Environmental effects on growth performance of Pacific oyster Crassostrea gigas cultured in the Seto Inland Sea, Japan, from 1990 to 2021

The Pacific oyster (Crassostrea gigas) has been cultured for its flesh in the Seto Inland Sea, western Japan, over the last half-century. Its production has been reported as ‘fluctuating’, yet little is known about changes in oyster growth performance throughout long-term culturing in this locality. To effectively manage oyster production under future environmental challenges, this study investigated the long-term environmental influences on oyster growth performance. Environmental data and oyster biological data were obtained from observations in Hinase waters, Seto Inland Sea, and compared for the two periods 1990 and 2015–2021. Water temperature has not significantly changed in this locality during the oyster culturing period. Lower salinity was found in July of 2015–2021 due to heavy seasonal rainfall, which had a negative impact on oysters, specifically on survival rate and total weight. A high growth rate and high meat weight at harvest were found in the individuals cultured during the period 2015–2021, yet oyster total weight showed no significant difference. Further research on shell characteristics is required to have a better understanding of oyster growth characteristics.