Habitat suitability assessment for native oyster based on temperature and salinity modelling in an estuarine environment

The European flat oyster, Ostrea edulis , has been harvested in Galway Bay, Ireland, for centuries, but the oyster populations in the bay have declined and are currently facing multiple threats. One major concern in the bay is the recurrence of heavy-rainfall, high-runoff and low-salinity events. In this work, a high-resolution hydrodynamic coastal model of Galway Bay is used together with experimental data on oyster mortality to identify areas with suitable combinations of temperature and salinity for native oyster restoration. A new coastal circulation model of Galway Bay is presented, and its performance is evaluated against in-situ temperature and salinity observations. Separately, oyster mortality under various combinations of temperature and salinity was examined in the laboratory and cumulative mortality curves were determined. These experimental data were used to develop an oyster mortality response model that, together with the temperature and salinity predictions from the hydrodynamic model, determines the total mortality over a given period. A Habitat Suitability Index for the Bay, with respect to temperature and salinity, is proposed, based on the distribution of total cumulative mortality that oysters would experience over their life span due to unfavourable conditions of temperature and salinity.