Abstract : Summer mortalities of the adult Pacific oysters Crassostrea gigas are an important economic concern. In 2015 and 2016, the mortality of hatchery origin spat comprising 4 diploid batches and 9 triploid batches as well as 12 batches of wild caught diploids was followed at 3 sites in Normandy. Abnormal mortalities (> 20%) were observed at one site only and were significantly higher in triploid animals (P < .05). Triploid oysters are believed to be partially sterile but a high level of gametogenesis was observed in all monitored triploid batches. In 2015, preliminary results revealed that triploid oysters underwent strong gametogenesis with mature gametes (stage 3) and 50% of them were non-perturbed (i.e. named alpha). In 2016, 42% of triploid oysters were alpha. This study revealed that triploid oyster maturation occurred in September, which corresponded to the time of high mortalities in Normandy.
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Maryline Houssin, Suzanne Trancart, Lucie Denéchère, Elise Oden, Beatrice Adeline, et al.. Abnormal mortality of triploid adult Pacific oysters: Is there a correlation with high gametogenesis in Normandy, France?. Aquaculture, 2019, 505, pp.63-71. ⟨10.1016/j.aquaculture.2019.02.043⟩. ⟨hal-03400414⟩