Climate change such as global warming affects marine ecosystems and fishery resources. The impacts to the species living in coastal regions are considered to become more serious due to a narrow range of inhabitation. Japanese scallop Mizuhopecten yessensis is an important species for Japanese fishery resources as it only lives in coastal regions, especially in Hokkaido. We estimated the dependency of the Japanese scallop on the sea surface temperature dependency(SST) in summer using the foreshore SST and Japanese scallop catch in Hokkaido observations. We also looked at the possible impact of global warming on Japanese scallop using a simplified index for suitable habitats for Japanese scallops and SST obtained by climate models in scenarios with varied CO₂ emission. Japanese scallops and relevant industries are projected to be at risk from SST rising in the future around the Sea of Japan and Funka Bay in Hokkaido basedon a scenario with intermediate CO₂ emission(RCP 4.5 scenario). We propose a simple estimation method applicableto many situations and the importance of observed data in coastal regions.

In order to quantify the influences of hypoxia on megabenthos in Mikawa Bay during the summer season, we analyzed the relationships of the occurrence of four megabenthic groups, flounder, swimming crab, prawn, and mantis shrimp,with environmental factors in the bottom water layer, dissolved oxygen concentrations(DO), water temperature, waterdepth, and bottom sediment types, using generalized linear models(GLM). The selected models in the four groupsrespectively included DO as an explanatory variable, which showed significant effects on the occurrence of all groupsin all cases. Using the resulting model, the DO at 50% probability of occurrence of the flounder, swimming crab, prawn, and mantis shrimp during the summer in the Bay were estimated as 3.9mg・l^-1, 3.5mg・l^-1, 4.7mg・l^-1, and2.5mg・l^-1, respectively. These figures are substantially higher than the LC₅₀ (50% lethal concentration)of laboratoryexperiments of previous studies. The results of this study indicate that the distribution of major megabenthos was influenced by DO, which possibly serves as a strategy to avoid death or hypoxia. We suggest that a DO level of>2.5mg・l^-1 was the lowest level that maintains a megabenthic community in Mikawa Bay during the summer.