Abstract
The Marine Strategy Framework Directive intends to adopt ecosystem-based management for resources, biodiversity and habitats that puts emphasis on maintaining the health of the ecosystem alongside appropriate human use of the marine environment, for the benefit of current and future generations. Within the overall framework of ecosystem-based management, ecosystem models are tools to evaluate and gain insights in ecosystem properties. The low data availability and complexity of modelling deep-water ecosystems has limited the application of ecosystem models to few deep-water ecosystems. Here, we aim to develop an ecosystem model for the deep-sea and open ocean in the Azores exclusive economic zone with the overarching objective of characterising the food-web and ecosystem structure of the ecosystem. An ecosystem model with 45 functional groups, including a detritus group, two primary producer groups, eight invertebrate groups, 29 fish groups, three marine mammal groups, a turtle and a seabird group was built. Overall data quality measured by the pedigree index was estimated to be higher than the mean value of all published models. Therefore, the model was built with source data of an overall reasonable quality, especially considering the normally low data availability for deep-sea ecosystems. The total biomass (excluding detritus) of the modelled ecosystem for the whole area was calculated as 24.7 t km-². The mean trophic level for the total marine catch of the Azores was estimated to be 3.95, similar to the trophic level of the bathypelagic and medium-size pelagic fish. Trophic levels for the different functional groups were estimated to be similar to those obtained with stable isotopes and stomach contents analyses, with some exceptions on both ends of the trophic spectra. Omnivory indices were in general low, indicating prey speciation for the majority of the groups. Cephalopods, pelagic sharks and toothed whales were identified as groups with key ecological roles in the ecosystem. Due to concerns on the use of ecosystem models with low confidence in exploring management decisions and ecological theories, the current version of this model should only be use with caution until biomass estimates are validated with survey data or the model is fitted to time
Highlights
The European Union (EU) Marine Strategy Framework Directive (MSFD) defines the marine environment as “a precious heritage that must be protected, preserved and, where practicable, restored with the ultimate aim of maintaining biodiversity and providing oceans which are clean, healthy and productive (EU Directive 2008/56/EC).” The MSFD requires member states to adopt an ecosystem approach to management of human activities that puts emphasis on maintaining the health of the ecosystem alongside sustainable use of marine goods and services
Large scale circulation is dominated by the eastward-flowing Gulf Stream, which forms a current system with many unstable eddies and meanders, the cold North Atlantic Current in the north, and the warm Azores Current in the south (Santos et al, 1995; Alves and Verdière, 1999; Johnson and Stevens, 2000; Bashmachnikov et al, 2009)
An ecosystem model for the Azores exclusive economic zone (EEZ) using 1997 as the reference year was built using various data sources. This reference year seemed appropriated for the purpose of the study since it will allow for model validation with data collected afterwards, but it represents a snap-shop of the ecosystem state
Summary
The European Union (EU) Marine Strategy Framework Directive (MSFD) defines the marine environment as “a precious heritage that must be protected, preserved and, where practicable, restored with the ultimate aim of maintaining biodiversity and providing oceans which are clean, healthy and productive (EU Directive 2008/56/EC).” The MSFD requires member states to adopt an ecosystem approach to management of human activities that puts emphasis on maintaining the health of the ecosystem alongside sustainable use of marine goods and services. The MSFD requires member states to adopt an ecosystem approach to management of human activities that puts emphasis on maintaining the health of the ecosystem alongside sustainable use of marine goods and services. MSFD encourages the implementation of an ecosystem-based approach to fisheries management that would take into account the environmental impacts of fishing. The EU’s Common Fisheries Policy (CFP) still is a single-species based fisheries management policy, implementing total allowable catches for target species. It has been criticized for failing in delivering longterm sustainability of the fish stocks and reducing the adverse effects of fisheries on the whole ecosystem (Beddington et al, 2007; Khalilian et al, 2010; Villasante et al, 2012).
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