Mapping the distribution of the Pacific oyster, Magallana gigas in Ireland.

Following multiple anecdotal accounts of recruitment of the Pacific oyster, Magallana gigas, in a number of bays in Ireland, Kochmann et al (2013) carried out the 1st targeted survey of settlement of this species in the wild in Ireland. Subsequent surveys (in individual bays) have described expanded recruitment in new bays and within existing waterbodies where recruitment has been previously described. To date, recruitment of this species has largely been confined to intertidal habitats.

AFMD have increasingly requested advice, from the MI, on the occurrence of M gigas in the wild. Specifically, they have asked what is the extent of this species in the wild (i.e. feral populations) and if there are management actions that can be used to mitigate any potential impact on habitats and species. 

In order to advise DAFM, it would be important to determine the current status of recruitment of the Pacific oysters in Ireland and identify certain conditions that favours successful establishment of the species. This has broad reaching implications and having these data will be useful to DAFM and other state bodies, e.g. NPWS, NBDC, BIM, EPA, among others.

The elevation of average sea water temperatures provides conditions that increasingly favour the successful recruitment of this species. In order to identify the current status of recruitment of M gigas, it is proposed to carry out surveys of M gigas in bays in Ireland, by replicating the survey effort of Kochmann et al (2013). The intertidal locations of most of the recorded recruitment has made surveying more accessible and feasible. 

The surveys will be carried out at the same sites and using (for the most part) the methodology devised by Kochmann et al (2008). It is anticipated that additional sites/bays might be considered given recent findings of recruitment, e.g. Kenmare River. In total it is expected that the 65 sites recorded by Kochmann et all will be repeated with an additional 15-20 sites to be considered also. 

Article 6 of the Habitats Directive requires that the impact of projects or plans, such as aquaculture enterprises, be appropriately assessed in relation to the feature (habitat, species) for which the site was designated, so that the likelihood of significant effects on the feature can be objectively estimated. Only when the likelihood of significance has been discounted can these activities be licensed in Natura 2000 sites. This project will determine the current status of recruitment of the Pacific oysters in Ireland and identify certain conditions that favours successful establishment of the species in a number of SPAs as dictated by the Aquaculture and Foreshore Management Division of DAFM and make recommendations in relation to subsequent licensing and management of aquaculture activities in the sites.

This project is essential to the delivery of aquaculture and Natura services under the PAF and Priority Area 2 of the EMFAF Biodiversity / Aquaculture programme.