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Spatial distribution, density and population structure of the Cortes geoduck, Panopea globosa in the Central Gulf of California

The geoduck clam Panopea globosa is a commercially important species because of its high market demand, particularly in Asia. The aim of this study was to analyze the effect of chlorophyll concentration, sea surface temperature, turbidity, and tidal cycle on density estimation, spatial distribution, and population structure of P. globosa in the central Gulf of California using remote sensing and field survey data. Specimen collections were conducted through semiautonomous diving from November 2009 to January 2011. A total of 10,114 clams were obtained with an average weight of 997 ± 212 g (80% ≥ 800 g), and an average length of 132 ± 12.5 mm (80% of all collected clams exceeded 130 mm, the minimum legal fishing size). P. globosa distribution displayed significant differences among the 3 patches of high density in the study area, but density was poorly correlated with the environmental factors.La almeja de sifón Panopea globosa es una especie de importancia comercial por su alta demanda en el mercado de Asia. El propósito de este estudio fue analizar el efecto de la concentración de clorofila, temperatura superficial del mar, turbidez y ciclo de mareas en la estimación de la densidad, distribución espacial, y estructura poblacional de la almeja P. globosa en la región central del Golfo de California usando datos de satélite y observaciones de campo. Los organismos fueron recolectados mediante buceo semi-autónomo, entre noviembre 2009 y enero 2011. Se recolectaron un total de 10.114 almejas con un peso promedio de 997 ± 212 g (80% ≥ 800 g), y una longitud promedio de 132 ± 12,5 mm (80% de los organismos recolectados estuvieron por arriba de 130 mm, que es la talla mínima legal de pesca). La densidad de P. globosa del área de estudio presentó diferencias significativas entre las 3 agregaciones identificadas con alta densidad, pero la densidad no estuvo correlacionada con ninguno de los factores ambientales considerados

Water temperatures In the Gulf Of California in may and june 1996 and their relation to the capture of giant squid (Dosidicus gigas D'Orbigny, 1835)

The relation between water temperature and the capture of giant squid in the Gulf of California was analyzed. Data were collected in May and June 1996 at 60 stations. Each fishing session lasted 30 minutes, and an average of 100 organisms per 0.5º · 0.5º square were caught. The hypothesis was that if water temperature is a factor affecting squid movement, we can infer that the catch of squid is successful in an optimum temperature range. With both exploratory and correlation analyses, the conclusion was that the hypothesis was true

Multi-model inference for growth parameter estimation of the Bigeye Croaker Micropogonias megalops in the Upper Gulf of California

Bigeye Croaker (Micropogonias megalops) is caught in the Upper Gulf of California (UGC) by local community fishermen from San Felipe in Baja California, Golfo de Santa Clara and Puerto Peñasco in Sonora, Mexico. For the sustainable management of this fishery, it is necessary to understand its growth cycle. We modeled the individual growth of M. megalops from the UGC using 4 growth models: von Bertalanffy growth model (VBGM), Logistic, Gompertz and Schnute. The parameters of each model and their confidence intervals (CI) were computed using the maximum-likelihood method. The best-fit model was selected using Akaike´s information criterion (AIC). According to AIC, the VBGM model fit best the data. The parameter estimated and CI were: 1) mean asymptotic length (L∞) in males 429 mm total length TL (CI 426-432 mm TL) and in females 461 mm TL (CI 457-464 mm TL); 2) the growth coefficient (k) in males 0.419 (CI 0.412-0.426) and in females 0.377 (CI 0.370-0.384). In conclusion, the VBGM adequately described the individual mean growth for M. megalops in the UGC.El chano norteño Micropogonias megalops es capturado en el Alto Golfo de California (AGC) por comunidades de pescadores locales de San Felipe en Baja California, El Golfo de Santa Clara y Puerto Peñasco en Sonora, México. Para la administración sustentable de la pesquería, es necesario conocer el crecimiento de la especie. Se calculó el crecimiento individual de M. megalops del AGC usando 4 ecuaciones: la ecuación de crecimiento de von Bertalanffy (ECVB), Logístico, Gompertz y Schnute. Los parámetros de cada modelo y los intervalos de confianza (IC) fueron calculados usando el método de máxima verosimilitud. El mejor modelo se seleccionó con el criterio de información de Akaike (CIA). Según el CIA, la ECVB es la que mejor describe los datos. Los parámetros y sus IC fueron: 1) Longitud asintótica promedio (L∞) en machos 429 mm de longitud total LT (IC 426-432 mm LT) y en hembras 461 mm LT (IC 457-464 mm LT); 2) el coeficiente de crecimiento (k) en machos 0,419 (IC 0,412-0,426) y en hembras 0,377 (IC 0,370-0,384). En conclusión, la ECVB describe adecuadamente el crecimiento individual de M. megalops en el AGC

THE RELATIONSHIP OF PLASMA pH AND ANION PATTERN TO MERCURIAL DIURESIS

Summer mortalities have been observed in French shellfish areas (including Normandy) since 1994, but origin of this syndrome remains unclear and is suspected to be caused by a combination of several interacting extrinsic (biotic and abiotic) and intrinsic (genetic, physiological, immunological) factors. The French research program, MOREST aimed to identify the origin of oyster summer mortality along the French coast, focusing on the interactions between oysters, their pathogens, and the environment. The present study analyzed spatio-temporal variation in growth, condition and mortality in spat, and half-grown and market-sized oysters reared from February 2000 to October 2003 at six stations within two different areas in the Bay of Veys, Normandy: Grandcamp (GR), and Gefosse (GE) that is more estuarine. These biological parameters were compared between years, age groups, and areas. Results showed that shell growth was significantly lower in the station highest on the shore and similar in the four other sites, whereas tissue growth and condition index were higher in the Gefosse area. Results also showed large interannual, interage, seasonal and spatial variation in oyster mortality. In 2001, mortalities were markedly higher than in other years and all batches and sites were affected by high mortality rates. Moreover oysters suffered much higher mortalities in their second and third years than as spat, and the difference between age classes was accentuated when mortality was high. Increases in mortality occurred when the gonad was most extensively developed and the peak coincided with the spawning and postspawning periods when gonad volume began to decrease. Spatial variability showed that mortality was higher in Gefosse than Grandcamp. Chronology and spatial variations in mortality highlighted the importance of timing and confirmed that mass mortalities may be closely linked to reproduction. The risk seems to be associated with high reproductive effort, partial spawning, and/or slow gonad resorption. Spatial variation also suggests that the study sites experience varying degrees of stress caused by biological changes and probable differences in water quality reflecting the influence of freshwater input in Gefosse where mortality is higher