The freshwater pearl mussel is one of the longest living invertebrates known, with a lifespan of over 100 years. It is also one of the most threatened species on the planet.
In Britain, because of pollution and poaching, it is virtually extinct. But now efforts to save the pearl mussel are finally succeeding.
Mei-Ling McNamara visits a unique captive breeding programme in Northumberland which uses baby sea trout to play host to the pearl mussel larvae.
Thousands of fish are being released in the wild, carrying the fragile mussels with them, and - despite all odds - the chances for this fledgling population are looking promising.
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