The concept of fish polyculture has been developed and applied widely in China. The principle is based on the mixing in the same biotope of several non competing animal species and utilization of different ecological niches. The intention is to obtain a better valorization of the renewable resources of the water body. Polyculture is a situation located between the natural ecosystem in which the energy flux is distributed over the many components of the system and monoculture where the flux is concentrated on only one species. In mono- as in polyculture the dietary biomass remains smaller than that produced by the ecosystem without any human intervention. However, the priviliged direction of the flux towads some species easier to harvest allows to collect a larger amount of consumable living matters. Polyculture has led to a marked production increase (generally the double of the production obtained in monoculture without any supply of fertilizers or feed supplements). The main difficulty arises from the choice of the different species and their respective stocking rates in the pond. The most currently mixed species belonging to temperate zones: the common carp and the Chinese carps. In Europe, polyculture is widely practised in USSR and in Rumania and is starting in Hungary, Yugoslavia and Poland. Other countries such as Israel have extended the range of associated species by using Tilapia and even grey mullets together with common carp and Chinese carps and sometimes freshwater shrimps or bivalves in coastal zones.