200 tonnes of oyster shell cultch has been deployed at two sites located North and South of the St Georges Oyster Fisheries Bed for the purpose of native oyster reef restoration The oyster shell was sourced from a Donegal oyster farm and the Marine Institute inspected it prior to deployment to ensure that the cultch presented no biosecurity concern to Galway Bay. BIM have conducted post deployment side scan sonaring of the cultch to capture it’s dispersment.
“To ensure Galway Bay continued to be protected with respect to bio-security cultch was examined by the Fish Health Unit of the Marine Institute prior to deployment. This examination verified the cultch was significantly weathered and could not in all likelihood harbour diseases or parasites that would pose a risk to oyster farms or native oyster stocks in the Bay.” – Dr. Oliver Tully, Shellfish and Environment Team Leader, Fisheries Ecosystems Advisory Services, Marine Institute
Native oysters are currently spawning in Galway Bay and are dispersing their larvae into the water. The larvae are looking for a suitable substrate to attach themselves to and the oyster shell cultch is an ideal substrate for larval settlement when the goal is oyster habitat restoration.
Oyster shells have multiple overlapping folds which gives them a large surface area and allows for larvae to easily grip the shells. The densely packed oyster shells with the larvae attached to them eventually become a cluster of interlocking living oysters. The heavily packed oysters grow in unique shapes which means they are unsuitable for seafood markets and accordingly there is no incentive to fish them.
Alternatively these native oysters will be left to grow naturally and will produce larvae in years to come that will stock oyster fisheries and wild oyster reefs alike. The cultch will be closely monitored over the coming months to investigate how it performs at the sites it has been deposited and whether many native oyster larvae will settle on the cultch.