Sustainable large‐scale production of European flat oyster (Ostrea edulis) seed for ecological restoration and aquaculture: a review

Abstract

The conservation and active restoration of European flat oyster (Ostrea edulis) populations are a major focus of ecological restoration efforts to take advantage of the wide-ranging ecosystem functions and services this species provides. Accordingly, additional and new demands for seed oysters have arisen. In commercial aquaculture (mariculture), the production of O. edulis is still largely based on natural seed collection. Considering the specific requirements, related to ecological restoration, such as the absence of pathogens and the preservation of high genetic diversity, the current supply is insufficient. Despite the development of breeding and controlled reproduction techniques for this species since the late 1930s, seed production today is mainly based on empirical concepts. Several of the issues that producers still face are already subjects of research; many others are still unanswered or even unaddressed. This review provides a summary of all available knowledge and technologies of O. edulis seed production. Furthermore, it provides a detailed reflection on implications for restoration, future challenges, open questions and it identifies relevant research topics for sustainable seed supply. The study covers the following aspects on (i) biology of the species, (ii) stressorsincluding pathogens and pollutants, (iii) genetics, (iv) history of production technologies, (v) seed production in polls, (vi) seed production in ponds and (vii) seed production in hatcheries. Future research needs on sex determinism, gametogenesis, cryopreservation, nutrition, selective breeding, pathogens and disease, and the development of reliable protocols for production are highlighted.

Worldwide overview of reproduction, juvenile collection, spat production and cultivation of pen shells

“…is supported by pediveliger larvae and spat produced in hatcheries, 93 which is possible because the hatchery rearing of C. gigas is well-established 94 ; however, hatchery rearing has not been accomplished for all species. Although hatcheries operate upon the same principle of replicating a biological cycle similar to all bivalve species under controlled conditions, 95,96 each species requires particular conditions. Thus, no commercially reliable techniques have been established for some species despite years of research.…”

Genome-Wide Association and Genomic Prediction of Growth Traits in the European Flat Oyster (Ostrea edulis)

“…Despite the demand for shellfish continues to increase ( Botta et al, 2020 ), the level of O. edulis production is stagnant. One of the main factors that hinders the growth of the industry is the lack of a substantial and steady supply of oyster seed (i.e., juveniles) (see Colsoul et al (2021) for a review). Hence, the optimization of oyster larval production in hatcheries and spatting ponds is key for future European flat oyster aquaculture, as well as for restoration projects, which are also expected to rely on sustainable sources of juveniles for restocking ( Pogoda et al, 2020 ).…”

Molecular identification, life cycle characterization, and hatchery seed production of dwarf oysters from the Ebro Delta (Spain)

“…Individuals found in association with pen shells appear to be an adequate source of broostock, although given the endangered status of this species (García-March et al, 2020) the finding of individuals might become a limiting factor for restoration (Brumbaugh and Coen, 2009). Yet, we were able to grow larvae and obtain healthy spat, thus opening the door to the possible culture of the species for wild release, the best strategy for oyster conservation (Colsoul et al, 2021). Our results point that Shellfish Diet 1800 ® is not an adequate diet for the hatchery and nursery production of O. stentina despite positive results in other species (Rikard and Walton, 2012;Southgate et al, 2016, Wassnig and Southgate, 2016.…”

“…In particular, the highest survival rates of up to 98% were obtained for larvae fed with a mixed diet of C. neogracilis and T. lutea (1:1 cell volume) and maintained throughout the planktonic life at 25 °C using a flow-through rearing system (Robert et al, 2017). The progressive development of hatchery production techniques for this species since the late 1930s (Colsoul et al, 2021) suggest that the culture of O. stentina could also be improved using other diet formulations, daily rations, water temperature and/ or rearing system. In addition, since broodstock released larvae only two days after field collection, the potential effects of parental nutrition in progeny are unknown and could have limited larval development (González- Araya and Robert, 2018).…”

“…Since O. stentina does not have a commercial interest, its wild reintroduction could constitute a new paradigm for assessing the efficiency of previous 'restoration' efforts (Coen and Luckenbach, 2000). Besides, an enhanced resilience of O. stentina to the disease caused by the protozoan parasite Bonamia exitiosa Hine, Cochennac and Berthe, 2001, has been reported (Hill et al, 2010), which might be an additional trait favouring the effectivity of this oyster species for ecological restoration and the recovery of ecosystem functions and services (Colsoul et al, 2021).…”