Bureau of Commercial Fisheries Biological Laboratory, Galveston, Tex. Circular 16 1 Washington, D. C. 1963 The Bureau of Commercial Fisheries Biological Laboratory, Galveston, Tex. , and its field stations, conduct fishery research in the Gulf of Mexico as part of the work of the Bureau's Gulf and South Atlantic Region (Region 2), which comprises the eight coastal states from North Carolina to Texas. Office of the Regional Director, Seton H. Thompson, is in the Don Ce-Sar Federal Center, P. O. Box 6245, St. Petersburg Beach, Fla. Biological Research Biological Laboratory, Brunswick, Ga. Biological Laboratory, Beaufort, N. C. Biological Laboratory, GuLf Breeze, Fla. Biological Laboratory, Galveston, Tex. Biological Field Station, Mianni, Fla. Biological Field Station, St. Petersburg Beach, Fla. Biological Field Station, Pascagoula, Miss. Industrial Research Exploratory Fishing and Gear Research Base, Pascagoula, Miss. , auxiliary base at Brunswick, Ga. Marketing - Marketing Offices in Dallas, Tex. ; Jacksonville, Fla. ; and Pascagoula, Miss. Technology - Technological Laboratory, Pascagoula, Miss. Resource Development Statistical Center, New Orleans, La. ^Operating as an independent field station after January 1, 1962. 11 CONTENTS Page Report of the Director 1 Staff 7 Shrimp Fishery Program 10 Spawning populations 13 Larval distribution and abundance 18 Currents on the continental shelf of the northwestern Gulf of Mexico 23 Identification of shrimp larvae 28 Abundance of juvenile shrimp 31 Brown shrimp mortality studies 33 Pink shrimp life history 35 Industrial Fishery Program 38 Industrial bottomfish fishery in the north central Gulf of Mexico 39 Western Gulf bottomfish survey 42 Estuarine Program 45 Ecology of nursery areas 47 Effects of engineering projects on estuaries 52 Physiology and Behavior Program 55 Tolerances to environmental factors 57 Experinnental growth studies with postlarval brown shrimp. . . 6l Use of anesthetics in metabolism studies with penaeid shrimps 63 Special Reports 64 Chemicals toxic to the red-tide organism 64 Results of the Trinity Bay study 67 The Colorado River -Matagorda Bay study 70 Movement of water masses in Galveston Harbor 75 Estuarine water observations during a 24-hour cycle 77 Marking spiny lobsters, Panulirus argus, and blue crabs, Callinectes sapidus, with biological stains .... 83 Small beam net for sampling postlarval shrimp 86 The use of Atkins-type tags on shrimp 88 Iminersion staining of postlarval shrimp 90 A device for measuring live shrimp 92 Distribution of pink shrimp larvae and postlarvae 93 Library 95 Seminars, Meetings, and Work Conferences 97 Publications 98 Manuscripts In Press 100 Manuscripts Submitted 101 COVER: The East Lagoon Field Station, completed and operative in 1962, only 4 miles from the main laboratory, affords an opportunity to work on living material in almost natural conditions. Ill REPORT OF THE DIRECTOR George A. Rounsefell Research Highlights of the Past Year Experiments in marking shrimp at sea by staining proved highly successful. With this new tool, we were able to mark and release shrimp carefully graded as to size. The analysis of the data from several hundred recaptured by the shrimp fleet dennonstrated that the pink shrimp (Penaeus duorarum) grow very fast. Nevertheless, the mor- tality rate is so high that a larger total harvest can be made if fishing for them commences at relatively small sizes. By means of counts of postlarval shrimp entering Galveston Bay during the spring of I960, 1961, and 196Z, and data on the catch per unit of effort of resulting juvenile shrimp in the Galveston Bay system, we were able to predict in late spring that the abundance of shrimp in 1962 would ex- ceed that of 1961, and might equal that of I960. Two of the stained pink shrimp released on the Sanibel Island grounds were recovered 116 days later on the northwest portion of the Tor- tugas Grounds, showing that these two grounds may not have discrete popula- tions. The increased funds obtained in 1961 allowed us to commence si- multaneous biological and hydrographical sampling on the continental shelf out to 60 fathoms along an 800 -mile stretch of coastline from Brownsville, Tex., to the Mississippi delta. It is hoped that these data, if collected for several years, will show the causes for the year-to-year variations in the survival of the larval forms of shrimp. Gulf States Marine Fisheries Commission The Commission has continued to support research to aid in solving industry problems and has been instru- mental in obtaining increased resources for research. The Commission has fornned a committee of biologists from each of the participating states and the Bureau of Connmercial Fisheries to meet under its sponsorship to discuss research problems and to aid in the standardization of research techniques. Shift in Pesticide Program Over the past 2 years, small programs on the effects of pesticides were carried on at Bureau of Commercial Fisheries Bio- logical Laboratories both at Galveston, Tex. , and Gulf Breeze, Fla. With in- creased emphasis to be placed on this important work, it is being concentrated at Gulf Breeze and has been discontinued at Galveston. Termination of Red-Tide Field Operations Research on red tide was thrust upon the Bureau after the severe red-tide outbreak along the west coast of Florida in 1947. At that time, even the identity of the causative organism was unknown. Public hysteria (caused both by the littering of the beaches with millions of dead fish and the irritating effect on the lungs and throat of the toxin carried as an aerosol) demanded immediate action, and a great deal of money and effort were expended in merely monitoring by fast boat and air- plane the areas where outbreaks might occur. Despite the handicap of at- tempting to carry on research while parrying the innpatient attacks of an indignant public demanding action -- any kind of action -- considerable knowl- edge was accumulated. The causative organism, a naked dinoflagellate (Gymnodinium breve Davis), was successfully reared in both unialgal and pure cultures. Much has been learned of the effects of various physical and chemical factors on its survival and growth, and of the concentrations of the organism re- quired to exude sufficient toxin to render sea water toxic to other organisms. Several years of field collection of this red-tide organism with con- current measurements of salinity, temperature, and chemical composition of the water have failed to show any limiting relation between abundance of the organism and levels of phosphorus, nitrates, nitrites, copper, etc. The or- ganism does not thrive in water of low salinity. Outbreaks appear to coincide with periods of heavy land drainage when wind velocities are low, especially if the light winds are blowing toward the shore. It would thus appear that the overblooms occur when and where nutrient -laden fresh water mixes with the salt waters of the Gulf. During the field operations, numerous hydrographic data were gath- ered that are of great value to other fishery investigations. Certain of these observations will be continued, but field work on red tide as such has been terminated. This does not mean that broader knowledge being gained in our other estuarine work will not eventually contribute to a greater knowledge of the causes of these sporadic outbreaks. One phase of red-tide work is being continued. It is the search for a chemical agent that will control the red-tide organism without harming other valuable organisnns. A report on current progress appears elsewhere in this report. St. Petersburg Beach Field Station Upon termination of red-tide field ac- tivities, it was necessary to decide on the future role of this field station. Since the station has excellent hydrographic observations since 1957 for Tampa Bay and the adjacent waters of the Gulf, it was decided that Tampa Bay would be a suitable area for conducting needed research on the estuaries of the east- ern Gulf. The field station is now operating independently of the laboratory at Galveston. Research Vessel Several naval architects formally expressed their opinion that the funds available for construction of the proposed laboratory research vessel are insufficient to construct and equip the type of vessel needed. Ne- gotiations for an architect are, therefore, being held in abeyance unless or until adequate funds become available. East Lagoon Field Station The sea-water laboratory on East Lagoon in Galveston (illustrated on front cover) was dedicated by Assistant Secretary of the Interior, Frank P. Briggs, during the meeting in Galveston of the American Fisheries Advisory Committee. Four rooms for controlling temperatures within a narrow range for studies of shrimp physiology are nearing completion. Increased Tempo of Research Effort It is instructive to occasionally glance back over your shoulder and see where you have been in comparison with where you are going. Biological research in fisheries in the Gulf of Mexico has lagged behind other areas but appears to be gathering steam. The shrimp fishery of the south is the most valuable U. S. fishery, and we have exam- ined the research publications of the Bureau of Commerfial Fisheries on this subject as an index of fishery research effort in the area. Shrimp research by the Bureau in the Gvilf of Mexico began in 1931 with headquarters in New Orleans and continued in a small way until about 1948. For almost a decade thereafter, active field work was discontinued. The third phase was reactivation of shrimp research at the Biological Lab- oratory in Gaiveston in the late 1950 's by means of Saltonstall -Kennedy funds. The fourth phase comnnenced in mid-1961 when, through efforts of the Gulf States Marine Fisheries Commission, regular funds were appropriated that have permitted large-scale biological and hydrographic sampling off the Gulf coast between the Rio Grande and the Mississippi Rivers, and port sampling of commercial landings to supply data needed for studying the dynamics of the populations. I 1 REPORTS OP RESEARCH 1931-1946 I 1 (PORMER NEW ORLEANS LABORATORY! ^^^^ CONTRACT RESEARCH ^^^ BIOLOGICAL LABORATORV, GALVESTON In the first table and the figure, the pages of published research are sho\vn by 5-year periods. The work begun in 1931 was modestly financed. The very small staff and lack of facilities severly limited the type and amount of work that could be undertaken. Despite these handicaps several very credit- able reports were published. Eventually, it became apparent that without nnuch better statistics, more staff, and adequate laboratory and seagoing facilities, little further progress could result, and work was held in abeyance. In 1956, the statistical branch of the Bureau inaugurated the present system for collecting detailed statistics on shrimp landings by species, size, area, depth, and amount of fishing effort in- volved. At the same time, the Bureau prepared to resume research on shrimp at the Biological Laboratory in Galveston. Certain phases of the work were carried out by contract with universities. These include the development of a technique for staining shrimp by the University of Texas, a detailed atlas of the morphol- ogy of the white shrimp (Penaeus setif- erus) by Tulane University, and studies on size distribution of pink shrimp on the Tortugas grounds by the University of Miami. Currently, the University of Miami is studying the distribution of pink shrimp larvae in relation to cur- rent patterns. That the research is gathering momentum is indicated by the great in- crease in published reports in the 1957- 61, 5-year period. The estimate of re- ports forthcoming in the 5 -year period commencing with 1962 (see the first ta- ble and the figure) is undoubtedly con- servative, as it is based largely on pages of manuscript in press by June 30, 1962. Furthernaore, it has taken some time to tool up. The staining and handling tech- niques for marking shrimp have been considerably improved, and through underwater release of marked shrimp directly onto the bottom, we can now mark shrimp at sea. The sea -water system completed last year is permitting further improvement in marking methods and is also invaluable in holding and rearing larval shrimp for identifying the species in these young stages. The future con- struction of a small but modern research vessel to study the environment on the Research reports on shrimp biology in the Gulf of Mexico emanating from the Bureau of Commercial Fisheries. Estimates for the 5-year period com- mencing in 1962 are explained in text. continental shelf would be an important step toward understanding the causes of annual fluctuations in survival of the larvae from different broods. Published pages of biological research on Gulf of Mexico shrinap by the Bureau of Commercial Fisheries (as of June 30, 1962) 5 -year period 1931-48 work by the former New Orleans Laboratory Contract research for the Bureau Biological Laboratory at Galveston Annual reports 1927-31 4 1932-36 162 1937-41 95 1942-46 36 1947-51 34 1952-56 106 1957-61 13 297 1962- ? ca. 114 40 Other In press 2/ 200 25 307 Total 4 162 95 36 34 106 624 372 Total 450 297 154 225 307 1,433 1962-66 estimate 250 200 860 II 1, 310 \_l Work performed by Universities of Texas and Mianai, and Tulane University. 2./ Manuscript pages in press June 30, 1962. 3./ Estimated from number pages published and manuscript pages in press during first 6 months of the 5 -year period. The broad scope and complexity of the problems encountered be- come apparent if one notes the subject matter of the reports already published or in press. Other research at the Biological Laboratory also has an impor- tant bearing on shrimp conservation. Thus, postlarval shrimp enter the es- tuaries, settle to the bottom, and grow rapidly for a period of 2 to 3 months before starting their return journey to the open Gulf. It is imperative that these estuarine nursery areas be preserved from pollution, encroachment, or undesirable hydrographic changes. Our estuarine research is aimed at de- termining the most suitable conditions for various species, including shrimp. Pages of research by the Bureau of Commercial Fisheries on various phases of shrimp biology. Subject Published pages In annual laboratory report—/ Other Manuscript pages in press Total pages Summaries and research programs Problems of shrimp industry Life history of white shrimp, including migrations Taxonomy and morphology Sampling equipment for taking young stages Early life history Distribution and abundance of larvae Ecology of shrimp nursery areas Effects of pesticides on shrimp Nutrition and respiration Predation on shrimp by juvenile fishes The bait shrimp fishery Techniques for marking shrimp with stains Bibliography of shrimp literature Length -weight relationship Migrations of pink shrinnp Migrations of brown shrimp Size distribution on Tortugas grounds Currents on the Tortugas grounds Trends in population abundance 62 113 131 223 3 3 12 107 9 8 13 9 11 4 9 24 4 43 143 20 14 5 7 5 62 14 15 13 37 15 255 62 113 131 223 6 156 9 8 37 11 4 33 47 143 20 19 7 67 14 283 114 972 307 1,393 1./ Exclusive of this 1962 Annual Report. STAFF George A. Rounsefell, Laboratory Director Joseph H. Kutkuhn, Assistant Laboratory Director Biological Laboratory at Galveston, Tex. Field Stations at St. Petersburg Beach and Miami, Fla. and Pascagoula, Miss. Shrimp Fishery Program J. Bruce Kimsey Thonnas J. Costello Donald M. Allen William C. Renfro Robert F. Temple Edward F. Klima David L. Harrington Harry L. Cook Carl H. Saloman Harold A. Brusher Kenneth N. Baxter Ray S. Wheeler Charles E. Knight Clarence C. Fischer Clyde A. AUbaugh Orville D. Brown Thomas W. Turnipseed James M. Lyon Aubrey A. LaF ranee Imogene A. Sanderson Alice Murphy James P. Gilmore Christopher D. Noe David S. Greene John G. Migliavacca John H. Tweedy Donald R. Nelson Andrew E. Jones Joseph J. Ewald Richard L. Aaron Program Leader Head, Field Station Biologist Biologist Biologist Biologist Biologist Biologist Biologist (transferred 1/62) Biologist Biologist Biologist Biologist Biologist Biologist (resigned 6/62) Biologist (resigned 5/62) Biologist Biologist Aid Technician Technician Summer Aid Summer Aid Summer Aid Summer Aid Aid (Intermittent) Aid (Intermittent) Aid (Intermittent) Aid (Intermittent) Aid (Intermittent) Galveston Miami Miami Galveston Galveston Galveston Galveston Galveston Miami Galveston Galveston Galveston Galveston Galveston Galveston Galveston Morgan City Aransas Pass Galveston Galveston Galveston Ft. Myers Beach Galveston Galveston Galveston Miann.i Miami Miami Miami Miami Estuarine Program Joseph J. Graham Anthony Inglis Richard A. Diener Charles H. Koski Cornelius R. Mock Gilbert Zamora, Jr. William Laming Terry C. Allison Domingo R. Martinez Genevieve B. Adams Industrial Fishery Program Joseph H. Kutkuhn Charles M. Roithmayr Richard J. Berry James G. Ragan Jerry T. Goff Ronald J. Arceneaux Biologist (transferred 10/61) Biologist Biologist Biologist Biologist Aid Aid Svimmer Aid Summer Aid Statistical Clerk Biologist (Program Leader) Biologist Biologist Biologist Summer Aid Summer Aid Galveston Galveston Galveston Galveston Galveston Galveston Galveston Galveston Galveston Galveston Galveston Pascagoula Galveston Galveston Pascagoula Galveston Physiology and Behavior Program Edward Chin David V. Aldrich Zoula P. Zein-Eldin John G. VanDerwalker Don S. Godwin Roger M. Friedberg Biologist (Program Leader, resigned 2/62) Galveston Physiologist (Program Leader from 2/62) Galveston Biochemist Galveston Biologist (transferred 12/61) Galveston Aid Galveston Aid Galveston Red-Tide Program (terminated 6/62) William B. Wilson David V. Aldrich Billie Z. May Alexander Dragovich John H. Finucane John A. Kelly, Jr. Gordon R. Rinckey John D. McCormick Lucius Johnson, Jr. Biologist (Program Leader, resigned 6/62) Biologist (to 2/62) Chemist (transferred 1/62) Biologist (transferred 1/62) Biologist (transferred 1/62) Biologist (transferred 1/62) Biologist (transferred 1/62) Master, M/V KINGFISH (transferred 1/62) Chemistry Aid (transferred 1/62) Galveston Galveston St. Petersburg Beach St. Petersburg Beach St. Petersburg Beach St. Petersburg Beach St. Petersburg Beach St. Petersburg Beach St. Petersburg Beach 8 Chemistry and Sea~Water Laboratories Kenneth T. Marvin Raphael R. Proctor, Jr. Larence M. Lansford Elroy L. Young Library Stella Breedlove Chief Chemist Chemist Technician Aid Librarian Galveston Galveston Galveston Galveston Galveston Technical Services Ruth W. Yanch Ester E. Sell Daniel Patlan Petronila C. Prado Mary E. Hippie Nellie P. Benson Secretary Secretary (resigned 2/62) Draftsman Scientific Stenographer Clerk-typist (transferred 1/62) Clerk -stenographer (part time) Galveston Galveston Galveston Galveston St. Petersburg Beach Mianni Administration and Maintenance Lawrence E. Wise Laura M. Hernnann Corinna L. Denbo Glo S. Baxter Peter M. Villarreal Robert L. McMahon Tidas C. Alcorn Administrative Officer Galveston Asst. Administrative Officer Galveston Purchasing Clerk Galveston Clerk-stenographer Galveston Maintenanceman Galveston Maintenanceman Galveston Maintenanceman Galveston SHRIMP FISHERY PROGRAM J. Bruce Kimsey, Program Leader 6ALVEST0N Broadly stated, the basic objective of the Shrimp Fishery Program is to obtain an understanding of the dynamics of the total population. This in- cludes the preexploited as well as the exploited phases of the commercially important shrimp species. More specific objectives are associated with pre- dicting yield and rationalizing exploitation so that maximum production levels can be maintained. A study of offshore shrimp populations began in January 1961 with the sampling of 1 1 stations between Galveston, Tex. , and Cameron, La. , and was completed in January 1962. Some of the results are presented as pro- ject reports in this annual report, while other data are still being analyzed. In September 1961, the original sta- tion pattern was expanded to in- clude four additional, six-station transects. In January 1962, fur- ther changes were made, and the offshore sampling study currently consists of 10, six-station tran- sects, ranging from the Missis- sippi River to the Rio Grande River. Two shrimp trawlers, BELLE OF TEXAS and MISS AN- GELA, are chartered to carry out the sampling. The 60 monthly stations are equally divided be- tween 7j, 15, 25, 35, 45, and 60 fathoms. At each station a 45 -foot shrimp trawl is towed 1 hour, a 20 -minute plankton tow is made with a Gulf V plankton sampler, and current, salinity, and temper- ature measurements are made at various depths. Beginning in Feb- ruary 1962, drift bottles and sea- bed drifters have been released. The seabed drifter is a plastic umbrellalike device that barely maintains itself on the bot- tom, which it touches lightly by the tip of the "handle. " Even very small water movements will cause it to drift along the bottom. 20 40 I 60 _) NAUTICAL MILES Station pattern for 1961 cruises between Galveston, Tex. , and Cameron, La. 10 Station pattern adopted in January 1962 for the expanded shrimp program. 11 The research cruises are providing information on distribution and extent of spawning of commercial as well as associated noncommercial species of shrimp, according to season and area. The same information is also being obtained for the larval stages. Closely allied to the latter study is the shrimp larval identification project which successfully reared three more species of shrimp to the protozoea stage. In addition to expanding the offshore aspects of the program, mark and recapture experiments designed to obtain information on movements, growth, and fishing mortality of offshore stocks of commercially exploited shrimp were begun. Three experiments were completed. Pink shrimp were marked with biological dyes on the Tortugas grounds in September 1961 and on the Sanibel grounds in April 1962. A similar marking experiment on brown shrimp (Penaeus aztecus) was completed off the central Texas coast in April 1962. Using data from the Tortugas study, it has been possible to make the first estimates of fishing mortality of a commercial shrimp population. Ex- cellent growth rate information was also obtained. The commercial fisheries statistics obtained by the Branch of Sta- tistics are now being supplemented by biologists sampling the commercial shrimp catch for species and size composition at selected Gulf ports. In 1961, there was a 35-percent drop from I960 in poundage of shrimp landed in the South Atlantic and Gulf states. Much of the industry was in distress and seeking assistance regarding the future of the fishery. In early 1962, enough information on various aspects of the brown shrimp life history was available to make a prediction for improved shrimp prospects during the 1962 season. This prediction was based on comparable measures of shrimp abun- dance obtained since 1959. Indexes of abundance were obtained for postlarvae at the Galveston entrance and for juvenile shrimp from the Galveston Bay com- mercial bait fishery statistics. In I960 and 1961, a strong correlation was ob- tained between the postlarval and juvenile indexes and the subsequent catch of commercial-size shrimp. In 1962, the postlarvae and juvenile indexes for the February -April period v/ere similar to those of the good offshore fishing year of I960. Bait shrimp (juvenile) production in May 1962 was the highest ever recorded for that month. Primarily on the basis of these observations, good to excellent fish- ing was predicted for the 1962 season. 12 Spawning Populations William C. Renfro and Harold A. Brusher During 1961, 17 cruises were made in the area between Galveston, Tex. , and Gameron, La. , to as far as 100 miles offshore. At each of the 11 stations in the area, a 45-foot shrimp trawl was towed for 1 hour. Penaeid shrimps taken were counted, sexed, and measured, and predetermined num- bers of females of each species were dissected to obtain samples of ovary tissue. Ovary samples were fixed in Bouin's solution and returned to the lab- oratory where they were prepared as stained slide mounts. Cytological exam- ination of all brown shrimp (Penaeus aztecus) ovary sections to determine stage of ovary development was recently completed. Of 1, 374 brown shrimp ovary sections examined, 262 are from small females less than 140 mm. total length. The ovaries of most (73%) of these smaller specimens are either undeveloped or in very early stages of develop- ment. Less than 10 percent are in the "yellow" or more advanced stages of development. "Developing" and "yelloAv" stage ovaries are most prevalent (79%) in females 140 mm. or larger, indicating that these two stages consume most of the time in the process of ova maturation. Less than 3 percent of the larger females sampled were undeveloped or in early developmental stages. This sug- gests that there is no "resting" or "dormant" stage in this species. Apparently in this area, once a brown shrimp female reaches sexual maturity, ova gener- ation and maturation continue unabated throughout the remainder of her life. Very few brown shrimp were found at the 7 2 -fathom stations during the first 5 months of 1961. In June, small shrimp began to naove offshore from the estu- arine nursery grounds. Almost all females taken in 72 fathoms from June through December were small with "undeveloped" or "early developing" ovaries. There was little evidence for spawning of bro\vn shrimp in 72 fath- oms. The spawning condition of brown shrimp collected during 1961 betw^een Gcdveston, Tex. , and Cameron, La. (~1 -D««eiop'na 13 Females found at the 15-fathom stations from June through Decem- ber were of two sizes, either small with immature ovaries or larger, more mature specimens. Females from the deeper stations (25 and 45 fathonris) were consistently larger and in advanced stages of ovary developnnent. The presence in an ovary of (1) ripe ova undergoing resorption, (2) cell components remaining after ripe ova had been resorbed, and/or (3) ab- normally large nunnbers of follicle cells is taken as evidence of prior spawn- ing. By use of these criteria, many females classified as "developing" or "yellow" are also classified as having previously spawned. Females with ripe and spent ovaries or which had previously spawned were found in one or more depth zones during every cruise. The percentage of ripe and spent females in the 15-fathom depth zone was greatest from mid- April to early May and during November. The highest percentages of ripe and spent ovaries occurred at the 25-fathom stations in February, April, from late June to late July, and frona late August through mid-December. In the 45- fathonn depth zones, the percentage of ripe and spent females was highest in mid-April, from late May through June, and from late August through early October. The percentage of ripe and spent brown shrimp in the 1961 samples. In addition to determining the spawning condition of the offshore shrimp populations, we also obtained data on abundance, distribution, size, and species composition. In Septennber 1961, four transects of six stations each were added to the original 1961 sannpling patterns. Two of these were located to the west of the Freeport, Tex. -Cameron, La. , sampling area, and two were located to the east. Data for population characteristics other than spawning condi- tions from these transects as well as from the original pattern have all been analyzed. 14 During the 24 cruises made between January 1961 and January 1962, 246 1-hour trawl samples were taken. Eleven species of penaeid shrimp were taken, although 97 percent of the total catch was made up of only five species, i.e., brown shrimp, white shrimp (Penaeus setiferus), rock shrimp (Sicyonia brevirostris and S. dorsalis), and Trachypeneus similis. The large number (10, 880) of one species of rock shrimp, S. brevirostris, suggests this penaeid may be present in sufficient quantities to support a commercial fishery. Numbers of shrimp caught, according to species and depth range taken in 246 1-hour tows made between January 1961 and January 1962 Fathoms Species 7i 15 25 35 45 60 Total Penaeus aztecus Penaeus setiferus 1,828 7,988 73 594 38 1.914 39 446 4,019 378 342 5,798 4, 173 1,280 27 9 1 4,212 3, 155 798 87 3 1 1,414 1,072 1, 511 300 8 1,442 261 349 64 213 3 185 54 1 13, 100 8, 366 Penaeus duorarum Sicyonia brevirostris Sicyonia dorsalis Trachypeneus similis Trachypenaeus constrictus Solenocera vioscai 415 10, 880 6,869 3,645 66 278 Solenocera atlantidis Xiphopeneus kr^yeri Parapenaeus longirostris 9 447 5 Total of all species 12,920 16.027 8,256 4,305 2, 332 240 44,080 Number of tows 76 62 44 12 42 10 246 15 The three species of commercial shrimps (brown, white, and pink) made up 50 percent of the total catch. Their abundance, distribution, and size have been compared with several oceanographic characteristics. The center of abundance for these three commercial shrimps is in the western transects southeast of the Freeport-Pass Cavallo area. The greatest number of brown shrimp (63%) is taken in the 15- to 25-fathom range. Almost all of the white shrimp (99%) are taken at the Ij- fathom stations. Pink shrimp, although taken in small numbers, occur only at the Vj- and 15-fathom stations. Large numbers of juvenile brown and white shrimp in the offshore fishery at the Tg-fathom stations in the western transects suggest the impor- tance of the Galveston -Matagorda Bay complex as nursery grounds. 100- 150- zoo ' 150 7'^ FATHOMS 1 5 FATHOMS 25 FATHOMS -1 1 1 r— -1 1 1 r- 45 FATHOMS JAN ' FEB ' HAD ' APR ' H^V • JUN ' JUL ' AUQ ' SEP ■ OCT ' NOV < DEC II ' ' ^ ^ "°i e z < 100 £ - T5 SO Size range of brown shrimp in 1961 according to depth and month. Brown shrimp increase in average size with increase in station depth. The time of offshore movement for juvenile brow^n shrimp is indicated by a sharp increase in catches of small immature brown shrimp at the Ij- fathom stations in June. This movement apparently continues until Decennber. The catches of brown shrimp at the 7^-fathom stations are snaall from January through May, but the individuals are consistently larger. 16 Nearly all of the white shrimp are taken at the 72-fathom stations, so no comparison with depth zones is possible. There is, however, an evident seasonal variation in size caused by the migration of juvenile white shrimp from estuarine nursery areas to the offshore grounds. This is first evident in September and again from December through January, after which an in- crease in average size is evident until August. Day /night comparisons show a definite catch increase for brown shrimp at night at all depths, while the greatest catches of white shrimp were taken in day trawls. 3 100- < O 75- I IE 111 a. S 3 Comparisons of day and night catch per unit of fishing effort for brown shrimp between Galveston, Tex., and Cameron, La., in 1961. Based on the examination of 21, 466 shrimp of commercial impor- tance, the sex ratios for both white and brown shrimp show a 1:1 relationship which is relatively constant at all depths sampled. 17 Larval Distribution and Abundance Robert F. Temple The examination of the plankton samples from 17 cruises nnade during 1961 in the offshore areas between Galveston, Tex. , and Cameron, La., is completed. At each of the 11 stations in this area a 20-nriinute, "step- oblique" plankton tow was made with a Gulf V plankton sampler. These sam- ples are used in studying the early life history of shrimp, particularly the dis- tribution, abundance, and survival rate of larvae. Eggs are not found in the samples, but the occurrence of the nauplius, the first stage after hatching, can be used as an indication of spawning. Commercially important shrimp, genus Penaeus, connprised 18 per- cent of the total catch of 14, 218 larvae of the family Penaeidae, while non- exploited shrinap of the genera Trachypeneus, Sicyonia, Solenocera, Para- penaeus, and Xiphopeneus constituted the remaining 82 percent. All larvae have been identified, and their seasonal and areal distribution and abundance tabulated and graphed. The majority of larvae, genus Penaeus, were caught at 7^-fathom stations between May and October. Larval abundance was greatest in July and August. Spawning, based on the occurrence of nauplii, began in May and con- tinued until October. The seasonal distribution of larvae coincides closely with changes in bottom temperatures. Indications are that Penaeus in this depth zone spawns at temperatures over 75' F. Average monthly bottom temperatures (° F. ) for 7|^-fathom stations March April May June July August September October November 62. 6» 66.6° 76. 1" 80. 5» 83.4° 82. 6» 80.6° 77. 3° 65.4° Penaeus larvae of one stage or another were taken every month of the year at the 15-fathom stations. Two general peaks of abundance were noted in April and September. Three distinct periods of spawning, indicated by the oc- currence of nauplii, were evident at 15-fathom stations: the first in April , the second the last of June and first of July, and the third in September. The high- est level of abundance, observed in September, was approximately three times greater than any peak noted at the 7^ -fathom stations. Penaeus larvae were more abundant at 25 fathoms than at any other depth. In the first 8 months, January to August, the abundance of larvae in- creased, with the greatest level of abundance occurring from September through November. Spawning at this depth first occurred in May. Additional spawning, although in varying degrees of intensity, was evident from July through Decem- ber. At the 45-fathom stations, larvae were taken sporadically throughout the sampling period. The highest level of abundance was observed in Septem- ber. Nauplii, although not abundant, occurred in June and September. 18 lOOn 7i/2-fm. STATIONS (4) ^m. - ■ »ni|.iiiaiii.p 5-fm STATIONS (3) 2 10 The distribution of Penaeus larvae in the offshore area between Galveston, Tex., and Cameron, La., in 1961. 19 Distribution and Abundance of Nonexploited Species Larval Penaeidae of genera other than Penaeus were not encountered at the Tj-fathom stations until the nniddle of May. In the ensuing months they persisted at this depth, fluctu- ating slightly in abundance until the first of November, when they reached their highest level of abundance. Immediately thereafter they disappeared. Spawn- ing in the 7^-fathom zone appears to have begun the latter part of May and continued until the first of October. Nauplii are most abundant, however, in June and July. 7i/J-fm STATIONS (4) The distribution of non-Penaeus larvae in the offshore area between Galveston, Tex., and Canneron, La., in 1961. 20 The seasonal distribution and abundance vary considerably at the 15 -fathom stations from those at the shallower stations. The larvae of one stage or another of the nonexploited shrimp were present throughout the entire year, although in varying degrees of abundance. Two peaks of abundance are noted: one in June and the other in September. Nauplii are most prevalent in March and the first of December. The level of abundance of penaeid larvae at 25 fathoms fluctuated radically from February to July. Two peaks of abundance are evident: one in March and another in June. In the ensuing months, August through November, a level of abundance similar to that of March and June was reached and main- tained until November. In December, there was a sharp decline in the abun- dance of larvae. Nauplii were caught sporadically over the entire sampling period with the greatest abundance in March. The overall larval abundance in this depth zone was not as great as at 15 fathonns, however. At the 45 -fathom stations the peaks of abundance occurred in April and October. Larvae are less abundant, however, than at shallower stations. The few nauplii taken at this depth were taken in February and September. Penaeus larvae of one stage or another were present the entire year at 15-, 25-, and 45-fathom stations. The majority of larvae at Tg-fathom sta- tions, however, were caught between April and November. Indications are that temperatures have a direct effect on the seasonal occurrence of Penaeus larvae at the 7|^-fathom stations. The highest level of abundance was at 25-fathom stations between September and November. All larval stages of Penaeus were most abundant at 25-fathom sta- tions. Nauplii at 15- and 25-fathom stations were 3 to 16 times more abun- dant than at either 7|^- or 45-fathom stations. Protozoeae at 25-fathom stations were the most abundant larval stage encountered. It would appear that larvae at 25 fathoms are probably either Penaeus aztecus or P. duorarunn, since P. setiferus, very seldom inhabit these depths. Annual catch per standard tow of larvae of exploited shrimp Station Mysis depth Nauplii Protozoeae stages Postlarvae fm. Number 'Number Number Number 7i .51 .52 .40 .23 15 1.57 .79 .60 .71 25 2.30 15.23 2.13 1.89 45 .15 4.41 .52 1.45 21 Larvae of one stage or another of nonexploited shrimp are present the entire year at 15-, 25-, and 45-fathom stations, although in varying de- grees of abundance. The occurrence of larvae at the 72-fathom stations ap- pears seasonal, inasmuch as larvae were taken only between May and Novem- ber. As was the case in Penaeus larvae, a direct correlation is evident be- tween the seasonal occurrence of larvae and increasing bottonn temperatures. All larval stages, except the nauplial stage, were more abundant at 15-fathom stations. Nauplii were more abundant at Tj- a^nd 15-fathom stations. Protozoeae at 15-fathom stations were the most abundant larval stages encoun- tered. The larvae encountered at 45-fathom stations were deep-water shrimp, i. e. , Solenocera and Parapenaeus. Annual catch per standard tow of larvae of nonexploited shrimp Station Mysis depth Nauplii Protozoeae stages Postlarvae fm. Number Number Number Number 7i 2.33 13.05 7.95 .40 15 2.26 34.45 28. 16 2.57 25 1.08 12.31 13.86 .55 45 .08 3.44 2.61 .03 22 Currents on the Continental Shelf of the Northwestern Gulf of Mexico JUNE 14-15, 1961 \ OSOOV /„ 0300 < /0900 10 I I ^.^^300 r ^4 TIDE CHANGES t555 2140 0549 J. Bruce Kimsey and Robert F. Temple The three commercially important species of shrimp, i.e., brown (Penaeus aztecus), white (P. setiferus), and pink (P. duorarum), all spawn offshore where the eggs hatch. This may occur at distances ranging from a few miles to as much as 150 miles offshore and at depths down to 60 fathoms. The larvae move shoreward while passing through a series of developnnental stages, arriving at the passes into the bays and estuaries as postlarvae. It is not known whether the shoreward migration is aided by water currents or the larvae arrive under their own power with no outside aid. A study to determ.ine the role water currents play in the movenaent of larvae from offshore spawning grounds to the inshore nursery grounds has been a part of the Shrimp Fishery Program since 1961 when the Savonius rotor current meter was first used. Analysis of cur- rent data collected with this current meter during April through October 1961 has been completed. The data were obtained by tak- ing instantaneous readings every 3 weeks at 1 1 sta- tions in waters adjacent to Galveston. Station depth ranged from Tg to 45 fathoms. At each station, current observa- tions were made at 10 feet below the surface, mid- depth, and 10 feet from the bottom. To complement these data, three 24-hour current studies were under- taken at one 15 -fathom sta- tion (Station "H"). In an attempt to obtain a generalized cur» rent pattern fronn the in- stajitaneous monthly ob- servations, current roses were constructed for each station and depth. Although the results are not con- clusive, indications are Progressive vector analysis of 24 -hour current observations made at a 15-fathom station off Galveston, Tex. 23 JULY 20-21, 1961 TIDE CHANGES 1/^ 10 ft. \oe( \0900 IS22 2232 02IB 0837 AUGUST 30-31 1961 45 ft. 80 ft. Imoo X ■^li500 / 1 — >/ooo \l700 TIDE CHANGE 1238 .TOOV ,^— IndkoiM Tid* CMnff* that (1) currents decrease in velocity with an increase in depth, (2) the strong- est longshore currents occur at the Tj -fathom stations located off Galveston and San Luis Pass, and (3) although a few 2-knot currents were observed, the majority were less than 1 knot at all stations. The purpose of the 24-hour current studies conducted in June, July, and August at Station H were twofold: (1) to check the validity of the instan- taneous monthly readings and (2) to measure the residual current and deter- mine, if possible, the influencing factors. Analysis of the first 24-hour current study substantiated the belief that instantaneous readings, although measuring the direction and speed of the current at that time, could conceiv- ably result in an erroneous concept of the residual current. Further analysis of the data indicated that if continuous monthly ob- servations could be made at a permanent station, a residual monthly current pattern could be established. It should then be possible to relate existing re- sidual currents directly to some physical factors, such as water density, winds, or tides. Progressive vector analysis of the currents at three depths during the June study revealed a wide current variation between depths. The vector diagrams for the surface and bottom, currents strongly suggest currents in- fluenced by tidal action. Some discrepancies exist, however, between the noted changes at Station H and the tidal gauge at the Galveston Channel. The distance between these two points (48 nautical miles) probably accounts for these anomalies. Mid-depth currents (45 feet) appeared to be less subject to these tidal changes. The resultant currents at the three depths were variable. The current at 10 feet was moving 287° at 1.7 knots, the 45-foot current flow- ing 226° at 4.4 knots, and the 80-foot current flowing 133° at 1. 5 knots. Dur- ing this period, a 10-knot southeast wind prevailed. In the July and August studies, the variations noted in June were not evident. In July, all depths exhibited an easterly current with the velocity de- creasing as depth increased. Prior to the July observations, a south to south- east wind averaging 11 knots had prevailed for 8 days. The water currents, moving to the right of this force, were probably a direct result of these winds. The curtailed August observations revealed a similar picture. Cur- rents at all three depths, flowing southerly, appear to be the result of a north to northeast wind averaging 10 knots which had prevailed for 6 days prior to the observations. Fronn these limited data, it is impossible to establish a monthly cur- rent pattern for either June, July, or August. Utilizing clinaatological data and Galveston Channel tide tables, however, we could detect relationship be- tween observed currents during a 24-hour period, winds, and tides. Indica- tions were that currents 48 nautical miles south of Galveston are influenced by tide and wind action. In February 1962, the current study utilizing the Savonius rotor current meter was expanded by the addition of drift bottles and seabed drifters. Twelve drift bottles, six of which are ballasted with sand, and six seabed drifters are released at each of the 60 monthly stations. 24 Because they are more influenced by winds, the nonballasted bot- tles reach the shore more quickly than the ballasted bottles. The rate of drift is determined from the bottles with the shortest period of drift. Onshore winds tend to accelerate the rate, while offshore winds, which are more com- mon in the winter, slow the shoreward movement. The rate of drift bottle return decreases during "poor weather when few people frequent the beaches and markedly accelerates during the tourist season. The unusually large in- flux of Sargassum weed on the north Gulf coast in the spring of 1962 covered bottles and discouraged beach use. These factors, together with other more subtle influences, make the calculation of current velocities from drift bottles alone somewhat tentative. The instantaneous measurement of current velocity with the Savonius rotor current meter should strengthen the drift bottle data. 30- • aRtltos* points -330-doy directional orrows with drift 8p««d in knots. TEX. 28 .... \vr / ^ GULF OF MEXICO 30 -28 96° 94° 92° 90° Surface drift on the continental shelf of the Gulf of Mexico in February 1962 as deduced from drift bottle releases. 25 In February 1962, the direction of surface drift over the continental sheH in the northwestern Gulf of Mexico was generally westerly, ranging in rate from 0.4 to 0. 7 knots. An easterly drift of 0. 3 to 0. 6 knots was observed between Brownsville and St. Joseph Island, Tex. The higher rate is near the shore. There are indications of a large clockwise circulation developing in the vicinity of Port Aransas. Returns for the mmths of March through June tend to corroborate this impression, but its exact nature is not yet clear. A second smaller eddy apparently exists in the area off Grand Isle, La. The seabed drifter previously described is a plastic umbrellalike device that barely maintains itself on the bottom, so that even very small water movements will cause it to drift along the bottom. It is largely depend- ent for its return, therefore, upon capture in shrimp trawls, although many liberated at inshore stations have been found on the beach. Their rate of re- turn, except for the beach finds, is closely related to fishing effort, which varies extensively according to time and area, causing returns from this source to be slow and erratic. Shrimp trawlers in the Gulf of Mexico carry a minimum of navigation equipment, and the location of the return is often too vague to be of use. Despite these limitations, some useful information has been obtained. During February 1962, bottom drift, based on 16 returns, was generally easterly or opposite to surface drift except in the area off Grand Isle, La. , where the bottom drift was northerly or westerly. The direct measurement of water movements by drift bottles and seabed drifters is continuing; indirect measurement by analysis of density currents is planned. Comparison of returns for ballasted and nonballasted drift bottles as of July 1, 1962 Month of Released Returned Compos ition of returns Possible days release Ballasted 1 Nonballasted out Number Number Percent P ercent Number Feb. 720 108 40.6 59.4 123-132 Mar. 720 213 41.8 58.2 95-102 Apr. 720 135 29.6 70.4 65-73 May 720 62 25.8 74.2 39-43 June 720 16 18.9 81. 1 7-12 26 Number of drift bottles returned as of July 1, 1962 Month of release Released Returned Days out 0-30 31-60 61-90 91-129 Number Number Number Number Niimber Feb. 720 37 20 30 21 Mar. 720 78 59 65 11 Apr. 720 70 67 8 May 720 38 24 June 720 16 Number of seabed drifters returned as of July 1, 1962 Month Released Returned of Days out release 0-30 31-60 61 -90 91-129 Number Number Number Number Number Feb. 360 6 6 3 1 Mar. 360 14 6 5 2 Apr. 360 25 14 6 May 360 2 4 June 360 1 27 Identification of Shrimp Larvae Harry L. Cook An illustrated key to the genera of penaeid larvae found in the north- western Gulf of Mexico was completed. We were able to assign to genera the reference specimens taken from plankton samples by comparing them with larvae obtained fronn rearing trials as well as with illustrations in the litera- ture. Solenocera and Parapenaeus mysis and postlarval stages, missing from routine plankton samples, were obtained during a special cruise of the M/V SILVER BAY off the mouth of the Mississippi River. The key is in two parts. The first, designed mainly for those unfamiliar with pe- naeid larvae, distinguishes penaeid larvae from the more prevalent forms of nonpenaeids found in the plankton samples. It also defines the stages of penaeid larvae. Five nauplial, three protozoeal, and three mysis stages were the general rule, except for Solenocera and Para- penaeus, which have more than three mysis stages. The second part deals with the genus identification of the protozoeal, mysis, and postlarval stages of the littoral penaeidae of the northwestern Gulf of Mexico. The key in- cludes illustrations of Parapenaeus, Penaeus, Sicyonia, Solenocera, Trachypeneus, and Xiphopeneus and is now being tested in the lab- oratory. Considerable effort was spent to dif- ferentiate the species of larval Penaeus. As the most accurate way to do this is by examin- ing larvae of known parentage, special short cruises were made to catch ripe females that would spawn in the laboratory. The efforts were successful, and from females that spawned in the recirculating sea-water system, larvae were reared through Protozoea I for Penaeus aztecus, Sicyonia brevirostris, and Trachypeneus similis. Protozoea III of Solenocera sp. , dorsal view. (Left an- terior appendages not shown.) Most of the larvae preserved were in good con- dition, and sufficient material was obtained for detailed descriptions. In conjunction with the rearing trials, experiments were made with temperature control, rearing media, and food. It appears that temperatures above 23* C. are required for optimum growth in the laboratory. Larvae reared at temperatures of 24' and 28 "C. were very active and developed rapidly. Those 28 reared below 23° C. grew slowly and showed little movement, all dying before reaching the first protozoeal stage. Brown shrimp (P. aztecus) eggs spawned at 22. 5" C. , hatched slowly, and even though the temperature was raised to 23. 5" C. prior to hatching, the larvae were never as robust as larvae of S. brevirostris and T. similis, hatching at 24° C. Brown shrimp nauplii that were active at 2375° C. ceased all movement when the temperature was low- ered to 22. 5° C. After the temperature was raised to 25. 5° C. , they again became active. No optimum temperature was noted for brown shrimp larvae. Larvae of S. brevirostris did best at 24° C. , and those of T. similis at 28° C. ~ Temperatures that yielded the best results in the laboratory were higher than those in the area of the Gulf where the females were taken. Tem- peratures in the Gulf ranged from 20. 5° C. at the bottom to 22. 0° C. at the surface. Miquel's sea water with soil extract added was found to be a more satisfactory rearing medium than natural sea water. Although, in some in- stances, the total number of larvae reaching Protozoea I was the same in the natural sea-water control, the larvae in the Miquel's were always more active with more setae. It appears that though nauplii do not actively feed, they do utilize some nutrients in the water. Efforts to supply a suitable food for the larvae have been unsucess- ful. Protozoea I were introduced into cultures of unidentified diatoms and protozoans. Several of the larvae exhibited trails of fecal material, indicat- ing feeding had occurred, but none molted to Protozoea II. A primary diffi- cxilty is the lack of live specimens to experiment with. In order to secure living protozoeal and mysis stages, live plankton was brought to the laboratory. The penaeid larvae obtained were alive and active. Other organisms in the plankton included carid, sergestid, and mysid larvae, some of which were isolated along with the penaeid larvae. While the nonpenaeid larvae fed and underwent several molts, the penaeid larvae did not appear to feed and died before molting to the next stage. In an effort to find characteristics for separating Sicyonia dorsalis from S. brevirostris, we examined and measured 413 Sicyonia protozoeae and mysis~stages from plankton samples. Slight morphological differences were noted in the protozoeal stages only. The protozoeae were separated into two groups by a difference in the pigmentation of the eyes and by the presence or absence of musculature in the rounded lobe, which is the anteriormost portion of the body. A size difference was also apparent between the two groups of larvae. Connparison with larvae reared in the laboratory proved one group to be S. brevirostris. The other group is assigned to S. dorsalis, the only other member of the genus which maintains a sizable adult population within the sampling area. 29 Larvae from five different cruises representing three major con- centrations of larvae were examined. A seasonal variation in size was ob- served. Larvae taken in March and April were the largest, the June group smallest, and those in September were intermediate. The difference in size was not due to these groups being composed of different species, since the morphological differences noted previously were found in each group and compensated for. There seems to be, then, a seasonal variation in size, which can in turn be correlated to temperature. When the temperature is low, the larger larvae are encountered, and when the temperature is high, the smallest larvae are found. 90 -1 85 uj 80 q: — : ^^ QC^ 75 »- 70 65- 60 / MAR APR -Temperature 10' below surface -Temperature 10' above bottom A-Largest larvae found B -Smallest " " C- Intermediate larvae found 1 1 \ \ 1 I MAY JUN JUL AUG SEP OCT NOV The relationship between larvae size and bottom temperatures. 30 Abundance of Juvenile Shrimp Kenneth N. Baxter To obtain a possible index of later abundance of adult shrimp, the monitoring of the passage of postlarval shrimp into Galveston Bay was begun November 1959- Samples are taken semiweekly using a hand-drawn, beam trawl fitted with a plankton net in the cod end. A station was established in- side the entrance to Bolivar Roads near the south jetty on the sand flats (SF on figure). Samples were taken at this station from November 1959 to May 1961 and from August 11. 1961. until September 8, when flood waters from Hurricane Carla cut a channel 200 feet wide and 14 feet deep through the sand flats adjacent to the jetty, making the station site inaccessible. A new mon- itoring station was then located on Bolivar Peninsula in a cove off State High- way 87 opposite the abandoned lighthouse (BSF on figure). This station was occupied from September 25 to November 21 of 1961. when a third station site was selected on the beach, midway between the north jetty and the Fort Travis ruins on Bolivar Peninsula (NJSF-1 on figure), where twice weekly sampling is currently being carried on. , . ^ , The sample is taken in the following manner. A stake is driven into the ground at the shoreline. A 150 -foot nylon cord is attached to the stake arfd stretched taut parallel to the waterline. Using the cord as a constant radius., the operator pulls the net assembly along the bottom in a half circle. The ef- fective length of the tow is 426 feet, the volume of water sam- pled is 2.477 cubic feet, and the area of bottom traversed is 1,958 square feet. These are average measurements and vary according to the shoreline 's configuration. Through the winter months, great variations in num- bers of postlarvae between sam- pling periods appeared to be re- lated to fluctuations in tempera- ture. Follovsring rapid drops in temperature, very few postlarvae were coUected. and on several occasions numbers of dead postlarval penaeids were noted. For instance, on March 1, 1962, about 75 dead postlarvae were found in the sample. This was after a Postlarval sampling stations at the entrance to Galveston Bay. 31 drop in air tennperature to below 35° F. the previous night. On March 12, 1962, nearly 500 dead postlarvae were found in the sample following a similar drop in temperature. Between January 1961 and June 1962, water temperatures ranged fronn -2.0° to 34.0° C. Although salinities ranged from 7. 6%o to 31.4%c during the same period, there was no apparent correlation between salinities and the number of postlarvae present. The bait shrimp industry of the Galveston Bay system is of consider- able economic importance. This phase of the shrimp fishery has grown rapidly since the first survey was begun November 1956. Production has increased from 225, 000 pounds reported by Chin for June 1957 to April 1958 to an esti- mated 943. 400 pounds in I960 and 731, 200 pounds in 1961. The number of active bait dealers decreased from 130 in May 1961 to 92 in May 1962. Many bait camps and bait boats were destroyed in September 1961 by Hurricane Carla. Approximately 20 percent have not been replaced. In 1961, for the first time in 6 years, bait shrimp were available continuously through the winter. During the winter of 1962, however, very little bait shrimp was taken from the area. This is believed to be due pri- nnarily to unusually low temperatures during the first quarter of 1962. Most of the bait retailed in the Galveston area during this period was trucked in frona Matagorda Bay and Sabine Lake. The annual bait shrimp catch for 1961 consisted of approximately 60 percent white and 40 percent bro^vn shrimp. The occurrence of pink shrimp and Trachypeneus sp. was limited. neither accounting for more than 2 percent of the catch during any given month. March and April Tows Postlarvae taken May catch/effort for Total Per tow brown bait shrjmp Number 1960 17 1961 15 1962 16 Nunnber Number 9,908 582.8 429 28.6 4,246 265.4 Pounds per hour 29.8 18. 3 30.4 . Sampling postlarvae with a small beam trawl. 32 Brown Shrimp Mortality Studies Edward F. Klima 28°- 96 L_ A mark-recapture experiment on brown shrimp, Penaeus aztecus, initiated during April 1962 is expected to yield preliminary estimates of fish- ing mortality and information on movement of the stocks of shrimp off the Texas coast. Over 2,400 shrimp were caught, stained with fast green FCF, and released in a 100-square-mile area ranging from 21 to 24 fathoms south- east of Pass Cavallo. Reports from the statistical branch of the Bureau of Commercial Fisheries indicate that this area was the most heavily fished section along the Texas coast in April 1962. In addition, about 1,700 shrimp were tagged with Petersen disc tags, and released in the same depth range south of Port Aransas and southeast of Freeport. To obtain reliable estimates of fishing mortality, it is necessary to be able to roughly define the population. Since little is known concerning the movement and the population structure of brown shrimp in the northwestern Gulf, the stained shrimp were released in the area of the heaviest fishing con- centration, and the tagged shrimp were released in adjacent areas. Any movement into or out of the staining area should be evident, and some idea of the population structure will be obtained. Because of the nonspecific stain mark and the large area of re- lease, it is not possible to determine the exact distance traveled for any given recovered individual. To min- imize this difficulty, the center of the staining area is considered to be the point of release for all of the stained shrimp. One hundred and twenty -five stained and eight tagged shrimp were recovered through June 6, 1962. Sixty -two percent of all of the recoveries were recap- tured less than 15 miles from the release areas. These shrimp ap- peared to have moved randomly, because approximately equal num.- bers were recovered in all direc- tions from the release position. Fifty marked shrimp traveled more than 15 miles. Of these, 46 moved in an easterly direction, ■while 4 Direction and distance of movement of moved in a westerly direction, brown shrimp marked in April 1962. OFFSHORE MARKING AND RELEASE SITE (APR 19621 RECAPTURE SITES ESTUARINE MARKING AND RELEASE SITE (MAV 19591 96' 33 Thirty -three shrimp were recaptured in water shallower (16 to 19 fathoms) than in the release areas; no shrimp were recaptured in deeper water. The information obtained from the return of marked shrimp indi- cates no immigration into and little long-distance movement out of the staining area. The stocks of shrimp off Pass Cavallo appear to have made a short- distance nnovement in an easterly direction. Since marked shrimp are still being returned, and the catch and effort data are not yet available, no attempt has been made to estimate fishing mortality. Shrimp recovered Distance moved fronn release area General direction of movement Easterly Westerly Total Number Nu mber Number 38 46 83 41 2 43 2 2 4 2 0 2 1 0 1 Nautical miles 15 or less 16 - 30 31 - 45 46 - 60 61 - 75 84 49 133 Seabed drifters, which indicate the direction of bottonn currents, were released along with marked shrimp. The return of these drifters indicates that there was a slow westerly current in the staining area. At present, there are only two stains. Trypan blue and fast green FCF, that are suitable marking agents to use on shrimp for growth and mor- tality studies. To increase the versatility of the staining technique, laboratory experiments are being made to find additional stains. Primary marks such as fast green FCF are now used exclusively. These stains are obvious and, with familiarization, are easily seen by fisher- men. Secondary marks are not so obvious and are identified by visual, chemical, or fluoronnetric examination in the laboratory. The use of a series of secondary marks with primary marks increases the number of possible experiments that can be carried on at one time. To date, 34 stains, dyes, and inks have been tested for use as either primary or secondary marks. Of these, only certain nunnbering machine inks, blue and green, show promise as primary marks for short-term experiments of no more than 50 days. Preliminary results indicate that several fluorescent pigments might prove suitable as secondary marks when used with one of the biological stains. These fluorescent pigments do not fade, nor are they shed from the shrimp during molting and were easily detected under ultraviolet light 61 days after marking. Two other materials which might be useful as secondary marks are red and blue checkwriter inks. The inks were also visible at the site of injec- tion 61 days after marking. A clear solvent which fluoresces white under ultraviolet light and mixes readily with fast green shows promise as a poten- tially good secondary mark. Further experiments are presently being made to deternnine the suitability of these pigments and inks as secondary marks. 34 Pink Shrimp Life History Thomas J. Costello Projects designed to furnish information on the life history of the commercially important pink shrimp, Penaeus duorarum, have been under- taken by the Bureau of Commercial Fisheries in south Florida. Through research contracts with the Institute of Marine Science at Miami, extensive data on the identification and distribution of pink shrimp larvae have been accumulated. Primarily by use of mark-recapture experiments using bio- logical dyes as marking agents, Bureau of Commercial Fisheries biologists have obtained information on the migration, growth, mortality rates, and geographical range of juvenile and adult pink shrimp stocks. 'oorijoas rmiMiitiG onouios A HCi.EASE Sir* fo« Mioxeo smi ^■1 aXEA JHBiMP CAPTUOEO FOH • I RECAPTURE • I-S AECAPTUKES MARQUESAS • /'"-iA'' " / "€r wesr 0 to 20 30 I . I . I I I NAUTICAL MILES Release and recapture sites for pink shrimp marked on the Sanibel and Tortugas grounds in 1961 and 1962. Geographic Range The geographical range of Tortugas pink shrimp is grad- ually being outlined. Nine mark-recapture experiments involving 106,779 pink shrimp have shown, through recoveries by commercial shrimping vessels, that shrimp inhabiting the Florida Bay and Shark River areas are part of the pop* ulation fished on the Tortugas grounds. Evidence to date indicates that shrimp from Pine Island Sound on Florida's w^est coast and fronn Biscayne Bay and Barnes Sound, on the east coast, do not contribute to this fishery. 35 Migrations Juvenile pink shrimp make extensive movements in migrating fronn estuaries to offshore waters. Experiments during the past year reveal that adult pink shrimp have rather limited movements after reaching water depths of 7 to 13 fathoms. Of 2, 091 pink shrimp marked with biological dyes and released near the center of the Tortugas grounds in September 1961, 443 (22%) were recovered by commercial fishing vessels during a period of 85 days. Movement of the marked animals was generally west and northwest. The greatest movement recorded for any marked shrimp of this group was about 27 statute miles. In March 1962, 2,496 pink shrimp were captured, marked with bio- logical dyes, and released at randonn on the Sanibel grounds west of Naples, Fla. By May 21, 1962, 453 (18%) had been recaptured by commercial shrimp trawlers. The greatest movement recorded for any of this group was 82 nau- tical miles. Two of the marked shrimp released on the Sanibel grounds were recovered near the northwest border of the Tortugas grounds after 115 days at liberty. One marked shrimp released in lower Pine Island Sound in December I960 was recovered in 9 fathoms on the Sanibel grounds in November 1961. Growth Some useful pink shrimp growth data w^ere obtained from the Tor- tugas experiment begun in September 1961. Shrimp (2,091) were individually measured prior to marking and release. These had a narrow size range of 83.0 to 93. 5 nam. total length. Growth was calculated for 97 males and 82 females which had been at liberty from 29 to 36 days. Average grov^h for males having an initial mean total length of 89. 3 mm. was 15. 6 mm. per month. Average growth for females having an initial mean total length of 90. 5 mm. was 18. 0 mm. per month. Regression analysis of growth for the entire group of recoveries shows similar growth over the entire period dur- ing which recoveries were made. This experiment depicts the surprisingly rapid rate at which these prerecruits grow as they enter the trawling grounds and are subjected to fishing. Mortality Offshore mark-recapture experiments on the Tortugas and Sanibel grounds have demonstrated the feasibility of using this method in es- tinnating the natural and fishing mortality rates of shrinap. Survey of Species of Penaeus Shrimp in South Florida During the year, additional samples of shrimp were collected and examined to determine the distribution and seasonal occurrence of three species of the genus Penaeus occurring in south Florida waters. Since P. duorarum, P. brasiliensis, and P. aztecus are extremely difficult to separate unless mature, such informa- tion is necessary to evaluate the research on the more abundant P. duorarum. Monthly samples collected in Biscayne Bay, Fla. , during I960 and 1961 showed the following species composition: 36 P. brasiliensis Period (balance P. duorarum) Percent October 19 Novembe r -May- 1 and less June 30 July 41 August 11 September 14 October 4 '^Repeated in second year. A sample of shrimp captured by the Bureau of Commercial Fish- eries charter vessel M/V SILVER BAY in 40-60 fathoms southwest of Al- ligator Reef (in the Straits of Florida) was found to contain specimens of P. brasiliensis along with the P. duorarum and P. aztecus previously re- ported from that area. 37 INDUSTRIAL FISHERY PROGRAM Joseph H. Kutkuhn, Program Leader Gulf of Mexico fisheries for industrial -type fishes have developed rapidly in recent years and probably have not yet reached their full potential. Of the 1961 United States catch of nonfood fish, more than 40 percent was taken in the Gulf region. Practically all of this came from the 300 -mile stretch of coastal waters off Mississippi and Louisiana. The question now being asked is whether or not extension of present fisheries to the east and west of this area would be feasible. It is anticipated that research by the Industrial Fishery Program will provide at least a partial answer. Two well-defined fisheries produce the total volume of species harvested in Gulf waters for industrial purposes. The menhaden fishery operates with purse seines and large -capacity vessels in the nearshore shal- lows, its catch being reduced to oil and meal. The bottomfish fishery, which employs otter trawls and smaller vessels, ranges farther offshore and is sup- ported by a wide variety of demersal fishes (mainly sciaenids) heretofore classified as "trash" species. Most of its production is used in the manu- facture of petfood. Research on menhaden populations is currently conducted by the Bureau's laboratory at Beaufort, N. C. , and that concerned with bot- tomfishes is directed from the Laboratory at Galveston and its Field Station in Pascagoula, Miss. A project designed to survey the species and size composition of landings made by the "petfood" fleet at Pascagoula has functioned since 1958. Its principal objectives are to observe changes that nnay occur in the fish populations as a result of exploitation and to obtain life history information for the dominant species. Work at the Galveston Laboratory is closely coordinated with the offshore studies by the Shrimp Fishery Program described elsewhere in this report. Monthly trawl samples of fish obtained systematically on the con- tinental shelf between the Mississippi Delta and the Rio Grande River are providing information on patterns of seasonal and geographic distribution for the nnajor demersal species. Since a few of these sampling sites are in the area fished by the existing industrial (bottomfish) fishery, comparative analysis of commercial and research statistics will enable us to make a realistic appraisal of the potential that the western Gulf holds for this fish- ery's expansion. 38 Industrial Bottomfish Fishery in the North Central Gulf of Mexico Charles M. Roithmayr The Fishery Gulf landings of demersal fishes processed for petfood mink- food, fish meal, and crab bait fell from about 81.0 million pounds in I960 to 76. 9 million pounds in 1961. The lower catch in 1961 was due not to a dintiin- ished resource but to a 40 -percent decrease in the total number of fishing trips and, presumably, a comparable decrease in actual fishing effort. Despite the increased demand for fish meal, two reduction plants that processed fish during part of I960 did not resume operations last year. Reflecting changes in dennand as well as changes in fleet composi- tion and distribution, the overall average catch per vessel -trip increased in 1961 from 12 to 19 tons. Examination of catch records compiled for 6 percent of the industrial -fish fleet over the period 1960-61 revealed an average in- crease of 27 tons per trip for large vessels (50 or more tons capacity) fishing in 2 to 20 fathoms east of the Mississippi Delta. The aame vessels fishing west of the Delta and in similar depths realized only a 12 -ton increase. Small- er vessels (less than 50 tons capacity) fishing east of the Delta exhibited a 7-ton increase, whereas, a 10-ton decrease was indicated for trips made west of the Delta. In 1961, an estimated 30 percent more trips were made east of the Delta by the larger boats, this being primarily responsible for a propor-, tional increase in the catch from that area. Greater activity and consequent Typical industrial -fish trawler of the "Florida" design (right), Typical industrial -fish trawler of the "Biloxi" design (left). 39 production east of the Delta occurred during September-December when suc- cessful trawling west of the Delta was precluded due to bad bottom and accum- ulations of debris resulting from Hurricane Carla. A standard unit of effort was established to furnish a reasonable in- dex of fish abundance and measure of fishing success on the grounds. Prelim- inary analysis of 1961 data shows that the average catch per 1 -hour tow using a standard 65-foot, balloon-type otter trawl was 0. 62 tons west of the Delta and 0.51 tons east of the Delta Five species accounted for approximately 81 percent of the 1961 industrial bottomfish catch. Atlantic croaker, Micropogon undulatus, again topped all species by a wide margin. Comparative data for the period 1959-61 are shown in the accompanying graph. The year-to-year stability of catch 25 r Connparative landings of dominant bottomfish species taken by industrial -fish fishery off north central Gulf coast, 1959-61. 1959 I960 1961 composition (in terms of the major contributing species) is particularly note- worthy. Life History Studies An intensive sampling project at the Galveston Labora- tory's Field Station in Pascagoula, Miss. , is furnishing basic information on the life history and general biology of Atlantic croaker; spot, Leiostomus xanthurus; sand seatrout, Cynoscion arenarius; and silver seatrout, C. nothus. A major portion of this project involves the study of variation in relative strengths of successive age groups ("year classes") of each species. Because attempts to validate the scale nnethod of age determination are not yet com- plete, analysis of length distributions of the samples, despite its acknowledged subjectivity, has had to be relied upon for age assessment. Findings reported in the following discussion, which is restricted to the Atlantic croaker, must therefore be viewed as preliminary. On a semiweekly schedule over the period July 1961 to May 1962, 7, 500 croakers were examined for total length, weight, sex, and maturity from commercial catches nnade east of the Mississippi Delta (2-20 fm. ) and landed at Pascagoula. Subsampling provided the scale samples being examined to decide on the feasibility of their use in determining age. After being com- piled in 5-mm. classes and connbined according to month of sampling, the plotted length measurements are shown in the accompanying figure. 40 I9S9 1956 t 01 UER Two distinct size groups contributed to catches of croaker in July 1961. Individuals in the smaller group were 9. 5 to 16.0 cm. long, with the mode occurring at about 13. 5 cm. They increased in average size through- out the summer and by October were 12.0 to 18. 0 cm. long (mode at 16. 0 cm. ). Associated data on sexual maturity showed a preponderance of ripe fish in 4 to 17 fathoms between Sand Island Lighthouse, Ala. , and Chandeleur Island Lighthouse, La. , during September -November. Assuming this to be the principal spawning period and drawing also from earlier life history studies conducted in Texas and Louisiana estuaries, it is postulated that the l6-cm, modal group present in October 1961 was the result of spawning in the fall of 1959, and therefore may be identified as the 1959 year class. Modal positions for this year class remained relatively constant from January through May, varying only slightly between 16. 5 and 17. 5 cm. Dur- ing this period it was the most important year class contributing to the industrial bottomfish fishery. The larger size group evident in July contained individuals ranging from 16. 5 to 20. 5 cm. with the mode at 18. 0 cm. These grew at such a rate that by October they ranged in length from 18.0 to 22. 0 cm. , with the mode at 19.0 cna. This group, which in- cluded fish from the 1958 as well as earlier year classes, gradually decreased in density, exhibited little apparent growth, and was characterized in May by a mode of 20. 0 cm. In January 1962, a subdominant group of smaller fish with a nnodal length of 12. 5 cnn. entered the fishery and is assumed to have been a migrating (estuary to Gulf) as well as faster growing (and hence "selected") segment of the I960 year class. The 8-cm. modal group appearing in May 1962, can be attributed to the fall spawning in 1961, and henceforth identified as the 1961 year class. Assuming that the major modes of the croaker's length frequency distribution indicated successive age groups, it is tentatively concluded that insofar as the croaker is concerned, the industrial bottomfish fishery of the northeastern Gulf depends largely on 1 - and 2-year-old fish. 5 10 15 20 25 TOTAL LENGTH IN CENTIMETERS Length frequency distributions for Atlantic croaker taken east of the Mississippi Delta, July 1961 to May 1962. 41 Western Gulf Bottomfish Survey- James G. Ragan A full year's sampling of bottonnfish populations in the Gulf between Cameron, La. , and Freeport, Tex. , has been completed. This was under- taken to determine the relative composition of bottomfish resources in the area and to provide biological and statistical data on the more common species. Five-pound samples of fish were drawn from catches made with 45- foot, 2-|-inch nnesh flat trawls, towed for 1 hour at each of 1 1 strategically lo~ cated stations. These stations ranged in depth from Ij to 45 fathoms and were occupied every 3 weeks. After species identification, each fish was measured for length and weight, and examined for sexual maturity. Weighing specimens of Atlantic croaker. Combined over the entire year, the sample material revealed the presence of 1 1 1 species, of which the following 6 accounted for an estimated two-thirds (by weight and number) of the overall trawl catch. 42 Species Liongspine porgy, Stenotomus caprinus Atlantic croaker, Micropogon undxilatus Seatrout, Cynoscion sp. Inshore lizardfish, Synodus foetens Rock sea bass, Centropristes philadelphicus Shoal flounder, Syacium gunteri Perc ent P ercent by weight by number 35 39 11 8 7 8 6 2 4 3 3 6 LONGSPINE PORGY ATUflNTtC CROAKER ROCK SEA BASS SHOAL FUOUNOEB MISCELLANEOUS LLL 50 0 50 0 50 O PERCENTAGE COMPOSITION Composition of bottomfish resource in northwestern Gulf of Mexico. The longspine porgy was the most common species encountered in all months except December when it was replaced by the seatrout (see graph). With the exception of the rock sea bass aaid lizardfish, habitats of the major species appear definable on the basis of depth. The longspine porgy, for example, was abundant only at depths greater than 20 fathoms. The croaker and seatrout dominated catches at the shallow -water stations, while the shoal flounder was taken almost exclusively at 15 fathoms. 43 The trawl -sample data (accompanying table) indicate that fish con- centrations •were greatest at the nearshore stations during the warm months and at the offshore stations during the cold months. Thus it appears that seasonal movements are largely governed by water temperature which fluc- tuates widely in the nearshore shallows. Average weight of all species taken at indicated depths throughout 1961. Figures are based on trawl hauls standardized over a 3 -mile towing distance. Depth Spring Summer Fall Winter Fathoms Pounds Pounds Pounds Pounds 7i 104 525 160 64 15 221 129 209 153 25 149 126 152 227 45 98 53 94 103 An expanded sampling program, comprising 60 stations arranged systematically on the continental shelf from the Rio Grande River to the Mississippi Delta, was begun in January of this year. In addition to sup- plying information on the fishes present in a previously unstudied area, this program should provide a connparison of fish concentrations on the grounds now being fished with those in the more westerly part of the Gulf, and thereby afford a means of assessing the potential of unexploited stocks. 44 ESTUARINE PROGRAM George A. Rounsefell, Acting Program Leader In the lower reaches of rivers and where they meet the sea, the environment is unlike either the typical river or sea. These nnarshes, la- goons, and partially enclosed bays between the fresh water of the river and the salt water of the sea are called estuaries. They furnish habitats in which many commercially important species of fish and crustaceans spend all or a particular portion of their life. Many of the more important Gulf species are quasi-catadromous, that is, the adults spawn at sea, but the young live in the lower salinity water of the estuaries. Because of the necessity to understand the effects of an expanding number of manmade changes in the estuaries, a research program was begun in 1959 to explore basic ecology and the type and scope of research necessary to predict the effects of engineering projects upon fishery resources. Before i^iB *ra»«._ ^^; ■« Bringing a sample trawl on board the TOMMY BOX in Galveston Bay. 1959, some data on estuaries in the Galveston area were obtained during the field operations of other Laboratory projects. The estuarine work is now divided into two basic projects: 1. The estuarine ecology project is intended to determine the types of habitats suitable for various species of fish and invertebrates, the effects of environmental factors, and their interrelationships. 2. The evaluation of estuarine data and of engineering projects has a twofold purpose: (a) to examine existing data for a clearer picture of the 45 present status of our knowledge in order to determine how to best plan future research without duplication of effort and (b) to evaluate the effects of engi- neering projects upon estuarine biota. During the year, the outboard cruiser POGO was replaced with a 17 -foot fiberglass "Boston Whaler, " powered by a 75-hp. outboard motor. This acquisition increases the consistency of field sampling because of its speed and seaworthiness. The 40 -foot dies el -powered vessel TOMMY BOX was acquired for work in the deeper smd more distant inshore waters. Con- siderable remodeling and hull repairs were required before putting this ves- sel into service. During the coming year, because of the limited staff, the tempo of field work will be reduced until the series of data already obtained can be ad- equately analyzed and reports written for publication. This will also prevent collection of data which analysis of existing data may show are not required. Series of available hydrographic data and conconaitant biological samples. Month 1957 1958 1959 I960 1961 1962 Jan. C C C C o C o T Feb. C C C o T C o T Mar. C C C o T C O T Apr. L C C C o T C O T May L L C C O C o T June L L C c C o C o T July L C c C o c o T Aug. L c c C o c o T Sept. L c c C o c o T Oct. L c c C o c o T Nov. L c c C o c o T Dec. L c c C o c o T L = Lufkin Bayou on south side of West Bay O = Offatts Bayou C = Clear Lake T = Trinity Bay 46 Ecology of Nursery Areas Anthony Inglis The role of the inshore waters in the economy of the seas requires clarification, but we know that many species of marine fishes and invertebrates spend at least part of their early life histories in these rich and shallow waters. The brackish streams, marshes, lagoons, and bayous, which are components of estuarine systems, have even been commonly referred to as "nursery areas" by both the scientist and the lay fisherman. Since 1957, studies have been made on the ecology of nursery hab- itats in segments of the Galveston Bay system. Lufkin Bayou on the south shore of West Bay was first chosen for a study on the habitat differences of the three commercially important shrimps, the brown, white, and pink, but had to be abandoned a year later due to dredging in the area. In 1958, Clear Lake, a bay on the western shore of upper Galveston Bay, was selected because it sup- ports a large and successful bait shrimp fishery. In I960, the study was ex- panded to include Offatts Bayou, a deeper, more saline, and less turbid water body situated in the western part of the City of Galveston on Galveston Island. Offatts Bayou supports no major fishing with the exception of a winter sport fishery for the spotted seatrout, Cynoscion nebulosus. In the winter of 1961, the study of a fourth area. Trinity Bay, was undertaken to determine the prob- able effects on the estuarine fauna of reduced Trinity River discharge due to numerous engineering projects planned for the watershed. A report on the Trinity Bay studies appears elsewhere in this report. For convenience this discussion is limited to the 24-month period May 1960 to April 1962, during which field investigations in Clear Lake paralleled those in Offatts Bayou. Bi- weekly sampling carried out at each location on al- ternating weeks included hydrological and meteor- ological observations as >vell as S-nninute trawl hauls for biological spec- imens. Both surface and bottom temperature as well as salinity were measured. •c TEMPERATURE 30- 25- 20- 15- 10- "'^^■:<. V _^;/ X X" 5- .-Offolts BOyou 0- .-CleOr LC I 1 1 < 1 , 1 1 1 1 1 1 1 1 1 1 — T 1 1 1 30-, 25- 20- 15- .-^" • ^ """X/- SALINITY ^ /*~ — 10- 5- 0- 1 1 1 1 1 I I 1 1 1 1 1 1 1 1 1 1 / / 1 I 1 1 1 MAY JUN JUL AUG SEP OCT NOV DEC JAN FES MAR APR MAY JUN JUL AUG SEP OCT NOV DEC JAN FEB MAR APR 1960 1961 1961 1962 Average monthly bottom salinities and temperatures for two Galveston Bay habitats. 47 Trinity River HOUSTON 0 L 5 10 J 1 MILES GALVESTON ISLAND GU L F O F M E X IC O Galveston Bay system. 48 Monthly mean bottom temperatures for the two areas were similar, reaching peaks of about 30° C. in June I960 and 28° C. during June -September 1961. (See accompanying graph.) Lows of about 12° C. were recorded during December I960 to February 1961 and of 10° C. in January 1962. This latter measurement was recorded as a cold front passed during the period January 11-15. Sustained low temperature led to the formation of a 2-inch cover of ice on portions of Clear Lake and Offatts Bayou. Monthly mean bottom salinity in Clear Lake, due to a direct source of fresh water through Clear Creek and a narrow elongated connection restrict- ing the intrusion of more saline waters from Galveston Bay, was continually lower than that recorded for Offatts Bayou, which lacks any sizable source of fresh water and has a broad connection with West Bay. The difference ranged from about 7%o to as much as 23%o during the study period. Heavy rainfall dur- ing the months of June and July resulted in a generally lower midsunnmer sa- linity than was noted for a similar period in I960, especially in Offatts Bayou where the bottom salinity, which averaged between 28%o and 29%o for July of I960, averaged less than 1 5%o in July 1961. The midsummer drop in salinity is usually more clearly defined in Clear Lake than in Offatts Bayou and seems to occur with predictable frequency. Thus the average spring and fall salinity in Clear Lake ranges from biob to 87cio while the summer salinity ranges from 3%o to 57oo. From the last week of June through the second week of July in 1961, the bottom salinity averaged less than l%o. In September 1961, the passage of Hurricane Carla caused a second drop in salinity. Forty -five species of fish and invertebrates were taken by trawl- ing in Clear Creek, and fifty -five in Offatts Bayou. The larger number of species taken in Offatts Bayou is characteristic of the more marine portions of Texas estuaries. However, the average number of organisms per trawl haul Clear Lake (256 trawl hauls) White shrimp 21. 019 Atlantic croaker 15. 558 Brown shrimp 10, 082 Large scale menhaden 2, 934 Bay anchovy 2, 781 Spot 2, 202 Blue crab 1. 817 Sand seatrout 1. 628 Grass shrimp 664 Striped mullet 434 Subtotal 59. 119 36 other species 1, 192 Total 60, 311 Offatts Bayou (433 trawl hauls) Spot 9, .846 Bay anchovy 4. ,448 Atlantic croaker 3, 455 White shrimp 2, 074 Brown shrimp 2, 056 Pinfish 1, 346 Grass shrimp 226 Large scale menhaden 212 Blue crab 181 Atlantic threadfin 120 23, 964 45 other species 662 24, 626 49 was more than four times greater in Clear Lake. This trend for greater num- bers of individuals but fewer numbers of species in the lower saline waters as compared to the marine is characteristic. Unfortunately, these figures are in terms of numbers, not biomass. The accompanying data show the total catch of each of the 10 most abundant species in the trawl samples from Clear Lake and Offatts Bayou during the period May I960 to April 1962. Both brown and white shrimp were considerably nnore abundant in Clear Lake than in Offatts Bayou though their periods of abundance in the two locations coincided closely. White shrimp show peaks in abundance in both estuarine habitats during the month of September and low points during March. Brown shrimp reach their greatest abundance in May and June and the least in the month of January. Analysis of the accompanying figure reveals that both species show a sharp decline in catch per unit of effort for 1961. This agrees with Fish and Wildlife Service statistics and reports for both the bait shrimp fishery and the regular commercial fishery. Sizes of the two species w^ere comparable in both areas, ranging in the case of brow^n shrinnp from tiny postlarvae to large juveniles (12. 5 g. , 115 mm. ) and, in the case of white / /\ CLEAR LAKE / '-. \. • - Wh't» ahfi 2^ OFFATTS BAYOU y^- ■\ MAY JUN JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC JAN FEB MAR APR I960 1961 1961 1962 Monthly catch per unit of effort for brown and white shrimp between May I960 and April 1962 in two Galveston Bay habitats. shrimp, from postlarvae to subadults (16. 5 g. , 130 mm. ). The smaller sizes were relatively more abundant in Clear Lake, while Offatts Bayou samples con- tained proportionally higher numbers of the larger sizes. The number of blue crabs taken in Offatts Bayou during the 24 months of study was considerably less than that in Clear Lake. Immature or juvenile crabs of both sexes made up the bulk of the Clear Lake catch. Mature individ- uals, mostly males, made up the greater part of the Offatts Bayou catch. Finfish catches, with several exceptions, followed the same picture of lower catches per unit of effort in Offatts Bayou than in Clear Lake. The spot was the nnost abundant single species taken in Offatts Bayou, contrasting with its rank of the fourth nnost common fish in Clear Lake. Catch -per -unit - of -effort data compare fairly well in the two areas, but the peak of abundance 50 of this species is reached 1 or 2 months earlier in Offatts Bayou than in Clear Lake. The secondary peak of abundance which normally occurs in October or November in Clear Lake was only slightly evident in Offatts Bayou. This sec- ondary peak of abundance is closely associated with the normal rise in salinity in Clear Lake during these months. The greatest abundance of this species is associated with areas of higher salinity in the Galveston Bay area. The bay anchovy was the second most abundant fish in Offatts Bayou samples and the third most abundant in Clear Lake samples. This species, which is considered to be the most important forage fish in Texas estuaries, probably occurs in far greater abundance than indicated by trawl sannples. The catch per unit effort of this species, however, was roughly comparable in the two areas. Peaks were reached in Clear Lake in October I960 and August 1961, whereas, lows were recorded for December I960 and January 1962 in Offatts Bayou. The above studies are being modified toward a broader program to investigate the entire Galveston Bay system. The detailed work of the last 5 years is scheduled to be published as quickly as the data can be analyzed. Sampling fish and crustaceans in Offatts Bayou with a small bottom trawl. 51 Effects of Engineering Projects on Estuaries Richard A. Diener The value of estuaries as nursery and feeding grounds for many commercially important species of fish and crustaceans is reflected in Texas landings, of which approximately 98 percent by weight are of species in some way dependent on estuaries. The cumulative effects of water development practices upon these estuaries and upon the allied commercial fish production will likely be extensive. Our present knowledge does not permit us, however, to make accurate predictions of these effects upon marine fishery resources. Although the effects of development projects cannot yet be evalu- ated accurately, several types of changes may be foreseen. The most ob- vious alteration of existing conditions would be reduction of fresh-water dis- charge through greater consumptive water use and increased total evaporation due to more exposed surface area in res- ervoirs. A reduced discharge of fresh water may alter the suitability of estuarine areas by raising their salinity; by varying salinity, circulation, and water inter- change patterns; by draining surrounding marsh areas through the lowering of river levels; by reducing silt load and thus al- tering deposition rates; and by reducing inflow of terrigenous nutrient materials required for primary productivity. As human population increases with accompanying expansion of agricul- tural and industrial interests, it is logical to expect an increase of pesticides and other pollutants entering the estuaries with the waste waters and runoffs. In- fluence of inshore waters upon the hydrol- ogy and food cycles of offshore waters has not been clearly defined, but is another factor which must be considered when assessing the effects of drastic modifi- cations of river systems and their associated estuaries. The Nueces River of Texas affords an excellent example of the many extensive water development programs proposed for the various watersheds draining into the Gulf of Mexico, either directly or indirectly through the es- tuaries. From its headwaters in Edwards County in south central Texas, the Nueces flows southeasterly for some 315 miles terminating in Nueces Bay, a segment of the Corpus Christi Bay system. As the Nueces River is the larg- est tributary of the Corpus Christi estuarine systenn, it is one of the chief factors determining hydrological conditions therein. Typical spoil retention dike used to keep spoil from fill- ing in and thus destroying valuable marsh habitat. 52 Traversing one of the population centers of south Texas, the Nueces' waters are considerably exploited by industrial, agricultural, and municipal interests. A single large impoundment above Corpus Christi supplies the major portion of irrigation in the semiarid counties of the Nueces valley. Mun- icipal and industrial uses, particularly in the vicinity of Corpus Christi, place a further drain on flows in the lower reaches. Expanding populations and the resulting agricultural and industrial needs will place additional dennands upon river flows. These new demands will be met by the construction of approxi- mately seven more reservoirs along various reaches of the river systenn and by increasing the capacity of the existing reservoir. Various federal agencies, including the Bureau of Reclamation, the Soil Conservation Service, and the Corps of Engineers, are considering means of utilizing flows of other Texas streams in addition to that of the Nueces. The United States Study Commission recently submitted a report proposing a water supply and control program for the entire state of Texas. Large variations of climate exist in the state, and consequently, fresh-water supply is most crit- ical in the arid and semiarid southern and western regions. The proposed method of alleviating this imbalance is to divert the "surplus" runoff from the major streams and transport this water to the semiarid lands by means of a system of canals and pumping stations. Surplus runoff is considered as all nonexploited flows entering the estuarine systems. A further indication of an expanding economy along the Texas coast is the increased number of navigation channels, mineral developments, and general construction projects which alter in varying degrees the estuaries and their suitability as marine habitats. Projects for realignment, maintenance, and addition of navigation channels - chiefly those associated with the Intra- coastal Waterway - are frequently submiitted for an evaluation of their effects upon marine fishery resources. General construction projects, a term em- bracing such itenis as small fills, mineral drilling facilities, wharf construc- tion, pipeline crossings, and others, generally have minimum effects upon marine fishes. Severe alteration of water circulation and interchange through "canalization" and segmentation of the estuaries by channels and the result- ing spoil banks, is the principal danger from navigation projects, aside from the actual physical loss of habitat. This is a major problem in Louisiana where canalization is changing marshland ecology through increased salt- water intrusion. Navigation projects often can be modified so that spoil dis- posal results in a minimum loss of habitat. Individual construction projects of a general nature are usually not sufficiently extensive to be considered detrimental. In large numbers, however. 53 they may produce serious cumulative encroachment upon available and irre- placeable estuarine habitats. Lacking sufficient knowledge in specific areas concerning species utilization or hydrological effects, we can usually only recommend the maintenance of existing conditions. Recognizing the above problems, program personnel during the past year and under the present system of coordination with the Branch of River Basin Studies nnade 180 appraisals of engineering projects potentially affecting estuarine fishery resources. Of this number, all but six involved Texas waters. The majority of these resulted from more than 325 Corps of Engineers public notices and letters received during the year and screened to determine which projects could materially affect estuarine and marine fishery resources. Sections pertaining to these fishery resources in 40 Bureau of Sport Fisheries and Wildlife draft reports were also reviewed. Evaporation losses from irrigation ditches may reduce necessary fresh- water inflow to estuaries. 54 PHYSIOLOGY AND BEHAVIOR PROGRAM David V. Aldrich, Program Leader Since midyear, this program has been specifically directed toward laboratory experiments dealing with the environmental requirements of com- mercial shrimps, primarily in postlarval and juvenile stages of development. One goal - to determine limiting and optimal levels of salinity and tempera- ture - is being approached in three ways: (1) observing survival of shrimp ex- posed to known salinity and temperature combinations, (2) observing the se- lection of a temperature or salinity range by shrimp placed within a continuous linear gradient, and (3) comparing the growth rates of shrimp held at known salinity and temperature conditions. Much of our progress has been made possible by adapting available equipment and developing new devices. Examples of this type of activity are the successful modification of laboratory incubators for survival studies, com- pletion of vertical water columns with salinity and temperature gradients for behavior experiments, development of a method for preventing postlarval shrimp from junnping above the water's surface in aquaria (reducing "false mortality" during growth and survival studies), and finding a practical lab- oratory diet for small shrimp. Laboratory results obtained using brown shrimp, Penaeus aztecus, indicate that postlarval as well as juvenile stages can tolerate a wide range of salinity levels (5%o-35%o). It is particularly noteworthy that this conclusion is based not only on the results of short-run survival experiments but also on the more sensitive indices of environmental suitability provided by behavior and grovi^h studies. The survival work further showed that the range of tolerance to salinity narrowed considerably at the lowest temperature level tested (7» C.). Preliminary results of comparative survival experiments suggest that juvenile shrimp tolerate a wider range of temperatures than do postlarvae. Such physiological changes during development within a species may have an important bearing on the patterns of distribution and movement characteristic of young shrimp. It may be that the relatively stable temperature of offshore spawning grounds is more conducive to the survival of larvae and early post- larvae, whereas the larger and hardier forms can tolerate the less static con- ditions encountered in the more fertile nursery areas of the bays. We hope that another sensitive physiological index - oxygen consumption - can also be used to measure influences of environmental factors on shrimp. To this end, potential anesthetics are being tested in an effort to stabilize physical activity and thus permit accurate assessment of basal met- abolic activity through measurennent of oxygen consumption. 55 •"( Checking incubator temperatures during a survival study. One phase of future work will investigate the combined influences of salinity and temperature on growth of shrimp in experiments which will be made feasible with the completion of four controlled -tenaperature rooms now^ under construction. 56 Tolerances to Environmental Factors David V. Aldrich The behavioral phase of this project started with the exposure of small (13-28 mm. total length) brown shrimp to continuous linear salinity gradients. These gradients are of the vertical type, in which density differ- ences associated with differences in salinity tend to maintain stratification within the water column. Using evaporation -concentrated sea water and dis- tilled water, continuous gradients ranging from l%o to 70%o are estab- lished in a 7 -liter column 4 feet high. (See photo. ) After a shrimp is in- troduced into the column at a salinity level equivalent to that of the medium from which it came, the animal's movements up and down the gradient are observed. To minimize observer bias in this operation, 100 determina- tions of a shrimp's level in the gra- dient are taken regularly at preestab- lished 15-second intervals. Prelim- inary tests showed that (1) such sa- linity gradients are extremely stable and (2) the shrimp, although usually found on the bottom of experimental tanks, are quite capable of swimming continuously at levels above the bot- tom for 12 hours or longer. In pro- viding no resting place for the animal within each salinity range, this type of apparatus continually forces the shrimp to swim to remain within a salinity range of its choice, fre- quently encountering and avoiding the levels which lie above and below this range. Thus, results should suggest avoidance limits, which may be significant in regard to the nat- ural distribution of these animals. The grouped results of 13 such experiments using juvenile brown shrimp acclimated in a sa- linity of about 27fo« clearly show that the shrimp occupied low salinity ranges within the gradient column Determining salinity gradient with conductivity meter. 57 .^K just as frequently as they chose more saline levels, up to and including the 30%c-34'/oo range. (See figure next page. ) Maximum concentrations oc- cupied by individual shrimp varied from 49'/oD to TOyoo, and minimum con- centrations from l%o to 10%o, again indicating widely separated avoidance limits for this species. Small (1-in.) brown shrimp swim- ming in experinnental salinity gra- dient. The horizontal reference line just below the shrimp indicates the 21%o level; the next line above marks the 13%o level. The influence of acclimation to high or low salinities is suggested by the results of similar experiments which tested two shrimp grown at 5%o and two held for 3 days at 53%o-54'/oo. The obvious differences between fre- quency distributions of these two groups seenn to reflect the salinity history of the experimental animals. Moreover, data for the low-salinity group are much less widely distributed than are those for the high-salinity group. The small number of shrimp tested to date, however, limits the confidence with which these differences can be associated with salinity acclimation. Present plans are to repeat this type of work in order to determine the extent of behavior variability within and between individuals. Future work will also extend this approach to other species, beginning w^ith white shrimp, and to another important environmental factor - temperature. A study of the effect of salinity and temperature on survival of small brown shrimp has also been undertaken. Using five incubators, 24-hour sur- vival tests involving a two-factor, five-level experimental design were con- ducted with postlarvae and juveniles. Within each experiment, initial salinity and temperature conditions (25%o-27%o and 22 ''-25" C. , respectively) were the same for all shrimp. Changes to final experimental conditions were made over a 12-hour period for each group by making periodic changes until the desired conditions were obtained. 58 30-1 2 SHRIMP ACCLIMATED AT 53-54 %o SALINITY 2 SHRIMP ACCLIMATED AT S-'/oo SALINITY SHRIMP ACCLIMATED AT 26-30 7oo SALINITY inliiiiiiiiSBiiiii 1 cn ^ ■ ■■ <3- 1 cn ' ) ' ^ \^ iTi CD 1 ^ 1 C\J CJ r<1 ro ^ t in in «£> (0 t^ ' 6 in O in O in o in O in o <\i OJ ro ro T T m in (O (0 N SALINITY RANGES °l oo Frequency distribution of times that small brown shrimp selected certain salinity ranges. 59 Here again, results show a broad range of salinity tolerance for postlarvae at Z5" or 30° C. (See accompanying table.) As temperature was lowered, however, the tolerance range was progressively reduced. At 35", some mortality occurred at all five salinity levels, suggesting that this tenn- perature is very near the upper absolute limiting level for postlarvae of this species. Number of postlarval brown shrimp surviving various temperature -salinity conditions. Pooled results of two experiments. (10 = 100 percent survival.) Temperature (° C.) 37 7 15 25 30 35 7 10 10 10 7 ? 34 7 10 10 10 7 ! 1 25 10 10 2 10 7 10 10 10 9 4 7 5 0 1 10 10 1 A similar experiment on juvenile brown shrimp showed only 4 per- cent mortality at 13° C. (including all salinity levels) and 8 percent mortality at 35°. Comparison of these figures with those for postlarvae (24 percent at 15° and 48 percent at 35°) suggests that juveniles tolerate a broader range of temperature. Increased tolerance to temperature changes might have con- siderable adaptive significance for shrimp of this size, since they are nat- urally exposed to the changeable conditions characteristic of estuarine environments. Much additional work of this type is needed, e. g. , (1) repetition of above experiments, (2) testing of salinity and temperature levels which will more closely define limiting levels, (3) tolerance comparisons between species, and (4) testing for acclimation effects. 60 Experimental Growth Studies With Postlarval Brown Shrimp Zoula P. Zein-Eldin Studies of shrimp growth rate as an index of the suitability of sim- ulated environmental conditions were begun this year. In the first series of experiments to determine a practical diet capable of supporting growth in the laboratory, we compared the growth and survival of postlarval brown shrimp fed various foods. These diets included: live brine shrimp (nauplii); brine shrimp plus a species of filamentous brown alga; the brown alga alone; ground mullet; ground shrimp; and a species of filamentous blue-green alga. Salinity in test aquaria was maintained at ZSfoo with room temperature ranging from 23° to 27° C. The experiment began with 150 postlarvae per aquarium. At intervals of 5 to 7 days, 10 shrimp were removed from each test aquarium, weighed, their length naeasured, and preserved. The mean weight of shrimp in each test group is indicated in the accompanying figure. Data for both 100- S I 50-1 DIET — Brine Shrimp ■ — Ground MuUet (or Shrimp) — Blue-Green Algo — Brown Alga Laboratory growth of postlarval brown shrimp fed various diets. (Salinity: 25%c) diets containing brine shrimp were combined, since the addition of the brown alga increased neither the growth nor the survival rate but merely afforded a hiding place during periods of molt. Growth data from the groups fed ground nnullet and ground shrimp were similarly combined. It is quite apparent that a diet of live brine shrimp, yielding a mean growth of 2. 8 mg. per day and a maximum rate of 7. 8 mg. per day, gave far better results than any of the other diets. Neither of the algal diets produced good growth, and, in addition, the rate of survival for animals fed the brown alga alone was less than half that of the animals fed brine shrimp (33 percent as against 80 percent). The ground-meat diets tended to foul the experimental aquaria, making them impractical food items. It was concluded that live- animal foods are by far the most satisfactory, not only in terms of growth 61 but also in terms of application and degree of utilization by the experimental animals. Food supply seemed to be a limiting factor regardless of whether or not brine shrimp were included in the diet. With the brine shrimp diet, the growth rate dropped noticeably in the experiment's later stages, during which the amount of food supplied was obviously inadequate for the nunnber of animals present. With brine shrinnp as the only food involved, a second experiment was undertaken to determine the effects of salinity on the growth of postlarval brown shrimp. Four levels of salinity were established, viz. , 5%o, 10%o, 25%c, and 40%«. These were adjusted over 48-hour periods by adding distilled or concentrated sea water to the "control" sea water (ZBfoo) to obtain the desired level. As in the preceding experiment, 10 animals were removed at 4- or 5 -day intervals for weight and length measurements. The accompanying figure shows that consistently better growth was obtained in all salinity groups than in the previous experiment with the diet group fed live brine shrimp, (cf. fig- ure for experiment described in previous section. ) This naay have been partly due to the use of fewer animals in the salinity test aquaria (100 as against 150 animals in the diet experiments). There was, how- ever, significantly greater growth at 25%o than at any of the other sa- linity levels, this being noted at all stages of the experiment. No significant differences in gro^vth could be detected among the other salinity groups. The mean rate of increase was 3. 8 rng. per day (0. 6 mm. per day) with a maxi- mum in Z5%o of 9. 8 mg. and 0. 8 mm. per day. The greater growth at 25foo may be related to a de- creased survival rate (more food per animal), since only 36 percent of the animals survived, as against 68 percent in each of the other sa- linity groups. These findings suggest that for immature brown shrimp good growth and survival are pos- sible over wide salinity ranges, provided an adequate food supply is available. This should stim- ulate reexamination of the hypoth- esis that young shrinnp require low salinity levels for adequate growth. Laboratory growth of postlarval brown shrimp at four levels of salinity. (Diet: Live brine shrimp nauplii. ) 62 Use of Anesthetics in Metabolism Studies With Penaeid Shrimps Zoula P. Zein-Eldin During the past 3 years, studies of oxygen consumption in two species of Penaeus have enabled us to determine a standard rate of metab- olism for each. Since differential physical activity in experimental animals may be a major source of variability in the measurement of oxygen uptake, the possibility that it might be eliminated by general anesthesis is being exam- ined. For this purpose, the anesthetic should act rapidly, have an effective period of at least 1 hour (to permit accurate respirometry), and be nontoxic. Of the seven compounds tested (sodium pentabarbital, ethclorovynol, methyl- parafynol, tribromoethanol, chlorobutanol, menthol, and M. S. 222), none seem to meet all the above requirements at any given concentration. The effective anesthetic dose for postlarval shrimp was found in all cases to be at least 10 times greater than that for fish of comparable weight. Moreover, there is a very narrow concentration range in which rapid sedation can be obtained and maintained without fatality. Present tests are investigating the feasibility of using a high initial concentration to induce sedation, followed by a reduced maintenance dosage. 63 SPECIAL REPORTS Chemicals Toxic to the Red-Tide Organism Kenneth T. Marvin and Raphael R. Proctor The current project was started in March 1959 to find a chemical means of controlling intense plankton blooms and thus preventing the damag- ing effects of the red-tide organism, Gymnodinium breve. Previous control attempts have been made by applying copper in both solution and powdered form (copper sulfate) to affected areas. Large-scale experiments employ- ing tons of material dennonstrated, however, that although copper can give temporary relief in localized situations, it is neither economically nor chem- ically feasible for large-scale control. Present research involves the screen- ing of nearly 5, 000 primarily organic chemicals in a search for a material with which the desired degree of control would be feasible. Preliminary tests evaluated all chemicals as toxicants for G.breve. These tests, which were covered in last year's laboratory report, permitted separation of those materials toxic at concentration levels of 0. 04 p. p. m. (parts per million) or less from those that were not. The latter group was discarded. This year we decided that to be economically suitable, a potential control material must be toxic to G. breve at a concentration of 0.01 p. p.m. or less. We therefore separated the ". 01" chemicals from the ". 04" group. The procedure involved was similar to that covered in the previous report. Each chemical in the ". 04" group was retested three times at five concentra- tions ranging from 0.04 to 0.0004 p. p.m. Two that were toxic at 0.0004 p. p.m. were further tested at 0.0001 p. p.m. In this manner, 32 compounds toxic at 0.01 p. p.m. or less were separated from the ".04" group. Current activity centers on determining the selectivity of the ". 01" group. The material being sought must be toxic to G. breve, but at the same time have no harmful effect, either directly or indirectly, on commercially important species. Our approach to the problem considers short-term effects only. Any control material recommended as a result of this study should therefore be used cautiously until long-term effects are ascertained. The study consists of observing the effects of chemicals in the ".01" group on the young of various species of marine life found in Galveston Bay and Gulf coast waters. Each chemical is tested at five concentrations rang- ing from 0.01 to 1.0 p. p.m. Tests are conducted in 10-liter, all-glass aquaria, each of which contains 10 specimens of the organism being tested in 8 liters of treated water from our recirculating sea-water system. All chem- icals are initially prepared in an alcohol solution, hence alcohol as well as untreated-sea-water controls are included with every trial run. One -tenth (0. 10) p. p.m. was arbitrarily selected as the threshold level. Any chemical that kills 50 percent or more of any test organism at or below this level within the 24-hour test period is rejected. Thus far, all but 64 Each chemical is tested for its effect on the young of various species of marine life. eight chemicals have been eliminated. (See accompanying table; blank spaces indicate temporary nonavailability of test organisms. ) A source of variation over which we have no control and one that could have a profound effect on the results of this project is differential toxic- ity of some chemicals with respect to source of supply. For example, we had to replenish our supply of 3-5-hexadienoic acid, 2-oxo-6 phenyl which, as shown in the accompanying table, is one of the two most toxic materials tested. The new compound, which is supposedly the same as the original, has not proved toxic to G. breve at any of the levels tested. Difficulty in finding new sources of supply for some of our materials is also causing concern. For example, our supply of mercury acetate, (2, 3- dimethoxy tetramethylene) bis-, one of the two most toxic materials tested, is exhausted. The original supplier no longer exists, and to date we have been un- able to find a new one. Now being planned is a second series of tests through which the chem- icals that have passed the selectivity tests will be rechecked to determine their minimum toxic level for G. breve in relatively large volunnes of culture. Each com.pound will be checked at five concentrations, viz., .01, .003, .001, .0003, and . 0001 p. p.m. in 5 liters of G. breve culture. This will be a 500-fold in- crease in volxime over previous tests and should give an indication, among other things, of the surface -volume effect. Mortality estimates will be made after 24, 48, and 72 hours, follow- ing which selectivity tests will be made on important marine species. To min- imize water-quality variables.tests will be made in G. breve media instead of water from the recirculating sea-water system.. Potential control chemicals will also be tested in synthetic sea-water mediunn containing both commercially important species and a sublethal population level of G. breve. 65 (U > C -0 (0 a (D A^xoui ^ 0 GO irTJTT^S ID (U h /Aovnnxxi V •— 1 o * •tH n o qsjCBj^ O (sdox^Saui) +j u -«-> C CI C! q-BJCo 9nxg 0) o o o 1 qBJO M DO (U (U PJ a ci O O ■<*< -"^ O O O O •— • >-i .-H o o o o o o o • • • • • • • o o o o o o o a (i I ni u u v >^.5 sci a j3 O o >- c Pi (U V ^ ^ (h 3 1 0) 1 ffi o 1 X iTt 0 ^ • fO (M O d d a nl u 0 a) .H I (U - a a '^ o " M .2 [X4 -3 o o d « o d o o d 1 >> 1 >^ .2 -d 43 ■(-> (D -S ^ is(2-hydr 5-chlorop hylamino mo salt 1 o •f-t ■M •1-4 o 0 N C! - :S 0) ■d a '0 o •rH a CI. o O DO x> < o oT a n 4J — 1 nJ (0 O 1 -M U . ° c a a •H X> (Tl 1 •— 1 0 'd o 1 •? o o o o a ulfid -brc is-d utyn :3 0) W o -- o „ 28.5 UJ 28 0 It S 275H o 27 0 26 5 WATER AND AVERAGE AIR TEMPERATURE '^":_^ — -I 1 1 1 1 1 1 r 31 5 -310 505 300 295 29.0 285 280 -27.5 27.0 26.5 n 1 1 1 ', 1 1 1 1 1 1- 0830 1030 1230 1430 1630 1630 2030 2230 0030 0250 0430 Observations made on East Lagoon, Galveston Island, during a 24 -hour cycle. 80 o o O O in o O o o ro o o BTUOUIUIV . . . . o CO fM o ro ro in f— ( in ^ o '^ o O CO sO <-H r- ^ o (\j ro + + apixoip . • . • . . . , , + + ' o ro o^ 00 v£) r- f— 1 in t- o + + a c o uoqj-B^) o ro 00 M ro 00 I-H CM (M ro (M ro I-H fM (M fM ro o in siia^TU ■H •4-1 nJ in -a;Hj;i]s[ 1— t d »-H 1— ( ^H I-H (—* I-H I-H I-H >-H r-H uaSXxo in sO O^ o 00 o ro ro (M 00 r- I-~ (M (— ( 00 ro ■* o ^ 00 <-H vO in sO paAXOSSTQ in fM in" .-H O in ^d in 3JT-mN d OJ fM fM ro fM (M fM '^ ■* ro ro O ■eiuoxiiixiY ro ^H -* in ro O ^ o o o o d f-H ro ro O vO in 00 o in apixoip r~- ro ro o O sO t^ sO CO o + + + + uoqapQ o^ ^H d fM in ^' r^ I-H ^" fM + ^_^ CQ rg fM ro ro fM (M ro (VJ 1— ( c 94Tj[;iu .— ( 00 sO o --H O (M ro fM fM o O o -3;bjjim 1— ( d d ^H f—i >— t I-H I-H I-H r-H f-H I-H -M n -M w U9 3X.XO o ^ 00 ^ \>- fM 00 fM I-H ro ro ■<*< ro o o vO 00 fM vO O^ ro t^ O r^ paA^OSSIQ • • • . . . . . . in in in fM 00 r-H in in (M 31T-I1TN O f»^ fM ro fM »-H fM fM r-H I-H fM BIUOXIXUIY fM O O O o O O O o o O ++ ro o 00 viD ^ ^ »-H ^ '^ sO spixotp ^ in 00 Tj- O ^£) O ^ ro ^ + + + + uoqjHQ ^H CT^ co' vD vO O vO O r~ d + + ►-H + ro O i-H o fM O fM O fM O ro O ro O fM ro o fM O 00 O 3:jtj:jtu o -aiBJixisi f—t 1— t I— ( 1— « *-H I-H I— t d I-H I-H o • •H ■M *** (t! uaSAxo F-t r^ o 00 o ro t^ o ro (M r- I-H o ro r^ in ro ^ in I-H O O in 00 PSAXOSSTQ in in in r- 00 00 r- r- in in sO sO ** tsj fM ^ Tj* (M fM fM o ■* o o r-H a^T-i^TN eg fM fM fM fM (M (M ^ (M fM i-H fvj * o (M ro ^ in sO r^ 00 (T- O I-H fM poiJadE I-H I-H — ' X to 2 0 . (1) a r-H a, g tti iii/i + + + I fM o (M o z I ro o tuO O DO i u i ■K- ^i- * iqSn^^a y[z^a 31 paaa^Xfjun IT) i—i in in ro in ro ro tM* + ■K- r- co ro o* r-H pajs^XTJ a;Ht{dsoi{d + fO r^ O ro o o o O 4- ro f-H O o T^^ox * CM t—i i— « M ro ^H ro i—i •«■ CO CO CO CO a c o •H ■M CO 9:t-eqdsot{d vO CO o vD ■^ v£) o ro sO in ro ro ■ DTu-eSaoui CX3 en t-H m O ro ro ro ro O CO in CO o -43 ro in ro CO CO ro ro CO r- in i.^n Tl^qd -oj;oxi{0 (SJ *-H »-H I-H f-H r— 1 f-H I-H ^H I-H ^H i~i ^H i~~t T) u •fH u :^u^x■eAInb^ r^ vO in v£> vO ro ^ CO ro o vD o 00 00 ro ro asomq-ea V d o o 1— t f-H ro CO ^H CO • o o o ^H :3 o paaaiXXjun a^Hixasoifd 00 p— t o ^ 00 r^ nO O^ I-H O r-H o o ro T^^oj, IT) CO I-H ro f-H CO ro CO ro 00 ro in ro ro ro ro ro in paja^XU aj-Bt{dsoqd {vi (vi fSJ (si ro • ro ro CO CO* ro CO* CO* cj ro TB^ox (0 t— 1 I— 1 a in in in 00 ro r- 00 vO ■* 00 ■<*< CJN 00 r- a^-Bqd90i{d 0 u • fH ■!-> ■(-» diu-gSjoux vD i-H o o ro PO ro o ro o ro ro O CO o CO i-H CO 00 o CO -XI o ro sO 00 ro o +-> (0 ,.^.. TT^Mfl -oaoxMO i-H ON r— 1 ro CO I-H ro o rj ro CO ro CO ro CO 00 CO 00 CO f-H ro 00 -x> 01 :;uax'BATnba asouxq-eav r-H i-H (M ro ro ro -^ CO ^H o o o o o (0 paaaixTJun ajBqdsoqd T^^ox + ■K- O ro in ro ro ro • ro ro CO ro O CO + * in ro f-H ro CO o in 00 ro' u A>k* * ro in ro + * ro CO* + * ^H CO + •K- CO CO •4-> paJ^:^XTJ a^Bixdsoqd X^^ox n *** -O in O ^ vO O in r~ in vO un in vJ3 in a:tBqdsoqd o diuhSjoui rsi rg CO 00 rj ro • CM CO ro CO CO* CO* CO CO • f-t ■l-> *** CO ..•En n^H < ro 00 f-H o I-H CO* i-H I-H F-H CO f-H > < poiaacj ^qSiXABQ ^xa^a 82 Marking Spiny Lobsters, Panulirus argus, and Blue Crabs, Callinectes sapidus. With Biological Stains Thomas J. Costello, Donald M. Allen, and Carl H. Saloman Biological stains injected into penaeid shrimp produce a lasting mark and have been used extensively in mark-recapture experiments. Suc- cess of the stain injection method suggested that such a procedure could be used to mark other decapods. Since the spiny lobster (Panulirus argus) and the blue crab (Callinectes sapidus) have commercial importance and are available in south Florida waters, these two species were selected to test their acceptance and retention of biological stains. The injection equipment consisted of j-cc. tuberculin syringes with 27-gauge, ^-inch hypodermic needles. A larger syringe, perhaps 2 cc. , would be preferable for extensive field use. Two stains were used, one a 0. 25-percent aqueous solution of Trypan blue, the other a 0. 5-percent solu- tion of fast green FCF. The spiny lobster has a physical structure comparable to that of a penaeid shrimp; therefore, the quan- tity of stain per g. used for shrimp weighing about 30 g. was multiplied proportionately to mark the lobsters, which weighed roughly 180 g. each. Injection was made laterally into the abdomen at the articulation of the fourth and fifth segments, where the needle was inserted its full length at an angle of about 45 degrees. Al- nnost immediately after injection, the lobsters acquired a general faint bluish or greenish tinge, depending upon the stain used, which could be seen through the more transparent portions of the exo- skeleton. However, all color which could be seen externally disappeared within 2 days. After 40 days, the agile and healthy -appearing survivors were killed. The gill filaments of all the lobsters were clearly marked with either green or blue. Molting in one individual did not affect stain retention. The concentration and volume of stain injected seem adequate to mark spiny lobsters of the size used. INJECTION SITE Points for injecting marking stains into spiny lobsters and blue crabs. 83 Blue crabs proved more difficult to mark successfully than lob- sters. Injections were made in the ventral surface of the swimming leg, at the articulation of the coxa and basis. This often produced a very faint, tem- porary discoloration which could be seen externally overall. Most of the crabs molted at least once during the holding period. When killed after 40 days, the crabs marked with fast green FCF had a distinct green color in the gill filaments. Those marked with Trypan blue had a fair blue color in the gill filaments, suggesting that they were administered an inadequate amount of stain. The results indicate that to insure optimum marking and survival particular attention should be given to the amount of stain selected in respect to individual crab weight. A marking technique is most useful if a marked animal can be readily recognized at the time of recapture. Since the exoskeleton of both spiny lobsters and blue crabs is opaque, marked individuals would not nor- mally be noted when first captured. As the Florida spiny lobster industry is now conducted, recovery of marked individuals together with the neces- sary biological information would present a problem. Spiny lobsters nnay be marketed as whole animals either live or dead. Therefore, the gills are not normally exposed until the lobster reaches the consumer. Spiny lobsters may also be sold as "tails, " in which case the entire cephalothorax is re- moved by the producer. The gills of an intact lobster, however, either alive or dead, can be examined for stain by lifting the carapace with needle -nose pliers. The stain injection technique of nnarking spiny lobsters would prob- ably be limited to studying local populations, where captures could be exam- ined by trained observers. There are several methods of marketing blue crabs. Soft-shell crabs and large male crabs are marketed alive. Consequently, they are generally in the hands of the consumer when the carapace is removed. The great majority of blue crabs, however, are utilized in the production of picked crab meat. In this process, blue crabs are cooked, the carapace removed, and the meat picked, usually in a plant near the area of capture. The stained gill filaments do not fade with cooking so there is a good op- portunity to recover marked individuals, together with the desired biolog- ical information. 84 Species and stain Specimens injected Average weight Amount of stain Initial deaths Specimens* alive at end of 40 days Visibility of stain Lobsters; Number Grams Milliliters Number Number Trypan blue Fast green FCF 3 180 0.42 1 2 distinct 3 180 1.08 0 2** distinct Crabs: Trypan blue 6 90 0. 16 1 3 fair Fast green FCF 6 90 0. 30 0 5 distinct Do. 5 75 0.20 3 1 distinct Do. 1 9 0.05 0 1 distinct * Four crabs escaped during holding period and have not been included among survivors. !=* One lobster was killed after molting at the end of 22 days - stain distinct. 85 Small Beam Net for Sampling Postlarval Shrimp William C. Renfro Postlarval peijaeid shrimp entering estuarine nursery grounds through Galveston Entrance have been sampled twice weekly since November 1959. Study of these samples has shown seasonal fluctuations in immigration and size composition of white and grooved shrimp postlarvae. Small beam net used for sampling post- larval shrimp. To catch postlarvae in shallow areas along the shore, a net was designed which could be easily handled by one man wading. Essentially it is a small beam trawl or bar net. The body is cut from a single piece of nylon netting 75 by 68 inches, having 50 openings per square centimeter. The fin- ished net is 5 feet wide on both the head and footropes by 28 inches long. The throat is a canvas cylinder 8 inches long and 12 inches in diameter sewed to the end of the body. Over the throat is tied a conventional 12-inch, No. 1 mesh plankton net with a removable bucket. This plankton net can be 86 readily removed because it is secured to the larger net (or body) by means of a cord and ring arrangement. A 7-foot, 3/l6-inch stainless steel cable with lead weights serves as the footrope. The headrope is threaded through five, 2 3 /8-inch -diameter sponge floats. Ends of the footrope and headrope are attached to a 6-foot, 3/4-inch stainless steel pipe which functions as the beann. In operation, the net is pulled by a bridle attached to the ends of the pipe. When pulled slowly, the pipe drags along the bottom frightening postlarvae off the bottom and into the net mouth. The standard practice is to attach a nylon cord to a stake driven into the ground at the waterline. The cord is stretched taut parallel to the waterline and used as a constant radius as the net is pulled along the bottom in a half circle. This naethod assures that the length of tow, bottom, area, and volume of water strained will be the same for each sample. Organisms regularly taken with this gear include: penaeid shrimp 5 to 50 mm. long; Mysis larvae and adults; crabs and crab larvae; amphipods; arrow worms; fish eggs and fish 4 to 75 mm. long; ctenophores; diatoms; and many other small planktonic and benthic animals. In one 425-foot tow, 4,700 penaeid postlarvae were caught. _ S«om9 Sewed Together \ I "^ " With Nyloh Threod And Tope V / L ^ /fs// ^ \/ f'~ *■ ^L^^^^'""'^ y ^ » N V \ • ^^ e LoogConvot Sl««ve Sewed H.r« / N r \ A /• b • « ^>. ,o--J! 12" ■"»■ 1 < ' V y N ' \ ^ \ ' Ns ^jy N • ^T V /- 1 N ^^>. / / i V X X N • / \ N • / 1 N / V n 3-,jj" J Pattern for cutting mesh body of beam net. 87 The Use of Atkins -Type Tags on Shrimp Donald M. Allen and Thomas J. Costello An ideal tag should be easily recognized by a casual observer, yet have no abnormal effect upon movennent, growth, or survival of the tagged aniinals. In the case of crustaceans, such as shrimp, the tag must be re- tained through successive molts. Petersen disk tags have been used extens- ively to mark shrimp since 1934. Such tags are easily recognized and are retained through molting. The information derived from experiments in which shrimp were marked with Petersen disks has contributed greatly to our knowledge of certain aspects of shrimp biology. Observations reveal, however, that shrimp tagged with Petersen disks undergo excessive mor- tality, which apparently increases as the size of shrimp marked decreases. An additional disadvantage is the fact that such tags restrict shrimp agility, which could affect normal movement and survival. The deleterious effects of the Petersen disk tag may, in part, be attributed to trauma, resulting fronn continued impalement on the rigid nickel pin, the excessive weight of the plastic disk-nickel pin assembly, and the in- creased Awater resistance to the disks which may "toe out" as the shrimp moves forward. The latter deficiency is particularly apparent >vhere extra pin length is allowed between the disks for growth. In recent years, shrimp have been marked with biological stains which apparently have little, if any, effect upon movement, growth, and sur- vival of marked individuals. The biological stain marks are retained through ecdysis. Although stain marks are not recognized as readily as nnechanical tags and their use requires an intensive recovery campaign, the stain-marking technique has been used successfully to study growth, migrations, and mor- tality rates of commercial shrimp populations. However, there is still a need for a numbered tag which can be used to follow growth and migrations of indi- vidual animals. It is probably not possible to design a mechanical tag ^vhich can favorably compare with a biological stain mark in respect to the effect upon shrimp survival and movement. However, a modified Atkins tag conrunonly used on fish has several advantages over the Petersen disk tag when used for marking shrimp. This tag is composed of a small oblong strip of cellu- lose acetate (0. 8 mm. thick and inscribed with printed information) secured to a short length of monofilament nylon line, which has a loop in the free end. The tag is attached to the shrinap by means of a slender surgical needle (in- testinal thin), which has had the eye cut open on one side. The nylon loop is hooked by the needle eye, and the needle is inserted laterally through the muscle tissue of the first abdominal somite of the shrimp, taking care to avoid the nerve cord and gut. After the nylon line is drawn through, the plastic strip is passed through the nylon loop twice, securing the tag in posi- tion. 88 -> >- ^:.w." ^''o Shrimp tagged with the Atkins -type tag have been held with a con- trol group for 3\ months in a salt-water pond. During this time, they passed through a series of molts. Growth of tagged shrimp was comparable to that of untagged individuals. Comparisons of the more obvious differences be- tween the Atkins-type tag and the Petersen tag revealed the following: Weight - The Atkins -type tag is slightly heavier than water and weighs only one -eighth as much as the Petersen tag (Atkins tag and nylon line, 0. 0292 g. ; Peter- sen tags and pin, 0. 233 g. ). Water resistance - The ob- long plastic strip of the Atkins - type tag trails the shrimp dorso- posteriorally to the point of at- tachment. In this position, and with its small size, it presents a very narrow surface to the flow of water, probably creating less water resistance than the Peter- sen tag. Attachment - The time re- quired to attach each tag is ap- proximately equal. Both tags are attached to the shrimp through the first abdominal somite. The Atkins- type tag is attached to the shrimp with 3 -pound -test monofilament nylon line, diameter 0. 3 mm. while the Petersen tag is affixed with a nickel pin, 0. 9 mm. in diameter. It appears that the relatively thick, rigid pin causes more tissue damage than the thin, pliable nylon line. Indications are that the Atkins tag, relatively streamlined, lightweight, and flexible, is an im- provement over the Petersen tag and may be particularly useful for tagging small-sized shrimp. Final evalu- ation, however, must await experiments which compare survival rates of shrimp tagged with Atkins tags, with those of unmarked shrimp and shrimp tagged with Petersen disks. The position of attachment for the Atkins tag on shrimp and the mod- ified needle used to insert the mono- filament nylon harness. 89 Immersion Staining of Postlarval Shrimp Ray S. Wheeler The purpose of this preliminary inn^mersion staining study was to find a nontoxic substance that would stain postlarval shrimp vividly enough to render them easily detectable with the unaided eye and would persist for an extended period. Postlarval shrimp are so small that neither tagging nor injection of biological stains is feasible. Eleven stains have been screened as possible larval shrimp stains. These include six liquid food colors (Brand A green, red, blue, and yellow; Brand B red and green), an Easter egg dye, and four biological stains (neu- tral red medium, Bismarck brown Y, Nile blue A, and neutral red). The postlarval shrimp used in this study measured 10 t 1 mm. They were held in recirculating sea-water tanks or aquaria until they had be- come adjusted to these conditions, after which they were immersed in the various stains. During the testing period, the animals were not fed. The effectiveness of the stains was observed at varying time inter- vals of 1, 3, 5, and 10 minutes with different stain concentrations. Two indi- viduals were stained simultaneously in each combination and afterward placed in separate petri dishes. The results of each experiment were observed for 7 days. Control animals were handled in the same manner, except that no stain was added. Liquid food colors were used at concentrations of 100, 50, 25, and 12^ percent of the commercial stock solution. Sea water was used in making dilutions. Solutions made from dry biological stains, and the Easter egg dye varied from 333:1 to 1,280,000:1 by weight. Stains were found to differ in persistency, intensity, and toxicity. The uptake of stain varied between individuals even though they were stained simultaneously in the same container. Liquid food colors (Brand A) were found to be nontoxic at 100 per- cent concentration for the maximum time interval of 10 minutes. Shrimp stained with the red, blue, and green colors appeared quite brilliant at the higher concentrations, although color intensity diminished at the lower con- centrations and shorter immersion intervals. Even at the lower concentra- tions, stained shrimp were easily distinguished when released among a group of unstained shrimp. Color was concentrated in the digestive tract with only little staining noted in the thoracic or abdominal tissue. Of the three colors, red seemed initially to be the most conspicuous and stood out with the great- est brilliance. Although each of these colors faded toward the end of the 7- day test period, fading was most noticed in the brilliant red coloration, which became pinkish red. This faded shade of red could be confused with the nat- ural red pigmentation that occurs near the base of the appendages of some small shrimp. 90 Yellow food coloring (Brand A) was light in color, lacking the con- trast necessary to make it readily distinguishable. For this reason it was regarded as unsuitable. Shrimp stained with green food color (Brand B) showed good color- ation of the gastric mill and gut. Immediately after staining, signs of distress were noted and heavy mortality occurred overnight. This stain was therefore regarded as unsatisfactory. Red food color of Brand B demonstrated the same qualities as those of Brand A. At concentrations of 1,000:1 by weight, the Easter egg dye was neither toxic nor did it stain. Neutral red medium at the lower concentrations failed to stain and at the higher concentrations proved to be toxic. The color imparted by Nile blue A, although faint at the higher con- centrations, showed promise in that it was not toxic. The color within the ab- dominal tissue persisted throughout the observation period. Neutral red was not toxic and demonstrated good staining qualities at the higher concentrations and longer time intervals. The digestive tract was colored a dark red and the abdominal tissue a lighter red. This color persisted throughout the observation period. Bismarck brown Y was not intense enough nor was there enough contrast to make it easily detectable. Mortality was low. In addition to the standard tests, two groups of postlarvae were stained and held for 2 weeks in 15 -gallon aquaria. The aquaria bottoms were covered with sand, and Mysidacea were introduced as food. Group 1 was stained with Brand B red food color, while neutral red was used in group 2. Although mortality was low, the intensity of the stain in group 1 diminished each successive day until on the 3d day many of the shrimp had lost their color entirely. On the 4th day, we examined each individual and found that only 7 of the 50 originally stained had retained enough color to make them easily distinguishable with the unaided eye. Twenty -three others bore enough stain to be distinguishable under the binocular microscope. Sev- eral digestive tracts contained sand, suggesting that the dye had been elim- inated in the feces. In group 2, some color had faded, but enough color was retained in the digestive tract and abdominal tissue at the end of the 2d week to nnake it distinguishable with the unaided eye. As previously indicated, the work presented here is preliminary. Indications are, however, that additional work will yield a suitable stain. 91 A Device for Measuring Live Shrimp Donald M. Allen Growth studies of shrimp using the nnark -re capture method require a rapid and accurate method of measuring large numbers of the living animals, Previous experience using vernier calipers to measure carapace length and conventional fish-measuring boards to measure total length showed these methods to be unsuitable. The grip required to secure a live shrimp for meas- urement may injure the animal, and the time involved is prohibitive. These problems are magnified when dealing with very small shrimp, which are both agile and fragile. l-«j&^i«j&JT|B-j«|ojo|o!|(^.t^ 1^ 1^ 1^ DOWL PLUG TOP VIEW Shrimp measuring de- FRONT VIEW vice made of plastic tubing. SIDE VIEW A simple device to measure live shrimp w^ith none of the above dis- advantages was developed. The device, essentially a calibrated trough with a handle, is constructed of clear plastic tubing having a 1/8-inch wall. The length and diameter of the tubing are- determined by the sizes of the shrimp to be measured. For shrimp ranging from about 60 to 140 mnn. total length, an 1 1 -inch length of 3/4-inch tubing is used. Five inches of tubing is retained as a handle. The trough is formed by removing, lengthwise, one-half of the re- maining 6 -inch section of the tube. A short, slightly tapered plastic dowel is forced into the tube where it joins the trough and cemented. The exposed end of the secured dowel forms a base line for calibration and measuring purposes. To determine absolute total lengths, a strip of millimeter paper, appropriately numbered, is taped to the convex surface of the transparent trough where it can be easily read but not become worn. To rapidly separate large numbers of shrimp into preselected size groups, variously colored strips of plastic tape, each representing a narrow size range, are affixed to the trough at appropriate distances from the base line. In use, the device is held by the handle in one hand. A shrimp is laid in the trough with the tip of the rostrum touching the exposed dowel end. The trough restricts movement and holds the shrimp in an extended position so that an accurate total -length measurement can be made with a minimum of handling or pressure. Using this device, several hundred live shrimp can be measured per hour with practically no mortality. 92 Distribution of Pink Shrimp Larvae and Postlarvae C. P. Idyll, Albert C. Jones, and D. Dimitriou University of Miami, Institute of Marine Science (Contract No. 14-17-0002-4) Research on the production and distribution of planktonic larvae and postlarvae of pink shrimp, Penaeus duorarum, was performed by the Institute of Marine Science of the University of Miami. Over a thousand plankton hauls were made and hydrographic data collected on 20 cruises from July 1961 through May 1962 to the Tortugas Shelf. In addition, infor- mation on water currents was obtained on two cruises in August and Sep- temper 1961, and previously collected current data were sumnnarized. The currents in shallow water less than 15 meters in depth are primarily tidal. At depths from 15 to 33 meters, resultant currents show both tidal and wind-driven components. Beyond depths of 33 meters to the western side of a salinity ridge, whose position varies seasonally, the cur- rents are wind driven with no visible effects from the tide. To the west of the salinity ridge and to the limits of the area sampled, the currents are density currents. JFMAMJJASONO|JFMAMJJASONO|JFMAMJJASONOJJFMAMJ 1959 I960 1961 1962 Relative abundance of pink shrimp larvae and postlarvae and average bottom water temperatures on the Tortugas Shelf from January 1959 to April 1962. 93 The velocities of the resultant tidal and wind-driven currents are small and apparently are not sufficient to account for transport of shrimp larvae from the offshore spawning grounds to mainland nursery areas. The density currents are of higher velocity but generally occur west of the prin- cipal spawning area. In August and September 1961, however, a southwest- erly density current was observed on the spawning grounds. The spawning season of pink shrimp, as indicated by the presence of young stages in the plankton, extends throughout the year. A seasonal peak in spawning occurs in spring or sunruner and generally is associated with ris- ing water temperatures. In I960, a seasonal peak in spawning occurred in nnidsummer. In 1961, the spawning peak was in the spring. It was followed by low spawning intensity during the sumnaer, associated with low tempera- ture of the bottom water over much of the spawning area. The average age of pink shrimp in the plankton increased from 5. 5 days at the western edge of the spawning area to 29. 7 days near the mainland. This increase suggests a movement from the spawning area across the Tor- tugas Shelf towards the mainland but does not exclude the possibility that planktonic stages nnay also move toward the Florida Keys. Shrimp of greatest average age were taken off the principal entrances to the Whitewater Bay es- tuary, which is known to be a nursery area for the Tortugas pink shrinap. Since resultant currents of the Tortugas Shelf do not move in an easterly di- rection, it is apparent that at least the older planktonic stages do not freely drift in the water mass but either actively swim across the Shelf towards shallow water or take advantage of the east-west movement of tidal currents. 94 Library Stella Breedlove At the end of fiscal year 1962, the library contained a total of 11,779 items. This number represents an increase of 2,871 items and in- cludes 273 volumes of books and journals added during the year. Unbound journals, reprints, microfilms, photographs, translations, and miscellan- eous material are included in the remainder. All items have been cataloged or entered in the records maintained by the library. Use of the library has increased during the year. The total num- ber of reference questions, excluding directional questions, has been esti- mated at 1, 012, and the items loaned total approximately 2, 500. A notice- able increase in attendance and use of publications in the library has also been evident. There were 63 items borrowed from other institutions for the use of the staff, and 175 volumes were loaned to other libraries and laboratories, A total of 125 volumes of journals and miscellaneous publications was bound or prepared for binding during the year. Work was connpleted on the alpha- betical list, with cross references, of the material shelved in the journal file. This list serves as a guide to the material that is shelved following the class- ified book collection. Complete cataloging of the collection of translations was accomplished. Over 50 laboratories and Government offices were contacted for official publications of interest to this laboratory, with a favorable response in each case. A list of library acquisitions was prepared and distributed weekly to staff members, including those at the field stations, also to selected Serv- ice laboratories and other laboratories requesting inclusion on our mailing list. The library compiled a list of recent publications in the field of fisheries and related sciences for the quarterly issues of the Transactions of the American Fisheries Society. The library assisted in the evaluation survey by the National Sci- ence Foundation on the use of translated Soviet scientific journals. Program leaders and selected scientists of the laboratory staff participated in this survey. I compiled a list of Service publications for the Sumxner Science Institute, Baylor University, and gave similar assistance to other educa- tional projects. The Chief of the East Gulf Estuarine Investigations included the library in his visit to the laboratory. Library practices prior to the estab- lishment of the independent field station at St. Petersburg Beach, Fla., were reviewed, and consideration was given to future cooperation between the two libraries. The acting librarian of the Biological Laboratory, Brunswick, Ga. , spent 3 days in the library to obtain infornnation on library techniques, 96 principally in Service libraries. Since that time, questions concerning various phases of library practice have been handled through correspond- ence. An additional 16 feet of shelving were added to the library, mak- ing a total of 463 linear feet. Space is limited, however, and additional shelving is needed to incorporate new material in the collection. Assistance in the library during the year was linnited to typing correspondence. Statistical Summary of Library Collection On hand Additions On hand 1961 1962 1962 Books 1, 657 211 1,868 Journals 352 62 414 Journals (unbound) 890 164 1,054 Reprints 1.930 290 2, 220 Institutional 3, 210 2,081 5,291 Other 869 63 932 Total items 8.908 2, 871 11,779 96 SEMINARS Bottom types and salinities. Anthony Inglis Gulf of Panama anchoveta tagging. Edward F. Klima Fisheries of Taiwan. Mr. Po-wei Yuan, Formosa Invertebrate indicators. David V. Aldrich Shrimp fecundity studies. Harold A. Brusher Marine reptiles - recent and fossil. Richard A. Diener Yucatan and Campeche shelf geology. William B. Wilson Shrimp spawning populations. William C. Renfro Currents and their influence on the distribution of brit herring in the Gulf of Maine. Robert F. Temple Currents on the continental shelf of the northern Gulf coast. J. Bruce Kimsey Engineering projects in Louisiana. Charles R. Chapman, Vicksburg, Miss. The origin, uses, and associated fauna of the pelagic Sargassum weed. Charles H. Koski MEETINGS ATTENDED* American Institute of Biological Sciences, Lafayette, Ind. , August (1) American Society of Limnology and Oceanography and the Instrument Society of America, Woods Hole, Mass. , September (1) American Fisheries Society, Memphis, Tenn. , September (1) Water for Texas, College Station, Tex. , September (1) Gulf States Marine Fisheries Commission, New Orleans, La. , October (2) First National Shallow Water Research Conference, Tallahassee, Fla. , October (2) Giolf and Caribbean Fisheries Institute, Miami, Fla. , November (4) American Fisheries Advisory Committee, Galveston, Tex. , December (6) Bureau of Commercial Fisheries Laboratory Directors' Meeting, Galveston, Tex. , January (6) Texas Shrimp Association, Brownsville, Tex. , January (1) Gulf States Marine Fisheries Commission, Galveston, Tex. , March (4) WORK CONFERENCES* Bureau of Commercial Fisheries Meeting on Instrumentation Requirements, Stanford, Calif. , October (1) Lake Pontchartrain Hurricane Study Meeting, State Marine Laboratory, Grand Terre Island, and New Orleans, La. , September, December, and January (1) American Mosquito Control Association, Galveston, Tex. , March (2) Trip to examine Louisiana and Texas estuaries and visit to Corps of Engineers Waterways Experiment Station, Vicksburg, Miss. , April (1) Texas Shrimp Association, Brownsville, Tex. , April (2) Attendance shown in parentheses. 97 PUBLICATIONS Allen, Donald M. , and T. J. Costello. 1962. Grading large numbers of live shrimp for marking experi- ments. U. S. Fish and Wildlife Service, Progressive Fish- Culturist, vol. 24, no. 1 (January), p. 46-48. Costello, T. J. 1961. Use of stains in shrimp mark -recapture experiments. ICNAF North Atlantic Fish Marking Symposium, May 1961, Contribution No. 23, 5 p. Costello, T. J. , and D. M. Allen. 1962. Survival of tagged, stained, and unmarked shrimp in the presence of predators. Proceedings of the Gulf and Caribbean Fisheries Institute, 14th Annual Session, 1961, p. 16-20. Dobkin, Sheldon. *196l. Early developmental stages of the pink shrimp, Penaeus duorarum, from Florida waters. U. S. Fish and Wildlife Service, Fishery Bulletin 190, vol. 61, p. 321-349. Dragovich, Alexander, and Billie Z. May. 1962. Hydrological characteristics of Tampa Bay Tributaries. U. S. Fish and Wildlife Service, Fishery Bulletin 205, vol. 62, p. 163-176. Kimsey, J. Bruce. 1962. Rate of metabolism and food requirements of fishes, by G. G. Winberg. [A reviev^^/ Transactions of the American Fisheries Society, vol. 91, no. 1, p. 129-130. Kutkvihn, Joseph H. 1962a. Conversion of "whole" and "headless" weights in commercial Gulf of Mexico shrimps. U. S. Fish and Wildlife Service, Special Scientific Report--Fisheries No. 409, 7 p. 1962b. Recent trends in white shrimp stocks of the northern Gulf. Proceedings of the Gulf and Caribbean Fisheries Institute, 14th Annual Session, 1961, p. 3-l6. 1962c. Research at the Galveston Biological Laboratory. In Pro- ceedings of the First National Coastal and Shallow Water Research Conference, October 1961. National Science Foundation and the Office of Naval Research, Tallahassee, Florida, p. 251-256. 98 Marvin, Kenneth T. , Larence M. Lansford, and Ray S. Wheeler. 1961. Effects of copper ore on the ecology of a lagoon. U. S. Fish and Wildlife Service, Fishery Bulletin 184, vol. 61, p. 153-160. Rounsefell, George A. 1962a. Relationships among North American Salmonidae. U. S. Fish and Wildlife Service, Fishery Bulletin 209, vol. 62, p. 235-270 1962b. Introduction to the study of animal populations, by H. G. Andrewartha. [a review/ Transactions of the American Fisheries Society, vol. 91, no. 3, p. 330. Temple, Robert F. 1962. Measuring the production of marine phytoplankton, by J. D. H. Strickland. /A vewie-wj Transactions of the American Fisheries Society, vol. 91, no. 1, p. 129. U. S. Fish and Wildlife Service. 1961a. The Florida red tide, by Staff of the Bureau of Cormnercial Fisheries Biological Laboratory, Galveston, Texas. U. S. Fish and Wildlife Service, Fishery Lecuflet 506, 8 p. 196lb. Galveston Biological Laboratory Fishery Research for the year ending June 30, 1961. U. S. Fish and Wildlife Service, Circular 129, 82 p. VanDerwalker, John G. , and Edward Chin. 1962. A device for feeding brine shrimp to fishes. Transactions of the American Fisheries Society, vol. 91, no. 2, p. 230-231. Contract research. 99 MANUSCRIPTS IN PRESS Aldrich, David V. Photoautotrophy in Gymnodinium breve Davis. Science (10 MS. p.). Chin, Edward, aind John G. VanDerwalker. The relative toxicities of some chlorinated hydrocarbons to postlarvae of brown shrimp and blue crab. U. S. Fish and Wildlife Service, Special Scientific Report — Fisheries (15 MS. p. , 2 figs.). Kutkuhn, Joseph H. Gulf of Mexico commercial shrimp populations - trends and character- istics 1956-1959. U. S. Fish and Wildlife Service, Fishery Bulletin 212, vol. 62 (173 MS. p., 25 figs.). Marvin, Kenneth T. , and Larence M. Lansford. Phosphorus content of some fishes and shrimp in the Gulf of Mexico. Publications of the Institute of Marine Science (10 MS. p. ). Proctor, Raphael R. , Jr. Stabilization of the nitrite content of sea water by freezing. Limnology and Oceanography (5 MS. p. , 1 fig. ). Renfro, William C. , and Harry L. Cook. Early larval stages of the seabob, Xiphopeneus kr^yeri (Heller). U. S. Fish and Wildlife Service, Fishery Bulletin (37 MS. p., 20 figs. ). Rounsefell, George A. The Bureau of Commercial Fisheries Biological Laboratory, Galveston, Texas. U. S. Fish and Wildlife Service, Circular (31 MS. p., 37 figs.). 100 MANUSCRIPTS SUBMITTED Kutkuhn, Joseph H. Dynamics of a penaeid shrimp population and management implications. U. S. Fish and Wildlife Service, Fishery Bulletin (82 MS. p., 13 figs.). Marvin, Kenneth T. , C. M. Proctor, and J. E. Stein. Factors affecting the reliability of chlorinity analyses. Limnology and Oceanography (16 MS. p.). Rounsefell, George A. Marking of fish and invertebrates. U. S. Fish and Wildlife Service, Fishery Leaflet (26 MS. p. , 1 fig. ). MS #1271 GPO 940442 101 MBL WHOI Llbfary Serials 5 WHSE 00232 Created in 1849, the Department of the Interior — America's Department of Natural Resources — is concerned with tlie man- agement, conservation, and development of the Nation's water, fish, wildlife, mineral, forest, and park and recreational re- sources. It also has major responsibilities for Indian and Territorial affairs. As the Nation's principal conservation agency, the Depart- ment works to assure that nonrenewable resources are developed and used wisely, that park and recreational resources are con- served for the future, and that renewable resources make their full contribution to tlie progress, prosperity, and security of the United States — now and in the future.