The Pacific oyster (Crassostrea gigas) is included in Annex IV of Council Regulation (EC) 708/2007 concerning use of alien and locally absent species in aquaculture. Article 2(5) of the Regulation specifically exempts those species listed in Annex IV from the provisions of the Regulation, with the exceptions of articles 3 and 4. Article 4 requires Member States to ensure that all appropriate measures are taken to avoid adverse effects to biodiversity, and especially to species, habitats and ecosystem functions which may be expected to arise, inter alia, from the spreading of these species into the wild.
The exemption in the Regulation for the Pacific Oyster is that it has been in production for many years and has been moved from jurisdiction to jurisdiction. Based on the results of a research study the Marine Institute has confirmed that Pacific oysters (Crassostrea gigas) have reproduced in a number of Bays in Ireland, including Lough Swilly. It has not, however, been demonstrated that the presence of C. gigas has resulted in ecological damage to marine communities within the Lough.
In response to the presence of Pacific oysters in the Lough, a fishery, regulated by Inland Fisheries Ireland, has developed for feral oysters which would appear to have resulted in the removal of considerable biomass of Pacific oysters from the Lough over the last 2 years. In addition, oyster aquaculture operations have started to use triploid Pacific oysters which are considered, for the most part, reproductively sterile and, therefore, will reduce the contribution of larvae from this source.
The Marine Institute is in the process of finalising an “Appropriate Assessment” under Article 6 of the Habitats Directive and this will include management recommendations in respect of oyster production in the Lough.