2023 Volume 79 Issue 17 Article ID: 23-17150
The mortality rate of Pacific oysters cultivated in Hiroshima Bay has consistently remained elevated. Various factors, including elevated water temperature, decreased salinity, competition with other organisms, and depletion of oxygen from bottom sediments, have been proposed as potential causes of the oyster mortality. However, a definitive cause has yet to be established. This study aimed to address this gap by conducting a five-year field experiment to determine oyster mortality rates and investigating the relationship between water temperature, salinity, and oyster mortality in Hiroshima Bay spanning the years 1988 to 2020.
The findings of this study indicated that the main causes of oyster mortality were a decrease in dissolved oxygen at depths of approximately 10 m and an increased number of spawning events triggered by high water temperatures at depth of approximately 0.5 m and 5 m. The mortality rate was higher in years with high accumulated surface water temperatures since 2000.
