Native Oyster Nursery Update

This summer marked another milestone in our mission to restore native oysters across Northern Ireland. At our three nursery sites - Belfast Harbour, Bangor Marina, and Glenarm Marina - we’re seeing promising signs of recovery of this endangered species, thanks to three years of dedicated effort and support from passionate volunteers. Hear how the oysters are progressing and meet the exciting new marine species thriving alongside them.

Belfast Harbour

Our newest nursery at Belfast Harbour was installed in November 2023 and, since then, we have had several unexpected yet exciting sightings of Anguilla Anguilla, the critically endangered European eel. These rare creatures are found in the rivers and estuaries that they must traverse on their return from their spawning grounds in the Sargasso Sea, in the west Atlantic. We have been lucky enough to see them during two different stages of their life cycle: the ‘glass eel’ in January and February, as well as the ‘elvers eel’ in June and July.

In June, we held training sessions for new volunteers, who then dedicated their summer months to recording vital native oyster measurement data. In just three months, the oysters showed a growth rate of 19.44% from 72cm in June to 86cm in September, which is fantastic.

Juvenile Eels Comparison — The two different stages of the eel life cycle discovered at Belfast Harbour: the ‘glass eel’ in January and February, as well as the ‘elver eel’ in June and July.

Bangor Marina

This summer, we welcomed another addition to the Bangor nursery species list: the worm Leodice harassi. Little is known about this elusive native species, as there have only been 15 records in Northern Ireland and 120 verified reports around the UK. This new and rare finding highlights the important role native oysters play in enhancing biodiversity and the wider significance of our efforts.

The native oysters in the marina are still growing strong but the most interesting finding is the increase in their weight from 193.7g in April to 244.25g in August, followed by a decrease to 198.1 g in September. These changes suggest that the oysters went through one spawning cycle over this period, with peak larval release happening in August, helping to boost the population of oysters in Belfast Lough.

Leodice harassi Sea Worm — *Leodice harassi found at Bangor Marina Oyster Nursery.*

Glenarm Marina

It was clearly a good summer for growth across our nurseries with the oysters in Glenarm growing by 6.98% from 86cm in April to 92cm in September.

We also recorded a new species of sea squirt, one of my favorite species, Clavelina lepadiformis, also known as the light bulb sea squirt. This species can be found around the coasts of Britian and Ireland and gets its name from its transparent tunic (outer covering) and visible yellow/white internal organs, that make it look like a lightbulb! Our drives up to Glenarm Marina over the summer months were also made better by sightings of bottlenose dolphins along the Antrim coast on more than one occasion!