Feasibility of the sustainable freshwater cage culture in Hungary and Romania

The intensive cage culture has an adverse effect on the quality of waters due to the high nutrient discharge of intensive fish culture. The combination of the intensive cage and the extensive aquaculture exploits the advantages of traditional pond farming and intensive fish culture systems. Valuable predatory fish species can be produced in the intensive part of the system, whilst the integration of an extensive pond as a treatment unit results in decreased nutrient loading to the environment and increased nutrient recovery in fish production. The combination of cage and pond fish farming is a new method for predatory fish production in fishponds. By the exploiting of the traditional fish ponds with intensive fish production in cages makes possible for the traditional carp farmers to increase their production capacity, diversify the cultured species and recycle the nutrients within the Introduction. Development of the European aquaculture industry showed a significant growth in production volume during the last fifty years. However in the last 10-20 years all the growth can be attributed to marine cage culture, as there were no rise in the production in other subsectors of European aquaculture: freshwater fish farming has been stagnating since the 90's, while brackish aquaculture and marine shellfish farming has gone through a serious depression in the last 10-15 years. Cage mariculture went through the most serious technological development and economic rationalisation (cost cutting) in the latest years making salmon farming and mediterranean fish farming the most competitive subsectors of European aquaculture. Nowadays marine cage culture (mainly salmon, trout, seabream, seabass and - to a lesser extent - cod farming) accounts for more than 60 percent of total European aquaculture and contributes 75 percent to total finfish culture. European freshwater aquaculture is currently based on a larger number of species, although carp and rainbow trout are still the dominant species. The demand for carp or low valued herbivorous fish is constant or slightly decreasing (Adamek et al 2009), but there is a significant need for valuable boneless carnivorous fish. However, the common carp production in pond fish farms in Central Europe will be dominant in the future; new production techniques can be applied for increasing the profitability of the farms. European finfish aquaculture is dominated by marine cage culture (salmonid and Mediterranean fish species), which accounts for 70-75% of total European finfish farming both in terms of quantity and value (FAO FishStat Plus). Mariculture in cages went through the most serious technological development and economic rationalisation (cost cutting) making salmon and seabream/seabass farming the most competitive subsector of European aquaculture with nearly 6 percent annual growth in the last decade while inland aquaculture and shellfish farming has been stagnating. Although freshwater cage aquaculture is very important in Asia (China, Vietnam, Indonesia and Philippines are the largest producers, mainly catfish and tilapia are produced in cages), in Europa it is not notably prevalent yet. The most remarkable freshwater cage culture in the region is reported from Russia and Turkey, more than 10,000 tonnes of fish farmed in freshwater cages in these countries (Cardia & Lovatelli