Pilot Study: Determining the geographic origin of European Eel with Stabile Isotopes (SI)

The European Eel (Anguilla anguilla) is an endangered species with a complex life cycle including long migrations in the ocean. Its continental range extends from North Africa in the south to northern Norway in the north and includes large parts of Europe. A sustainable stock management requires efficient techniques to trace the origin of the eels. This pilot study investigates the application of the SI ratios of carbon (d¹³C), hydrogen (d²H), nitrogen (d¹⁵N) and oxygen (d¹⁸O) to trace back the origin of individual eels. Therefore, eels from two fresh water habitats (River Ems and Mirower See) and one saltwater habitat in Germany (Buger Bodden, Baltic Sea) were analysed. Furthermore, eels of different sizes were compared in order to assess if body size has an influence on SI composition in eels. Muscle and liver tissue were analysed from each collected animal. The SI in the samples span ranges as d¹³C from – 37.7 to – 18.6 ‰, as d²H from – 204.6 to – 92.2 ‰, as d¹⁵N from 10.4 to 18.9 ‰ and as d¹⁸O from 14.0 to 24.6 ‰. There was no significant difference of d¹³C and d¹⁵N between the two tissue types but between the three habitats. Additionally, we observed a significant difference of d¹⁵N between big and small eel at the same location and interpreted this as an effect of age depending food differences. For liver tissue there is a significant difference in d²H and d¹⁸O between Ems and Buger Boden as well as between Ems and Mirower See.