Carbon and nitrogen isotope signals in eel bone collagen from Mesolithic and Neolithic sites in northern Europe

► δ13C and δ15N isotope signals as discriminatory evidence. ► Discriminate between freshwater, estuarine and marine ecotones. ► δ13C isotope signals are consistent with marine origin. ► Small inland eel bone sample size. ► δ15N ratio against eel length data show a strong positive correlation.