Overwintering and Greenhouse Technics in Aquaculture Suat DİKEL University of Çukurova Faculty of Fisheries Results and Discussion Water temperature is a primary environmental factor affecting the development and growth of aquatic animals. To achieve year around aquaculture production, water temperature must be maintained within physiologically acceptable ranges. A common way to do this is to place the production units in enclosed structures where the air and water is less affected by outside weather. Greenhouse structures, commonly used in vegetable and floricultural productions, are being recognized as economical options for indoor aquaculture because greenhouses are generally inexpensive structures to erect. However, heating a greenhouse in winter is expensive, especially given current high energy prices. For this reason, making an accurate estimate of heating costs to ensure the economic feasibility of a proposed system is essential, since heating costs account for a significant portion of the total energy requirements for recirculating aquaculture productions (Singh and Marsh, 1996). Introduction Word of Overwintering is probably translation of Norwegian overvintre in 1890-95; over- + winter. It’s meaning that is the process by which some organisms pass through or waits out the winter season, or passes through that period of the year when "winter" conditions (cold or sub-zero temperatures, ice, snow) make normal activity or even survival difficult or near impossible. It used in aquaculture for many years. Water temperature is one of the most important factors in aquaculture. Various significant activity like development of ovarian and egg, organization of immunity system, living creatures' gaining weight are realized under effect of water temperature. Fish growth can be optimized in a controlled environment. Control of water and environmental temperature is so important for a successfully aquaculture operation. Especially culture of warm water species like tilapia and cat fish can be carried out that on condition using greenhouse technics in relatively cold regions like Turkey. Optimum temperature is generally more important for aquatic species than land animals. Conclusion Aquaculture involves the raising of freshwater or marine organisms in a controlled environ- ment to enhance production rates. The main species reared in this way are carp, catfish, bass, Tilapia, frogs, mullet, eels, salmon, sturgeon, shrimp, lobster, crayfish, crabs, oysters, clams, scallops, alligators, mussels and abalone. It has been demonstrated that more fish can be produced in a shorter period of time if greenhouse technology is used for aqua -culture pond and raceway heating rather than water dependent upon the sun for its heat. When the water temperature falls below the optimal values, the fish lose their ability to feed because their basic body metabolism is affected (Johnson, 1981).