The European Flat Oyster

Person in charge

Sonia Ternengo

Problematic issues

Reduction in natural bivalve populations due to overfishing and diseases (parasitosis). Reduction in aquaculture production of hollow oysters.

Objectives

State of natural sites in Corsica. Evaluation of collection periods and methods. Managing the development cycle from laying to fixation.

Description

In Corsica the reserve of Diana is a rich body of water that allows for a diverse shellfish farming activity. Faced with the issues posed by the cultivating of hollow oysters, the diversification of shellfish farming activities is an opportunity to consider, especially since the reserve has flat oyster beds, Ostrea edulis. The flat oyster found in the reserve of Diana is a genetic variety of O. edulis specific to Corsica. Indeed, this species, present since Roman times, seems adapted to the environmental conditions of the habitat and has withstood the various epizootic diseases (Bonamiose and Marteliose) that decimated this European species. Today, this species is undergoing the introduction into intensive farming of the hollow oyster Crassostrea gigas. However, since 2008, the latter have known a severe epidemic of a virus of the Herpes family (OsHV-1) threatening the French oyster farming which is experiencing a significant crisis endangering companies and the profession. Faced with the relative shortage that is beginning to take hold on the hollow oyster market in France, the flat oyster O. edulis, of exceptional taste and quality, could be the subject of strong consumer demand and represent a definite economic interest in Europe.

Steps to be taken

The purpose of our approach is to enhance the understanding on the stock levels of flat oysters in Corsica, their laying periods and their reproductive capacity to improve conservation, management and the enhancement methods for this oyster resource along certain parts of the Corsican coastline to ensure environmentally, economically and socially viable production (fishing, aquaculture). To compensate for the decrease in the natural populations of flat oysters farmed by harvesting of aquaculture professionals, a scientific approach to hatchery production of flat oysters is envisaged in a closed environment and managed on the Stella Mare research and experimentation platform. Breeding control and incubation trials of paediatric larvae of O. edulis up to the ‘eye’ stage will be conducted in hatcheries, using small closed-loop experimental incubation units. Experiments will focus on optimising breeding conditions in these structures (feed, water, renewal, temperature, density, etc.). There is in this instance a strong technological lock that is essential to be able to control: the sensitive and delicate stage of the nursery and that of metamorphosis to increase the survival rates when these larvae settle on the collectors.