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Development of monotoring quidelines and modelling tools for environmental effects from Mediterranean aquaculture



In northern Europe, Canada, Tasmania and recently in Chile, considerable efforts have been made to assess interactions between aquaculture and the environment. Most models, guidelines, monitoring procedures, and environmental quality standards are, however, directed toward salmon farming. Although scientific knowledge on the impacts of salmonid farming has progressed substantially, very little is known of fish farming impacts in the Mediterranean. In the last decade aquaculture of sea bass (Dicentrarchus labrax) and gilthead sea bream (Sparus auratus) has experienced a period of exponential growth in the Mediterranean region. This process needs to be controlled in order to ensure a sustainable development of the aquaculture industry and to consider other aspects of an integrated management of the coastal zone, including tourism, fishery, and environmental protection.

Established guidelines for an initial impact assessment need to be complemented by subsequent impact monitoring.

Despite the rapid development of aquaculture in coastal areas of the eastern Mediterranean little has been published on the environmental impacts of this industry. Also, protocols, monitoring systems and techniques for the control of marine cage fish farms in Mediterranean conditions do not currently exist. In general, it has been assumed that these will, at least qualitatively, follow the pattern established in northern latitudes. Strategies developed and proven for salmon culture in northern Europe and elsewhere deliver comprehensive concepts, but need to be modified and adapted to the ecological particularities of the Mediterranean Sea. In addition to differences in the species cultured, the climate, the current regime, and the level of eutrophication, differences in the composition and diversity of fauna and flora between the North Atlantic and the Mediterranean Sea need to be addressed.

At eastern Mediterranean coastal sites, surface water temperatures are higher and water currents are generally weak, being driven by density and wind with an insignificant tidal component. Many areas are highly oligotrophic and may be phosphorus rather than nitrogen limited. Some evidence from acoustic and video surveys and diving surveys has suggested that the effects of mariculture on the benthic environment around fish cages in Greece are very much less than those typically experienced in comparatively eutrophic areas, for example in Scottish sea lochs. It has also been reported that large numbers of wild fish occur around the cages, in mid-water and near the bed and the suggestion made that the fish were responsible for consuming much of the waste food from the farm. Thus evidence of impact effects based on experience from studies of North Atlantic salmonid farms may well be unreliable if used for establishing controls for the Mediterranean mariculture industry. Environmental impact models which attempt to predict the degree of accumulation of wastes were developed and validated in strongly tidal North Atlantic areas and do not include terms relating to consumption of wastes by wild fish. Such models should be used with great caution, if at all, in non-tidal Mediterranean environments.

In order to address these concerns, the