The importance of marine resources for the Neolithic hunter-fisher-gathers of the Pitted Ware Culture of Gotland, Sweden, is well documented through zooarchaeological analyses and diet studies of human remains. Terrestrial areas were important for living and supplementing the diet but the extent of the terrestrial territories and regions of land use for different groups is largely unknown. The presence of euryhaline species in recovered zooarchaeological assemblages indicates that freshwater fishing or fishing in the brackish estuaries of the Baltic Sea was part of the subsistence practises. To explore if the inland freshwaters of Gotland were used and, if exploited, where they were located, 18 teeth from euryhaline fish from the Pitted Ware Culture site Ajvide on Gotland were selected. The Sr-87/Sr-86 isotope ratios in the fish teeth were analysed using laser ablation-multi collector-inductively coupled plasma-mass spectrometry and correlated with an updated bioavailable baseline of Gotlandic water sources. Through this approach, the habitational origin of the fish was shown to primarily stem from at least six freshwater sources located in the west-central area of Gotland, in close relation to the site, with a few individuals originating from within the Baltic Sea. The study highlights the significance of ichthyoarchaeological analysis in understanding the territorial practice of past foraging societies and recommends further studies on euryhaline species to expand our knowledge of fish habitat, human resource utilization and land use.

Fish and fishing in the Baltic Sea during the Middle Ages is partly known through research on historical records and zooarchaeological materials, and combinations of them. Due to the uneven distribution of written records and research focus, much is known about the large-scale cod and herring fisheries in the southern parts of the Baltic Sea. However, in the northern parts of the Baltic Sea, both large-scale and small local fisheries are less researched. This article considers the species richness, resource availability, and human selection identifiable in these sources. Zooarchaeological material from the Franciscan friary on the island of Kökar in the Åland archipelago will be discussed in relation to zooarchaeological and written sources from the Castle of Kastelholm (Åland). Historical records identify the friary as having taxation rights to large-scale seasonal catches of cod in the outer archipelago; how the friary collected this toll is unclear. It has been assumed, based on the historical records, that cod was the most consumed fish at the site. This study revealed that the zooarchaeological assemblage does not support the interpretation of cod as the most important fish for consumption at the friary during the Medieval Period (AD 1450–1530).