ABSTRACTS
(Volume 12, March 2000)



FECUNDITY OF LITOPENAEUS SETIFERUS, FARFANTEPENAEUS AZTECUS AND F. DUORARUM, IN THE SOUTHWESTERN GULF OF MEXICO

Martín Pérez Velázquez and Adolfo Gracia1

Instituto de Ciencias del Mar y Limnologia. Apartado Postal 70-305. México D. F., 04510, México, Phone (5) 622 5779, Fax (5) 616 0748, 1E-Mail: gracia@mar.icmyl.unam.mx

ABSTRACT
Fecundity of white shrimp, Litopenaeus setiferus, brown shrimp, Farfantepenaeus aztecus, and pink shrimp F. duorarum and relationships to gonad weights and total and carapace length were estimated. Ovigerous females were collected in the southern Gulf of Mexico in February, May, August and November 1993. Fecundity was estimated by means of a gravimetric method. The equations relating fecundity to total weight and fecundity to gonad weight were linear in the 3 species. However, an exponential relationship was found between fecundity and carapace length in L. setiferus and F. aztecus. Of the relationships examined, gonad weight was considered a more precise indicator of fecundity. Fecundity estimates ranged from 70,647 to 558,270 eggs for 0.203 and 5.639 g gonad weight of L. setiferus, from 23,298 to 494,292 eggs for 0.061 to 2.561 g gonad weight in F. aztecus and from 138,618 to 225,543 eggs for 0.120 to 0.998 g gonad weight in  F. duorarum.
 

FEEDING HABITS OF JUVENILE LANE SNAPPER LUTJANUS SYNAGRIS FROM MISSISSIPPI COASTAL WATERS, WITH COMMENTS ON THE DIET OF GRAY SNAPPER LUTJANUS GRISEUS

James S. Franks and Katherine E. VanderKooy

The University of Southern Mississippi, Institute of Marine Sciences, Gulf Coast Research Laboratory, 703 East Beach Drive, Ocean Springs, MS 39564

ABSTRACT
Stomach contents analysis was used to quantitatively describe the diets of juvenile lane snapper, Lutjanus synagris, and juvenile gray snapper, Lutjanus griseus, from the northern Gulf of Mexico. Juvenile snapper were collected by trawling at two estuarine, deep channel sites in Mississippi coastal waters from September 1996 to January 1997. Lane snapper (n = 53) and gray snapper (n = 12) both consumed a variety of prey organisms, but primary prey were amphipods, decapods (shrimp and crabs), and fishes. The most important prey items for lane snapper based on percent Index of Relative Importance (%IRI) were shrimp remains (44%IRI), the shrimp Latreutes parvulus (23%IRI) and fish remains (13%IRI). Fishes of the genus Anchoa (43%IRI), shrimp remains (21%IRI) and the amphipod Corophium sp. (13%IRI) dominated the gray snapper diet.  Intraspecific comparisons of lane snapper diet revealed significant overlap between collection sites, seasons and fish sizes.
 

POSSIBLE SUSTAINED EFFECTS OF HURRICANES OPAL AND ERIN ON THE MACROBENTHOS OF NEARSHORE HABITATS WITHIN THE GULF ISLANDS NATIONAL SEASHORE

Chet F. Rakocinski, Sara E. LeCroy, Jerry A. McLelland and Richard W. Heard

The University of Southern Mississippi, Institute of Marine Sciences, Gulf Coast Research Laboratory, 703 East Beach Drive, Ocean Springs, MS 39564

ABSTRACT
Possible sustained effects of hurricanes Opal and Erin on the macrobenthos of nearshore habitats of the Florida district of Gulf Islands National Seashore were assessed. Pre-hurricane macrobenthic data originating mainly from a large-scale faunal inventory conducted during 1993 were compared with posthurricane data collected one year after the 1995 disturbances. Nearshore habitats examined included both exposed and protected sand beaches, as well as grassbed and lagoon sites. Within one year after the hurricanes, few faunal effects could be discerned at exposed beach sites, whereas possible faunal effects were apparent in protected nearshore habitats. Abundances of 4 major epifaunal crustacean taxa were notably lower one year after the hurricane disturbances. Assemblages of relatively stable nearshore habitats appeared to be more diverse but less resilient than assemblages of unstable nearshore habitats, possibly reflecting the extent of disturbance normally experienced by assemblages within those habitats.
 

OCEANIC AND NERITIC ICHTHYOPLANKTON AT THE EDGE OF THE CONTINENTAL SHELF IN THE SOUTHERN GULF OF MEXICO

César Flores-Coto, Fernando Flores-Hernández, Faustino Zavala-García, Virgilio Arenas-Fuentes, María Adela Monreal-Gómez and David Alberto Salas-de-León

Instituto de Ciencias del Mar y Limnología. Universidad Nacional Autónoma de México. Cd. Universitaria. Apdo. Postal 70-305. México 04510 D.F.

ABSTRACT
Oceanic and neritic ichthyoplankton were examined at a single sampling site at the edge of the continental shelf in the southern Gulf of Mexico. Double oblique tows were made with a 60 cm Bongo net fitted with 505 µm mesh netting. Collections were taken every 2 hours over a 24 h period during spring, summer and fall of 1992. Fish larvae were described as either oceanic or neritic depending upon adult lifestage habitat. The larvae of 59 taxa were collected in spring (50 oceanic, 9 neritic), 53 in summer (26 oceanic, 27 neritic) and 55 in fall (22 oceanic, 33 neritic). Larvae were least abundant during spring and most abundant in fall, for both oceanic and neritic taxa. Highest abundances of larvae were collected at night indicating increased gear avoidance during daylight.
 

THE AMERICAN NERITIC COPEPOD CTENOCALANUS HERONAE VEGA-PÉREZ AND BOWMAN (CALANOIDA) IN THE GULF OF MEXICO, WITH COMMENTS ON THE TAXONOMY OF THE GENUS

E. Suárez-Morales1 and A. León-Oropeza2

1El Colegio de la Frontera Sur (ECOSUR), A.P. 424, Chetumal, Quintana Roo 77000, Mexico
2Instituto Mexicano del Petróleo, A.P. 14-805, Mexico, D.F. 07730, Mexico

ABSTRACT
A single adult female specimen of the calanoid copepod Ctenocalanus heronae Vega-Pérez and Bowman was collected during a zooplankton survey carried out in February 1997 in Campeche Sound, the central-southeastern portion of the Gulf of Mexico. The taxonomy of the genus Ctenocalanus Giesbrecht is still unclear. Characters used to separate the species have been considered rather subtle. In this paper the taxonomic illustrations of the specimen collected are accompanied by a revision of the taxonomic features commonly used to identify the species. New, previously overlooked characters such as the cephalosome/urosome ratio, the shape of the 5th legs and particularly the structure of legs 1 and 2, are presented and might turn out to be useful to separate some of the species. This record of C. heronae in the Gulf of Mexico also represents the first reported occurrence of the genus in the Northwestern Tropical Atlantic and increases remarkably the known distribution of the species from the 24°S to the 18°N.
 

RELATIONSHIP BETWEEN PEA CRAB (PINNOTHERES MACULATUS) PARASITISM AND GONAD MASS OF THE BAY SCALLOP (ARGOPECTEN IRRADIANS)

Paul A. X. Bologna1 and Kenneth L. Heck, Jr.

1Rutgers University Marine Field Station, 800 Great Bay Blvd., c/o 132 Great Bay Blvd., Tuckerton, NJ 08087, (609) 296-5260 x255, bologna@imcs.rutgers.edu
University of South Alabama, Department of Marine Science, Dauphin Island Sea Lab, P.O. Box 369, Dauphin Island, AL 36528

ABSTRACT
We investigated the prevalence of pea crabs (Pinnotheres maculatus) in bay scallops (Argopecten irradians) from 1994 through 1996 in a scallop population from St. Joseph Bay, Florida. We also assessed their impacts on scallop reproductive potential. Our results showed that prevalence in bay scallops varied between 0 and 20% and were extremely low during 1996 (<2%). Comparing Gonadal-Somatic Indices (GSI) between infested and non-infested bay scallops in samples assessed the impact of pinnotherid parasitism. Results showed that GSI was significantly reduced in infested individuals compared to non-infested individuals of the same size range (t12 = 2.3, P <0.04). These results suggest that P. maculatus infestation may lower the reproductive potential of individual scallops, but the low rates of parasitism may only minimally impact the host population.
 

LUNAR PERIODICITY AND BIOLUMINESCENCE OF SWARMING ODONTOSYLLIS LUMINOSA (POLYCHAETA: SYLLIDAE) IN BELIZE

Gary R. Gaston1 and Jennifer Hall2

1Biology Department, University of Mississippi, University, MS 38677 USA
2 International Zoological Expeditions, South Water Caye, Stann Creek District, Box 231, Dangriga, Belize

ABSTRACT
Few benthic polychaetes have the notoriety of the bioluminescent "glowworm", Odontosyllis luminosa San Martin, 1990, that inhabits soft-sediment habitats of the Caribbean. A few nights after a full moon, apparently during most months of the year, a most unusual phenomenon occurs. Female glowworms leave the sediments, swim toward the water surface, and release a bioluminescent egg mass, causing a bright green glow near the water's surface. The female's luminescence attracts the males, which also glow briefly. The tiny worm has a bright glow, and viewing it is a favorite pasttime in the Caribbean. Over 50 years ago investigators linked the bioluminescence of Odontosyllis with the mysterious lights described by Christopher Columbus in November 1492. Reproduction of 0. luminosa peaks during summer, when the water's surface is brilliantly lit with females for 10-15 min on the first few evenings following a full moon. Spent females apparently survive to spawn again. They return to the sediments to build new tubes after spawning.