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Research Document - 2005/034

Eutrophication Impacts of Marine Finfish Aquaculture

By Strain, P.M.


This paper describes eutrophication and examines how wastes from netpen finfish aquaculture contribute to that process. A number of eutrophication definitions are examined, with the conclusion that eutrophication is essentially an increase in the flow of energy and cycling of nutrients by the ecosystem. Two eutrophication classification schemes and their associated indicators are discussed, showing that eutrophication must be considered in the context of individual environments. Mass balance models that are used to calculate the amounts of eutrophying wastes from finfish farms are described, together with other measurements that yield information about the fates of aquaculture wastes. Results of these calculations show that most dissolved and particulate wastes from farm sites are transported far from farms, even ones located in depositional environments. Given the right combination of the intensity of farming and the carrying capacity of the receiving environment, finfish aquaculture can produce eutrophication impacts on scales of kilometers to tens of kilometers and can change the structure and functioning of the ecosystem in significant ways on these scales. Finally, the management implications of eutrophication caused by finfish aquaculture are discussed with a focus on those processes that influence environmental quality on large scales, the so-called far-field or bay-wide effects. A management approach that does not consider the potential for large scale eutrophication may be ignoring one of the most significant potential impacts of some marine finfish culture operations.

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