2The aim of this research is the isotopic characterization of archaeological fish species to freshwater, brackish, and marine environments, trophic level, and migration patterns, and to determine intra-species variation within and between fish populations differing in location within central and northern Europe. Thus carbon and nitrogen stable isotope analysis was undertaken on collagen extracted from 72 fish bone samples from eight Mesolithic and Neolithic archaeological sites in central and northern Europe. Thirtysix (50%) of the specimens analysed produced results with acceptable carbon to nitrogen atomic ratios (2.9-3.6). The fish remains encompass a wide spectrum of freshwater, brackish, and marine taxa (n = 12), and this is reflected in the δ 13 C results (-24.5‰ to -7.8‰). The freshwater/brackish fish (pike, Esox lucius; perch, Perca fluviatilis; zander, Sander lucioperca) had δ 13 C values that ranged from -24.2‰ to -19.3‰, while the brackish/marine fish (spurdog, Squalus acanthias; flatfish, Pleuronectidae; codfish, Gadidae; garfish, Belone belone; mackerel, Scomber scombrus) ranged from -14.9‰ to -9.4‰. Salmonidae, an anadromous taxon, and the eel (Anguilla anguilla), a catadromous species, had carbon isotope values consistent with marine origin, and no evidence of freshwater residency (-12.7‰ to -11.7‰). The δ 15 N values had a range of 6.2‰ (6.5‰ to 12.7‰) indicating that these fish were on average feeding at 1.7 trophic levels higher than their producers in these diverse aquatic environments. These results serve as an important ecological baseline for the future isotopic reconstruction of the diet of human populations dating to the late Mesolithic and early Neolithic of the region.