Conservationists are celebrating after evidence that endangered mussels in a West Cumbrian river have begun to breed for the first time in 13 years.
There are around 300 freshwater mussels in the River Irt, which flows from Wastwater. They live for around 120 years and need their larvae to be inhaled by salmon or trout. The larvae lives on the gills of a fish for around a year before dropping off.
Conservationists have been monitoring the mussels in the river and the last time this process was recorded was 2010. Mussel numbers have declined sharply and only a handful of populations remain in England.
The mussels need a specific habitat to thrive – the larvae must land on areas that contain clean and stable sand or gravels in which they bury and grow.
Working with partners including the Environment Agency, Natural England, National Trust and local anglers, West Cumbria Rivers Trust has been working to bolster the population by undertaking habitat improvements.
The work, which has taken place over a number of years, was funded by the Environment Agency, Natural Course, Natural England, Lake District National Park, Cumbria Community Foundation and Biffa Award, among others.
The trust has also been working with the Freshwater Biological Association to release juvenile mussels bred in captivity in the hope that the population would increase.
The team were undertaking a routine monitoring visit when the evidence was found. They also found mussels persisting across the sites where the captive bred mussels were released, meaning these new introductions have survived two winters in the river.
The team also found a mussel introduced during an earlier release programme from 2017. Now classed as a sub-adult, it had grown significantly since its release.
Chris West, the trust’s River Irt project officer, said: “It’s thrilling to find evidence that the population is reproducing. All our previous monitoring has found no evidence of reproduction, so this is heartening to see. It’s also reassuring to see the mussels released into the Irt are thriving.
“These plus more that we plan to release over the coming years will significantly boost the population number.”
