Habitat and resource segregation of two sympatric seals in the North Sea

The study of ecological niche segregation in sympatric species is essential to understand ecosystem functioning and its response potential changes. In the North Sea, grey harbour seals may present competition for food resources sustained by intense fishing activities recent increase seal populations. order coexist reduce inter-specific competition, must segregate at least one aspect their niches: temporal, spatial or resource segregation. We aim foraging distributions between these Sea. Therefore, we analysed stable isotopic composition C, N S (δ13C, δ15N δ34S values), concentrations Hg Se blood from Blood samples were collected on 45 37 sampled along German Scottish coasts. Stable isotope ratios performed with an ratio mass spectrometer coupled N-C-S elemental analyser automated analyses. Total mercury (T-Hg) determined atomic absorption spectroscopy ICP-MS. multi-tracer approach shown partitioning within living Data indicate 1) offshore distribution as reflected lower values T-Hg higher 2) inshore because concentrations. SIAR mixing model revealed 3) a more selective diet compared 4) importance sandeels high values. Lastly, ellipse overlaps coasts suggested 5) sharing resources, possibly due number this area during season - all year except breeding moulting periods. provides robust discrimination among