Fish Pass Fact File: Lower Darwen

River: River Darwen

Length connected: 2.5 km

Area connected: 1 Ha

Completed: September 2018

Contractor: Bailey Contracts Ltd

Lower Darwen weir dates back to the mid-1800s when it supported the local mills and is one of many structures on the River Darwen which link back to Darwen’s industrial history. Like many of these structures the weir no longer serves a purpose but has remained on in situ blocking the migration on fish.

The weir is located on a relatively secluded section of the river and is not accessible to the public, although it is in close proximity to residential, recreational, and businesses and can be views from the River Darwen Parkway Local Nature Reserve.

An appraisal deemed a full or partial removal too high risk due to this weir close proximity to this developed area. Instead a rock ramp bypass has been created around the left-hand side of the weir which follows the approximate path of the overspill from the river. This serves a duel purpose as not only will it enable fish migration but will also stabilise the weir structure and the banking.

A radio tagging study of brown trout carried out after the fish pass was opened confirmed that fish were using the pass to easily pass the weir.