Recirculating aquaculture systems - the promising technology for aquaculture

New farming conditions (limitations in water quality and quantity, cost of land, limitations on water discharges, environmental impacts and diseases) and unfavourable Lithuanian climatic conditions force to seek new production methods for intensive aquaculture. The way for solving these problems is the water recirculating in fish growing facility. Recirculating aquaculture systems (RAS) are gaining wider acceptance in the last years. The fully controlled environment the water organisms are grown in gives such systems many advantages over traditional growing methods like ponds, cages or basins. Physical and chemical parameters of water here are ensured using wastewater treatment technologies. In spite of the advantages like water saving, high productivity, environmental impact decrement, RAS are not common in aquaculture because of high investment costs, energy expenditures and more complicated operation. The investigations of such systems are directed at technology improvement in order to lower the production costs and simplify the systems operation. Simple RAS was constructed in greenhouse of JSC ,,Kietaviškių gausa" for investigation. The RAS consisted of standard components employed for water treatment in order to meet recirculated water quality parameters demand for reared fish. The RAS under investigation consisted of the following components: four fish rearing units, concrete channel with arranged plate mechanical filter, fixed bed biological filter, airlifts for biofilter water supply and secondary filtering bed for biofilter backwash, aeration tower with water distribution rotating arm. Pump and air blower were used to meet water recirculation and water treatment technological demand - air supply for airlifts and air powered biofilter backwashing. The growth of the (European) wells catfish (Silurus glanis L.) was evaluated in the systemVytauto Didžiojo universitetasŽemės ūkio akademij