Elemental analysis of wild Japanese cormorants captured for Ukai fishing in Ishihama coast, Hitachi City, Japan.

Japanese cormorants (Phalacrocorax capillatus) used for traditional Ukai fishing are captured exclusively from the Ishihama coast in Hitachi City, Japan. Despite the long cultural history of this practice, information on trace element exposure in these birds remains limited. This study analyzed the elemental composition of feathers to assess environmental exposure and potential health risks in cormorants used for Ukai fishing. Feather samples were collected from wild cormorants captured in spring and autumn, as well as from captive individuals. Concentrations of ten elements (Al, Cr, Mn, Cu, Zn, As, Se, Cd, Hg, and Pb) were determined using inductively coupled plasma mass spectrometry (ICP-MS). Captive cormorants showed significantly higher concentrations of several elements, including Cr, Cu, Zn, Se, Hg, and Pb, than wild individuals. Among wild birds, those captured in spring generally exhibited higher elemental concentrations than those captured in autumn. Mercury levels in wild cormorants remained below thresholds associated with adverse biological effects, whereas individuals from one captive facility exceeded this level. However, Se:Hg molar ratios were greater than 1 in all groups, suggesting a potential protective role of selenium against mercury toxicity. These results provide the first baseline data on trace element exposure in Japanese cormorants captured for Ukai fishing. The findings indicate that wild-caught birds are generally within safe exposure levels, while highlighting the need for continued monitoring of captive individuals to ensure their long-term health and welfare.