Plans have been submitted to create a new channel in Denver to help fish migration.
The Environment Agency has applied to West Norfolk Council to create the fish pass close to the Denver sluice gates.
Staff hope to excavate a 70m trench which will contain a concrete channel with metal and plastic baffles to help the fish.
The agency has discovered that the Denver complex, with its five-sluice structures and two locks, is affecting the migration patterns of aquatic life in the area. If planners give the green light, the agency hopes to have the pass completed by next spring.
An agency spokesman said: “The fish pass will enable fish entering the river from The Wash, such as eels, sea trout and lamprey to freely migrate upstream to reach areas to mature, or to breed.
“Many other freshwater fish species which can currently be washed over the sluices in flood conditions will be able to re-colonise by moving back upstream through the pass.
“Routine monitoring has shown that our current sluice structures limit fish migration.
“The fish pass will help this and is needed to fulfil requirements under the Eel Regulations and the Water Framework Directive legislation.
“The project is currently at the design stage but aims to complete construction by April 2015.
“The work will achieve the objectives of European environmental legislation, as well as improving the river ecology and fish populations for Fenland anglers.
“Over the forthcoming weeks, the Environment Agency will be applying for Planning Permission and Water Resources Licences for the fish pass.
“Both will be available for public viewing and comment.”
Denver Sluice Gates play a critical role in the navigation, water level and flood risk management of the Great Ouse.
Denver’s first sluice was constructed in 1651 by Dutch engineer Sir Cornelius Vermuyden to aid navigation but this collapsed in the 1700s.