Cumbrian freshwater pearl mussels reproduce for the first time in 13 years

Everyone working on the LIFE R4ever Kent project was absolutely delighted to learn that not only had evidence been found of Cumbrian freshwater pearl mussels reproducing for the first time in 13 years, but that the story had also made the BBC News! This went out on TV and you can also read the full BBC News online story here.

The freshwater pearl mussel is a critically endangered species that’s native to the rivers of the Lake District. It’s found only in very clean rivers and streams that are low in calcium and other nutrients.

Some of the biggest threats facing pearl mussels in the wild are pollution, nutrient enrichment, high sediment loads coming from land run-off, and climate change. The future status of the pearl mussel is heavily dependent on the restoration of their habitat, as well as an increasing in their overall population size through captive breeding.

Many of the existing wild populations are ageing, with the youngest mussels in the river being over 70 years old due to juveniles being most affected by poor habitat conditions.

It’s not helped by the fact that reproduction relies on encystment – a complicated process that involves the females releasing glochidia (larvae) which need to be inhaled by fish to survive. The glochidia clamp on to the gills of salmon or trout where they will live for around a year before dropping onto gravel in the riverbed, where they will bury themselves and grow.

Yasmin AliEskandari, Freshwater Pearl Mussel Project Officer on the LIFE R4ever Kent project commented, “This species of mussel (Margaritifera Margaritifera) takes around 12 years to reach reproductive age and can live to be over 100 years old.”

Those shown in the video here [insert video somewhere on page] are being bred in captivity at the Freshwater Pearl Mussel Species Recovery Centre are four years old, “So this cohort have quite a way to go!” says Yasmin.

The Freshwater Pearl Mussel Ark, established by the Freshwater Biological Association in 2007 has been breeding juveniles from several English populations in order to boost wild populations and has started releasing juveniles back into their native rivers.

Evidence that this is working was found by the team at the West Cumbria Rivers Trust when they discovered that the freshwater pearl mussel has started reproducing in the River Irt for the first time in 13 years.

Chis West from West Cumbria Rivers Trust 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.”

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