Endangered freshwater pearl mussel successfully bred at Mayo Marine facility

This spring, scientists at the Marine Institute’s Newport Research Facility in Co Mayo have had great success breeding juvenile freshwater pearl mussels in captivity. This milestone marks a crucial step in the long-term effort to save one of Ireland’s most critically endangered species.

The success comes as part of a long-running conservation breeding programme, a collaboration between the Marine Institute, the National Parks and Wildlife Service (NPWS), and Evelyn Moorkens and Associates, initiated in 2020.

This year, thousands of young mussels dropped off their salmon hosts and were successfully recovered by the team. These juveniles will now be carefully reared in a controlled environment for up to eight years before being released into the wild.

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“Captive breeding gives us a window of opportunity for very vulnerable populations of mussels, especially where habitat restoration is not happening quickly enough, and there is a lag-time between taking measures and seeing the benefit in the habitat,” said Dr Elvira de Eyto, zoologist and research lead for this conservation programme.

Freshwater pearl mussels are natural water purifiers, living buried in riverbeds and helping to maintain clean water for fish and other aquatic life. But the species has suffered sharp declines due to habitat loss, pollution, river drainage, and deteriorating water quality, leading to an ageing population that struggles to reproduce.

One of the biggest challenges is the mussel’s complex life cycle as juveniles must attach to the gills of a salmon or trout for their first 10 months, then drop off and settle into clean gravel riverbeds. Any disruption to water quality, such as excess silt, sediment, or algal growth can severely reduce juvenile survival.

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The Newport facility’s captive breeding programme targets this vulnerable life stage and builds on work being carried out across Europe in more than 40 breeding facilities. The overall aim is to improve early survival rates for these precious creatures and complement habitat restoration efforts.