Wildlife returns to the Ribble after weir removal work
Rare fish and insect life are enjoying a restored section of the Ribble just weeks after a redundant weir was removed to renaturalise the water flow.
Site surveys have confirmed the formation of a natural "riffle" upstream of the weir as the river rediscovers its natural flow. Removal of the weir will increase biodiversity and ease the movement of all fish – but particularly migratory fish like salmon, smelt, lamprey and eels.
A shoal of young salmon was spotted downstream of the former Samlesbury Weir en route back to the sea, where they will reach maturity before returning to the river to spawn.
The restoration work is part of the new Ribble Life for Water Scheme supported by the Water Environment Grant administered by the Environment Agency, and funded by the European Agricultural Fund for Rural Development. Samlesbury Weir caused significant problems for the river and riverine wildlife delaying and impeding movement, exposing them to pollution and predation.
In recent years, number of salmon have decreased significantly, with angling catches dropping by up to two thirds since 2010. Young salmon or "smolts" heading back to sea are significantly delayed by even the smallest weir, suffering significant losses from predators. Eel numbers have also seen a significant decline across the UK and this work is crucial in aiding their recovery. Adult eels also migrate downstream, with tiny eels or "elvers" returning to fresh water to mature before heading back to the sea to spawn.
Although these juvenile eels are able to "wriggle" over the weir out of the water, this means they are exposed to predators and poachers. Removing the weir will reduce the losses of eels and slow the significant decline in eel populations.
Environment Agency scientists studied oxygen levels and freshwater insect numbers upstream and downstream of the weir and concluded that the weir’s removal should support increased insect life which will help fish, bird and bat populations.
Oxygen readings taken since the weir removal have confirmed that – even in the current near-drought conditions – oxygen levels remain very high.
Jack Spees, Ribble Rivers Trust CEO, said: “This whole project has been underpinned by science, with our colleagues at the Environment Agency providing essential baseline data on oxygen levels, geomorphology and invertebrate populations. Over the next 12 months, natural processes will enable the river to further naturalise, creating more diverse and varied habitats, improving the habitat for fish and invertebrates. We will be carrying out extensive follow-up monitoring of invertebrates to monitor the changes as they unfold.”
Keith Ashcroft, Environment Agency Area Director, said: “I am really pleased that the hard work of Environment Agency and Ribble Rivers Trust staff has come to fruition in the removal of Samlesbury Weir. The sharing of scientific evidence with our partners is important to enable us to tackle difficult projects such as this one and I am proud that Water Environment Grant funding has finally made it possible. The benefits to a range of river species will be considerable and it is wonderful to see a more natural and healthy River Ribble developing already.”