(to see presentation)

It is well known that farmed fish release substantial amounts of nutrients into the marine environment, particularly nitrogen and phosphorus. There are several mass balance models inferring the amount of nutrient wastes from the amount of production of a fish farm. However, this information should be used in a relevant context or it could be very misleading. In particular, it is important to address the problem of environmental impacts at a relevant scale taking into consideration the appropriate hydrographic features and the assimilative capacity of the recipient water body. A series of examples are presented, addressing the issue of change in water quality and nutrient loading at local, mesoscale and regional scales. Most of the fish farms are likely to be sited in areas of relatively intense water currents and therefore it is unlikely that the water quality in the immediate vicinity of an individual farm would be severely affected. At the large spatial scale (such as the entire Mediterranean) the effects are also small in comparison to other sources of nutrient discharge. At intermediate scales, such as a zone for aquaculture development it is more likely that effects could be readily detected. However, these effects are not necessarily negative: recent data have shown that there might be a positive effect on the local fisheries in oligotrophic environments. On the other hand, the release of nutrients might damage large macrophytes such as Posidonia oceanica through a series of indirect effects.

Dr. Ioannis Karakassis Biologist, PhD in Marine Ecology. (1991, Univ. Crete, Greece). Since 1993 team leader on ecology of coastal ecosystems and biodiversity in the Institute of Marine Biology of Crete, After 2001 Assistant Professor and Head of the Ecology and Biodiversity Laboratory Technical University of Crete. Project manager for 10 national RTD projects on anthropogenic effects on the marine environment. Research on aquaculture-environment interactions includes coordination of a national research project, participation in 4 ongoing EU projects (MERAMED, AQCESS, BIOFAQS, MedVeg) and in the MARAQUA concerted action (FAIR DG XII). Member of the national committee for establishing criteria on site selection for marine fish farming. FAO expert for assessing the strategic plan for the expansion of fish farming in Cyprus. Member of ESF-EMaPS group for the preparation of the European Science Plan on Marine Biodiversity and of the working group on benthic indicators established by IOC/UNESCO. Author and co-author in more than 35 reviewed publications.

Contact details: Ecology and Biodiversity Lab, Dept Environmental Engineering, Technical University of Crete, Chania 73 100, Greece.  E-mail: karakass@mred.tuc.gr