UK’s largest fish pass now complete and open for fish migration

The Colwick fish pass. Credit: Jackson Civil Engineering

Nottingham’s Colwick Country Park is now home to the largest fish pass in the country thanks to the completion of the Environment Agency’s £12 million project.

After two years in construction, the Colwick (Holme Sluices) fish pass on the River Trent is now complete and ready for fish to reach their spawning and feeding grounds.

The flagship project opens up the River Trent and its tributaries for migratory fish, including salmon, trout and eels, making more habitat accessible for fish.

It is part of the Environment Agency’s work to improve fish passage across the country and provides a significant step in restoring the River Trent catchment to its former glory for salmon and other coarse and migratory fish.

Fish will now be able to navigate past the Environment Agency-owned Holme Sluices, a major flood risk management structure built in the 1950s which helps to protect Nottingham from flooding. 

Simon Ward, Fisheries Technical Specialist at the Environment Agency, said:

“We are excited to see the completion of the country’s largest fish pass after two years of construction, and many more years in the planning stages. 

“The fish pass will open up the River Trent for all fish species and is the first scheme of the ambitious Trent Gateway Partnership which aims to remove all barriers to fish migration along the River Trent – the third longest river in the country.

“There are a number of barriers to fish migration within the River Trent catchment, including Holme Sluices, which is the largest barrier to the natural migration of fish in the Midlands. By installing fish passage, it will become easier for salmon and other fish to reach their spawning and feeding grounds.

“We are working with partners to improve the situation and hope that the Colwick fish pass will serve as a catalyst for other Trent Gateway projects, which will in turn enhance the river and boost the local economy.”

The fish pass includes a 2-metre-high fully automated radial gate which constantly monitors the water levels and flow rates in the River Trent. The pass will then open and close based on the differing water levels throughout the year.

The pass is divided into 20 ascending chambers into which water flows through narrow slots. Fish of all species swimming upstream to lay their eggs in the gravel riverbeds of the Trent tributaries such as the River Dove and the River Derwent will be able to pass through these slots and rest in the chamber above before continuing.

The project also includes an eel pass to help support the critically endangered European eel; and a public viewing platform above the water, with highly visual interpretation boards to inform and advise visitors about the local wildlife in and around the river, including the fish that are expected to use the pass.

The Colwick (Holme Sluices) fish pass is 200m long, 6m deep and 6.5m wide. 

The direct environmental benefits of the fish pass will be £18.6 million. This includes 60km of river improvement from poor to good status for fish, as well as 60km of new spawning habitat immediately upstream of the barrier. It will also aid interconnectivity with numerous other fish passage schemes previously constructed upstream by the Environment Agency.  

Holme Sluices is a major flood risk management structure that was built in the 1950s as part of a large-scale flood defence scheme and helps to protect Nottingham from flooding.  It spans the River Trent and maintains different upstream and downstream water levels, leaving fish unable to pass through.

The decline of migratory fish in the Trent catchment dates back to the Industrial Revolution, when large weirs were built to open up the river for trade. While some fish were able to overcome these barriers not all of them could.

The Environment Agency fisheries service has a statutory duty to maintain, improve and develop migratory and freshwater fisheries as set out in the Environment Act 1995. The interpretation of this is set out in Ministerial guidance as: 

  • to ensure the conservation and maintain the diversity of freshwater and migratory fish, and to conserve their aquatic environment;
  • to enhance the contribution migratory and freshwater fisheries make to the economy, particularly in remote rural areas and in areas with low levels of income; and
  • to enhance the social value of fishing as a widely available and healthy form of recreation.

For further details about the project visit: 


Please enter your comment!
Please enter your name here