Reservoirs, built to store water, often adversely affect fish production: downstream, as a consequence of flow regime modification and upstream, as a consequence of the change from relatively shallow free flowing habitat to deep, still water habitat.   Construction and management of dams and reservoirs often fails to take into account the food and nutrition security and economic values associated with fisheries.  With appropriate management, the many millions of small reservoirs and their associated irrigation command areas, represent a potentially huge opportunity for increasing inland fishery production. Fish yields and related economic opportunities can be increased by pro-actively managing reservoir and operation of dams and water-control structures for fisheries, both within the impoundment and downstream. FAO  has   developed a  range of    advisory   documents on the  effective use of   reservoirs and small  water bodies for fisheries.

Other advisory material covers the issues of  improving  the connectivity  of  rivers and floodplains for fisheries and particular with respect to fish passage in large dams. Guidelines on  habitat rehabilitation have also been produced.