Concentrations of five metals together with hematological and morphological parameters were measured in three coastal fish species collected in two sites of the Antarctic Peninsula. Furthermore, we assessed isotopic niche widths among fish populations to better understand their trophic ecology. Nothotenia coriiceps from Fildes Bay displayed high concentrations of Fe and Cu, while those from South Bay had higher concentrations of Cd. All fish from South Bay had higher Zn levels than specimens from Fildes Bay. Effects such as biomagnification of Fe, increased fish metal levels and niche width expansion of Nothotenia coriiceps and Harpagifer antarcticus could be attributed to suboptimal environmental conditions in Fildes Bay. Our findings suggest that early warning signals in coastal Antarctic fish may be linked to increased metal bioavailability as a result of climate change and increased human pressure.