Inge Bødker Enghoff

Stable Isotope Evidence for Late Medieval (14th–15th C) Origins of the Eastern Baltic Cod (Gadus morhua) Fishery

Although recent historical ecology studies have extended quantitative knowledge of eastern Baltic cod (Gadus morhua) exploitation back as far as the 16th century, the historical origin of the modern fishery remains obscure. Widespread archaeological evidence for cod consumption around the eastern Baltic littoral emerges around the 13th century, three centuries before systematic documentation, but it is not clear whether this represents (1) development of a substantial eastern Baltic cod fishery, or (2) large-scale importation of preserved cod from elsewhere. To distinguish between these hypotheses we use stable carbon and nitrogen isotope analysis to determine likely catch regions of 74 cod vertebrae and cleithra from 19 Baltic archaeological sites dated from the 8th to the 16th centuries. δ13C and δ15N signatures for six possible catch regions were established using a larger sample of archaeological cod cranial bones (n = 249). The data strongly support the second hypothesis, revealing widespread importation of cod during the 13th to 14th centuries, most of it probably from Arctic Norway. By the 15th century, however, eastern Baltic cod dominate within our sample, indicating the development of a substantial late medieval fishery. Potential human impact on cod stocks in the eastern Baltic must thus be taken into account for at least the last 600 years.

Snapshots of past fish faunas: paleo-oceanographic perspectives from the Baltic and Black Seas

Analyses of fish remains from sediment cores make it possible to detect not only commonly caught fish from prehistoric times, but also species without any economic importance, though of significance value of palaeoecological reconstructions. In this study, fish bones from sediment cores reaching as far back as several thousand years ago and taken in the Baltic and Black Seas were analysed. All fish remains examined postdate the last glaciations and are from the last marine/brackish stages of both seas. In the Baltic cores, over 13 species were found, the most abundant ones being sand-eel and clupeids (herring and sprat). Flatfish (flounder) was mostly only present in the core taken near Bornholm. One layer in a core from Gotland Deep was especially rich in bones from juvenile sand-eel, with 1 g of material containing over 265 individuals. In the Black Sea cores, more than 5 different species were found: sprat, anchovy, whiting, Mediterranean sand-eel and several nearly complete pipefish which could be identified to the endemic Syngnathus schmidti. The cores from the two seas exhibit common features. All species found were euryhaline, and species that are commercially important today were documented back in time before industrial fishing for them began. The results of this study leads to methodological recommendations regarding dating of material from sediment cores and retrieval of fish remains.