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International audience; The ecosystem model OSMOSE-WFS was employed to evaluate natural mortality rates and fishing scenarios for Gulf of Mexico (GOM) red grouper (Epinephelus mono). OSMOSE-WFS represents major high trophic level (HIT.) groups of species of the West Florida Shelf, is forced by the biomass of plankton and benthos groups, and has a monthly tin-se step. The present application of the model uses a recently developed 'stochastic mortality algorithm' to resolve the mortality processes of HTL groups. OSMOSE-WFS predictions suggest that the natural mortality rate of juveniles of GOM red grouper is high and essentially due to predation, while the bulk of the natural mortality of adult red grouper results from causes not represented in OSMOSE-WFS such as, presumably, red tides. These results were communicated to GOM red grouper stock assessments. Moreover, OSMOSE-WFS indicate that altering the fishing mortality of GOM red grouper may have no global impact on the biomass of the major prey of red grouper, due to the high complexity and high redundancy of the modeled system. By contrast altering the fishing mortality of GOM red grouper may have a large impact on the biomass of its major competitors. Increasing the fishing mortality of red grouper would increase the biomass of major competitors, due to reduced competition for food. Conversely, decreasing the fishing mortality of red grouper would diminish the biomass of major competitors, due to increased predation pressure on the juveniles of the major competitors by red grouper. The fishing scenarios that we evaluated may have slightly different impacts in the real world, due to some discrepancies between the diets of red grouper and its major competitors predicted by OSMOSE-WFS and the observed ones. Modifications in OSMOSE-WFS are suggested to reduce these discrepancies. (C) 2015 Elsevier B.V. All rights reserved.

The spatial dynamics of the red grouper Epinephelus morio plays a fundamental role in the fishery management on the Campeche Bank, where it is overfished. The objective of this study was to characterize the spatial dynamics of this population. We used a dynamic model of spatial distribution to estimate population movement rates between adjacent areas. The model was applied using information on catch per unit effort and length-frequency distributions for the Mexican mid-sized fleet that operated in the area in the period 1973-1977. These data were chosen to ensure that the information would reflect the condition of the resource before overfishing. It was possible to quantify the spatial dynamics of the red grouper and the results were consistent with previously known movement patterns. The results showed different movement rates and temporal patterns of movement for different population sectors. The spawning aggregations and the seasonal upwelling occurring in the eastern part of the Bank were considered as key factors influencing the pattern of population movements. La población del mero rojo Epinephelus morio del Banco de Campeche está sobreexplotada. La dinámica espacial del mero juega un papel fundamental en la gestión de la pesquería. El objetivo de este estudio fue caracterizar la dinámica espacial de la población del mero en el Banco de Campeche. Se utilizó un modelo dinámico de distribución espacial para estimar tasas de movimiento poblacional entre áreas adyacentes. El modelo se aplicó con información de las capturas por unidad de esfuerzo y de distribuciones de frecuencias de longitud provenientes de la flota mediana mexicana que operó en la zona de 1973 a 1977. Estos datos fueron elegidos para asegurar que la información reflejara el estado del recurso antes de la sobrepesca. Fue posible cuantificar la dinámica espacial del mero y los resultados concordaron con patrones de movimientos conocidos anteriormente. Los resultados mostraron distintos patrones temporales de movimiento para los diferentes sectores de población. Se considera que las agregaciones de desove y la surgencia estacional que ocurre en la parte oriental del Banco son factores clave que influyen en el patrón de los movimientos de población.