8 March 2012 Bioeconomic analysis of the area impacted by a sea bream farm in Gran Canaria, Spain Rabassó-Krohnert1, Miguel and Hernández, Juan M. In last decades, global aquaculture production has increased, diversified, intensified and technologically improved. Current and forecast production figures (FAO 2010) show its huge potential as an income-generating activity and its essential role in food security and poverty mitigation. Nevertheless, aquaculture production includes some negative effects on the surrounding area where the farm is located, such as effluents (e.g., food discards, nutrients, metals, other chemical products), escapes or attraction of foreign species, competition with other activities, and visual impact to the local population. In some instances, the combined effects— exacerbated by inadequate farm management— may result in serious ecological and socioeconomic consequences (e.g., destruction of natural habitats or disease epidemics). These externalities or undesirable effects have led to increased concern or distrust about the sustainability of marine aquaculture in net pens in technologically advanced societies. Enrichment of organic matter in the environment derived from emissions from marine net-pens has attracted the interest of researchers. Many such studies use models to quantify biophysical mechanisms regulating material releases, such as metabolic processes related to the emissions of organic matter and other nutrients, dispersion of these materials, and impacts on the natural environment. The farm is normally considered to be a static system. Proposed models do not consider changes in management strategies that may influence the ecological impact of emissions. Fish Production and Material Emissions Model The research team of aquaculture economics and management of the University of Las Palmas de Gran Canaria (Spain) has developed a bioeconomic model based on simple biological and physical relationships. The model estimates the mass of emissions from a marine fish farm, the dispersion of those emissions, and their effect on the surrounding area. Annual production, harvesting size, Fig. 1. A bioeconomic model for a marine net-pen system. and other management factors are included as variables in the model. This methodology allows estimation of the economic results and environmental impacts derived from alternative management decisions on the farm and may help farm owners, government regulators, and local citizens consider the economic and environmental effects of production. The bioeconomic model is assembled from separate modules that integrate biological, physical, economic, and managerial elements in the production and environmental impact from a marine aquaculture farm (Fig. 1). Biophysical components of the model are represented in modules located on the right side of Figure 1. The biomass growth module provides information on fish size throughout the culture period, depending on fish weight and water temperature. The amount of food supplied during the growth period is estimated in the food supplied module, which is also determined by fish size and water temperature. The nutrient balance module estimates the flow of nitrogen, phosphorus, and organic
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