The aim of this study was to explore the effects of diet and habitat on the Hg levels of Japanese anchovy at different growth stages. We measured the amounts of Hg and stable carbon and nitrogen isotopes in the muscle and stable carbon and oxygen isotopes in the otoliths of 54 Japanese anchovy specimens obtained from the open seas of the Northwest Pacific Ocean (39°2'N ∼ 42°30'N, 154°02'E ∼ 161°29'E) between June and July 2021. Body length had a significant effect on δ