Mercury (Hg) contamination in deep-sea ecosystems is of increasing concern due to its strong bioaccumulation potential and implications for seafood safety. However, depth-resolved information on Hg speciation and tissue-specific accumulation in deep-sea fish remains limited, particularly in semi-enclosed marginal seas such as the East Sea of Korea. In this study, total mercury (THg) and methylmercury (MeHg) concentrations were...