Tracing 600 years of long-distance Atlantic cod trade in medieval and post-medieval Oslo using stable isotopes and ancient DNA

Marine resources have been important for the survival and economic
development of coastal human communities across northern Europe for
millennia. Knowledge of the origin of such historic resources can provide
key insights into fishing practices and the spatial extent of trade
networks. Here, we combine ancient DNA and stable isotopes (δ13C, δ15N,
non-exchangeable δ2H, and δ34S) to investigate the geographical origin of
archaeological cod remains in Oslo from the eleventh to seventeenth
centuries CE. Our findings provide genetic evidence that Atlantic cod was
obtained from different geographical populations, including a variety of
distant-water populations like northern Norway and possibly Iceland.
Evidence for such long-distance cod trade is already observed from the
eleventh century, contrasting with archaeological and historical evidence
from Britain and other areas of Continental Europe around the North and
Baltic Seas, where such trade increased during the thirteenth to
fourteenth centuries. The genomic assignments of specimens to different
populations coincide with significantly different δ13C values between
those same specimens, indicating that multiple Atlantic cod populations
living in different environments were exploited. This research provides
novel information about the exploitation timeline of specific Atlantic cod
stocks and highlights the utility of combining ancient DNA methods and
stable isotope analysis to describe the development of medieval and
post-medieval marine fisheries.