REPORT OF THE

BUREAU OFCOMMERCIAL FISHERIESBIOLOGICAL LABORATORY

GALVESTON, TEXAS

FISCAL YEAR 1967

0!%

UNITED STATES DEPARTMENT OF THE INTERIORFISH AND WILDLIFE SERVICE

BUREAU OF COMMERCIAL FISHERIES

Circular 295

UNITED STATES DEPARTMENT OF THE INTERIOR

U.S. Fish and Wildlife Service

BUREAU OF COMMERCIAL FISHERIES

REPORT OF THEBUREAU OF COMMERCIAL FISHERIES

BIOLOGICAL LABORATORY,GALVESTON, TEXAS

Fiscal Year 1967

Milton J. Lindner, DirectorRobert E. Stevenson, Assistant Director

Contribution No. Z6l, Bureau of Connmercial FisheriesBiological Laboratory, Galveston, Texas

Circular 295

Washington, D.C.December 1968

The Bureau of Commercial Fisheries Biological Laboratory, Galveston, Tex.,and its field station in Miami, Fla., conduct fishery research in the Gulf of Mexico aspart of the work of the Bureau's Gulf and South Atlantic Region (Region 2), whichcomprises the eight coastal States from North Carolina to Texas.

Office of the Regional Director, Seton H. Thompson, is in the Federal OfficeBuilding, Room 668, 144 First Avenue South, St. Petersburg, Fla. 33701.

Biological Research:

Biological Laboratory, Beaufort, N.C.Radiobiological Laboratory, Beaufort, N.C.Biological Laboratory, Brunswick, Ga.Biological Laboratory, Galveston, Tex.Biological Laboratory, Gulf Breeze, Fla.Tropical Atlantic Biological Laboratory, Miami, Fla.Biological Laboratory, St. Petersburg Beach, Fla.Biological Field Station, Miami, Fla.

Industrial Research:

Exploratory Fishing and Gear Research Base, Pascagoula, Miss., auxiliarybase at St. Sinnons Island, Ga.

Marketing--Marketing offices in Atlanta, Ga.; Dallas, Tex.; Pascagoula,Miss.; and St. Petersburg, Fla.

Technology-- Technological Laboratory, Pascagoula, Miss.

Resource Development:

Loans and Grants office, St. Petersburg, Fla.Statistical Center and Market News office. New Orleans, La.

CONTENTS

Page

Report of the Director 1General 1Laboratory facilities ZPublic relations Z

Foreign visitors ZForeign trainees ZLaboratory activities Z

Library 3Publications 3Manuscripts in press ...... 4Manuscripts submitted 4

Shrimp biology program 5Distribution and abundance of larvae 5

Seasonal trends in abundance 6Overwintering of postlarval brown shrimp 6

Taxonomy and culture of shrimp larvae 7Larval food studies 7Responses of larvae to varying light intensities 7

Cultivation of shrimp in artificial ponds 8Population estimates 9Overwintering studies 9Present activities , 9

Ecologically associated organisms 10Food studies 10Botton-i fauna survey 10Plankton study 10

Florida Bay ecology studies 10Seasonal changes in relative abundance of postlarvae of pink shrimp entering the

Everglades estuary 12Variations in abundance of juvenile pink shrimp emigrating fronr^ the Everglades

National Park estuary to the commercial catch 13

Shrinnp dynamics program 14Migration, growth, and mortality of commercial shrimps 15Postlarval and juvenile shrimp 1^

Postlarvae 16Juvenile shrimp 17Inshore current patterns 17

Studies of postlarval shrimp in Vermilion Bay 18Prediction of commercial harvest 18Postlarval shrimp identification 18

Estuarine Program 18Effects of engineering projects 19

Effects of habitat modification 19Habitat rehabilitation 20

Texas coast hurricane study project 22Ecology of western Gulf estuaries 23

Hydrology 23Studies on the emigration of brown and white shrimp 24Brown shrimp 25White shrin-ip 26Character for identification of postlarval penaeid shrimp 26

Evaluation of estuarine data 27

Estuarine Atlas 27

Fish food study 27

Experimental biology progrann 28Shrimp metabolism 28

C ONT ENTS- - Continued

Page

Growth and survival of estuarine-marine organisnns 29Survival ^°

Growth 30Effect of container size 30

Gulf oceanography program 30Reconnaissance survey 31

Energy budget and circulation dynamics 33Sea-air interaction study 33

Level-of-no-motion study 33

Trends in oceanic conditions 33

REPORT OF THE BUREAU OF COMMERCIAL FISHERIESBIOLOGICAL LABORATORY, GALVESTON, TEXAS

Fiscal Year 1967

ABSTRACT

Progress of research is reported. Emphasis is on shrimp, and the researchinvolves the fields of biology, population dynamics, ecology, and oceanography.

REPORT OF THE DIRECTOR

GENERAL

This Laboratory has five research pro-grams--Shrimp Biology, Shrimp Dynamics,Estuarine, Experimental Biology, and GulfOceanography. Although seemingly different,each progrann is designed, either directlyor indirectly, to provide information thatwill permit optinnum use of stocks of com-mercial shrimp in the Gulf of Mexico. Morespecifically, our research is designed todefine the entire life histories of the species;to detern-iine the response of the species tofishing and to their environment; and todescribe in time and space the environ-mental variations.

Each of the five programs has a nunnberof individual projects. Progress made inthese projects during fiscal year 1967 con-stitutes the bulk of this report, but 1 sum-nnarized here some of the highlights of ourresearch.The refining of our techniques for rearing

larval shrimp spawned in the laboratory en-abled us to culture successfully tens of thou-sands of postlarvae. Our major problenn hasbeen to grow algal foods in quantities suf-ficient to sustain larval growth and survival.In one rearing experiment, however, enoughpostlarval white shrinnp were reared to stockone of the experinnental ponds in which weare studying the feasibility of rearing shrimpunder seminatural conditions.

After being placed in the experimentalpond, the shrimp grew rapidly for 35 days,but then growth virtually ceased. When theshrimp were harvested, 84 percent of theoriginal stock had survived and the projected

yield of whole shrimp was 575 pounds peracre (645 kg. per hectare).A nnajor breakthrough toward management

of a fishery was realized from nnark-recapture studies on the pink shrimp of theTortugas grounds. From these studies, wedetermined that natural mortality was con-siderably lower than had been previouslyreported. Of even greater significance, wealso determined the optimum size at whichto begin fishing for pink shrimp on the Tor-tugas grounds. The success of these studieshas led to renewed efforts to establish similarcriteria for the brown and white shrimpfisheries.

Although the importance of estuaries asnursery grounds for many commercial ma-rine species is well documented, modifica-tion of these waters along the Gulf coastby residential, industrial, and agriculturalexpansion is increasing at a tremendous rate.Our ecological studies in Galveston Bay haveshown that the shore and submerged plants,particularly in shallow water, provide nurseryhabitats for the young of shrinnp and otherspecies. Destruction of these plants, by what-ever means, makes the estuaries useless asnursery grounds.

Field observations on the occurrence ofwhite, brown, and pink shrimps indicate thatenvironmental factors affect the distributionof the species. The extreme conditions oftolerance by the three species were, how-ever, unknown. In the laboratory, tests madeunder controlled conditions showed that theability of shrimp to tolerate extremes oftemperature and salinity varied with thespecies and age (or size) of the shrimp.

We completed oceanographic cruisesthroughout the Gulf, during which bottomsamples and hydrographic n-ieasurennents wereobtained. The data from these cruises arebeing analyzed and interpreted to discoverthe oceanic environmental factors that causefluctuations in fxipulations of shrimp as wellas other commercial species of fish andshellfish. A bottom water mass, probably ofAntarctic origin and not previously reportedin the Gulf, was identified from hydrographicdata collected during the first "All-Gulf" cruisemade in February- March 1967.

Of particular interest to fisheries werethe evaluations made at this Laboratory ofphotographs taken during the Gemini spaceflights. We determined from these photo-graphs that a major advance infishery sciencecan come from a sound ocean-space researcheffort.

LABORATORY FACILITIES

The expanded activities and the increasedpersonnel in the Director's Office made severalphysical changes necessary. The ConferenceRoom, Director's Office, and Assistant Di-tector'8 Office were relocated and refur-bished. The south porch of one building wasenclosed to provide additional laboratory•pace, and laboratory furniture was installed,A second structure and about 0.8 acre ofland adjacent to the Laboratory complex wereacquired from General Services Administra-tion under a lease agreement for the expandedSpace Oceanography Project.A replacement tank truck (2,500-gallon ca-

pacity) was acquired to transport sea waterfrom the East Lagoon to our recirculatingsea-water laboratory,

PUBLIC RELATIONS

Neatly one thousand visitors were givenLaboratory tours or taken on field trips, orboth. Of 800 students and instructors, 360were from 10 universities, 163 were from6 high schools, and 277 were from 6 gradeschools.Other public relations activities included

Consultations with foreign visitors and trainees,lectures to student and civic groups, andcooperation with universities.

Foreign Visitors

During the year the Laboratory had 49visitors from 8 foreign countries. On Sep-tember 9, five Mexicans visited the GalvestonLaboratory to discuss anticipated problemsof disposal of waste material from a phosphateplant to be built at Coatzacoalcoa (PuertoMexico), Veracruz, Mexico, The group in-

cluded: Dilio Fuentes, Direccion General dePesca SIC, Campeche; Cesar Mendoza Trejo,Direccion General de Pesca, Mexico, D. F.;Luis Galvez and Hector Lopez, DireccionGeneral de Obras Maritimas, Mexico, D. F.;and Ing, Gmo. Cabrera, Fertilizantes Fosfata-dos Mexicanos, Mexico, D, F. Another groupfrom the Technological Institute, Monterrey,Mexico, included: Loustaunau Javier, Jose I.Flores Ugarte, Luis A. Coutte, Manuel Robles,Ezequiel Montemayor, Sergio Flores Cavazos,and Daniel Barrera. Also visiting were: Gmo.Chavez Salcedo, Hector Romero, and VictorMartinez from the Estacion de Biologia Marina,Veracruz, Mexico. Other foreign visitors were:H. Schaefer, Monterey Institute of Technology,Monterey, Mexico; E. L. Bousfield from theNational Museum of Canada, Ottawa, Ontario,Canada; Antonio Cortes, EmpacadoraEscuinapa, Escuinapa, Sinaloa, Mexico; G. C.Phillips, Unilever Research Laboratory,Aberdeen, Scotland; Amine Keyvanfar, SouthernFisheries Company, Tehran, Iran; Klaus Tiews,Assistant Director of the Institute for Coastaland Inshore Fisheries, Federal Research Lab-oratory, Hamburg, Germany; and Arthur C.Simpson, Ministry of Agriculture Fisheriesand Food, Fisheries Laboratory, Burnham onCrouch, Essex, England, On June ZZ, 1967,this Laboratory was host to 17 scientistsfrom Brazil and 8 from Mexico. The sched-ule of events included talks by R. E. Steven-son, Assistant Laboratory Director; Dale F.Leipper and James Arnold, Texas A&M Uni-versity, College Station, Tex.; A. G. Alexiou,U.S. Naval Oceanographic Office, Washington,D.C.; and H. R. Bullis, Jr., Director, Bureauof Comniercial Fisheries Exploratory Fishingand Gear Research Base, Pascagoula, Miss.

Foreign Trainees

The Laboratory had two trainees: C. S.Subrahmanyam, a student from India, andVictor Fernando Carrillo Martinez, Estacionde Biologia Marina, Veracruz, Mexico.

Laboratory Activities

Seven staff members discussed the Labora-tory's role in fisheries before school andcivic groups.

The Laboratory Director was invited bycommittee members of the University of TexasMedical Branch in Galveston to participatein the submission of a proposal from theUniversity of Texas to the U.S. Public HealthService for development of a medically orientedMarine Biological Institute in Galveston.

The Laboratory Director has been invitedto serve, with Lyle St. Amant, Gordon Gunter,and Robert Ingle, on a committee to selecta university to administer a grant for agraduate fellowship being established by theAmerican Shrimp Canners Association.

During the year, a contract was negotiatedwith the Lunar Receiving Laboratory of theNational Aeronautics and Space Administra-tion. We will supervise and train personnelas well as provide facilities for receivingand holding invertebrate animals used intheir experiments.

After the acquisition of the R/V Geronimoin the latter half of fiscal year 1966, wennade several cruises to various portionsof the Gulf to collect oceanographic data.In addition, the Graduate Research Centerof the Southwest, Dallas, Tex., charteredthe vessel to undertake a normal refractionseismic exploration survey along the Texasshelf and slope.On two occasions during the year, the

Laboratory Director served as an Adviserwith a U.S. delegation sent to confer withdelegates of foreign countries. In Honduras,the U.S. shrimp fishery off the Caribbeancoast of that country was discussed; in Mexico,negotiations for a shrimp fishery treaty wereundertaken.

Colored photographs of the earth's watermasses taken from earth-orbiting spacecraftshow features that interest meteorologistsand oceanographers, among others. The As-sistant Laboratory Director has studied manysuch photographs and gave 23 illustratedlectures during the year. Emphasis was onoceanographic features which heretofore havenot been seen in their entirety and knowledgeof which may have substantial impact on thefisheries of several countries.

Between June 12 and 24, FAO (Food andAgricultural Organization of the United Na-tions) sponsored the World Conference onthe Biology and Culture of Shrimps and Prawnsin Mexico City, Mexico. The Laboratory wasrepresented by nine staff mennbers, and ninemanuscripts were presented. In addition, theLaboratory Director served as convenor forthe section on "Resource Appraisal."

LIBRARY

At the close of fiscal year 1967 the librarycollection had about 26,400 items. Includedin the additions for the year were 303 vol-unnes of books and bound journals and 2,679reprints and miscellaneous publications.

The increase in circulation of library ma-terials and in reference services emphasizesthe trend of growth established during thelast few years. Other than the Laboratorystaff, the library serves the faculty andstudents of Texas AtM Marine Laboratory,other educational institutions, industrial or-ganizations, and individuals.

In addition to current activities, specialprojects accomplished during the year includecompletion of the reclassification of the bookcollection, the current inventory, and revi-

sion of selected indexes. Work on new indexeswas continued. A weekly list of library ac-quisitions was distributed to the Laboratorystaff and selected laboratories.A statistical summary of the library col-

lection for fiscal year 1967 is given in table 1.

Table 1 .--Statistical summary of library collection, 1966-67

BooksJournals (bound)Journals (Unbound)ReprintsPublications from State and

Foreign offices, etcOthe r

Total Items

On hand1966

2,837685

1,823

3,636

12,902

1,518

Additions

1967

271

32

253

366

1,912148

On handJune 30, 1967

3,108717

2,0764,002

14,8141,666

PUBLICATIONS

Armstrong, Reed S.1967. The subtropical underwater of the

eastern Gulf of Mexico. Con-i. Fish.Rev. 29(3): 46-48.

Armstrong, Reed S., John R. Grady, andRobert E. Stevenson.1967. Cruise "Delta I" of the GERONIMO.

Com. Fish. Rev. 29(2): 15-18.Baxter, Kenneth N., and William C. Renfro.

1967. Seasonal occurrence and size dis-tribution of postlarval brown and whiteshrimp near Galveston, Texas, withnotes on species identification. U.S.Fish Wildl. Serv., Fish. Bull. 66: 149-158.

Chapman, Charles R.1966. The Texas Basins Project. Amer.

Fish. Soc. Spec. Publ. 3: 83-92.Cook, Harry L., and M. Alice Murphy.

1966. Rearing penaeid shrimp fronn eggsto postlarvae. Proc. Southeastern Ass.Game Fish Comm., 19th Annu. Conf.pp. 283-288.

Kutkuhn, Joseph H.1966. The role of estuaries in the develop-

ment and perpetuation of commercialshrimp resources. Amer. Fish. Soc,Spec, Publ. 3: 16-36.

Lindner, Milton J.1966. What we know about shrimp size and

the Tortugas fishery. Proc. GulfCaribbean Fish. Inst., 18th Annu. Sess.,pp. 18-25.

Marvin, Kenneth T., and Raphael R. Proctor,Jr.1966a. Laboratory evaluation of red-tide

control agents. U.S. Fish Wildl. Serv.,Fish. Bull. 66: 163-164.

1966b. Comparison of two methods of N-ethylcarbazole carbohydrate analysis.U.S. Fish Wildl. Serv., Fish. Bull. 65:683-684.

Munro, J. L,., and D. Dimitriou.1967. Counts of larval penaeid shrimp and

oceanographic data from the TortugasShelf, Florida, 1962-64. U.S. FishWildl. Serv., Data Rep. 16, 40 pp. on1 microfiche. [Research under Bureaucontract.]

Trent, W. Lee.1967. Attachment of hydrofoils to otter

boards for taking surface samples ofjuvenile fish and shrimp. ChesapeakeSci. 8(2): 130-131.

Wheeler, Ray S.1967. Experimental rearing of postlarval

brown shrimp to marketable size inponds. Com. Fish. Rev. 29(3): 49-52.

Zein-Eldin, Zoula P., and George W. Griffith.1966. The effect of temperature upon growth

of laboratory-held postlarval Penaeusaztecus . Biol. Bull. (Woods Hole) 131(1): 186-196.

MANUSCRIPTS IN PRESS

Aldrich, David V., Carl E. Wood, and KennethN. Baxter.A behavioral connparison of postlarval

Penaeus aztecus and P. setiferus , withregard to burrowing as a response toreduced temperature. Bull. Mar. Sci.(21 MS. pp., 3 figs.).

Knight, Charles E., and Richard J. Berry.Recovery data for marked pink shrimp,

Penaeus duorarum Burkenroad, re-leased on the Florida Tortugas groxindsin 1965, U.S. Fish Wildl, Serv,, DataRep, (83 MS. pp., 1 fig,).

Mock, Cornelius R.Natural and altered estuarine habitats of

penaeid shrimp. Proc. Gulf CaribbeanFish. Inst., 19th Annu. Sess. (19 MS.pp., 5 figs.).

Moore, Donald.Nomenclature of the spotted triggerfish

of the eastern Atlantic Balistespunctatus, Copeia (8 MS. pp., 4 figs.).

Triggerfishes (Balistidae) of the westernAtlantic. Bull. Mar. Sci. (51 MS. pp.,9 figs.).

Temple, Robert F., and Clarence C. Fischer.Seasonal distribution and relative abundance

of planktonic- stage Penaeus spp, shrimpin the northwestern Gulf of Mexico,1961, U.S. Fish Wildl. Serv,, Fish,Bull. (28 MS. pp., 10 figs.).

Trent, Lee,Size of brown shrimp and time of emigration

from the Galveston Bay system, Texas,Proc. Gulf Caribbean Fish. Inst., 19thAnnu. Sess. (14 MS. pp., 4 figs,).

U.S. Fish and Wildlife Service.Annual report of the Bureau of Comnnercial

Fisheries Biological Laboratory, Gal-veston, Texas, fiscal year 1966. U.S.

Fish Wildl. Serv., Circ. (107 MS, pp,,49 figs,),

MANUSCRIPTS SUBMITTED

Armstrong, Reed S,, and John R. Grady,GERONIMO cruises the entire Gulf of Mexico

in late winter. Com, Fish. Rev, (8 MS,pp., 4 figs.).

Berry, Richard J., and Kenneth N, Baxter.Predicting brown shrimp abundance in the

northwestern Gulf of Mexico. Proc,FAO World Conf. Biol, Cult, ShrimpsPrawns (38 MS. pp., 13 figs.).

Berry, Richard J., and Robert C. Benton.Discarding practices in parts of the Gulf

of Mexico shrinnp fishery. Proc. FAOWorld Conf. Biol. Cult, Shrimps Prawns(26 MS. pp., 6 figs.).

Cook, Harry L,A method of rearing penaeid shrimp larvae

for experimental studies. Proc. FAOWorld Conf. Biol. Cult. Shrimps Prawns(10 MS. pp., 2 figs,).

Cook, Harry L., and Milton J, Lindner,Synopsis of biological data on brown shrimp

Penaeus aztecus aztecus Ives, 1891,Proc, FAO World Conf, Biol. Cult.Shrimps Prawns (63 MS, pp,, 1 fig.).

Costello, T. J., and Donald M. Allen.Mortality rates in populations of pink shrimp,

Penaeus duorarum , on the Sanibel andTortugas grounds, Florida. U.S. FishWildl. Serv., Fish. Bull. (36 MS. pp.,8 figs.).

Synopsis of biological data on the pink shrimpPenaeus duorarum duorarum Burken-road, 1939. Proc. FAO World Conf.Biol. Cult. Shrimps Prawns (88 MS.pp., 6 figs.).

Kutkuhn, Joseph H., Harry L. Cook, andKennethN. Baxter.Distribution and density of prejuvenile

Penaeus shrimp in Galveston En-trance and the nearby Gulf of Mexico(Texas). Proc. FAO World Conf.Biol. Cult. Shrimps Prawns (40 MS.pp., 6 figs,).

Lindner, Milton J., and Harry L. Cook.Synopsis of biological data on white shrimp

Penaeus setiferus (Linnaeus) 1767.Proc. FAO World Conf. Biol, Cult,Shrimps Prawns (73 MS. pp., 1 fig,).

Munro, J. L., A. C. Jones, and D. Dimitriou,Abundance and distribution of the larvae

of the pink shrimp ( Penaeus duorarum)on the Tortugas Shelf of Florida. U.S.Fish Wildl. Serv., Fish. Bull. (51 MS.pp., 10 figs.). [Research under Bureaucontract.]

Parker, Jack C, and Cornelius R. Mock,Length-weight relations and condition fac-

tors of three sciaenid fish species

from the Galveston Bay system, Texas.Publ. Inst. Mar. Sci, Univ. Tex. (7 MS.pp., 1 fig.).

Pullen, Edward J., and W. Lee Trent.White shrimp ennigration in relation to size,

sex, temperature, and salinity. Proc.FAO World Conf. Biol. Cult. ShrimpsPrawns (18 MS. pp., 4 figs.).

Pullen, E. J., C. R. Mock, and R. D. Ringo.A net for san-ipling the intertidal zone of

an estuary. Linnnol. Oceanogr. (6 MS.pp., 2 figs.).

Ringo, Robert D., and Gilbert Zamora, Jr.A penaeid postlarval character of potential

taxonomic value. Publ. Inst. Mar. Sci.Univ. Tex. (9 MS. pp., 1 fig.).

Stevenson, Robert E.Local winds along the Southern California

coast seen from Gemini V. Weather-wise (9 MS. pp., 4 figs.).

Stevenson, Robert E., and Dale F. Leipper.Influence of the hurricane on the structure

of the thermocline. Proc. HurricaneSymp., October 10-11, 1966 (pt. I--7MS. pp., 8 figs.; pt. II-- 12 MS. pp.,7 figs.; pt. III--7 MS. pp., 6 figs.).

Yokel, B. J., M. A. Roessler.and E. S. Iversen.Data report on juvenile stages of pink

shrimp( Penaeus duorarum) and on

fishes collected in Buttonwood Canal,Florida, December 1962 to June 1965.U.S. Fish Wildl. Serv., Data Rep. (25MS. pp.). [Research under Bureau con-tract.]

Zein-Eldin, Zoula P., and George W. Griffith.An appraisal of the effects of salinity and

temperature on growth and survival ofpostlarval penaeids. Proc. FAO WorldConf. Biol. Cult. Shrimps Prawns (20MS. pp., 5 figs.).

SHRIMP BIOLOGY PROGRAM

Research in this program varied from fieldstudies to determine whether postlarval brownshrimp overwinter in the Gulf of Mexico tolaboratory studies designed to develop methodsfor raising large quantities of diatoms tofeed mass cultures of larval shrimp. Morespecifically, the research consisted of study-ing: (1) the distribution and abundance oflarval shrimp in the Gulf of Mexico; (2) methodsfor identifying and cxilturing shrimp larvaeas well as the culturing of diatonns for feedinglarval shrimp; (3) cultivation of shrimp inartificial ponds; (4) organisms ecologicallyassociated with shrimp; and (5) the ecologyof pink shrimp in Florida Bay.

Also, personnel at the Institute of MarineSciences, University of Miami, under con-tract with the Bureau of Commercial Fish-eries, studied the movements of postlarval andjuvenile pink shrimp into and out of theEverglades National Park estuary. Whetherin Texas or Florida, our endeavors, althoughdiversified, were designed to provide a betterunderstanding of the life histories of shrimpin the Gulf of Mexico.

Biologists in this program were authorsor coauthors of 12 scientific reports, pub-lished or submitted for publication, on var-ious phases of the life history of shrimp.These articles, submitted to various sci-entific journals and serials, should be avail-able to researchers and industry within ayear.

The annual progress report of each projectfollows.

Robert F. Temple, Program Leader

DISTRIBUTION AND ABUNDANCEOF LARVAE

All plankton samples collected in 1964 wereexamined in the laboratory during fiscal year1967. We collected the samples with Gulf Vplankton nets along transects perpendicularto the coasts of Louisiana and Texas. Stationdepths at which sannples were taken rangedfrom 7 to 110 m. (4-60 fathoms). Since 1962,sampling in these waters has included 1,568metered hauls. Examination of the catcheshas provided information on the relativeabundance and seasonal distribution ofplanktonic- stage penaeid shrimp. Grouped bydepth zones, the numbers of samples takenin 1962-64 in Texas and Louisiana watersare presented in table 2.

Table 2. --Number of Giilf V plankton tows, by depth zones, taken inLouisiana and Texas waters, 196Z-64

Depth zone and area

Planktonic stages of five known genera of

penaeids-- Penaeus , Sicyonia , Trachypeneus ,Solenocera , and Parapenaeus --were taken in

plankton hauls. The data have been analyzed,

however, only for the commercial shrimps

of the genus Penaeus .

Seasonal Trends in Abundance

Seasonal trends in the abundance of Penaeus

spp. larvae (postlarvae excluded) in 1962-64

were similar in Lomsiana and Texas (fig. 1).Differences did exist between depths, however.

Catches in 7 to 13 m. (4-7 fathoms) of waterwere restricted to April-October; the yearlytrend was more unimodal here than at deeperdepths, where a definite bimodal trend wasevident. Catches of larvae at 27 m. (15fathoms) or deeper, in general, increased

in the spring from the winter low, decreasedin the summer, and were maxinnum in the fall.The only exceptions were in Texas in 1963and 1964, where catches at 27 to 64 m. (15 to35 fathoms) in the spring approximated thosemade in the fall.

Overwintering of Postlarval Brown Shrimp

Because of the bathymetric distribution ofadult white and brown shrimp, we believe thatlarval abundance trends in 7 to 13 m. (4-7fathoms) of water (fig. 1) reflect spawning

of white shrimp, and those in deeper water

the spawning of brown shrimp. Such an as-sumption creates a problem, however, for

the movement of most postlarvalbrown shrimpinto the GalvestonBay nursery area in January-April is well documented. The period of

1257-13 METER STATrONS

^A\

1-27-64 METER STATIONS

73- 110 METER STATIONS

/;'

,.;=f-,-^^-,.^..;^:;3:;^jb^..y-,40°W^ i I , ,Wr-f4-^Wi-rJMMJSNJMMJSNJMMJSN1962 1963 1964

Figure 1.—Abundance of Penaeus larvae by depth zones

in Louisiana and Texas waters, 1962-64.

time between the high catches of larvaeoffshore in the fall and the large catchesof immigrating postlarvae through GalvestonPass is unaccounted for unless the develop-ment of larvae is retarded offshore, or larvaeoverwinter offshore, or both.

To investigate the possibility of postlarvaeoverwintering offshore, we made cruises offGalveston between September and April towaters between the surf zone and to a depthof 12 m. (6-7 fathoms). Samples were takenon bottom with a specially constructed sledand in the water column with Clarke-Bumpusand half-meter nets. Postlarval brown shrimpincreased in numbers from October to Marchin a narrow zone of water along the coastbefore they entered the estuary (table 3).

Table 3 Catches of postlarval brown shrimp per 1 ,000 m. ^ (35.000 cubicfeet) of water filtered, by month and depth zone, September 1966 toApril 1967

Depth

0.2 0.3

LENGTH (INCH)0.4 0.5 0.6 0.7

>-

oz

O

80

40

80

40

80

40

80

40

80

40

80

40

80

40

80

40

SEP N = 32

_^a_

OCT N=4

NOV. N = 99

DEC. N=I9I

JAN. N= 185

FEB. N=333

MAR. N=2II

APR. N = 88

T 1 1 1 r T5 6 7 8 9 10 II 12 13 14 15 16 17

LENGTH (MM.)

Figure 2.—Length-frequency distribution of postlarvalbrown shrimp, September 1966 to April 1967.

indicate, therefore, that brown shrimp post-larvae do overwinter.

Robert F. Tennple, Project Leader

TAXONOMY AND CULTURE OFSHRIMP LARVAE

We directed most of our efforts during theyear toward growing mass cultures of foodfor penaeid larvae. Each successive rearingexperinnent resulted in increased numbers ofpostlarvae; 24,000 postlarvae were obtainedin the latest rearing trial. A study also wasmade to deternnine how varying light inten-sities affect larval behavior.

Changes made in larval culture procedureswere to increase the amount of aeration andthe supply of food. Aeration was supplied byairstones suspended near the sides of thetank as well as in the center. This addedaeration improves water circulation in thetank, which in turn, keeps the algal food insuspension. During the protozoeal stages,we are now adding 1 liter (1.1 quarts) ofdiatom culture to every 15 liters (4.2 gallons)of water in the larval culture tank (fig. 3).

Larval Food Studies

It appears that the largest problem remainingfor large-scale larval culture is that ofsupplying increasing volumes of diatoms aslarval shrimp food. Last year, to solve thisproblem, a series of diatom cultures werestarted to determine if mass cultures ofdiatoms could be grown in water from theLaboratory's recirculating sea-water systemby adding selected nutrients. Additions ofNO3, PO4, EDTA (ethylenediaminetetraace-tate), Fe, and a trace metal mixture wereused singly and in combination. The additionof nutrients increased the yield over thatobtained in unenriched water from the sea-water system without exception; we were ableto nnaintain open 30-liter (8.4-gallon) culturesof both Skeletonema costatum and Thalas -siosira sp.The additive supporting the best growth of

each diatom differed in different months (table4). No single additive gave consistently bettergrowth, but the combination of nitrate, phos-phate, and EDTA most often supported thebest growth of Skeletonema . Both diatomsgrew well on the same additives only inSeptember. One peculiarity was that in monthswhen Skeletonema required trace metals,Thalassiosira did not; and when Thalassiosirarequired them, Skeletonema did not. Never-theless, although both diatoms required dif-ferent additives to sustain highest growth,monthly fluctuations in their growth weresimilar. In January and February, the un-enriched sea water supported better growththan was obtained throughout the rest of theyear, even with the best additives. Resultsfrom these experiments suggest that some un-known factor(s) is affecting the growth of bothdiatoms differently and to a greater extentthan the additives being tested.

Skeletonema usually reached peak numbersin 4 to 5 days; Thalassiosira required 6 or 7days.

Responses of Larvae to VaryingLight Intensities

To determine the effects of light on larvalshrimp behavior, brown shrinnp larvae andpostlarvae were placed in a 10-cm. (4-inch)square plastic column 137 cm. (54 inches)high and were exposed to gradually increasinglight intensities (from 3 to 960 ft.-c.). Naupliiresponded photopositively to low light inten-sities and photonegatively to higher intensities.The attraction to low intensities became lesspronounced as development progressed; thirdmyses and postlarvae were not attracted tolow intensities. The design of the experimentdid not allow us to determine whether thelater stages were photonegative or just re-maining on, or near, the bottom in responseto gravity or some other factor.

Figure 3.—Containers used to culture shrimp larvae for experimental studies.

-Nutrients which sustained the highest growth of diatoms eachmonth, 1966-67

Month

Table 5. --Rate of movement of selected larval stages ofbrown shrimp toward a low- intensity light source

Larval stage

ECOLOGICALLY ASSOCIATED ORGANISMS Plankton Study

Our efforts during the year have been devotedto completing food studies, describing thebenthic fauna off Galveston, Tex., and assistingin starting a plankton study of the Gulf ofMexico which will be continued in the future bythe Gulf Oceanography Program.

Food Studies

Samples for studies of the food of brownshrimp were collected from January 1966 toJanuary 1967. Subsamples of brown shrimpwere drawn from catches made at night in12.7 to 63.6 m. (7 to 35 fathoms) of water offGalveston and Freeport, Tex.

The average amount of food, by percentage ofstomach capacity, was similar in males andfemales (fig. 5). Throughout the year, identifi-able contents were predominantly the remainsof squid and crustaceans. Occasionally, star-fish (echinoderms), nematodes, and fish partsalso were observed.

The food of four species of fish inhabitingthe brown shrimp grounds off Galveston Islandwere studied through the sunnmer of 1966. Inthe spring and summer, crustaceans weredominant food items of the Atlantic croaker,Micropogon undulatus ; silver seatrout, Cynos-cion nothus ; and shoal flounder, Syaciumgunteri . MoUusks and polychaete worms dom-inated the food items identified in the longspineporgy, Stenotonnus caprinus .

Bottom Fauna Survey

Our survey of bottom fauna off GalvestonIsland was the most intensive ever made inthis area. Samples were taken at stations indepths from 5.4 to 36.3 m. (3-20 fathoms). Allspecimens taken have been sorted to the majortaxonomic groups. On the basis of preliminaryidentification of the moUusks, the sannplesincluded about 16 species that have not beenpreviously reported from this area. Re-searchers at Texas A&M University, the U.S.National Museum, and the Canadian NationalMuseum are studying many of the moUusksand amphipods from these collections.

JAN PE8 M4R flPH MAY JUN JUL AUG SEP OCT NOV DEC JAN

Figure 5.— Relative abundance of stomach contents inmale and female brown shrimp, 1966-67.

During February and March, we made aplankton survey to compare the productivityof the waters in various parts of the Gulfof Mexico. Plankton samples were collectedat 87 locations throughout the Gulf. Thesesamples were taken from the upper 100 m.(55 fathoms) of water with a vertically towedcone-shaped (Hensen) net with a 3/4-m. (2.5-foot) diameter opening.

Plankton volunnes, measured in cubic centi-meters per 100 m.^ (3,534 cubic feet) ofwater filtered, are shown in figure 6 to delineateareas of high and low concentrations. Greatestvolumes were collected in the western Gulf,over and just beyond the Continental Shelfsouth of the Texas coast. Volumes weregenerally greater in the northwestern Gulf thanin the southwestern Gulf. In the eastern Gulf,plankton was sparse over the relatively deepwaters in the Yucatan Channel and the FloridaStraits.

Donald Moore, Project Leader

FLORIDA BAY ECOLOGY STUDIES

The shallow waters of Florida Bay and theFlorida Keys are important nursery groundsfor pink shrimp of the Tortugas grounds.Since 1965, we have made biological observa-tions on postlarval and early juvenile pinkshrimp in these extensive estuaries.

Postlarvae are sampled quantitatively onceeach nnonth on incoming night tides at WhaleHarbor Bridge near Islamorada (upper FloridaKeys). As part of a cooperative plan similarobservations are taken at three additional sitesin the lower Keys by biologists of the FloridaState Board of Conservation. This work hasestablished that large numbers of postlarvalshrimp enter Florida Bay from the AtlanticOcean and that recruitment continues through-out the year. Most postlarvae pass through theKeys into Florida Bay in late spring, summer,and early fall (fig. 7).We expanded the sampling of juvenile shrimp

in 1967. Quantitative sannples have been takenmonthly with a modified marsh net (fig. 8) atZZ widely distributed shallow-water sites.Earlier samples were taken with the unit-areasuction sampler designed by personnel at thisstation. Examination of samples from FloridaBay revealed that early juveniles increase inabundance during the summer and becomemost numerous during the fall. This concurswith the observation that postlarvae enterFlorida Bay before and during these seasons.

The data we have collected on incon-iingpostlarvae and early juveniles indicate thatthe distribution of early juvenile pink shrimpin Florida Bay depends primarily on the degreeof postlarval penetration. Maximum concentra-tions of early juveniles occur in the western

10

96°W 94° 92° 90° 88 84° 82°

Figure 6.— Plankton volumes collected from the upper 100 meters (55 fathoms) of waterduring February and March 1967.

MAM JUN1967

Figure 7.—Seasonal abundance of Penaeus postlarvae atWhale Harbor Bridge in upper Florida Keys, 1966-67.

(Average monthly catch per standard unit of effort.)

and southern portions of the Bay, generallyin areas that receive large volumes of water-flow from the Gulf of Mexico and the AtlanticOcean--a demonstrated source of postlarvae.Conversely, northeastern Florida Bay, whichreceives little waterflow from these sources,contains few early juveniles. At three stationsin the northeastern Bay, we collected no pinkshrimp during the first 6 months of sannpling.

The western and southern portions of theBay are characterized by more stable salinitiesand temperatures, lower turbidities, and moreextensive seagrass beds than generally occurin northeastern Florida Bay. In certain partsof northeastern Florida Bay, however, environ-mental conditions suitable for young pinkshrimp apparently do existfor extended periodsof time. Even at these times, however, fewjuveniles occur in northeastern Florida Bay.

Another important aim of the field work isto accumulate information needed as back-ground for "estuary-seeding" experiments. Ifproduction of juvenile shrimp in Florida Baydepends on the availability of postlarvae, itmay be feasible to introduce large numbersof young shrimp reared artificially to certainshrimp-deficient areas of the bay and therebyincrease production. Sampling has establishedthe usual abundance of pink shrimp and as-sociated organisms at each station. With thesebackground data, we may be able to determinethe effect of introducing large numbers ofyoung shrimp at a chosen location.

Thomas J. Costello, Project LeaderDonald M. Allen

11

!» 7

Figure 8.--Modified marsh net with retrieving line and bridle, for samplingjuvenile shrimp.

SEASONAL CHANGES IN RELATIVEABUNDANCE OF POSTLARVAE OF

PINK SHRIMP ENTERING THEEVERGLADES ESTUARY

During the fiscal year, sampling for post-larval pink shrimp, Penaeus duorarum , con-tinued in Little Shark River and ButtonwoodCanal, Everglades National Park, Fla. Pairedsurface and bottom hauls, each of 10-minuteduration, were made at about 45- to 60-minute intervals during night flood tides. Whenshrimp were abundant, samples were taken oneach of the four major moon phases. Duringthe winter, when abundance was lower, samplesweretaken only in new- and full-moon periods.A total of 35 trips to each collecting siteproduced 105 paired bottom and surfacesamples at Buttonwood Canal and 117 at LittleShark River.Abundance of postlarvae was highest in July

when the production of shrimp per 1 m.'' ofwater strained was 28.9 in Buttonwood Canal

and 7.7 in Little Shark River. Catches werehighest during new- and first-quarter-moonphases, and the bottom net consistently pro-duced higher catches than the surface net.Maximum catch per 1 m.^ for each samplingtrip to Buttonwood Canal and Little SharkRiver is shown in figure 9. Experiments arebeing made to determine if the apparentconcentration of postlarvae near the bottom isreal or is caused by the movement of thevessel (which may cause the postlarvae tosound).

After we discovered that shrimp reacted tosalinity gradients in aquaria, sampling pro-cedures were modified slightly to includecollection of salinity samples before the startof the night's fishing and at the midtime ofeach tow. These samples permit the measure-ment of salinity change in the time periodrepresented by each tow.The relation between carapace length and

total length of shrimp less than 4mm. (0.2 inch)carapace length is being examined as well as

12

1 BUTTONWOOD CANAL

11

emigrants were the same as have been de-scribed earlier for the shrimp moving out ofButtonwood Canal. The shrin-ip during periodsof high relative abundance observed in Januaryand September at Joe River were relatively-large juveniles, which averaged 14.0 mm. (0.6inch) carapace length or larger, and apparentlyentered the catches of small commercialshrimp 1 month later. Shrimp taken during theperiod of abundance observed in June weresmall juveniles, which averaged 11.2 mm. (0.4inch) carapace length, and apparently enteredthe commercial fishery Z months later.

Progress was made in the computer analysisof the data collected from the channel net inButtonwood Canal, This analysis is designedto determine the environmental factors mostimportant in influencing fluctuations in abun-dance of the emigrating juveniles and ex-pressing them in quantitative ternns. A multi-variate regression computer program devel-oped by the University of California, LosAngeles, is being used. This program producesa series of multiple linear regression equations

in a stepwise n-ianner. At each step, theprogram adds one variable to the regressionequation. The variable selected is the onethat makes the greatest reduction in the re-maining variation (error sunn of squares). Inprogressive steps, the residual variation isreduced until all variation is accounted for oruntil all the variables have been entered andthe rennaining variation is reduced to a mini-mum. The end product is a listing of independ-ent variables ranked according to their con-tribution in reducing variation, with theircorresponding regression coefficients. Theregression coefficients nnay then be used ina prediction nnodel to estimate the abundanceof emigrating shrimp.

C. P. Idyll, E. S. Iversen, andB. J. Yokel, Project Leaders

Institute of Marine Sciences,University of Miami

(Contract No. 14-17-0002-188)

SHRIMP DYNAMICS PROGRAM

To attain maximum use of a renewableresource, such as a shrimp population, de-tailed information describing the dynamics ofthat resource must be obtained. Major aimsof our research are to develop reliable tech-niques that can be used to forecast shrinnpabundance before the fishing season, todescribe patterns of movement of juvenileand adult shrimp, and to establish realisticestimates of their growth and mortality.Substantial gains were made during theyear in the assessment of changes in theshrimp fishery and in the development ofsophisticated techniques for predicting theharvest.

Analysis of systematic collections of post-larval and juvenile brown shrimp indicatedthat abundance indices developed for thesestages can be used to predict the relativemagnitude of offshore commercial shrimpsupplies. Although variation is greater incollections of postlarvae, predictions basedon them have greater potential value thanthose made from juvenile shrimp catchesbecause the data on postlarvae are availableearlier. The use of a plankton pump is beinginvestigated because the variation in post-larval collections may be a result of in-frequent sampling. The punnp will providesamples of migrating postlarvae at frequentintervals or continuously. The advantagegained by continuous sampling is that es-sentially all of the variation caused by en-vironnnental factors can be considered asrandom.

Several nnark-recapture experiments weremade along the Texas coast to measure growth,movennent, and mortality of brown shrinnpas they ennigrated from estuaries and enteredthe comnnercial fishery. A small internalplastic tag was used for the first time in thesestudies. Additional experiments are plannedfor estimating survival snd growth rates ofbrown and white shrimp in Texas andLouisiana waters. Such studies provide datarequired to construct and test mathennaticalmodels of exploited shrimp stocks. Analysisof data from mark-recapture experiments onthe Tortugas (Fla.) pink shrimp grounds pro-duced three similar but independent estimatesof natural and fishing mortalities. Rates ofnatural mortality were lower than have beenreported previously.Four manuscripts were completed during the

year on shrimp discarding practices in theGulf of Mexico, crop prediction from postlarvalshrimp indices, the Tortugas shrimp fishery,and estimating shrimp populations.

Contract research by the USL (Universityof Southwestern Louisiana) was devoted to thesystematic sampling of postlarval and juvenilewhite and brown shrinnp to deternnine theirseasonal abundance in Vernnilion and CoteBlanche Bays. Also, USL made laboratoryexperinnents to determine if protein extractsfrom postlarvae would aid in separating thespecies at that stage.

Kenneth N. Baxter, Acting ProgrannLeader

14

MIGRATION, GROWTH, AND MORTALITYOF COMMERCIAL SHRIMPS

Knowledge of shrimp movements, growth,and mortality is necessary for determining thebest time to begin harvesting shrimp and thefishing intensity that can be maintained withoutreducing a stock's reproductive capacity. Opti-mum fishing intensity will be of particularconcern if improvements in havesting methodsmake it possible to overfish our shrimp re-sources.

Recent studies of population dynamics havebeen directed toward making best use of avail-able shrimp stocks. As our knowledge of eachspecies expands, the probability increasesthat we will be able either to increase thevalue of shrimp harvests by stocking or tocontrol the factors causing shrimp mortality.Before efforts are made to increase shrimpproduction scientifically, however, completeinfornnation concerning movements, growth,and mortality must be established. Aspectswhich require special attention are: ( 1 ) relativemortality rates during specific periods of thelife cycle; (2) effects of the environnnent andpopulation density on growth and survival;(3) nnovements of shrimp in offshore waters;and (4) identification of individual populations.

Mark-recapture experiments provide directestimates of growth and migration and indirectestimates of mortality rates. Other sourcesof information such as catch per unit of effortby the commercial fleet are being used tocheck estimates of population parametersmade fronn mark-recapture experiments, butthe errors involved are usually greater thanthose in estimates based on mark-recapturedata.An evaluation of previous mark-recapture

experinnents indicates the three most import-ant sources of error to be (1) mortalities ofstained shrimp after release, caused by thestaining technique; (2) the paucity of recoverieswhen less than 5,000 stained shrimp are re-leased; and (3) our inability to identify in-dividual shrimp, which necessitates staininggroups of shrimp that cover a relatively largesize range.

Postrelease mortalities from marking andhandling influence estimates of growth ormigration only if mortality varies with shrinnpsize; such deaths, however, always adverselyaffect mortality estimates. Handling techniquesand facilities constantly are being modified tolessen their harmful effects. Live shrimp areheld at a temperature of 3° to 5° C. (5.4°-9.0°F.) lower than the water fronn which they weretaken, thus reducing their metabolic rate and in-creasing survival. Two lightweight refrigera-tion units were constructed for use on shoreor on research vessels at sea (fig. 11). Theseunits provide independent control of tempera-ture in individual tanks and reduce the mag-nitude of temperature change to which shrimp

must be subjected. Each unit has a 1-h.p.compressor and a l/Z-h.p. pump. The chillingtank was constructed from a piece of 10-inchpolyvinyl chloride pipe. Water with an initialtemperature of 21° to 24° C. (70°-750F.) canbe cooled 2.3° C. (4.1° F.) at a rate of 35gallons per minute.

Analysis of data from past mark-recapturestudies indicates that when marked shrimpare released directly into a fishery, largenumbers of recoveries may be expected withinthe first few weeks after release. Little infor-mation is gained when this occurs. We believethat because of high mortality rates, largenumbers of shrimp mustbe released if adequatenumbers are to survive beyond the first fewweeks.

The most satisfactory method for markingshrimp has been to inject into its abdomen abiological stain dissolved in distilled wateror a small amount of fluorescent pigment inVaseline.^ The biological stain passes throughthe shrimp's vascular system and localizes inthe gills whereas the fluorescent pigment re-mains at the point of injection. Past experi-ments have indicated that two biological stainsand four fluorescent pigments are suitable formarking shrimp. If one of the stains and oneor more of the pigments are used on eachshrimp, there are 10 possible distinctivemarks. To evaluate tne effects of these markson shrimp mortality, we injected one groupof shrimp with the biological stain and anothergroup with the biological stain and fluorescentpigment. A comparison of mortality ratesbetween these two groups and controls heldin the laboratory for 30 days after markingindicated that mortality increased when thestain and pigment were used together. Meansurvival time of the groups is shown in table 6.Because only a limited number of stains is

available for distinguishing size groups whenseveral separate releases are made into thesame population, we have expended consider-able effort to develop a method to identifyindividual shrimp. We have tested severaltypes of external and internal tags. Externaltags were attached at several sites on shrimp,but because the hole in the exoskeleton throughwhich the tag shaft extends did not heal prop-erly, infection usually resulted within 2 weeks.

Of the internal tags tested, an oval poly-vinyl chloride tag (0.27 mm. by 2 mm. by5 mm.) appeared to be most acceptable (fig.12). The most satisfactory insertion site isthe first abdominal segment. The tag isinserted with fine forceps through the jointbetween the cephalothorax and the abdomen.To date, its presence has not seriously af-fected molting or survival of the shrimp inlaboratory experiments. Field experimentsare underway which will enable us to compare

^Trade names referred to In this publication do notimply endorsement of commercial products.

15

Figure 11.—Lightweight refrigeration unit for cooling water in holding tanks.

the acceptability of the polyvinyl chloride tagand that of the Vaseline-pigment secondarymark.

Richard A. Neal, Project Leader

POSTLARVAL AND JUVENILE SHRIMP

We have learned that abundance indices ofthe postlarval and juvenile life history stagesof brown shrimp can be used to predict thesubsequent abundance of adults. The juvenileindex is more reliable, but predictions basedon postlarval indices have a greater potentialvalue because infornnation is available about2 months sooner. In 6 of the 7 years for whichdata are available, indices of abundance ofjuvenile brown shrimp, developed from Galves-ton Bay bait shrimp fishery statistics, have

Table 6.--Comparison of the survival time of shrimp marked withbiological stain and with biological stain plus fluorescent pigments

Mark

2UJ 200-

-

fishery harvest from U.S coastal waters, andmost species contributing to this harvest aredependent on estuaries during either somestage of their development or their entire life.

The major purpose of our Estuarine Pro-gram is to document the dependency of fisheryresources on estuaries, to determine the typesof estuarine habitat that are most important,and to assess the value of these habitats interms of production of renewable fisheryresources. We are nnaking additional effortsto determine how fishery resources are af-fected by nnodifications of the estuarine en-vironnnent, how to prevent excessive damage,how to restore altered areas, and how toimprove low-value habitats.

During the year, we developed new samplingtechniques and gear for studying the behaviorof brown and white shrimp emigrating in theGalveston Entrance. Resulting data on sizeand time of emigration were provided toState personnel and were used by them tomanage their shrimp fishery. Ultinnately, afterrefinement of the sampling techniques andtheir application, it should be possible toassess the contributions of a specific estuaryto the population of harvestable species in theGulf of Mexico. Such information is essentialfor establishing fishery values of estuaries.We also have learned that vegetation along

shorelines and beds of submerged plants inshallow water are major nursery habitatsfor young shrimp and many species of fish. De-struction of the vegetation by bulkheading,channel dredging, or spoil (from hydraulicdredges) eliminates these zones as nurseries.This knowledge has proven valuable in ouras-sessnnent of probable effects of private con-struction projects and has been responsible forconserving vital habitats in Texas estuaries.Our first efforts to transplant and establish

emergent vegetation on hydraulically depositedspoil in a shallow bay were partially successful.We learned how to stabilize the clumps anddetermined the most suitable water depth forvigorous growth. We still do not know, how-ever, how to accomplish these transplantingseconomically over large areas.We have negotiated successfully with the

Corps of Engineers for a hydraulic modeltesting program that will provide the informa-tion we need to evaluate how their hurricaneprotection plans will affect the hydrology ofGalveston Bay. Through this cooperative effort,we may develop a proposal that will providehurricane protection without impairing thevalue of the estuary for fishery resources.

Charles R. Chapman, Program Leader

EFFECTS OF ENGINEERING PROJECTS

Developnnent of coastal areas to meet hun-iandemands usually requires a considerable

amount of land and water alteration and re-arrangement. Consequently, deterioration ordestruction, or both, of estuarine habitatresults from construction projects involvingtributary control of fresh water, channeldredging, filling, bulkheading, marsh drainage,diking, levees, and salt-water barriers.

Work by private interests in navigablewaters requires a pernnit from the U.S. ArmyCorps of Engineers. Pursuant to the Fishand Wildlife Coordination Act, the Bureauof Sport Fisheries and Wildlife's Division ofRiver Basin Studies is responsible for advisingthe Corps of possible adverse effects thatthe proposed work might have on fish andwildlife resources. Frequently, constructionplans must be modified to reduce or elinninatedannage to natural resources. We assist per-sonnel of the Division of River Basin Studiesin evaluating all private construction projectsin the coastal areas of the western Gulf ofMexico. The number, type, and general locationof applications for private construction re-viewed during the fiscal year are listed intable 7.

In addition to private construction projects,we also review and evaluate Federal water-useprojects and occasionally ones proposed bythe Soil Conservation Service and Bureau ofReclamation. Additionally, during fiscal year1967, project personnel contributed to andreviewed drafts of 42 Bureau of Sport Fisheriesand Wildlife Reports on private and Federalconstruction projects.

It is innportant that we be capable of deter-mining specific effects of water-developmentprojects on fishery resources so that we canrecommend feasible measures for lesseningthe severity of damage or for increasinghabitat quality of previously damaged areas.Methods must be developed for accuratelypredicting long-range and immediate ecolog-ical changes resulting from different typesof construction. We also must develop meas-ures for preventing damage to the estuariesas well as for rehabilitating or improvingthenn.

Effects of Habitat Modification

Studies have been started to determine howthe estuarine biota is affected by environmentmodifications resulting fron-i channelization,hydraulic spoiling, bulkheading, and filling(fig. 15). The study area includes a locationthat is being developed for housing sites anda nearby unaltered area that is being studiedas a control. Both areas are typical smallbays with about 80 hectares (200 acres) of openwater, beds of submerged aquatic vegetation,and extensive peripheral tidal marshes.

Biological, hydrological, and physicalfeatures of both areas were assessed beforeconstruction to provide a basis for comparingeffects during and after development. These

19

Table 7. --Number, type, and location of proposed private construction projects inwestern Gulf of Mexico coastal areas reviewed during fiscal year 1967

^

Figure 15.—Valuable estuarine nursery area being converted to housing development on west GalvestonIsland.

^-'

Figure 16.— A former nursery area on west Galveston Island has been developed for housing by bulk-heading the natural shoreline and raising marsh elevation with fill from hydraulic dredging.

21

Figure 17.—Spartina altemiflora transplantings on recent hydraulically deposited spoil bank.

We are also experimenting with a syntheticfibrous material (fig. 18) to determine if itcan, under certain circumstances, be sub-stituted for natural vegetation. This materialwas attached to piers, bulkheads, and alongbarren shorelines to determine whether itwould attract microfaxina, penaeid shrimp,and other important estuarine species. Samplesof the biota taken under and in the nnaterialwere consistently more productive thansamples from nonvegetated areas. The artifi-cial habitat appears to be more attractive tosome fornns of marine life (including penaeidshrimp) than the natural habitat devoid ofvegetation.

Texas Coast Hurricane Study Project

Considerable effort was devoted to planningand negotiating with the Corps of Engineersfor appropriate hydraulic model tests thatwill assess the practicability of hurricaneprotection plans for the Galveston Bay area.The Corps of Engineers has constructed twohydraulic models to test inland penetrationof hurricane surges and to determine howthe proposed hurricane protection structureswill affect the hydrology of Galveston Bay.

The small-scale model (scale: l:3,000hori-zontal; 1:100 vertical) will be used to studythe penetration of stornn surges. It will alsobe used to assess, by measuring water eleva-tion, structural requirements in San Luis

Tidal Pass to provide for the existing tidalrange.

The larger scale Houston Ship Channelmodel (scale: 1:600 horizontal; 1:60 vertical)will be used to test and develop structuresfor hurricane protection that will not altersignificantly the existing hydrology in thebay systen-i (fig. 19). Fish and wildlife interestshave selected the water year 1965 (October 1,1964, to September 30, 1965) to representbaseconditions for model testing. After verificationof base conditions in the model, the hurricaneprotection plan will be introduced and thebase period test repeated. Comparison ofwater elevation and salinity with and withoutthe hurricane protection plan will provide ameasure of change to be expected in the baysystem. Through this cooperative effort, aproposal may be developed that will not onlyprovide hurricane protection, but also will notsignificantly alter existing conditions.A series of tests will be run in the large

model to reflect partial diversion of theTrinity River waters to the Houston ShipChannel where they would enter the bay. Thebase-year period will be tested with and withoutthe hurricane protection plan in place. Ifmajor hydrological changes occur with theprotection plan in place, additional tests willbe made with the necessary adjustments ton-iaintain desired conditions.Dye studies in which industrial and domestic

pollution are sinnulated will be included in all

22

'.-^^ •/

'^7r^'Ww^WW^:mS

Figure 18.—Simulating a natural environment with an artificial synthetic fibrous material.

model testing to obtain information on the rateand pattern of pollution dispersion.

Updating and analysis of historical fisheryharvest data of the Galveston estuary arecontinuing. These data will be used for project-ing influences on fishery resources caused bythe proposed plan for hurricane protection.

Richard J. Hoogland, Project Leader

ECOLOGY OF WESTERN GULF ESTUARIES

During the year we studied the hydrographyof Galveston Bay, emigration of brown andwhite shrimp, and methods for identifyingpostlarval penaeid shrimp.

Hydrology

During 1966, temperature and salinity meas-urements were made monthly, or sometimesmore frequently, at selected locations (fig. 2.Q)in Galveston Bay. Although temperature andsalinity values varied between areas withinthe bay during any one cruise, all data wereconnbined and averaged by cruise to depictgenerally seasonal trends for the entire bay(fig. 21). Also included are river discharge datafrom the Trinity and San Jacinto Rivers, thetwo largest sources of fresh water flowing intoGalveston Bay.

Average bottom water temperatures in thebay varied from 11.0° C. (51.8° F.) in Decem-ber to 30.5° C. (86.9° F.) in July. The highesttemperature, 36° C. (96.8° F.) was recordedin June, and the lowest, 5.0° C. (41.0° F.), inFebruary and December. Usually, fluctuationin temperature throughout the bay on a partic-ular date (indicated by the range in figure Zl)was greatest from November to March.

Stream-flow records for the Trinity andSan Jacinto Rivers indicate a large volume ofstream discharge in May. It is apparent thatthis flow of fresh water affected bottomsalinities throughout the bay. Average bottomsalinities were reduced to 1 p.p.t. (part perthousand) in Trinity Bay and below 10 p.p.t. inlower Galveston and East Bays. Recovery ofsalinities to levels that existed before the highdischarge required about 4 months in TrinityBay.

The importance of water temperature incontrolling the growth of brown shrimp andcausing juvenile white shrimp to start emi-grating from bays has been clearly demon-strated. Therefore, we are analyzing our dataon temperature and shrimp catch per unit ofeffort in Galveston Bay to determine if watertemperature can be used to predict the timethat (1) brown shrimp first become availableto the bait fishery and (2) white shrimp emigratefrom the bay.

23

iiiii* -

Figure 19.—The Galveston Bay model constructed by Corps of Engineers at Vlcksburg, Miss., that will be used totest proposed plans for hurricane protection. (Galveston, Tex., is located at bottom of picture. Note the Houston

Ship Channel extending the entire length of the dewatered model and the Texas City Channel extending from thecenter to the left, upper-central margin.)

Studies on the Emigration of Brownand White Shrimp

The use of closed seasons or minimum sizelimits to protect juvenile stages of commer-cially important species from commercialharvest is a common practice in the UnitedStates. Shrimping regulations for Texas coastalwaters, for example, dictate a 45-day closedseason during late spring and early sumnnerto protect juvenile brown shrimp as theyemigrate from the bays to offshore Gulf waters.This closure usually begins June 1 but can beadjusted to 15 days before or after June 1. Thedate of closure depends on the abundance andsize of juvenile brown shrimp in the bayswithin a particular year.

To select the closure date, Texas Parks andWildlife Department personnel depend on trawlsamples of shrimp (catch per-unit-of-effortdata) from the bays to estimate the time atwhich most of the shrimp are emigrating tothe Gulf. Samples are taken from a broadarea within each bay and are costly and time-consuming to obtain. Also, there is a lag (theduration of which is unknown) from the time

that shrimp are abundant in the bays until theybecome abtindant in near-shore Gulf waters.More accurate and less costly information

probably can be obtained on the size of shrimpand time of emigration by sampling in tidalpasses if adequate sampling techniques aredeveloped. Also, such techniques, when im-proved, will provide methods for estimatingthe relative (or absolute) contribution by eachbay of selected species to the offshorefisheries.We began sampling for shrimp at station

1 (see fig. 20) in the Galveston tidal pass inMay 1966 and continued through January 1967.A 0,6- by 3.0-m. (2- by 10-foot) net was usedduring the brown shrimp study. For eachseries of samples, the trawl was towed for 8minutes at the surface and 8 minutes on bottom.During the white shrimp study, 10-minute towswere made with a 1.2- by 3.0-m. (4- by10-foot) net at the surface, at middepth, andon bottom for each series. The objectives ofthe studies were to determine for juvenile andsubadult brown shrimp, or white shrimp, orboth: (1) peaks of ennigration, (2) size at whichthey emigrate, (3) sex ratio, (4) vertical

24

Figure 20.—Hydrographic stations in Galveston Bay and the trawl station in the Galveston tidal pass, 1966.

distribution, and (5) relations between tem-perature, salinity, size, and abundance.

Brown Shrimp

To estimate relative abundance of emigratingbrown shrimp, we combined all shrinnp caughtin bottom and surface trawls during the dayand night. Two peaks of emigrationoccurred--the first in mid-May and the second in mid-June. Because brown shrimp were leaving thebay when we began sampling, we do not knowthe magnitude of the first peak or when itstarted.

All shrimp caught in the tidal pass werecombined by weekly intervals to representthe size of emigrating brown shrimp duringthe study. Brown shrimp caught from May 14to 21 had a mean length of 58.0 mm. (2.3inches). Mean length was much greater (79.7nnm.; 3.1 inches) the following week (May 22-28)and tended to increase gradually for the restof the sampling period.A comparison of day and night catches be-

tween surface and bottom hauls indicated thatduring ebb tides, emigrating brown shrinnpremained close to the bottom during the dayand migrated vertically to surface waters at

25

Figure 21.—Bottom water temperature (mean and range), river discharge, and salinity in Galveston Bay, 1966.

night. During the day, bottom tows averaged0.85 shrimp per minute towed, and surfacetows, 0.01; at night bottom hauls averaged0.22 shrimp per minute and surface hauls,1.21. Mean lengths of shrimp, regardless oftime or depth, were similar.

White Shrimp

More white shrimp were caught in bottomtows than in midwater tows during the study.Large numbers of shrinnp were caught in sur-face tows on two sampling dates, but theywere absent in the surface tows during theday on all other sampling dates. Statisticaltests showed that catch per unit of effort in-creased significantly from surface to bottomduring the day. Vertical distribution at nightwas not determined because ebb tides usuallyoccurred during the day in the fall and wintermonths.

Peaks of white shrimp ennigration werecorrelated closely with rapidly decreasingtennperatures and salinities. The first peak ofemigration occurred October 19, when dailymean water temperature dropped from 24° to19° C. (75.2° - 66.2° F.). The next three peaksof emigration also coincided with drops intemperature. For the rest of the season, how-ever, the relation was not clear, probably be-cause temperature changes were not as greatand because emigration was more nearlyconstant. Emigrationoccurred at temperaturesbetween 19° and 8° C. (66.2° - 46.4° F.).

The mean lengths of shrimp caught on thesame date in surface, midwater, and bottomtows, and between sexes, were similar. Sizeat emigration decreased significantly with, and

was closely related to, a decrease in watertemperature. There was no obvious relationbetween salinity and size of emigratingshrimp.

Of 2,964 white shrimp caught in the tidalpass, 1,633 (55.1 percent) were females. Thesex ratio did not deviate significantly from a1:1 ratio.

Character for Identification of PostlarvalPenaeid Shrimp

Studies of the biology of postlarval brown,pink, and white shrimp have been hamperedby difficulties in differentiating betweenspecies. For postlarval shrimp 10 mm. (0.4inch) total length or less, published descrip-tions, provisional keys, seasonal occurrences,and size differences have been used success-fully to separate postlarvae of the brown andwhite shrinnp entering Galveston Bay. Theproblem remained, however, of species dif-ferentiation among shrimp between the lengthsof 10 mm. (0. 4 inch) and 25 mm. (1.0 inch).

In examining postlarvae from Galveston Bay,we noted a morphologic character by whichwe could distinguish brown from white shrimpat total lengths from 10 to 25 mm. (0.4 - 1.0inch): White shrimp lack spines on the dorsalcarina, whereas brown shrimp have spines onthe dorsal carina of the sixth abdominal seg-ment. This character is especially valuable inareas such as Galveston Bay where pink shrinnpare rare.On the basis of the examination of shrimp

of known parentage, we deternnined that thenumber of spines on the dorsal carina cannotbe used to separate postlarvae of brown and

26

pink shrimp. The number of spines for eachspecies generally increases with increasingsize, and for shrimp of a given length, thenumber of spines differs little between species.

W. Lee Trent, Project Leader

EVALUATION OF ESTUARINE DATA

Estuarine Atlas

The need for aninventory of estuarine areas,such as the one being planned and coordinatedby the ETCC (Estuarine Technical CoordinatingCommittee) of the Gulf States Marine FisheriesCommission is emphasized by competition forthese coastal waters by fish and wildlife re-sources on one hand and industrial, commer-cial, residential, and agricultural interestson the other. Documentation of the biologicalvalue of estuaries for perpetuating fish andwildlife resources is needed if the integrityof our estuaries is to be maintained.

The ETCC intends to standardize fieldmethods for collecting estuarine data andformats for recording all "atlas" data. Thesemethods and formats are to be used by theparticipating States and agencies. Alabama,Mississippi, and Louisiana receive financialassistance from Public Law 88-309 funds toinventory their estuarine area; the Gulf coastof Florida will be inventoried by the Bureau ofCommercial Fisheries; and Texas will par-ticipate to the extent funds and staff can bemade available.Assistance was provided an ETCC subcom-

mittee in preparing an outline for "AreaDescription." It was reviewed by the full com-mittee, and several changes were suggested.The final version, which includes a listing ofpriority items and standardized tables for re-cording data, was drafted in cooperation withthe Bureau of Commercial Fisheries BiologicalLaboratory, St. Petersburg Beach, Fla., andadopted by the ETCC for the Estuarine Atlas.

Assistance with the review of formats forthe "Biology" and "Hydrology" phases of theAtlas was also provided to the respective ETCCsubcomnnittees. The fornnat for "Hydrology"has been adopted by the ETCC, butthe "Biology"format is being revised and the "Sedimentology"format is being drafted by their respectivesubcommittees.

Fish Food Study

Clear Lake, a brackish bay on the westernside of Galveston Bay, has long been known asa valuable nursery area for commercially im-portant fish and crustaceans. The area hasbeen subjected to considerable investigationby personnel from Federal and State con-servation agencies. Much of this effort, how-ever, was restricted in scope, being linnited to

studies on the relative abundance and sea-sonal distribution of several selected species.Therefore, a study on the food of fish fromClear Lake was begun as an additional con-tribution to the biology of the lake.A total of 228 samples containing 5,016 fish

was collected with a small trawl from 10 loca-tions in Clear Lake. Of the 40 species in thesamples, 8 contributed 4,628 specimens andnnay be classified as "dominants"; the remain-ing 388 specimens were distributed among 32species.

The Atlantic croaker ( Micropogon undulai:us )and the sand seatrout ( Cynoscion arenarius )were most numerous with 2,342 and 1,041 spec-imens, respectively. Ninety-one percent of thecroaker stomachs and 85 percent of the sandseatrout stomachs contained food.

Mysidacea, copepods, plant nnaterial, fish,organic detritus, and annelids occurred mostfrequently in the stomachs of croakers;mysidacea, palaemonid shrimp, and fish madeup the bulk of the diet of the seatrout (table 8).

Table 8. --Percentage frequency of occurrence of different food

items in stomachs of 2,131 MleropoRon undulatus and Cynoscion

arenarius taken from Clear Lake, Tex.

Food item

Foraminifera

Bryozoa

Annelids

Crustacea;

Unidentified remains

Branchiopoda

Copepoda

Ostracoda

Cirripedia

f^sidacea

Amphipoda

Isopoda

Stomatopoda

Penaeid shrimp

Palaemonid shrimp

Crangonid shrimp

Crabs

Spiders

Insects

Clams

Squid

Fish

Plant debris

Unidentified organic debris

Mud and sand

0.0

0.0

0.3

1.8

0.0

4.0

0.0

0.0

67.2

2.5

0.4

0.1

4.4

29.8

0.0

2.0

0.0

0.1

0.0

0.0

24.8

4.9

2.0

1.5

1/ 23-160 mm. total length.

2/ 10-165 mm. total length.

3/ Items with less than 0.1-percent frequency occurrence.

27

Of lesser importance in the diet of these twospecies were foraminifera, bryozoa, bran-chiopods, ostracods, barnacles, amphipods,isopods, stonnatopods, penaeid and crangonidshrimp, crabs, spiders, insects, clams, andsquid.

The abundance of plant material and mudand sand in the stomachs of croakers sug-gests that this species forages for food in thevegetation bordering Clear Lake. On the otherhand, the paucity of these items in the diet of

the seatrout suggests that this species foragesin more open waters.

The tabulation and analysis of food data forthe dominant species will ultimately includedifferences in food items based on size, sea-son, and habitat. Food of the nondominantspecies can be tabulated only as total per-centage frequency of occurrence because sofew samples are available.

Richard A. Diener, Project Leader

EXPERIMENTAL BIOLOGY PROGRAM

We continued to study the effects of tem-perature, salinity, light, and food on laboratory-held penaeid shrimp. This information is usefulin defining natural nursery areas of variousspecies and in predicting the effects whichmanmade changes may have upon these areas.Our studies of salinity and temperature re-quirements of connmercially important penaeidshrimp will also be used to establish manage-ment techniques for pond culture.

During the year, we showed that the abilityof shrimp to survive extremes of temperatureand salinity depends on the size or age of theanimals tested, as well as on the species. Notonly are adult brown and white shrimp some-what less tolerant of extrenme conditions thanare juveniles, but also postlarvae of varioussizes show different tolerances. Laboratory-hatched postlarvae of brown shrinnp that were8 mm. (3/8-inch) in rostrum-telson lengthare less able to withstand low salinity andtemperature than are 12-mm. (l/2-inch) post-larvae. Such information may be of value indetermining the size of postlarvae used tostock ponds for shrimp culture.We also noted differences in the ability of

aninnals to regulate the concentration of theirbody fluids. Juveniles of white and brownshrimp appear to be better regulators of in-ternal salt content than the adults. This is re-flected in survival of animals exposed tochanges in external salinity as well as in thetotal salt content of the blood.

Zoula P. Zein-Eldin, Acting ProgramLeader

SHRIMP METABOLISM

Emphasis this year was on a study of theresponse of individual animals to selectedsalinities. Previous experiments indicated thatpostlarval brown and white shrimp could tol-erate wide ranges of salinity. We did not know,however, how salinity affected the individualanimal.

To study the effects of salinity on the indi-vidual, we measured the total osmoconcen-tration and the chloride content of the blood of

juvenile and adult shrimp taken from differentenvironments. Samples of shrimp blood weredrawn either from the heart or from the baseof a walking leg (fig. ZZ), The former methodwas used for the smaller shrimp and the latterwhen we tested a single shrimp on severalsuccessive days.

To date, we have tested blood sannples from80 brown shrimp (85-210 nnnn. total length;3.3-8.3 inches), 65 white shrimp (80- 140 mnn.;3.1-5.5 inches), and 27 pink shrimp (145-180mnn.; 5.7-7.1 inches). Brown shrimp wereexposed either in nature or by acclimation inthe laboratory to salinities ranging from 13 to35 p.p.t. White shrimp tested hadbeen exposedto a broader range of salinity; some specimenswere obtained from the fresh water of theTrinity River estuary and others had beenreared in our Laboratory and gradually accli-mated to 54 p.p.t. Adult pink shrimp testedhad been exposed to salinities ranging from17 to 42 p.p.t.Neither the brown nor the pink shrimp tested

have been able to regulate blood salt concen-tration at low salinity as efficiently as whiteshrinnp. Furthernnore, adult pink shrimp areless able to withstand lowered salinity thanare adult brown shrimp. These differencesmay be associated with the occurrence of thespecies in nature. White shrimp are oftentaken in waters of low salinity, but juvenileand adult brown shrimp are uncommon in suchwaters.Adult brown shrimp were acclimated to

specific salinities at two temperatures- -25°and 18° C. (77° and 63° F.)--to see whethertemperature influences the ability of the ani-mals to regulate the salt content of the bodyfluids. Animals at the lower temperature didnot appear to regulate as well as aninnals heldat 25° C. Similarly, postlarval brown shrinnpwere less able to survive salinity changes atlow temperatures than at high temperatures.An additional study was made this year to

determine the energy source used by thepenaeids. Determinations of total blood-reducing substances and of blood glucoseindicated that only traces of sugar were pres-ent in the blood of adult pink and brown shrimp.The absence of available energy sources in

28

mn

1

Figure 22.—Technician drawing blood from shrimp heart.

the blood may indicate a requirement .'orcontinuous feeding to supply energy.

Zoula P. Zein-Eldin, Project Leader

GROWTH AND SURVIVAL OFESTUARINE -MARINE ORGANISMS

This project is concerned primarily withdetermining the short-term tolerances of post-larval penaeid shrimp to salinity and tem-perature, and the optimum conditions forshrimp growth. During the year, we studiedthe survival of postlarval white and brownshrinnp exposed to selected con-ibinations oftemperature and salinity, and completed growthexperiments with two species of laboratory-hatched shrimp. Studies also were made todetermine the effect of container size ongrowth and survival of postlarval brown shrimp.

Survival

Three 24-hour experiments were made todefine the 80-percent survival limit of post-larval white shrimp. Test temperatures rangedfrom 7.5° C. (46° F.) through 37.5° C. (99° F.),and salinities ranged from Z through 45 p.p.t.Connbinations of salinity and temperature re-sulting in 80-percent survival are shown intable 9.We compared results of these experiments

with results of past experiments with brownshrimp. Postlarval white shrimp withstoodhigher temperatures and lower salinities thanpostlarval brown shrimp. Conversely, youngbrown shrinnp withstood lower temperaturesthan did white shrimp. Most postlarval whiteshrimp enter the estuaries later in the yearthan brown shrimp and are normally subjectedto warnner water. In the Galveston area, juve-nile white shrimp frequently penetrate the

29

Table 9.- -Percentage survival of postlarval white shrimp at variouscombinations of temperature and salinity

collected at stations less than 1 nautical mileapart with a chartered shrimp boat, Gus III .

Although our major effort has been devotedto the collection of data, three papers havebeen published on preliminary work connpletedduring three of the cruises. Also completedwas a new map (fig. 23) of the Gulf of Mexicoin a confornnal Lambert conic projection withthe depth contours in meters. Navigationalaidsare now generally lacking in the western Gulf,but after Loran stations are installed in thisarea, we plan to update the chart frequentlyfrom soundings obtained by the R/V Geronimo .

After completion of the cruise for groundsupport for the Gen-iini XII nnanned space flight,the Naval Oceanographic Office assigned twocontracts to this program: one to evaluatespace photography and its application to fish-eries and one to conduct a cruise in support ofthe first manned Apollo space flight.

John R. Grady, Acting Program Leader

RECONNAISSANCE SURVEY

Benthic and hydrographic samples were col-lected during two cruises of the R/V Geronimoto the west Florida shelf. Samples were takenas far north as Cape San Bias along transectswhich were about 93 km. (50 nautical miles)apart, except around the Dry Tortugas, wherethe effort was more concentrated. A total of416 benthic samples were taken, and 33 hydro-graphic stations were occupied across theContinental Shelf and slope. The stations weredistributed over the continental terrace to tietogether areas that have been studied in detailwith unworked areas.

Van Veen and orange peel grabs were usedto obtain sediment samples on the ContinentalShelf; a short coring tube was used over theslope and abyssal plain. These samples havebeen processed, and the textural and statisticalproperties computed. Results are being plottedon newly prepared charts of the area.On the southern, west Florida shelf, the

linnestone bottom is covered by a thin veneerof unconsolidated sediments which are chieflyof calcareous organic origin. Distribution andcomposition vary from zones of quartz-shellsand, roughly paralleling the coast, to analmost connpletely foraminiferal sand on theouter edge of the shelf and down the slope.Off the northern shelf, south of the Floridapanhandle, the inshore zone of the detritalcomponent is considerably more extensivethan on the southern shelf. The organic originof the sediments, particularly on the southernslope and shelf, appears to be the dominantfactor controlling the size distribution of par-ticles.

Fossil assemblages were dredged from theslope during the cruises to Florida waters.

We believe that these ancient forms mark oldstrand lines formed during the Pleistocenewhen sea levels were lower than at present.A cooperative cruise with Texas A&M Uni-

versity was nnade in Decennber along the183-m. (100-fathom) isobath off the Mexicancoast south of the Rio Grande. The objectivesof this cruise were: (1) to deternnine if anyresidual effects of Hurricane Inez were evi-dent in the waters over which it passed; (Z) toobtain bottom sediments along three transectsfor study and comparison with nnaterial pre-viously collected elsewhere in the Gulf; and(3) to locate and verify a large-scale feature,about 28 by 56 km. (15 by 30 nautical miles) indimension, shown on navigation charts asan eastward projection of the Continental Shelfnear Tampico, Mexico.

All objectives of the December cruise werefulfilled. Analysis of temperature, salinity,dissolved oxygen, and productivity data takenat depths across the track of Hurricane Inezshowed so residual effects of the storm. Shortcores of sediment were obtained at 14 stationson a 138.7-km. (75-nautical nnile) traverse offTecoluta and at 11 stations on a 101.7-km,(55-nautical mile) traverse off Punta Penon.Echo soundings along the transects revealedrugged ridge and trough topography with theaxis about parallel to the coast. In addition,although a number of echo sounding trackswere connpleted off Tampico, no projection ofthe Continental Shelf was observed. We con-sider it probably nonexistent, or mislocatedon navigation charts.

During the year, 2,473 water samples werecollected at depth on hydrographic surveysmade to coastal waters south of Louisiana,Mississippi, and Alabama in November for"ground-truth" support of the Gemini XIImanned space flight and throughout the Gulf ofMexico, including the Bay of Campeche andthe Yucatan Straits. The dissolved oxygen con-tent of these samples was determined aboardship and frozen samples of the water werebrought to our laboratory for analyses ofthe nutrient salts. Determinations of thephosphate-phosphorus and slicate-siliconcontent of these samples are nearing com-pletion.

The final cruise of the year in June wasmade to survey a large canyon crossing theouter slope about 333 km. (180 nautical miles)south of Galveston. Short cores were takenalong the axis of the canyon. Exploration ofthe canyon complex was prompted by a needfor a hydrographically acceptable area forwaste disposal near Galveston. Echo soundingtracks taken in this area will be used to updatethe conic projection of the Gulf of Mexicoprepared at this Laboratory.

John R. Grady, Project Leader

31

32

ENERGY BUDGET AND CIRCULATIONDYNAMICS

Sea-Air Interaction Study

During the year, data from a laboratorystudy were analyzed to describe rates ofevaporation and sensible heat exchange acrossan air-water interface. The objectives were tomeasure certain features expected to exist inthe few centimeters on either side of the inter-face, to correlate these features with thephysics of air-water interaction, and to derivea method for determining the rates of evapora-tion and sensible heat exchange. The featuresof interest were: (1) an evaporatively cooledlayer of surface water, (Z) temperature inver-sions in the lowest few centimeters of air,and (3) an intense moisture gradient in thelowest layer of air.

Characteristics of the temperature inver-sions are apparently related to the configura-tion of the associated moisture profiles. Be-cause the inversions seem to be associatedwith alternate layers of evaporation and con-densation in the air, they also must indicatethe exchange rates of heat and moisture betweenthe air and water. With increasing air-watertennperature differences, the exchange ratesseemingly do not increase linearly as pre-dicted by equations, but rather stepwise. These"steps" are apparently associated with thenecessity for a nnore efficient vertical flux ofheat and nnoisture.

Level -of-No-Motion Study

Determination of relative ocean currents bygeostrophic computations of serial hydro-graphic station data is a basic tool in oceanog-raphy. Converting the "relative" currents to"absolute" values is accomplishedby defining a"level-of-no-motion"; no acceptable technique,however, has been devised for defining theno-motion level. During the year, a method fordetermining this level was devised and is beingexannined by using data gathered in the Gulf ofMexico. If this technique proves correct, ourability to describe the ocean current structurewill be greatly improved.

Reed S. Armstrong, Project Leader

TRENDS IN OCEANIC CONDITIONS

A study to describe the physical propertiesof water of the Gulf of Mexico was begun duringthe year with three cruises (9th, 1 0th, and 1 Zth)of the R/V Geronimo .

One of the activities of the ninth cruise wasa hydrographic survey of the upper 300 m.(164 fathoms) of water over the slope of theContinental Shelf off Florida in the Gulf of

Mexico. Twenty hydrographic stations wereoccupied between June 30 and July 13, 1966.During August 4-18, about a month later, theR/V Alaminos (Texas A&M Research vessel)made hydrographic observations during acruise in the eastern Gulf. A comparison ofthe data from the two cruises indicated thepresence of two clockwise-rotating gyressuperinnposed on the mean flow. One gyre wasin the northern portion, and the other in thesoutheastern sector of the eastern Gulf. Bothgyres were still present in Februar