Settlement of Ostrea edulis is determined by the availability of hard substrata rather than its nature: implications for stock recovery and restoration of the European oyster

1. Since the collapse of the Ostrea edulis stock in the mid-1800s the oyster
has struggled to re-establish itself in self-sustaining assemblages in Europe.

2. It is now widely recognized that O. edulis is an integral component of a healthy biologically functional benthic environment and, as such, the restoration of wild stocks has become a matter of urgency.

3. A major limiting factor in O. edulis stock recovery is the availability of suitable substrate material for oyster larvae settlement.

4. This research re-examined the larval settlement potential of several naturally occurring in-situ shell materials (e.g. Mytilus edulis, Modiolus modiolus, O. edulis), with the aim of determining which shell material is the most appropriate for large-scale restoration projects.

5. A positive correlation between available shell material and settlement was determined, and analysis using permanova did not identify an attachment preference by O. edulis to any particular shell type.

6. The findings suggest that if restoration efforts were coordinated with applied hydrodynamic and habitat suitability modelling, in conjunction with naturally occurring shell substrate concentrations, a cost-effective recovery for O. edulis assemblages in the wild could be achieved.