<；P>；PROBLEM TO BE SOLVED: To improve efficiency and realize energy saving by means of an electrically driven heat pump instead of a boiler using heavy oil as the fuel, which has been used in a heat retention system of an aquaculture pond for eel to break through financial difficulties due to cost soaring for the heat retention of the aquaculture pond for eel because of a rise in crude oil price. <；P>；SOLUTION: The heat retention system of an aquaculture pond for eel includes a hot water replenishing pipe for directly supplying hot water to the aquaculture pond for eel and a heating and water-supplying pipe for indirectly heating so as to keep the water temperature of the pond heated, and includes heat pump equipment for producing the hot water supplied to the pipes. <；P>；COPYRIGHT: (C)2010,JPO&INPIT
