Oceanic and Neritic Ichthyoplankton at the Edge of the Continental Shelf in the Southern Gulf of Mexico

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

Why the Mexican Oyster Fishery in the Gulf of Mexico Is Underdeveloped?

The Mexican Oyster fishery in the Gulf of Mexico annually produces only 50,000 MT, 95% of Mexico oyster production. Oyster production has fallen drastically in most coastal lagoons, this decline has been attributed to factors as overfishing, mismanagement of natural oyster beds, environmental degradation and lagoons pollution. This work proposes strategies for oyster fishery management on Gulf of Mexico littoral. In order to achieve this goal oyster fishery diagnose for Tamaulipas, Veracruz, Tabasco and Campeche states were made for evaluation of ecological, economics, legal and social aspects trough information sources as statistical yearbooks, databases, and published information relative to regional oyster fishery, simultaneously visits to landing places where made and inquiries to production units, directives, fishermen and decision makers were done. Collected information was grouped and analyzed with SWOT analysis. Oyster fishery is carried on in 20 coastal ecosystems where works 51 production units with 2,955 active oyster fishermen. In every visited site were observed water pollution, coastal deforestation and or overfishing. National and international oysters markets cannot grow for several reasons including sanitary quality; there are no efficient models for oyster beds administration, no infrastructure for give oyster products additional value. Some of the strategies for solve these difficulties are, to make local diagnosis and promote social organization for control of water quality, market research for oyster products and laboratory seed production, register efficiently and responsibly catch statistics, to make official norms on size catch, fishing gear, fishing, reception, packing, commercialization, culture techniques, and cultured oyster sizes, these strategies and other programs may permit sustainable and biotechnological development in oyster fishery.Keywords: Fisheries Economics, Fish and Aquaculture Sectors Development, Fisheries Dynamic

Ecología alimentaria de camarones peneidos en los sistemas lagunar-estuarinos tropicales

Shrimps are an important resource in coastal lagoons because they use these ecosystems for their development. Although some authors classified the Penaeidae as detritivores, it was shown that their diet comprises a greater variety of food items. Many authors had reported that shrimps have a diversified diet that includes several elements of the benthic community. This review describes the feeding ecology of the shrimps in coastal lagoon-estuarine systems, with emphasis on the following: the effect of the environment on the shrimps’ natural food; techniques for identification of items in shrimps gut contents and stable isotope compositions; consideration of the importance of plants and small animals in the diet; and the effect of mangroves and lagoon-estuarine system on feed ecology. The abundance of penaeid appears to be primarily affected by stochastic variations in environmental factors. However, it has been found that the relationships between macroinfauna, macrofauna and environmental conditions in a tropical estuary may result in more interactions with their predators than a direct response to physical-chemical factors. The combination of the study of shrimps guts contents and stable isotopes shows a composition and seasonal variation in the diets, as well as the source of carbon and nitrogen contained in the shrimp’s tissues. In general, the studies suggest that herbaceous detrital inputs to the food web are dominant in supporting shrimps in salt marshes, but phytoplankton or benthic algae may be equally or more important food sources.Los camarones son recursos importantes en las lagunas costeras porque utilizan el ecosistema para su desarrollo. Aunque algunos autores clasifican a los camarones Penaeidae como detritívoros, se encontró que su dieta comprende una gran variedad de ítems. Muchos autores han reportado que los camarones tienen una dieta diversificada que incluye varios elementos de la comunidad béntica. Esta revisión describe la ecología alimentaria de los camarones en los sistemas lagunar- estuarinos, con énfasis sobre los siguientes aspectos: el efecto del ambiente sobre el alimento natural de los camarones; técnicas para la identificación de ítems en los contenidos estomacales de los camarones y la composición de isotopos estables; consideraciones sobre la importancia de las plantas y pequeños animales en la dieta; y el efecto de los manglares y sistema lagunar-estuarino sobre la ecología alimentaria. La abundancia de peneidos parece ser principalmente afectado por variaciones estocásticas en factores ambientales. Sin embargo, se ha encontrado que las relaciones entre macroinfauna, macrofauna y condiciones ambientales en un estuario tropical pueden resultar en más interacciones con sus depredadores que una respuesta directa a factores fisico-químicos. La combinación del estudio de los contenidos estomacales e isotopos estables muestra la composición y las variaciones estacionales en las dietas, también, como la fuente de carbón y nitrógeno contenida en el tejido de los camarones. En general, los estudio sugieren que la entrada de detritus herbáceos al tejido de alimentos son dominantes en la alimentación de los camarones en las marismas, pero el fitoplancton o las algas bénticas pueden ser fuentes de alimento igual o más importantes que los detritus herbáceos

Latitudinal changes of eufhasiid assemblages related to the morphological variability of the sound scattering layer along Baja California, Octuber 1994

Latitudinal changes in the euphausiid assemblages were compared to the morphological structure (size and compactness) of the sound scattering layer (SSL) during ten 24-h surveys made in October 1994 along the west coast of Baja California, México. During October, upwelling was found in the northern area from Punta Eugenia (28°N) to Ensenada (30°N) dominated by temperate species from the California Current System. In the southern sector of the peninsula, a northward movement of tropical waters transports a tropical zooplankton assemblage near Bahia Magdalena (24°N). The aggregation and the dispersion of the whole SSL (plankton and nekton) were investigated using a single beam vertical echosounder, Simrad EY-200, working at 200 kHz and the Hydro Acoustic Data Acquisition System (HADAS) that estimates patch variables of density and compactness. The size and shape of the SSL were obtained from the echogram visualization. The euphausiid species composition was obtained using an Isaacs-Kidd midwater trawl, bongo nets, and opening-closing nets. At Ensenada and Punta Eugenia, an area inhabited by a temperate euphausiid assemblage, large and dense SSLs were recorded over the continental shelf (mean sizes were 10-km and 7-km long with mean compactness of 15% and 19%). These regions were dominated by the neritic species Nyctiphanes simplex and the temperate species Nematoscelis difficilis, Euphausia pacifica, and Thysanoessa spinifera. In the southern area, a tropical euphausiid assemblage, dominated by Euphausia eximia, E tenera, and E. distinguenda, inhabits smaller and dispersed SSLs (mean size 5-km long and 11% compactness) located in the offshore area. The euphausiid biomass of the most abundant species indicated, N. simplex and N. difficilis, had their highest standing stock in the north (393 and 643 mg C 1000 m-3), with E. eximia in the southern area (186 mg C 1000 m-3). Euphausiid assemblage development in different biological environments, is evidenced by SSL morphology along the west coast of Baja California during autumn, is caused by strong latitudinal changes in physical oceanography that affect the biological interactions in each region

Hydroacoustical Evidence of Autumn Inshore Residence of the Pelagic Crab Pleuroncodes Planipes at Punta Eugenia, Baja California, Mexico.

A previously published conceptual model of the life history of the red crab Pleuroncodes planipes (Galatheidae) (Stimpson, 1860) reports that the center of distribution of this micronektonic crustacean is located at Bahía Magdalena, on the southwest coast of Baja California (25 to 24°20’ N). During spring, the highest abundance of mature females is found nearshore with abundance peaks of larval stages during February and March. Larval drift offshore is associated with a strong Ekman transport system, and the virtual disappearance of the adult pelagic and benthic population from the neritic region at Bahía Magdalena in late summer and autumn can be explained by an inshore-offshore migration. However, huge benthic-pelagic concentrations of this crustacean occur nearshore during autumn at Punta Eugenia (27 to 29° N). Circadian cycles of the spatial distribution of these aggregations were recorded with a single beam echosounder Simrad EY-200 (200 kHz) along Baja California during October 1994, March, June, and October 1995, and March and June 1996. Data obtained from Isaacs-Kidd midwater net trawls during October 1994 along Baja California were used to identify the red crab aggregations using hydroacoustics. The target strength of the red crab ranged between –50 and –54 dB. The largest aggregations were found in Bahía Magdalena during summer (June 1995 and 1996; 24 to 25°N) and nearshore at Punta Eugenia (27 to 28° N) during autumn and spring (March 1995 and 1996, October 1994 and 1995). These observations suggest that the conceptual model of inshoreoffshore adult population migration is valid for Bahía Magdalena, but apparently not for Punta Eugenia at least Turing autumn. At Punta Eugenia an abrupt change in the orientation of the shoreline enhances upwelling events and promotes semipermanent eddies, thus supporting the inshore residence of this adaptive omnivorous-detritivorous crustacean

Seasonal hydro-acoustical observations of small pelagic fish behaviour in Bahía Magdalena, Mexico

Bahía Magdalena, located on the southwest coast of Baja California Sur, Mexico (24°20'N, 111°30'W), is an important area for fishing of small pelagic fish. The Pacific sardine (Sardinops caeruleus) comprises more than 75 % of the total catch in the bay. Hydro-acoustic surveys were carried out in this bay using a single-beam echo sounder, Simrad EY-200 (200 kHz), during three oceanographic surveys (March, July and December 1996). Results demonstrate that in July more than 75 % of the positive observations (those echograms with more than 100 echoes in the volume sampled) and most of the echo counts were recorded in the 5–10-m-deep layer. During March and December, positive echograms in the upper stratum were below 50 % and most of the echo counts were detected in the lower layer (10–20 m). These results were related to the availability of Pacific sardine to the commercial fleet, specifically to the capture-per-unit-effort. Results support the hypothesis that sardines migrate during late summer and autumn and that a new recruitment occurs during the winter within the bay

Macrocrustáceos incrustantes en el Parque Nacional Sistema Arrecifal Veracruzano: biodiversidad, abundancia y distribución Encrusting macrocrustaceans in the Parque Nacional Sistema Arrecifal Veracruzano: biovidersity, abundance and distribution

Se analizaron la biodiversidad y los patrones de abundancia y distribución de los macrocrustáceos incrustantes, así como los registros nuevos y las ampliaciones de su ámbito geográfico. Fueron geoposicionados 6 sitios de muestreo en el parque arrecifal tomando en consideración la distancia de la costa, la geomorfología del ambiente arrecifal y la influencia de los contaminantes. En cada sitio se fijó una estructura de PVC con 6 placas artificiales entre los 8 y los 10 m de profundidad para la recolección de los macrocrustáceos incrustantes. Fueron identificados 8 161 organismos pertenecientes a 5 órdenes, 19 familias y 26 especies. De acuerdo con los valores de abundancia específica, dominaron el balano Amphibalanus amphitrite, seguido del tanaidáceo Leptochelia forresti y los anfípodos Ampithoe ramondi, Ampithoe sp. y Ericthonius brasiliensis. En este estudio se reconocieron 3 registros nuevos y 7 ampliaciones del ámbito geográfico. Finalmente, se comprobó la presencia de 2 grupos de macrocrustáceos, uno ubicado en el grupo norte y otro en el grupo sur del sistema arrecifal.<br>The biodiversity of encrusting macrocrustacean, abundance and spatial distribution patterns, as well as new records and range extensions were analyzed. Six sites were positioned in the reef park considering distance to the coast, the geomorphology of the reef environment and the influence of pollutants. At each site a PVC structure was placed with 6 artificial plates at a 8-10 m depth to collect the encrusting macrocrustaceans. A total of 8 161 organisms was collected that belong to 5 orders, 19 families and 26 species. The most abundant species was the cirriped Amphibalanus amphitrite, followed by the tanaid Leptochelia forresti and the amphipods Ampithoe ramondi, Ampithoe sp., and Ericthonius brasiliensis. Three new records and 7 range extensions were found in this study. Finally, the presence of 2 different groups of macrocrustaceans was detected, one in the southern part and another in the northern portion of the reef system