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Exploring the Gulf of Mexico as a large marine ecosystem through a stratified spatial model Vidal Hernandez, Laura

Abstract

The major fishing areas in the world consist of large shelf and adjacent areas, which maybe called Large Marine Ecosystems (LME). LME usually consist of a maze of subsystems, and studies on their various features and resources are usually compartmentalised by institutional and political entities. As a consequence, we know little about the integrated behaviour of these systems and the large-scale impact of economic activities. This research about the Gulf of Mexico LME integrates information from a variety of subsystems to construct an overall, spatially stratified mass-balance model using the Ecopath approach. Temporally and spatially explicit models were run using Ecosim and Ecospace to simulate diverse scenarios representing current and hypothetical changes in fishing effort. Maturity criteria suggest that the Gulf of Mexico was, in the 1980s and 1990s, a highly mature and relatively stable system, relatively resilient to impacts by the fisheries. However, the biomass of some groups were severely affected directly or indirectly (i.e., by-catch) and the landings of some groups are decreasing. Resources highly affected by the fisheries showed a potential for recovery, but tended towards new levels of abundance. Overall, the catches will not increase as greater fishing effort is applied. Spatial modelling highlighted the strong coupling nature between pelagic and demersal components of the ecosystem, and between the inshore and offshore subsystems. Estuaries are important to the integrity of the system. The design of Marine Protected Areas should be assessed on a per-species basis taking into account ecosystem information, because reduction of fishing mortality on some predators will affect the biomass of their prey species. Stratified spatial modeling was a useful tool to explore the dynamics of the Gulf of Mexico Large Marine Ecosystem.

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