CHAPTER XV MOLLUSKS Blank page retained for pagination MOLLUSKSl

By HARALD A. REHDER, Smithsonian Institution 2 . The Gulf of Mexico is, chronologically speak­ Indian fauna but have also some affinities with Ing, probably the least known body of water those of the deeper waters off the southern ~djoining the United States, and the mollusks of Atlantic coast of the United States. Its shores are as yet only imperfectly known. This is particularly the case with the area between PAST WORK DONE IN THIS AREA Cedar Keys on the Florida coast, and Sabine Pass GENERAL on the Louisiana-Texas border, and with the part of the coast line stretching between the mouth of The first publication that·gave a list of the the Rio Grande and the vicinity ·of Veracruz. mollusks found along the entire Gulf coast and The littoral fauna of the Gulf of Mexico may discussed their geographical ranges was Dall's be divided into two elements that inhabit different (1889) catalog, reprinted, with additions, in geographical areas. There is first the tropical 1903. Dall divided the southeastern coast into 10 elelllent found on the Florida Keys and north on geographical districts. Three of these districts the Gulf side of Florida to about Tampa Bay, covered the area included in this report: Florida the northwest coast of Cuba, and the Mexican Keys, from the Keys north to Charlotte Harbor, coast from Cabo Catoche on Yucatan north to West Florida, from Charlotte Harbor to the t~e vicinity·of Corpus Christi, Texas (and pos­ Mississippi Delta, and the deeper waters of the SIbly to near Matagorda Bay). This area forms Gulf east of longitude 90°, and Texas, from the the southern limit of the Gulf of Mexico and is Mississippi Delta to the Rio Grande, and the deep t~e only part of the Gulf area in which living, waters south to Yucatan. The broad extent of the fringing reef corals are found. Joubin's (1912) Texas district has led to the inclusion, in later representation of coral reefs in Tampa Bay is lists, of many species as being found in Texas that obviously an error. have not as yet been recorded from the waters of North of this tropical Caribbean area the fauna that State. This is true, for instance,of Johnson's takes on a more temperate character, showing an (1934) list mentioned later. ob\Tious relationship with that of the zoogeo­ Maury (1920, 1922) published a catalog of the ~r~Phical province generally known as the Caro- recent mollusks of the Gulf of Mexico in which llian. The physiography of this area is also in were included some Tertiary species. Johnson's gheneral different from that of the more southerly (1934) List of the Marine Mollusca of the Atlantic S ores. It is a region characterized mainly by Coast from Labrador to Texas came out post­ sandy beaches either on the mainland or on low humously. This check list, though not always,· ~hastal or barrier islands that are separated from indicates those species found along the shores of e lllainland by shallow lagoons or bays with the Gulf of Mexico. tasses or inlets between the individual islands. FLORIDA t 0 coral reefs are found in this area, although fhere are submerged coral banks off the coast as The west coast of Florida is better known from a ar north as northern Florida. malacological standpoint than any other section of shThe lllollusks of the deeper waters of the Gulf the area under discussion. Numerous catalogs ow, lllainly, a relationship with the West and annotated lists covering this area were pub­ ------lished in. the seventies and eighties: Calkins : iUbllshed by permission of the Secretary of the Smithsonian Institution (1878, 1880), Dall (1884), Simpson (1887, 1889). 'l'. ll: WOuld like to acknowledge the helpful suggestions received from Prof. . Pulley of the University of Houston. Melvill (1881) gave a list of the mollusks of Key 469 470 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

West, enumerating 123 species. In more recent scribed by R. A. Philippi. Singley (1893) gave years several papers have been published dealing an extensive list of the marine mollusks of the with the mollusks of Sanibel Island, near the Texas coast, listing 342 species. This contribu­ mouth of the Caloosahatchee River, in Lee tion, being based in part on Dall's (1889) cata­ County; Clench (1923, 1925) listed 89 species, logue, contained many species for which no records while Haas (1940) gave ecological notes on many from the waters of Texas proper are known. of the species found here. In the last few decades Mitchell (1894) published, privately, a list of some collecting has been done along the north­ Texas marine shells enumerating 81 species. The western coast (Lyman 1942; Schwengel and list was based on his own collecting and dealt McGinty 1942). The most complete work on the mainly with the mollusks of the Matagorda­ mollusks of western Florida is that by Louise Corpus Christi Bay area. Strecker's (1935) list Perry, Marine Shells of the Southwest Coast of of Texas marine shells appeared posthumously; it Florida, 1940, in which she describes 346 species contained 188 species, a number of which were most of which are illustrated. not in Singley's list. As an appendix Strecker gave a list of 176 species said by Dall to come from the ALABAMA-LOUISIANA Texas district but for which Strecker had no spe­ The published records for this area are cific localities. Stenzel (1940) published a list of fewer than for the Gulf coast of Florida or for 56 species from Point Isabel, Texas. A consider­ Texas. The first faunal list I have been able to able amount of ecologic!},l work is being carried on find is that by Vanatta (1904) who published a at the present time by workers at the Institute of list of mollusks from Horn Island, Mississippi. Marine Science at Aransas Pass (Hedgpeth, 1950; Cary (1906) enumerated 73 species from various Whitten et aI., 1950) as well as at the laboratory places along the Louisiana coast from Cameron of the Texas Game, and Fish Commission at in the western part to the Chandeleur Islands in Rockport. Recently, Pulley (1949 and 1952) pub­ the east. Whereas in Cary's list the proportion of lished on the mollusks of the Texas coast. His gastropods to pelecypods is 32 to 38, in the Horn 1952 pap('r is a comprehensive one, in which he Island list the proportion is 3 to 32. This seems has included, with appropriate comments, those to suggest that the shells of Horn Island were species previously l'l'corcled from Texas, but not gathered almost exclusively along the outer known to occur thcI'l'. beach and that further search on the lagoon side MEXICO of the island would bring to light further species. In 1929, Clench listed 23 species from various Onlv a few papers have been published on the molhl~ks ~1exico. localities in southern Louisiana in the Missis­ of the cast coast of Baker Si~a~~ sippi Delta region. Burkenroad (19a3) enu­ (1891) listed 216 spccies from Veracruz, merated 9 species of pteropods from the waters of Pl'Ogrpso, ano Campcche (the last three locahtlc Louisiana. The most recent list of Louisiana shells a1'p on the peninsula of Yucatan), and Hinkley (Harry 1942) gives 93 species from the vicinity of (1907) enumerated 47 marine shells from the Grand Isle and Barataria Bay. This report, the vicinity of Tampico. result of 12 years collecting by members of the CUBA staff of the Louisiana State University ~farille '1'lw oldl'r works on Cuban shells, such as those Laboratory staff there, shows how impoverished by d'Orbigny llnd Arango, gavc no speellC'fi local­ the fauna is in this part of the Gulf in comparison it'ies for tIll' 'rnnrinl' mollusks. In the Cutll1ogo de with that of the regions farther south on both los :\lo1uscos de Cub']" Aguayo and ,Tuume (1947­ . . .' 1 ,thwcst sides of the Gulf. 52) pubhslll'(1 some records from t w nOl 1- Coll- TEXAS coust of CubIt. Henderson's (1916) I)00 ~ tains also a gooll Ilict l1I'P of (hl' nortll\\'(,s(el'lll Tlw first enumeration of the mollusks of this ,, . f 010 - purt of the Gulf, and indeed of any purt of the coast of Cuha, nlthou~lI II(' ~ivps no lIst 0 " ,I url'a covered by this rrport, was that published lusks. Lit tIP colh'c( intr Sl'('IllS to Illtv!' been Cll1'lle< '" t I ('tweell by Frrdinand Roemer in his work on Tl'xas out nl()])lT thl' Plll't of till' Cuban COI1S ) I t "" I (' 1 . \. . l'p

DEEPER WATERS Mexico from Cabo Catoche to the vicinity of Port The first work on the fauna of the deeper waters Isabel, Texas, and possibly beyond to Corpus of the Gulf of Mexico was carried out in 1878 by Christi Bay. the United States Coast Survey steamer Blake As is to be expected, the mollusks of this area under the direction of Professor Alexander Agas­ show an obvious relationship with those of the siz. The mollusks gathered during this cruise West Indies and the entire Caribbean region. Were reported on by Dall (1886-89). Subse­ The list of species has of necessity been taken quently, the steamer Albatross of the United largely from our knowledge of the Floridian mol­ States Fish Commission made numerous stations luscan fauna. An interesting and more extended in the eastern part of the Gulf, the results of discussion of these associations can be found in which have been referred to in various scattered a report by Bartsch (1937). Papers. More recently, the Fish and Wildlife 1. Coral reefs, rocky outcrops, and jetties: Service vessels Pelican and Oregon have been Here we find a rich fauna of which I list only carrying out investigations in the Gulf of Mexico a few species. in the course of which they have gathered many Acanthopleura granulata Gmelin. interesting mollusks which have been only partly Acmaea pustulata Helbling. reported on. The commercial shrimp fishermen Fissurella cayenensis Lamarck. have been initiated by the amateur shell collectors Astraea americana Gmelin. N erita peloronta Linn6. into the practice of saving the mollusks brought N erita versicolor Gmelin. up in their nets, and in this way they are con­ N erita tessellata Gmelin. tributing many interesting finds. A preliminary Littorina ziczac Gmelin. report on some of these mollusks has recently Tectarius muricatus Linn6. Cerithium literatum Born. been published by Rehder and Abbott (1951). Batillaria minima Gmelin. Thais rustica Lamarck. ECOLOGY Cantharus tinctus Conrad. Conus mus Hwass. Under this heading are listed what seem to be B-iphonaria pectinata Gmelin. the most important biotopes present in the lit­ Arca zebra Swainson. toral zone of the Gulf of Mexico. No attempt Barbatia barbata Linne. has been made to go into a detailed description of Brachidontes exustus Linne. the various facies, zones, and associations. Lima scabra Born. I sognomon alatum Gmelin. Some of the species listed as occurring in one 2. Shallow water sandy stretches, shallow grassy Province or in one kind of habitat may, of course, bays, muddy flats: be found also in other areas. It should likewise Here the sand-burrowing mollusks are at home, be pointed out that because of the lack of careful and hence we find more pelecypods than in the collecting along much of the coast line of the Gulf preceding habitat. the extent and exact position of the transition Cerithium variabile C. B. Adams. areas between the Caribbean and Carolinian prov­ Epitonium lamellosum Lamarck. inces is at the present time still largely a matter Sinum perspectivum Say. of speculation. This is especially true of the fauna N atica canrena Linn6. of the moderate depths between the shore and the Busycon contrarium Conrad. deeper waters. M elongena corona Gmelin. Oliva sayana Ravenel. CARIBBEAN PROVINCE Olivella jloralia Duclos. Marginella apicina Menke. This zoogeographical area includes the north­ Conus pealei Green. West coast of Cuba from Cabo San Antonio to Terebra dislocata Say. lIabana, the west coast of Florida from the Dry Aplysia willcoxi Heilprin. l'ortugas and Key West north to probably Tampa Cardita jloridana Conrad. A nodontia alba Link. Bay (the northern limit of this province is some­ Lucina jloridana Conrad. What doubtful here but lies somewhere between Trachycardium egmontianum Shuttleworth. Sanibel Island and Cedar Keys), and the coast of Dosinia elegans Conrad. 472 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

Macrocalli8ta maculata Linne. A nadara bra8iliana Lamarck. Chione cancellata Linne. N oetia pondero8a Say. Donax lIariabilis Say. Trachycardium muricatum Linne. Dinocardium robu8tum Humphrey. 3. Brackish water estuaries: La8llicardium mortoni Conrad. This habitat is found all along the shores of D08inia disCU8 Reeve. the Gulf of Mexico. The mollusks listed here Macrocalli8ta nimbosa Humphrey. are found both on sandy and muddy bottom as Tellina alternata Say. well as on rocky substrata and on objects such as Tellina lIer8icolor DeKay. ~d Donax lIariabili8 Say. jetties pilings. Tagelu8 gibbu8 Spengler. Neritina reclillata Say. Barnea c08tata Linne. Batillaria minima Gmelin. Cerithidea 8calariformis Say. 2. Bays and lagoons, moderate to high sali.nity, Congeria leucophaeata Conrad. sandy or muddy bottom: Cyrenoida jloridana Dall. Cerithium lIariabile C. B. Adams. 4. Mangrove flats: N a88ariu8 acuta Say. N a88ariu8 lIibex Say. A few species are found predominantly in this Acteocina canaliculata Say. habitat. Pecten gibbu8 amplico8tatu8 Dall. LiUorina angulifera Lamarck. Vol8ella demi88u8 grano8i88imu8 Sowerby. Cypraea zebra Linne. Chione cancellata Linne. 18ognomon alatum Gmelin. Mercenaria mercenaria Linne. 08trea floridenBis Sowerby. Abra aequalis Say. M ulinia laterali8 Say. CAROLINIAN PROVINCE En8i8 minor Dall. This area extends from Cape Hatteras, North 3. Bays and lagoons, brackish water: Carolina, south to about Cape Canaveral on the N eritina reclillata Say. east coast of Florida, and from about Tampa Bay LiUorina irrorata Say. on the Florida west coast northward and west­ Polyme8oda carolinen8i8 Bose. ward along the shore of the Gulf to about Rangia cuneata Gray. Corpus Christi Bay, Texas. Some elements of this 4. Jetties and oyster reefs in bays: fauna on the western side of the Gulf may go Crepidula plana Say. farther south into Mexico, while some tropical Thais floridana Conrad. forms may reach the vicinity of Matagorda Bay. Anachi8 obesa C. B. Adams. Brachidontes recurvu8 Rafinesque. The shores of this area have a rather uniform CraS80strea lIirginica Gmelin. character, without coral reefs or mangrove vege­ tation. Instead we have mile on mile of sandy DEEPER WATERS OF THE GULF OF MEXICO beaches, often along low coastal islands, behind In these deeper waters we find many species which are lagoons, bays, and estuaries with vary­ that show a relationship with the tropical element ing degrees of salinity. Frequently we find oyster of the Caribbean area. We have, for instance, reefs on the lagoons and bays, but outside of these Terebra taurinum Humphrey (flammea Lamarck) oyster banks the only solid substrata are mainly and Sconsia striata Lamarck which extend into in the form of man-made structures such as the West Indies. Others are peculiar to the Gulf. jetties and pilings. The explorations that are now going on in the This province may conveniently be subdivided Gulf of Mexico and future dredgings will un· into the following ecological areas: questionably bring to light many more new and 1. Outersandy beaches and nearshore sandy areas: interesting forms. Epitonium angulatum Say. Gaza 8uperba Dall. (W) Polinice8 duplicata Say. Murex beaui Fischer and Bernardi. (W) Sinum per8pectillum Say. Oocory8 bart8chi Rehder. (G) Strombu8 pugili8 alatu8 GmeUn. FU8inus couei Petit. (G) Chicoreus Julllescen8 Sowerby. Scaphella junonia Shaw. (G) BU8ycon 8piratum plago8um Conrad. Conus 8ozoni Bartsch. (G) Olilla sayana Ravenel. PolY8tira albida Perry. (W) Anadara campechiensi8 GmeUn. PolY8tira tellea Dall.(G) GULF OF MEXICO 473

Terebra taurinum Humphrey. (W) CLENCH, W. J .-Continued Anadara baughmani Hertlein. (G) 1925. Additions to the list of marine shells of Sanibel, Aequipecten glyptus Verrill. (C) Florida. Nautilus 38: 93-95. A musium papyraceum Gabb. (W) 1929. Some land and marine shells from the Mississippi Pitar cordata Schwengel. (G) Delta region. Nautilus 43: 34-35. (W) Also known from the West Indies. DALL, W. H. (G) Known only or almost solely from the Gulf of 1884. On a collection of shells sent from Florida by Mexico. Mr. Henry Hemphill. Proc. U. S. Nat. Mus. 6: (C) Found also in the Atlantic off the south­ 318-342, pI. 10. eastern United States. 1886-89. Reports on the results of dredging, under the In this brief survey of our present-day knowl­ supervision of Alexander Agassiz, in the Gulf of Mexico (1877-78) and in the Caribbean Sea (1879-80) edge of the mollusks of the Gulf of Mexico I have by the U. S. Coast Survey steamer Blake . .. attempted to list some of the conspicuous species XXIX. Report on the Mollusca. Bull. Mus. Compo found in the various parts of the Gulf and have Zool., Harvard Coil., 12 (6): 171-318, pis. 1-9; 18: pointed out how little we actually know of the 1-492, pis. 10-40. mollusks. There has lately, however, been an 1889. A preliminary catalogue of the shell-bearing marine mollusks and brachiopods of the southeastern increase in interest in this region, and we can coast of the United States. Bull. U. S. Nat. Mus. 37, look forward to valuable contributions on this 221 pp., 74 pis. Washington. subject in the not too distant future. 1903. A preliminary catalogue of the shell-bearing marine mollusks and brachiopods of the southeastern BIBLIOGRAPHY coast of the United States. Bull. U. S. Nat. Mus. 37, ADAMS, A. C., and KENDALL, W. C. 232 pp., 95 pis. Reprinted. Washington. 1891. Report upon an investigation of the fishing HAAS, F. grounds off the west coast of Florida. Bull. U. S. 1940. Ecologicll:I observations on the common mollusks Fish Comm. 9 (1889): 289-312, pI. 3. of Sanibel Island, Florida. Am. Midland Nat. AGASSIZ, A. 24 (2): 369-378. 1878. No.6. (Letter No.2) to C. P. Patterson, Superin­ HARRY, H. W. tendellt Coast Survey, Washington, D. C., from 1942. List of Mollusca of Grand Isle, Louisiana, re­ Alexander Agassiz, on the dredging operations ... corded from the Louisiana State University Marine with the preliminary report on the Mollusca of the Laboratory 1929-41. Occ. Papers Mar. Lab., Louisi­ expedition by W. H. Dall. Bull. Mus. Compo Zool., ana State Univ., 1, 13 pp. Harvard CoIl., 5: 55-64. HEDGPETH, J. W. AGUAYO, C. G., and JAUME, M. L. 1950. Notes on the marine invertebrate fauna of salt 1947-52. Catalogo de los Moluscos de Cuba. 725 pp. flat areas in Aransas National Wildlife Refuge, Texas. Habana. Pub. Just. Mar. Sci. 1 (2): 103-119. BAKER, F. C. HENDERSON, JOHN B. 18lH. Notes on a collection of shells from southern 1916. The cruise of the Tomas Barrera. IX. 320 pp., Mexico. Proc. Acad. Nat. Sci. Philadelphia, 1891: 36 illus., maps. New York. 45-55. HINKLEY, A. A. BARTSCH, P. 1907. Shells collected in northeastern Mexico. Nau­ 1937. An ecological cross-section of the lower part of tilus 21: 68-72. Florida based largely upon its molluscan fauna. JOHNSON, C. W. Rep. Committee on Paleoecology Nat. Res. Council 1934. List of the marine Mollusca of the Atlantic coast 1936-37: 11-25. from Labrador to Texas. Proc. Boston Soc. Nat. BURKENROAD, M. D. Rist. 40 (1): 1-204. 1933. Pteropoda from Louisiana. Nautilus 47: 54-57. JOUBIN, L. CALKINS, W. W. 1912. Banes et recifs de coraux (Madr~pore8). Ann. 1878. Catalogue of the marine shells of Florida, with Inst. Oceanogr. 4 (2): 7 pp., 5 maps. notes and descriptions of several new species. Proc. LADD, H. S. Davenport Acad. Nat. Sci. 2: 232-253, pI. 8. 1951. Brackish-water and marine assemblages of the 1880. Additions to the marine shells of Florida. Valley Texas coast, with special reference to mollusks. Pub. Naturalist 2, Nov. Inst. Mar. Sci. 2 (1): 125-164. CARY, L. R. LYMAN, F. 1906. A contribution to the fauna of the coast of 1942. Dredging at Destin. Shell Notes 1 (2): 7-9. Louisiana. Gulf Biologic Sta., Cameron, La., Bull. 6, MAURY, C. J. pp.50-59. 1920. Recent molluscs of the Gulf of Mexico and CLENCH, W. J. Pleistocene and Pliocene species from the Gulf states. 1923. The marine shells of Sanibel, Florida. Nautilus Part I. Pelecypoda. Bull. Am. Paleontol. 8 (34): 115 37: 52-56. pp., 1 pI. 474 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

MAURY, C. J.-Continued ROEMER, C. F. VON. 1922. Recent Mollusca of the Gulf of Mexico and 1849. Texas. Mit besonderer Rucksicht auf Deutsche Pleistocene and Pliocene species from the Gulf States. Auswanderung und die physischen VerhitltnisBe des Part II. Scaphopoda, Gastropoda Amphineura, Landes, XIV, 464 pp., 1 map. Bonn. (Mollusca: Cephalopoda. Bull. Am. PaleontoI. 9, (38): 34-142. 451-457; new species by R. A. Philippi.) SCHWENGEL, J. S., and MCGINTY, T. L. MELVILL, ,T. C. 1942. Some new and interesting marine shells from 1881. List of the Mollusca obtained in South Carolina northwest Florida. Nautilus 56: 13-18. and Florida (principally at the island of Key West in SIMPSON, C. T. 1871-1872). Jour. Conch. 3: 155-173. 1887. Record of a two days' dredging cruise in Tampa MITCHELL, J. D. Bay, Florida. Conch. Exch. 1: 44, 52-53. 1894. List of Texas Mollusca. 22 pp. Victoria, Texas. 1889. Contributions to the Mollusca of Florida. Proc. Davenport Acad. Nat. Sci. 5: 45-72. PERRY, L. M. SINGLEY, J. A. 1936. A marine tenement. Science 84: 156-157. 1893. Contributions to the natural history of Texas. 1940. Marine shells of the southwest coast of Florida. Part I. Texas Mollusca. Fourth Ann. Rep., 1892, Bull. Am. PaleontoI. 26 (95): 260 pp., 39 pIs. GeoI. Survey Texas: 299-343. PUFFER, E. L., and EMERSON, W. K. STENZEL, H. B. 1953. The molluscan community of the oyster-reef bio­ 1940. Mollusks from Point Isabel, Texas. Nautilus 54: tope on the central Texas coast. Jour. Paleontology 20-21. 27 (4): 537-544, pI. 56. STEPHENSON, T. A., and STEPHENSON, ANNE. 1950. Life between tide-marks in North America. I. PULLEY, T. E. The Florida Keys. Jour. Ecology 38 (2): 354-402, 1949. Shelled mollusks of the Texas coast from Gal­ pIs. 9-15. veston to Port Aransas. Texas Jour. Science 1 (3): STRECKER, J. K. 62-68. 1935. Notes on the marine shells of the Texas coast. 1952. An illustrated check list of the marine mollusks Baylor Bull. 38 (3): 48-60. of Texas. Texas Jour. Science 4 (2): 167-199, 13 pIs. VANATTA, E. G. 1904. A list of shells collected in western Florida and REED, C. T. Horn Island, Mississippi. Proc. Acad. Nat. Sci. 1941. Marine life in Texas waters. Houston. xii 88 pp. Philadelphia 55 (1903): 756-759. REHDER, H. A., and ABBOTT, R. T. WHITTEN, H. L.; ROSENE, H. F.; and HEDGPETH, J. W. 1951. Some new and interesting mollusks from the 1950. The invertebrate fauna of Texas coast jetties; It deeper waters of the Gulf of Mexico. Rev. Soc. preliminary survey. Pub. Inst. Mar. Sci. 1 (2): 53­ Malac., Carlos de Ill. Torre 8 (2): 53-66, pIs. 8-9. 87, pI. 1. CEPHALOPODA OF THE GULF OF MEXICO 1

By GILBERT L. VOSS, Marine Laboratory, University of Miami

The taxonomy and biology of the cephalopods The first major contribution to the knowledge of the Gulf of Mexico have been neglected by of the cephalopods of the Gulf of Mexico was workers in the field of malacology, and conse­ made by Pickford (1945) in her study of the quently, records and reports are very meager. littoral octopods of the western Atlantic. Three LeSueur (1821) described the first species from of the six octopods treated in this study are this area when he gave the description of Onykia common to the Gulf of Mexico: Octopus vulgaris carribaea. De Blainville (1823) described several L., O. briareus Robson, and O. jlYUbini Robson. of the loliginid squids which are now known to The only other published records of Gulf of Occur in these waters, the fact which he failed, Mexico cephalopods are a record of O. burryi however, to record. Howell (1868) described Voss from the upper Gulf and comments upon its Loligo hemiptera, a new squid from the Gulf. distribution by Voss (1950, 1951b). Hedgpeth This species has since been shown by the author to (1950) records Loligo brasiliensis Blain. from the be synonymous with Lolliguncula brevis (Blain.). Texas jetties, but this is erroneous, the species Verrill (1882), in his report on the cephalopods involved being Lolliguncula brevis (Blain.) which of the northeastern coast of the United States, is also recorded in the paper. lists five species, only, as occurring in the Gulf of Thus it is seen that the cephalopodan fauna of Mexico region: Sepioteuthis sepioidea (Blain.), the Gulf of Mexico is comparatively untouched, Loligo gahi Orbigny, Lolliyuncula brevis (Blain.), and to date no surveyor monograph upon them Sthenoteuthis pteropus Verrill, and S. bartrami has been published such as has appeared for those (LeSueur). Of these, L. gahi Orb., which occurs of other areas such as the Mediterranean Sea or on the Pacific coast of South America and is not the Hawaiian Islands. According to some zo­ found in this area, has been a cause of much ologists the lack of published records indicates confusion ever since as it has been applied to the that maybe this area is fairly devoid of specimens. arrow squid, Doryteuthis plei (Blain.). However, an examination of the material, still From 1882 to 1934 the cephalopods of the Gulf unreported, from the Atlantis circumnavigation of Mexico were ignored due largely to the lack of of Cuba in 1937-38 presents another picture. sPecialists in this field. In 1934 Johnson's List The large collection made by that vessel and of the Marine Mollusca of the Atlantic Coast from recently examined by the author contains many Labrador to Texas appeared. In it, Berry (1934), new records for the Gulf of Mexico and several Who wrote the cephalopod section, records 64 species which are new to science. Of the entire species within its range of which only 15 species collection only a single specimen has been recorded are referred to Florida and the West Indies and in the literature (Pickford 1946). Only one specifically to the Gulf of Mexico. Since the initiation by the United States Fish Robson (1932) published an account of certain and Wildlife Service of the exploratory fishing by octopods sent him by van Hyning mostly from the Oregon an entirely new and rich cephalop­ the Gulf coast of Florida and this account was odan fauna has unfolded in the Gulf of Mexico. fOllowed in 1937 by Adam'~ report on the Mercator The collections made by this vessel are rather Collections and the description of a new species large and at this date (September 1952) are in the frorn Dry Tortugas, Octopus mercatoris, since process of being worked up by the'author. considered by Pickford (1945) to be synonymous From the material so far examined it appears with------O. joubini Robson. that there is a strong connection between the I Contribution No. 121 from the Marine Laboratory, University of Miami. 475 476 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE cephalopodan fauna of the Mediterranean Sea area that only generalities can be drawn. From and the Gulf of Mexico. The Oregon material, the literature and independent investigations it both benthic and pelagic, parallels very closely seems apparent that the octopods and decapods the material from the Mediterranean both in spawn during the spring, although there are in­ genera and species. Considering the sometimes dications that some spawning occurs throughout rather long planktonic life of many of the larval the year. In general, the octopods care for their forms and the sweep of the North Equatorial spawn by brooding over the eggs which are at­ Current into the Caribbean and thence into the tached either singly or in festoons beneath rocks Gulf of Mexico, such distribution is not surprising. or in old mollusk shells. Certain of the octopods, This close connection is best exemplified by the particularly those with large eggs (10-15 mm.), presence of Pteroctopus tetracirrhus (delle Chiaje), hatch out fully developed and immediately take up apparently quite common in the Gulf of Mexico, a benthic life. Others with small eggs hatch out as which was known previously only from the temporary members of the plankton and spend a Mediterranean Sea and a single record from the certain interval of time, from a few days to several Azores, and Scaeurgus 1tnicirrhus Orbigny, a weeks or months, in a drifting state after which related genus, which is well known in the Mediter­ they settle to the bottom. The decapods, at least ranean but not elsewhere in the Atlantic but was for the few examples known, attach their eggs recently reported by Voss (1951a) as occurring to the bottom either to rocks, algae, or other along the southeast Florida coast and presumably objects, and leave them uncared for until hatching in the Gulf of Mexico. whence they become part of the temporary plank­ Pickford (1946) reported the presence of ton; others attach their eggs to floating objects Vampyroteuthis injernalis Chun taken by the at or near the surface. Among many exceptions to Atlantis in 1,480 meters from the Gulf of Mexico. these are Vampyroteuthis injernalis Chun which This form has not been found in the Mediter­ reportedly has free pelagic eggs and Argonauta ranean presumably due to the shallowness of the argo L. in which the minute eggs are retained sill at the Straits of Gibraltar, a factor which within the egg case by the female. does not enter into the discussion of the Gulf of The length of life in cephalopods is uncertain Mexico due to the greater depth of the Yucatan and a matter of some dispute. Verrill (1882) Channel. A discussion of the bathypelagic con­ suggests that Loligo pealei LeSueur reaches ditions of this species may be found in the above­ maturity in about 2 to 3 years. The actual span mentioned paper. of life is uncertain but is believed to average, The extent of the distribution of the Caribbean at least in the smaller species, about 2 to 4 years. and Atlantic species into the Gulf of Mexico at Cephalopods may be either free-swimming open the present time is unknown. In the appended ocean forms such as the Ommastrephidae, benthic list of species known to occur in the Gulf of Mexico such as the Octopodinae, bathypelagic as the those with asterisks have been reported only Vampyroteuthidae and Spirulidae, or planktonic from the Gulf Stream in the vicinity of Miami or as in the Cranchiidae. In general, the Loliginidae, from the Florida Keys. Thus their presence in a group of great commercial importance in some the Florida Current which sweeps through the areas of the world and found in large numbers in southern portion of the Gulf of Mexico must be the Gulf of Mexico, are free-swimming forms assumed, yet they have not been reported from found in coastal waters never far from land. The the rather extensive hauls made by the Oregon. food of cephalopods consists mainly of crustaceans, One species investigated by the author, Sepioteuthis bivalve mollusks, and small fish. In return, they sepioidea (Blain.), is known from both sides of the furnish a considerable portion of the diet of many Gulf Stream from below its origin in the Lesser fishes. As many as 24 pairs of beaks of Argonauta Antilles to Bermuda, but there is no record of its argo L. have been taken by the author from the occurrence in the Gulf of Mexico proper. The stomach of a single sailfish (lstiophorus). Sprin~er cause of this rather peculiar distribution or limita­ (personal communication) records sucker dISC tion is not known. marks the size of a half dollar on the skin of fl, So little is known concerning the life histories of young sperm whale taken in the Gulf of MexicO, the cephalopods, especially the octopods, in our and I.l. single specimen of Architeuthis sp. badly GULF OF MEXICO 477 mutilated by sharks was taken from the surface Family OMMATOSTREPHIDAE: !llex illecebrosus (LeSueur), 1821. of the Gulf Stream off the Florida Keys. The Sthenoteuthis bartrami (LeSueur), 1821. specimen was measured by the author and es­ Sthenoteuthis pteropus Steenstrup, 1856. timated to be about 15 feet long when entire so Family CHIROTEUTHIDAE: that the presence of the giant squid in these Chiroteuthis lacertosa Verrill, 1881. waters is now confirmed. Family CRANCHIIDAE: The number of individual species of cephalopods Cranchia scabra Leach, 1817. found in the Gulf of Mexico is rather difficult Order OCTOPODA: to determine due to the previously mentioned Family VAMPYROTEUTHIDAE: lack of records. However, the completed results Vampyroteuthis infernalis Chun, 1903. of the Oregon explorations will materially increase Family STAUROTEUTHIDAE: our present knowledge of this interesting fauna. Grimpoteuthis umbellata (Fischer), 1883. The following list of species arranged in their Family OPISTHOTEUTHIDAE: taxonomic order includes species which have been Opisthoteuthis agassizii Verrill, 1883. taken from the plankton of the Gulf Stream off Family ARGONAUTIDAE: Miami and as such should be found in the portion *Argonauta argo L., 1758. of the Florida Current traversing the Gulf of "'Argonauta hians Solander, 1786. Mexico. Certain others have been reported thus Family TREMOCTOPODIDAE: *Tremoctopus violaceus delle Chiaje, 1830. far only from the Lower Florida Keys. Both of these O'roups are marked with asterisks, and only Family ALLOPOSIDAE: ~ot Alloposus mollis Verrill, 1880. those so marked have been actually found in Family OCTOPODIDAE: the Gulf of Mexico proper. Many more records Octopus briareus Robson, 1929. could be added from the Caribbean area, but as the O. vulgaris L., 1758. presence of these species in the Gulf of Mexico O. joubini Robson, 1929. has not been proved they are not included in the O. burryi Voss, 1950. Pteroetopus tetracirrhus (delle Chiaje), 1830. present list. "'Scaeurgus unicl:rrhus Orbigny, 1840. SYSTEMATIC LIST LITERATURE CITED Order DECAPODA ADAM, W. 1937. Resultats scientifiques des croisieres du navire­ Family SPIRULIDAE: ~cole BeIge Mercator. VI. Cephalopoda. Mem. Spirula spirula L., 1758. MU8. R. Rist. Nat. Belgique (Brussels), (2), 9: 4~-82. Family SEPIOLIDAE: BERRY, S. S. Rossia (Semirossia) tenera Verrill, 1880. 1934. List of marine Mollu8ca of the Atlantic coa8t Rossia (Semirossia) equalis Voss, 1950. from Labrador to Texas, by C. W. Johnson. Proc. Family LOLIGINIDAE: Boston Soc. Nat. Rist. 40 (1): 160-165.

Lolliguncula brevis (Blain.), 1823. BLAINVILLE, R. D. DE. Loligo pealei LeSueur, 1821. 1823. M6moire sur les especes du genre Calmar (Loligo, "'Sepioteuthis sepioidea (Blain.), 1823. Lamarck). Jour. de Physique 96: 116-133. Paris. Doryteuthis plei (Blain.), 1823. HOWELL, S. B. Family LYCOTEUTHIDAE: 1868. Description of two new species of cephalopods. Lycoteuthis diadema (Chun), 1900. Am. Jour. Conch. 3: 239. Family ENOPLOTEUTHIDAE: LESUEUR, C. A. Abraliopsis morisii (Verany), 1837. 1821. Descriptions of several new species of cuttle-fish. "'Thelidioteuthis alessandrinii (Verany), 1851. Jour. Acad. Nat. Sci. Philadelphia 2: 86-101. '"Pyroteuthis margaritifera (Ruppell), 1844. "'Pterygioteuthis giardi Fischer, 1895. PICKFORD, G. E. 1945. Le poulpe americain: a study of the littoral Oc­ Family ONYCHOTEUTHIDAE: topoda of the western Atlantic. Trans. Connecticut *Onykia carribaea LeSueur, 1821. Acad. Arts & Sci. 36: 3 701-811. Onychoteuthis banksii (Leach), 1817. 1946. Vampyroteuthis infernalis Chun, an archaic di­ Family ARCHITEUTHIDAE: branchiate cephalopod. I. Natural history and dis­ Architeuthis 8p. tribution. Dana-Report No. 29, 40 pp. 478 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

ROBSON, G. C. Voss, G. L.-Continued 1932. Notes on the Cephalopoda-No. 16. On the var­ 1951a. A first record of the cephalopod, Scaeurgus iation, eggs, and ovipository habits of Floridan unicirrhu8, from the western Atlantic. Bull. Mar. octopods. Ann. Mag. Nat. Hist. (10), 10: 368-374. Sci. Gulf and Carib. 1 (1): 64-71. VERRILL, A. E. 1951b. Further description of Octopus burryi Voss with 1882. Report on the cephalopods of the northeastern a note on its distribution. Bull. Mar. Sci. Gulf and coast of America. U. S. Comm. Fish and Fisheries, Carib. 1 (3): 231-240. Pt. VII, Rept. of the Commissioner for 1879, pp. WHITI'EN, H. L.; ROSENE, H. L.; and HEDGPETH, J. W. 211-450, 46 pIs. Washington, D. C. 1950. The intertebrate fauna of Texas coast jetties; a Voss, G. L. preliminary survey. Pub. Inst. Mar. Sci. 1 (2): 1950. Two new species of cephalopods from the Florida 53-87. Keys. Rev. Soc. Malaco. 7 (2): 73-79. SUMMARY OF OUR KNOWLEDGE OF THE OYSTER IN THE GULF OF MEXICO

By PHILIP A. BUTLER, Fish and Wildlife Service, United States iJepartment of the Interior

The American oyster, Crassostrea virginica, in attach to the roots of marsh grass fringing the the Gulf of Mexico is characterized perhaps most bayous and bays or settle secondarily on mussels of all by its versatility in adapting itself to differ­ growing in the marsh. With natural cultch fre­ ent habitat niches. There are few places where quently at a premium oysters are found attached at least a scattered growth of oysters is not found to crabs, turtles, and even on the shell of their along the 3,600 miles of tidal shore line from Cape worst enemy, the drill. Sable in Florida to the Rio Grande in Texas. More typically, reefs build up on the sticky mud The distribution of this oyster population is more bottom found in most of the coastal bays and impressive if we consider its area. There are estuaries along the Gulf shore. 1 The foundations probably more than 1,400 square miles of water of some of these reefs have persisted since pre­ bottoms along the Gulf coast suitable for and historic times. Successive generations of oysters, :more or less populated with oysters. In some attaching to the older oysters and dead shells, areas the oyster communities consist of small have created deposits many feet in thickness. isolated patches only a few yards in area which The living population forms an infinitesimal per­ are elevated like islands in a "sea" of too soft centage of the total mass on such reefs. In other :mud. Where the bottom is more firm the com­ areas, although the reef may have existed for in­ :munities may cover many acres, and reefs up to numerable years, the substratum of shell is rela­ 25 miles in length are not unknown. tively thin, comprising little more bulk than that Oysters establish successful colonies in the of the living oysters. In these cases, the high pop­ range from a foot above mean low water to a ulation density of commensals, which excavate the depth of 30 to 40 feet in some of the deeper chan­ valves, and perhaps chemical factors in the environ­ nels. Their occurrence is everywhere dependent ment lead to the rapid disintegration and disap­ on a suitable or rather a physically possible sub­ pearance of the old shells. stratum. They compete with the tree oyster for A fundamental requirement in the ecology of sPace on the mangrove roots; they cover bridge the oyster is the mixture of salt water from the footings and piles of old ballast rock, and have Gulf or ocean with the fresh water from land even been found 5 miles out in the open Gulf on drainage. The characteristics of the growing oys­ an oil well rigging (Gunter 1951a). ter community, dependent in large measure on In well-protected areas small clusters and the salinity level resulting from the admixture of single oysters become established on pure sand these waters, are governed not only by the average bottoms. On mud bottoms, too soft to support a salinity levels but also by the extremes of se

The majority of Gulf oyster communities fall canning stock. When cultivated they yield clus­ into one of four distinctive categories which I ters of two or three better shaped oysters that are classify on the basis of arbitrarily selected average suitable for the raw trade. The meats are of high salinity levels. Intergrades between the catego­ nutritional quality but are frequently insipid to ries and exceptions to the generalizSltions are nec­ the taste. The increased number of associated essarily common, but they do not seriously alter animals on these reefs leads to intense competi­ the over-all description. Permanent communities tion for both food and space. Barnacles and establish themselves and flourish within a salinity mussels are frequently present in such numbers range of 10 to 30 parts per thousand. In years as to interfere with oyster culture. While these of drought or of excessive precipitation populations communities prosper biologically in most years, may appear sporadically in areas normally having in times of drought they may experience severe salinity levels too low or high to support a losses due to predation by the drill. In flood years population. the growth of the population may be retarded for Oyster reefs located near the head of a typical several months. estuary comprise the first category. In such re­ The third category of oyster reefs is found gions the salinity ranges annually from 15 parts nearer the mouth of a typical estuary, in areas per thousand to 0 and averages near 10 parts per having an average salinity level of 25 parts per thousand or below. The sparse population reflects thousand. Annual fluctuJ.tions in salt content of the marginal nature of this environment. Oysters water range from a low of 10 to 12 parts per thou­ are mostly small and rounded, with smooth, whit­ sand in the spring to about 30 parts per thousand ish shells. The rate of spatfall is low, and al­ in the dry season. The community here is char­ though young oysters grow well their first season, acterized by unusually good growth, although this growth of older oysters is relatively slow. Average factor may be masked by the large amount of annual mortality rates are high, SInd the population shell erosion and predation. The variety of ani­ is periodically decimated by excessive fresh water mals living within the oyster community reaches in years of flood. Primarily, such reefs are of a maximum at this salinity level. The reprodUC­ commercial use as seed areas. In the occasional tive potential of the oysters probably reaches a years of drought these populations may show, maximum here too, but the high population den­ however, an excellent growth and yield a good sity found in communities at lower salinity levelS harvest. Typically, these oysters are free from does not occur here because of the large numbers most fouling organisms, and there are few preda­ of parasites and predators. Mortality rates of tbe tors or parasites present. These oysters have very young oysters are relatively high. Having many characteristics in common with populations survived its first season the oyster's chances for growing at or above mean low water regardless of survival are good. The 'shellshave a massive salinity level. appearance and may be greatly eroded. The The next definite community type is found valves show heavy concentric ridges, indicating where salinity levels fluctuate between 10 and 20 periods of fast growth rates. These communities parts per thousand with a yearly average near 15 are consistent producers of large market oysters parts per thousand. The population density of of excellent quality. But the environment baS oysters on these reefs reaches a maximum because its greatest value when used as a bedding ground. of high reproductive ability, availability of cultch, Medium-sized seed planted here quickly matures and a relatively low concentration of predators. and may be harvested before the usual predators The growth of individual oysters is moderately and parasites are established. The decreased spat good and quite uniform so that the population survival prevents the transplanted oyster fro J1l forms rather definite year classes. Oyster valves becoming "wrapped up" in young growth. The are usually smooth and dense, although in some periodic complete harvesting of these areas when areas they may have moderate infections of the used as bedding grounds prevents or greatly ~e­ boring sponge and clam. The oysters form large tards the accumulation of undesirable coDUllens d or small interlocking clusters, depending on the The fourth type of oyster community ~ fO~e nature of the bottom. Their narrow shape makes at the junction of the typical estuary WIth t _ them difficult to handle commercially except as waters of the Gulf where salinity levels are con GULF OF MEXICO 481 sistently high. Although oysters exist here the being unharvested, the population builds up until environment is just as marginal as °in the first it breaks the water surface. At low tide many category considered. The population is again oysters are exposed to the atmosphere. Growth characterized by its sparseness, slow growth rates, along the ridges of these reefs is usually less than and excessive mortality. The dearth of suitable that of the population average. The shells are cultch and the high concentration of predators are polished and have a reduced number of external important factors in the low survival rate of the and internal commensal organisms. The oysters spatfall. In most years the commercial impor­ are scattered in small clusters. There is a coarse tance and the reproductive capacity of reefs in substratum consisting primarily of shell fragments. this location are of negligible importance. Fol­ Buried inches deep in the substratum and usually lowing disastrous floods this community, by pro­ growing quite well, considering the seemingly viding larvae, may be the all-important factor in unorthodox position, there is often a fair number repopulating the flooded areas where the oysters of older oysters. Where depth of water over the have been destroyed. reef is greater, the clusters of oysters become Factors other than salinity levels may exert a larger, and the individual oysters attain a larger profound influence in determining the character average size. Although the oysters are very long, of the oyster community. The most important they are correspondingly narrow with deeply among these are the nature of the bottom, the concave attached valves and flat or even concave type of cultch, the amount of wa~er current upper valves. Attached to the older oysters may carrying a supply of food, and the degree of be three or four, perhaps more, younger genera­ artificial cultivation. It is signifieant that when tions. As a rule, the quality of meat of such young oysters are moved to a new environment oysters is inferior, although the amount of spawn they quickly acquire the attributes of the popu­ produced by them may be tremendous. The lation already present there. It is also of interest periphery of these reefs is often sharply defined, to note those instances in which a characteristic the outermost fringe of oysters showing luxuriant type of oyster has acquired a geographical name growth, while a foot beyond lies a muddy ooze too and becomes well-known in the trade. The prac­ soft to support a single shell. tical oysterman may discover that there are o~her The interdependence of the myriad of animals geographic locations which produce essent~ally associated in this oyster community forms a the same type of oyster; perhaps we find that' 100 complex system. In a stable environment their boatloads of "name" oysters are annually mar­ numbers and variety are strictly controlled by the keted from a geographic area which can produce availability of habitat niches even though their only 25 boatloads. This should not be regarded food supply is primarily obtained from without. as a case of deception on the part of the producer, Relatively slight changes in the external environ­ for a "name" oyster actually implies a certain ment may drastically alter, however, the entire quality of product and similar environments can make-up of the community. Produce oysters ~f essentially indistinguishable This description of the natural oyster commu­ quality regardless of how far apart they may be nity is probably equally applicable to the oyster geographically. community of past ages. The evidence for the Very specialized communities exist on wharf antiquity of the oyster in the Gulf is impressive, Pilings, especially in channels having a high and the early discovery of their value as food is Current velocity. Isolated marsh ponds may shown by the Indian shell middens which dot the Produce characteristic populations. Noteworthy coast line. Vast deposits of buried shell exist in alUong these is the occasional colony of "Ma­ all of the Gulf States. These banks are usually in rennes" oysters whose flesh is colored a deep green 8 to 10 feet of water under a layer of mud of vary­ by the abundance of a particular diatom in its ing thickness. The deposits range from a few fOod supply. inches to 25 feet and more in depth and no one Natural oyster reefs are still found occasionally knows their extent. For the most pa;t the oysters and were quite common at the turn of the century. on these old reefs did not grow to any larger size The only essential difference in their appearance i. e., live any longer, than oysters do today. Th~ f.rom that of cultivated reefs lies in the fact that, average shell size in many deposits is considerably 482 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE less than that found on a modern reef of planted coast because of the sustained higher temperature oysters, and we may assume that they did not levels during the summer months. The produc­ compare in quality with the cultivated oyster of tion of larvae and the resulting spatfall may today. show peaks of intensity in anyone or all of the The enormous quantity of shells in these buried summer months. At Pensacola the pattern is banks does not indicate an unusually high rate of quite variable from year to year, but during the productivity but rather speaks for the untold month of July larval production and spatfall are eons that passed in the formation of such deposits. consistently lower than during the rest of the These old reefs constitute an extremely valuable spawning season. These conditions contrast sig­ resource in modern times, since they are com­ nificantly with those on the Atlantic coast. In posed of relatively pure calcium carbonate Long Island Sound, for example, although there (Shearon 1951). The chemical industries of is scattered spawning during the summer period, Texas alone, in the decade beginning 1940, con­ the majority of spawn is produced in a relatively sumed more than 45 million tons of these shells. short time about the end of June (Loosanoff and Similar deposits are extensively exploited in Engle, 1940). The relative abundance of larvae Louisiana and to a lesser extent in the other Gulf in the plankton at Pensacola in the period 1949­ States. Examination of these reefs reveals strik­ 1951 shows a good correlation with the spatfall ing similarities to the natural communities we in the area, although the quantity present at any find today. Many of the buried shells show light one time seems small in comparison with the to heavy infestations with boring sponge; some amount of set produced. In this area there are shells are pitted with excavations like those made no commercial reefs; the oyster population is by the modern boring clam; encrusting bryozoans confined to pilings and similar locations out of are present; and of frequent occurrence are the reach of the conch. In Mississippi Sound, where shells of conchs, quite similar if not identical, the oyster reefs are extensive, 50 percent of the with the modern Thais. volume of plankton samples collected during the The diversity of habitats existing along the height of the spawning season may consist of coast of the Gulf causes a parallel diversity in the oyster larvae. pattern of growth and reproduction in the oyster Spat production is heavy but erratic all along so that we may draw a generalized picture of the the coast; in certain localities spatfall and sur­ course of events and indicate the significant vival are particularly good. As is true on the exceptions. Atlantic coast, the areas of best spatfall are fre­ In midwinter the gonad tissue of mature oysters quently areas of relatively poor growth. FroJ11 is inconspicuous, but by February or March, the earliest times Louisiana oystermen tranS­ depending on water temperatures, active game­ planted seed oysters from setting grounds east of togenesis takes place. The gonad may form a the Mississippi and placed them in areas west of layer a quarter of an inch or more in thickness by the delta where growth is especially rapid. It is the time spawning commences in early spring, quite possible that the poorer record of spat pro­ but frequently its thickness is far less. The gonad duction in high salinity areas is due to predation layer retains much of its original volume through­ rather than to a real decrease in setting rateS. out the summer; spawning continues regularly In the Pensacola area the cumulative spatfall until October. Mass spawnings of the popula­ during a season may be as high as 1,000 spat to tion are clearly defined and typically occur several the square inch. This intensity of spatfall poses times throughout the summer in a given location a significant problem to the oyster industry. In (Ingle 1951). This is in contrast to the condition areas where oysters set heavily they become SO in northern waters where a single mass spawning clustered in their growth that they are difficult.to of major importance usually occurs in early handle commercially and have meat of inferIor summer. quality. 1 Oyster larvae are found in the plankton in the Competent observers have reported spatfal period from April through October. It is probable during other months of the year at widely sepa- . . t nceS that their free-swimming period is significantly rated pomts along the coast, but these IllS a 1 shorter in these waters than along the Atlantic are exceptions to the general picture of larva GULF OF MEXICO 483 production. The number of spat produced under March when water temperatures range from 10° these circumstances is always quite small. The to 20° C. The major increases in size in New most reasonable explanation for this situation is England oysters take place in the summer months that oysters on the mud flats are induced to spawn at similar temperature levels (Loosanoff and No­ sporadically in the wintertime because of the mejko 1949). sharp elevations in temperature which may take The time required for a Gulf oyster to reach place in small, poorly circulating bodies of water. sexual maturity is significantly shorter than in Water temperatures of 10° to 20° C. in the main northern waters (Menzel 1951). Approximately bays and estuaries during the winter are not high one-third of the oysters setting in the early part enough to permit spawning but may permit, the of the summer become sexually mature by the growth and setting of the larvae produced in iso­ time they are a month old and still less than an lated bayous and marsh ponds. inch in diameter. It is probable that a majority Growth rates of oysters in the Gulf are reputed of the spat attain sexual maturity during their to be astounding when compared to the rates first season and make a significant contribution along the Atlantic coast. This reputation is based to the larval population of late summer. In other on impressions of oystermen, a few fortuitous words, it is a normal event for two generations of natural experiments, and a very meager amount oysters to be produced in this area each summer. of scientific data based on exceptional conditions. During the past century there have been many It is certain that during its first year the oyster changes of a temporary or permanent nature in grows to a length of two or more inches on the the continuity of oyster communities and in the average. Under special circumstances and under physical location of the reefs. Man has caused or experimental conditions at Pensacola a growth of accelerated many of these changes. Other changes 3 and 4 inches has been obtained in 12 months. due to the natural succession of events in an It should be noted that a growth of 2}~ inches estuarine environment are presumably of no during the first season is not at all unknown in greater importance today than they were in pre­ the Chesapeake area, and July spat have been historic times. reported growing to a length of 2% inches before The many rivers draining into the Gulf annu­ their first hibernation period in Virginia (Mackin ally deposit an enormous load of silt which pro­ 1946). Since the growth of oysters in the Gulf is duces multiple effects in the estuary. The major not interrupted by 11 hibernation period, it would silt load deposited in the delta gradually pushes be more surprising if they did not grow up to 3 the head of fresh water seaward. In the past 50 inches during their first year. In those cases years the Colorado River has filled in more than where oysters grow 5 to 6 inches in 24 to 36 months, 6,000 acres of upper Matagorda Bay, and delta and there are many such instances, the oysters are mud now lies on top of once productive oyster Usually of the inferior "coon" type. Oysters grow­ reefs (Baughman 1947, unpublished ms.). In its ing in crowded positions can increase in size only progress to the sea the water carries much silt in one direction, and so they soon become unu­ with it, and this has additional effects on the Sually long. Oysters growing as "singles" can oyster population. It C "eases the penetration increase in size in all directions, and single oysters of sunlight into the water, thus limiting the pro­ in the Gulf do not exhibit unusual growth rates duction of plankton, the oyster's food supply. after their first season (Moore and Pope 1910). Fine silt, by coating the old shells on the bottom, Cultivat,ion procedures developed since 1900 by makes them no longer available as cultch for the oystermen in Louisiana involve the transplanta­ young oysters (Butler 1951). tion of year-old seed to better growing areas and An entirely different type of change has been the marketing of the oysters from 18 to 24 or more brought about by man in the oyster areas west of lllonths later. Good-sized market oysters pro­ the Mississippi River. In this region a number of duced along the Gulf coast probably average three bayous in the past contributed a regular supply of or more years in age. In the Gulf area majo.r in­ fresh water to the bays and inlets along the coast. creases in growth, measured by length and WIdth, :Man has channeled these bayous and changed take place ill the months of November through their exits to the sea so that they contribute 259534 ()----;;4------:l:! 484 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE fresh water to the area only in times of flood. As Oyster reefs are normally established in posi­ a result of these changes in the drainage system tions protected during average storm conditions. the inner bays and lakes lying some distance The occasional hurricanes experienced in the Gulf from the coast, formerly entirely fresh, have now area may destroy large numbers of oysters in become saline enough to support large populations shallow water areas and on sandy bottoms. In of oysters. Connecting bays lying between them 1947, for example, many miles of reef along the and the Gulf have, in turn, become more salty north edge of Mississippi Sound were covered The increased salt content here encouraged the with mud by wave action and destroyed (Engle survival of the conch which has decimated or 1948). This area has shown no significant natural destroyed entirely many large reefs (Moore and rehabilitation in the past 5 years. Pope 1910). A secondary result from this chan­ We have mentioned some of the factors which neling has been an increase in erosion along the may permanently eradicate the oyster reef. shore. The annual load of silt brought down by There are other items which are of greater or the rivers or bayous no longer reaches the coastal lesser' importance in affecting the continuity of areas, where in the past it counter-balanced the populations. shore erosion and created a fairly stable coast line. Oreva8ses.-Disastrous but relatively temporary Shore erosion, now uncompensated, has destroyed changes result from exceptional floods from the some of the barrier reefs; formerly protected bays river basins. In 1890 the flood of the Nita are now open to the Gulf and cannot support crevasse extended east from the Mississippi River oyster populations. Conversely, some bays which and affected oyster reefs 180 miles away in Mis­ formerly had connecting channels to the Gulf have sissippi Sound. Forty miles of oyster reefs lying become landlocked by sand spits, and their between Lake Borgne and Biloxi were seriously oyster communities have largely disappeared. damaged at that time. The history of floods of the There probably has been no great net change in lower Mississippi River shows that, although they the amount of bottom available for oyster culture, may wipe out huge oyster populations in a short but the reefs have migrated inland away from the time, these populations are quickly reestablished, sea and have become more susceptible to the often at a more luxuriant level than prior to the effects of seasonal floods in their new location. crevasse. The annual spring floods occurring in There are some places along the coast where man most river basins cause some mortality in the has opened up channels and deposited spoil banks oyster population by lowering the salinity of the in the construction of inland waterways. These water, but in most years these losses are in­ operations have frequently changed salinity levels significant. permitting an increased survival of oyster Temperature.-The oyster is extremely versati~e predators and, in some cases, have buried reefs in in adapting itself to changes in temperature and IS mud. commonly found where the annual range is froIll Extensive changes in oyster communities have -20 to +300 C. The Gulf oyster is less a?­ also resulted from harvesting methods. Redfish customed to severe cold weather than its AtlantIc Reef in Galveston Bay, which was more than 5 coast relatives, and occasionally large numbers of miles in length, produced a large annual harvest oysters growing at mean low-water level are throughout the nineteenth century. In 1890, destroyed during sudden winter freezes. by the use of a tug and two power dredges, this Pollution.-Pollution has constituted a serious reef was eradicated in a single year (Baughman factor in the continuity of oyster populati~ns 1947, unpublished ms.). Overharvesting without during the past 50 years, but due to more effectIve replacement of shell cultch inevitably causes the control measures it is becoming of less importance. deterioration of a reef. In places where over­ , b Oysters have been destroyed in several areas ~ harvesting has continued until the dead shells supporting the reef as well as the live oysters the effluent from paper mills, for example, an have been removed, it has been a matter of but other industrial wastes are reputed to haveI . Th ontro a few years before the area deteriorated to such damaged large oyster-growmg areas. e c . t s au an extent that even nature could not rehabili­ of industrial wastes no longer constItu e tate it. unsolvable problem. PollutIOn. resuIt'mg froIll GULF OF MEXICO 485 domestic sewage 2 is of great importance, not as probable that none of these diseases greatly it affects the survival of oysters, but as it affects affects the reproductive potential of the oyster their food value to man. On the west coast of community. Florida alone, more than a dozen shellfish-pro­ Predators.-Man has been the most serious ducing areas have been closed to harvesting as a threat to the continuity of oyster populations health measure (Vathis 1950). To some extent because of his wanton methods of overharvesting. all of the Gulf States are faced with this problem. Overharvesting in the past has taken the form not Actually, the closing of polluted areas to harvest­ only of removing all the oysters from the reef but ing constitutes a conservation measure as far as also of removing the underlying cultch which the continuity of the oyster population is con­ made the reef possible. Reefs so destroyed do not cerned, but it results in a deplorable waste of a rehabilitate themselves naturally, and the cost of valuable food resource since satisfactory control replacing the foundations is not feasible econom­ measures are known. ically. Fortunately, our increased awareness of Disease.-The oyster is undoubtedly afflicted this problem during the past 50 years has reduced with a large number of diseases, but their effects the threat of overharvesting except in isolated upon the animal are, for the most part, imperfectly areas. known.' The recent demonstration of the infec­ The most serious natural predator of oyster tion by the fungus Dermocystidium marinum is a populations in the Gulf area is the conch or significant contribution to our knowledge of the oyster drill, Thais. The two forms of this species pathology of the oyster in the Gulf. The harmful have slightly different appearances; Thais f. effects of this parasite are greatest at high temper­ floridana occurs mostly east of the Mississippi atures and high salinity levels (Mackin 1951). River and Thais f. haysae, primarily west of the Some specific parasite may be the causative river (St. Amant 1938). Depredations due to agent of the disastrous mortalities which occur this conch are incalculable. In the Pensacola area among transplanted oysters in some areas of and in the southern reaches of Barataria Bay, for Louisiana during the hot summer months. These example, it makes oyster culture impossible. The mortalities, ranging from 35 to 95 percent of the snail is distributed wherever oysters are found at population in different areas, were unreported 20 salinity levels averaging above 15 parts per thou­ years ago. Their frequent occurrence since that sand. Its populations are periodically decimated time has necessitated entirely different cultural in times of flood and show enormous increases in techniques. Now, oysters for rebedding purposes times of drought. The snail reproduces during in these areas must be large enough so that a the summer months simultaneously with the few months' growth will make them suitable for oyster. Large individuals may deposit a half :marketing. In the past it was the practice to million eggs which develop into free-swimming bed much smaller seed oysters and let them grow larvae. After a plankton stage of unknown dura­ for 18 months or longer before harvesting (McCon­ tion the young snails settle to the bottom and nell 1950). commence feeding on oysters and other sedentary Oysters are widely subject to ~nfestation .with forms. Snails a millimeter in length and a week the sporozoan parasite NematopS'/,8. There IS no old can be found actively drilling oyster spat of evidence however that this micro-organism the same size and age. Large snails have been debilitat~s or is th~ cause of mortalities in the observed by the author eating spat at the rate of oyster (Landau and Galtsoff 1951). Of less four per hour under experimental conditions. common occurrence is the digenetic trematode, The snails are known to live Jor at least 3 years Bueephalus, whose larvae develop in and cause and possibly many more under normal circum­ the deterioration of the oyster gonad. Several stances.. Its vor.acious feeding habits, high re­ other unspecified diseases, as well as infections productIve capaCIty, and the fact that its larvae 'With bacteria have been reported recently for are distributed by water currents combine to oysters in B~ataria Bay (Mackin 1951). It is make this snail the :most destructive oyster pred­ ator in the Gulf environment. A few other gas­ t A detailed account of pollution In Gulf water III given In the last chapter of this book, pp. 666-676. tropods present, such as the moon snail, Polynices, 486 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE

may feed on oysters to a limited extent, but their soft, muddy bottoms extending into areas having relative importance has not been studied. lower salinity levels. All of these animals com­ The Gulf area is fortunate in not having to con­ pete with the oyster for food. Their injury to tend with the starfish which constitutes so serious the oyster is difficult to evaluate, but obviously a predation problem along the Atlantic seaboard. they force it to secrete excess amounts of shell in The black sea drum, Pogonias, is described fre­ order to keep the burrows of these organisms sep­ quently in the literature as a serious pest in the arated from the oyster meats. Both the sponge Gulf area (Moore 1907). This writer has no and clam form extensive excavations opening on first-hand experience with its activities, but the exterior surfaces of the shells, making the oystermen report it as a nocturnal visitor to areas shells friable and hard to handle commercially. containing newly bedded oysters. Large schools Such oysters usually have a massive eroded ap­ of fish may destroy thousands of bushels of oysters pearance, and typically, the meats are of inferior in a short time. Apparently this fish does not quality. The annelid lives on the internal surface attack the natural oyster reefs. of the valve where it is sealed off in a blister by Various species of crabs constitute a serious but the oyster. Its injurious effect is primarily a de­ imperfectly defined menace to the oyster popula­ crease in the esthetic appeal of oysters on the half tion. The blue crab, Callinectes, is a common shell, although in areas outside of the Gulf unusu­ inhabitant of the oyster reef, and there are many ally large colonies of these worms have suffocated observations of its activities in cracking open the oyster communities. soft new growth on oyster shells and eating the The commensal crab, Pinnotheres, of frequent meats. In limited areas the stone crab, Menippe, occurrence in oysters in high salinity areas along is an occasional marauder. Its massive claws the Atlantic coast where it may be occasionally are able to crack open oyster shells with ease. injurious, is uncommon in the Gulf. A related Mud crabs of the family Xanthidae inhabit the species, however, is often present in the bay oyster community in large numbers and undoubt­ scallop in Florida waters. edly consume many of the tiny spat. The list of The animals and plants associated with the predators includes the oyster "leech," Stylochus oyster community are legion. Some have import­ inimicus,2 and other polyclad flatworms of sev­ ance in competing with the oyster for attachment e.cal species which are common associates in the surface, and some in competing for food. Their oyster community. These worms may cause se­ biological and economic importance to the oyster rious damage, but evidence indicates that they are population are mostly a matter of conjecture. secondary rather than primary predators (Pearse The rela,tive abundance of the commensal forms and Wharton, 1938). They cause the greatest va.ries greatly from one oyster reef to another. harm in areas where oysters are already in a In low salinity areas these forms are relatively weakened condition because of some other factor. rare, but their numbers increase to species climaX In the healthy oyster community they are prob­ ably of little importance except in their role as at different higher salinity levels. The following scavengers. listing of the more common members of the com­ Commensals.-Three commensal animals occur munity does not indicate their relative numbers oJ' in numbers sufficient to affect the biology of the importance; anyone of them at some time or place oyster seriously. However, their injurious effects may completely envelop the oysters, decreasing are of greater importance to the oyster industry the available food supply and preventing the than to the continuity of the sppcies. The bor­ attachment of oyster spawn: ing sponge, Cliona, the boring clam, Martesia, and Algae, of various types. the blister worm, Polydora, dwell within til(' oyster Sponges, both encrusting aud boring. shell, existing at various population densities de­ Hydroids and anemones. pending upon the environment. The sponge and Polvchaete worms. clam are more prevalent in areas of high salinity. Otl;cr mollusks, including Anomia, Crepidula, Os/rea, Tlw annelid is more commonly associated with and III !/till/s. Barnacles. Br~'ozoa, both cneFusting an,l upright. '1 81V1ochllS Iron/ali:, Vl'rrill :ll'cording to L. H. H)"m:ul. S('(' pug-t.· 3Ul or this hook. Tlinicatcs. GULF OF MEXICO 487

In discussing the competition among sedentary would stimulate production as well as protect the organisms for space on the oyster reef it is im­ private planter. portant to note that in some areas the oyster is One of the unsolved problems in the Gulf area its own worst enemy. Huge numbers of spat is a method for economically controlling predation settle in areas large el~ough to support only one by the conch. When these methods are dis­ or perhaps two adult oysters. Obviously, in the covered, large and valuable areas that are now struggle for existence, the faster growing spat soon useless can be cultivated. Another and rather overrun and smother their neighbors. Where curious problem exists because of the unusually available cultch is limited, spat mortality may be intense spatfall in many regions. On the North enormous. Atlantic coast the first problem of the industry is At the turn of the century the United States to procure sufficient seed oysters for cultural Bureau of Fisheries made notable contributions to purposes, while along the Gulf coast the problem Our knowledge of oyster biology in the Gulf by is to dispose of the superabundance of seed. The conducting extensive surveys at the request of the too heavy spatfall produces badly clustered, several States. As a direct result of these studies, misshapen oysters; oysters that are almost impos­ conservation laws were enacted in Louisiana which sible to separate for market purposes without greatly stimulated the oyster industry. Oyster killing more than are saved. Oysters growing in cultivation practices were improved, and produc­ this manner rarely yield a select product. It tion iner ')ased significantly (Seferovich 1938). will be necessary to devise new cultural techniques Oysterll1en of that State made a regular practice to utilize this tremendous spatfall. These methods of obtaining seed oysters from reefs in low salinity must permit the attachment of only two or three areas east of the Mississippi River and replanting oysters to a piece of cultch and still supply enough Or bedding them west of the river in bays where cultch so that the vast numbers of spat present salinity levels were higher and the environment are not lost to the industry. fostered rapid growth. Such oysters became An economic problem of perhaps greater suitable for the market in 18 or more months. importance is a need for the controlled use of In the past 15 years this culture method has mechanized equipment in cultivating and harvest­ changed radically because of high summer mor­ ing the crop. The short supply of labor is a talities. As a result, the seed which are now significant factor in the lowered production of the bedded are actually market oysters, and they are industry. Hand methods are largely retained relaid for only a few months before harvesting. because their inefficiency constitutes, in a negative 'roday, Louisiana is foremost among the Gulf way, a conservation measure. But oystering States in conducting an active shelling and seed with hand methods is hard work and good cultiva­ Planting program, but other States are becoming tion requires nearly year-round attention. As a increasingly active in this regard. It is significant result, the labor pool is largely claimed by the that in Texas, where the least has been done in shrimp industry which offers high returns for a providing cultch for spat, the industry has seen relatively short season. The question of using its greatest decline. tongs or power dredges on the reefs is a recurrent Although the oyster has greatly decreased in argument. many sections of our Atlantic coast line because It is not irrelevant to consider, on a theoretical of man's activities, it is improbable that the basis, just what the Gulf oyster industry could immense oyster population of the Gulf could be produce in terms of food for man. Scientific eradicated. However, there are many once pro­ plantings made in Louisiana 50 years ago, the ductive areas in which the industry is now non­ experience of planters in that State since then, existent because of over harvesting and lack of and recent work done in Florida, all provide cultivation. The industry faces many problems in parallel figures on which to base our estimate. the Gulf area. A majority of them could be An acre of good oyster bottom, properly handled, resolved by the application of well-known and can produce 900 bushels per year under excep­ tested cultivation techniques by the enactment of tionally good circumstances, and in commercial SOund conservation measures based on established practice a yield of 500 bushels can be obtained. data and by the enactment of legislation which For this estimate I have arbitrarily selected a 488 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE figure of 300 bushels per acre per annum. A Florida coast in shallow water. It is a small, bushel of Gulf oysters will yield 4 pounds of flat oyster, up to 2 inches in length, yellow brown completely drained meat. When we assume that in color and most frequently found living inside at least 1,400 square miles of Gulf oyster bottoms of masses of the bread sponge. could be put into production, we find that on a The ecology of the oyster in the Gulf of Mexico sustained yield basis the industry could produce parallels, in many respects, conditions found along in excess of 500,000 tons of oyster-meat each the Atlantic seaboard. Where significant bio­ year. The entire production of the United States logical differences exist between the two areas, now approximates less than 10 percent of this they are due primarily to the higher temperature figure. levels of the Gulf environment. The biological There are at least three other species of oysters and economic problems facing the industry here in the Gulf, all members of the genus Ostrea have their counterpart in other oyster producing (Gunter 1951b). O. equestris is a small species areas. The industry in the South can include occurring discontinuously from Texas to Florida. among its distinctive advantages an unlimited area O. frons has been reported most frequently from for the expansion of cultivated grounds and a southern Florida, but it exists at Pensacola and seemingly inexhaustible supply of seed oysters. has been found off the Texas coast. These two LITERATURE CITED are quite similar; they exist at salinity levels usually above 25 parts per thousand and are most BUTLER, PHILIP A. commonly found at the junction of Gulf and bay 1951. Erosion and the littoral benthos. Shore and Beach 19 (1): 7-11, April. waters. Their setting periods coincide with the ENGLE, JAMES B. spatfall of O. virginica. In areas where one of 1948. Investigations of the oyster reefs of Mississippi, these species occurs with O. virginica they may Louisiana, and Alabama following the hurricane of be confused because of their superficial similarity September 19, 1947. U. S. Dept. Int., Fish and when about an inch in diameter. Large numbers Wildlife Service, Spec. Sci. Rept. No. 59. of O. equestris were actually transplanted in GUNTER, GORDON. 1951a. The West Indian tree oyster on the Louisiana Apalachicola Bay at one time on the mistaken coast, and notes on growth of the three Gulf coast assumption that they were seed of the commercial oysters. Science 113 (2940): 516-517. oyster. In the fall months O. virginica spat 1951b. The species of oysters of the Gulf, Caribbean quickly surpass the spat of Ostrea in length. At and West Indian regions. Bull. Mar. Sci. Gulf and the age of 1 year, O. frons and equestris still Caribbean 1 (1): 40-45. approximate one inch in both length and width, INGLE, ROBERT M. 1951. Spawning and setting of oysters in relation to although rarely they attain a length of 2% inches seasonal environmental changes. Bull. Mar. Sci. in an unusually favorable environment. In­ Gulf and Caribbean 1 (2): 111-135. ternally, both O. frons and equestris are dis­ LANDAU, HELEN, and GAIlrsOFF, PAUL S. tinguished from O. virginica by a variable number 1951. Distribution Of Nematopsis infection of the of denticles on the anterior edges of the valves oyster grounds of the Chesapeake Bay and in other and by the absence of pigment in the muscle waters of the Atlantic and Gulf States. Texas Jour. attachment area. These oysters are larviparous, Sci. 3 (1): 115-130. LOOSANOFF, V. L., and ENGLE, JAMES B. and during the summer months the mantle cavity 1940. Spawning and setting of oysters in Long Island frequently contains large numbers of offspring in Sound in 1937, and discussion of the method for pre­ a manner similar to the European oyster, O. dicting the intensity and time of oyster setting· edulis. Spat of the three oysters, O. frons, O. Bull. U. S. Bur. Fish., 1950,49: 217-255. equestris, and O. virginica were found in abundance --- and NOMEJKO, C. A. on the same cultch at Pensacola during the 1949. Growth of oysters, O. virginica, during different summers of 1949 and 1950. This mutual occur­ months. BioI. Bull. 97 (1): 82-94. MACKIN, JOHN G. rence of the three species in time and space is 1946. A study of oyster strike on the seaside of Virginia. probably infrequent. A third species, O. per­ Virginia Fish. Lab., College of William and MarY, mollis, the sponge oyster, is rather common on the Contr. No. 25, pp. 1-18. GULF OF MEXICO 489

~fACKJN, JOHN G.-Continued PEARSE, A. S., and WHARTON, C. W. 1951. Histopathology of infection of Crassostrea vir­ 1938. The oyster "leech" Stylochus tmmtcus Palombi ginica (Gmelin) by Dermocystidium marinum. Bull. associated with oysters on the coasts of Florida. Mar. Sci. Gulf and Caribbean 1 (1):72-87. Eco!. Monog. 8: 605-655. M:CCONNELL, JAMES N. ST. AMANT, L. S. 1950. Report of Division of Oysters and Water Bot­ 1938. Studies on the biology of the Louisiana oyster toms. Third Bienn. Rept., Dept. Wild Life and Fish., drill Thais floridana haysae Clench. Unpub. thesis State of Louisiana, 1948-49, pp. 309-320. Zoo!. Dept. Louisiana State Univ., and Agric. and M:EJNZEL, R. WINSTON. Mech. College, 108 pp. 1951. Early sexual development and growth of the SEFEROVICH, GEORGE H. American oyster in Louisiana waters. Science 113 1938. A survey of the Louisiana fresh oyster industry, (2947): 719-721. Pt. 1. Louisiana Conserv. Rev., Summer 1938, M: ooRE, H. F. pp.20-23. 1907. Survey of oyster bottoms in Matagorda Bay, SHEARON, W. H., JR. Texas. Rept. U. S. Comm. Fish., 1907, Doc. 610, 1951. Oyster-shell chemistry. Chern. and Eng. News pp.1-86. 29: 3078. --- and POPE, T. E. VATHIS, GEORGE. 1910. Oyster culture experiments and investigations in 1950. Biennial report, Florida State Board of Con­ Louisiana. Rept. U. S. Comm. Fish., 1908, Doc. servation, 1949-50, p. 48. 731,52 pp. Blank page retained for pagination OYSTER REEFS OF THE GULF OF MEXICO 1

By W. ARMSTRONG PRICE, Agricultural and Mechanical College oj Texas

Caswell Grave (1901, 1905) showed that linear, incoming alluvium-laden river waters. They seem ridge-shaped reefs of the common edible estuarine to form chiefly on the more stable bottom areas. oyster now known as Crassostrea virginica develop Along parts of the northwestern coast of peninsular from shell clusters at the more favorable shoreline Florida (28°15'-30°04' N. Lat.), off the mouth of or near-shore positions, growing out into a passing Atchafalaya Bay, Louisiana, and on the south and Current and elongate at right angles to it, then west shores of Marsh Island just west of the bny, branch or curve as the current is deflected by reef reefs of ('rassoslrea virginica occur in the Gulf of extension. This process seems to be valid for the Mexico within 5 or 6 miles from shore. Here, the reefs found in the bordering areas of many bays Gulf waters are locally diluted to the necessary and estuaries. Another class of reefs, elongated brackishness. Parallel with median channels, does not follow Several of the small reefs off Atchafalaya Bay Grave's process of terminal growth into a current have live oysters. Here a large flow of fresh from its flank but forms along n channel and water from the Mississippi enters the Gulf elongates parallel with the dominant currents of through its largest distributary, the Atchafalaya ~he channel. Paired reefs of this type are found River. Off the northwestern coast of Florida In many inner water bodies, as in central San compact limestones form the floor of the shallowly A.ntonio Bay, Texas, and the lower James River, submerged continental shelf. The peninsula has Virginia. The reefs of Atlantic estuarine rivers a widespread artesian water body fed by surface seem usually to be merely elevated ridges on large, waters entering through the extensively fissured Oval to quadrate oyster beds. Those of the Gulf limestones and the many sink holes of the karst COast are not characteristically surrounded by topography. Numerous up-welling springs are ~hickly occupied oyster bottoms except along their reported in the stream mouths along this coast, Ilhmediate flanks. and a few have been reported in the Gulf. '1'he Besides the linear ridge-shaped reefs, many very broad, shallow, gently-sloping continental short ridges, or rounded to oval forms are charted, shelf protects the near-shore waters from breakers lOcally called tow-heads. and surf, producing conditions in the Gulf similar Mudshell dredgers report that some reefs have to a lagoonal environment. The oyster reefs a total depth of some 18 feet or more, in places occur in these quiet waters of lowered salinity. with an interbedded layer or two of mud. Many They are distributed near shore where the artesian reefs of 'l'exas bays reach lengths of 1 or 2 miles, groundwater maps show the 10-foot contour on a few being 4 to 5 miles long. 'l'he longest reef the piezometric surface to be at the shoreline. cOlhplexes known are the two that curve broadly These Gulf reefs include forms that project out across the wide mouth of Atchafalaya Bay, Louisi­ from ashoreline and also broadly curved and offset ~na. The outer, more recently active reef complex forms that areroughlyparallel to the coast. Groups Is 25 miles long with many narrow channels of the latter have jumbled patterns of occurrence. through it. The older is dead and buried by LITERATURE CITED

SeVeral feet of sediment. GRAVE, CASWELL. t T~Ie known oyster reefs of most regions occur in 1901. The oyster reefs of North Carolina. A geological he Inner bays and estuaries in waters neither too and economic study. Johns Hopkins Univ., Circular exposed to heavy wave action nor too fresh from No. 151, 9 pp., April, 1901. 1905. Investigations for the promotion of the oyster and'eontrlbution from the Department of Oceanography of the Agricultural industry of North Carolina. Rept. U. S. Fish Comm., ----M:echanical College of Texas, College Station, Texas, No. 27. 1903,29: 247-341. Washington. 491