Combining the restocking of natural flat oyster beds through genetic selection and the development of new oyster farming practices: an integrated approach for the revival of the flat oyster Ostrea edulis

The flat oyster Ostrea edulis is the native European oyster species, with a distribution extending from the Norwegian Sea in the north to Morocco in the south, and eastward through the Mediterranean to the Black Sea (OSPAR, 2009). Since the 19th century, the flat oyster industry has been in decline, primarily due to habitat destruction, over-exploitation, irregular recruitment, and the emergence of the parasites Marteilia refringens and Bonamia ostreae in the 1970s. O. edulis is a species of both economic and ecological significance, and efforts to protect and restore it have become extensive in response to the gradual decline of European populations. The ecosystem formed by flat oysters plays a crucial role in stabilizing substrates, maintaining water quality, and providing habitat for other species. In 2018, we launched a selective breeding program focused on traits such as hardiness (including survival, growth, and resistance to bonamiasis) with the main goal of producing a broad array of biparental oyster families. These oysters are intended for reintroduction in various locations, aiming to restore natural oyster beds and facilitate reef development. This natural reef reconstruction could, in turn, increase larval emissions, which could be collected for aquaculture purposes. Additionally, the development of new cultivation techniques, such as shore-based flat oyster farming, may help diversify aquaculture practices for industry professionals. At the same time, achieving a thorough understanding and control of the reproductive cycle in this species, based on experimentations and analyses relying on a complete reference genome^1,2, opens the door to better-managed larval production in hatcheries, allowing the creation of strains that are well-suited for transfer to population restoration sites. This integrated approach—combining reproductive management, genetic selection, restoration of natural beds, and diversified cultivation practices—aims to revitalize the production of this species and support the restoration of marine ecosystems.

1. Boutet et al. 2022. doi: 10.1111/eva.13462

2. Bean et al. 2022. doi: 10.1111/eva.13465