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Understanding fishing practices through the zooarchaeological record offers crucial insights into past human-environment interactions, subsistence strategies, and the development of the modern fishery practices. Past fishing practices varied widely depending on geographical location, environmental factors, and cultural contexts. In this thesis, I explore fish and fisheries in the Baltic Sea from different time frames. Evidence from archaeological fishbones and teeth provides a direct link to fishing practices in the past. Species diversity and anatomical distribution patterns are used to explore fishing methods. Isotope analysis on fish teeth offers further refinement of ecological patterns, including fish migration and mobility. Using zooarchaeological materials from Gotland and Åland, this thesis identifies and discusses patterns in relation to climate change and cultural shifts from the Mesolithic until the Early Modern Period. By applying the theoretical framework of negative space and values the formation of past assemblages and the remains excavated in the present are evaluated. Using strontium isotope analysis, the likely origin, fresh or brackish water, of euryhaline fish on Gotland is explored. The results indicate that fluctuations in aquatic habitat utilisation are tied to environmental shifts and influenced by cultural preferences and values.  To understand how fish are transformed from living creatures to products for human consumption, Medieval zooarchaeological material from Åland was used to investigate shifting patterns in the transportation of cod from a local fishery.  A possible difference in fish products was identified related to the Gotlandic sources. This has implications on how the written record might be interpreted. The aspects above are discussed in a diachronic way and modern concepts such as fishing down the food web are used to examine the sustainability of past fisheries. The findings contribute to broader discussion on past aquatic resource utilisation and fish's value and identities at different time frames in the Baltic Sea context. Highlighting the significance of fishbone analyses and the potential to incorporate archaeological data in contemporary sustainability discourse. 

Coastal vegetated habitats, including submersed aquatic vegetation (SAV), provide three-dimensional structures essential to marine organisms and supporting key ecosystem services. In the Baltic Sea, eutrophication favours filamentous algae that can outcompete SAV, shifting habitats from long-living canopies to minute, ephemeral assemblages, affecting vegetation-associated fauna. Rising densities of three-spined stickleback (Gasterosteus aculeatus) in the central Baltic Sea have been linked to reinforcing filamentous algae dominance through predation on invertebrate grazers.

Ecological dynamics unfold within broader social-ecological contexts, where people and ecosystems influence one another, changing over time. This thesis asks how variation in coastal vegetation shapes faunal communities, and what historical human habitat use and fishers’ ecological knowledge can reveal about these dynamics. To address this, I used an interdisciplinary approach centred on Gotland, Sweden, (central Baltic Sea), with complementary insights from Salina, Italy (Tyrrhenian Sea). Five questions were examined: how SAV and filamentous algae shape epifaunal communities; how they affect juvenile and adult sticklebacks; which habitats were historically used on Gotland to capture euryhaline fish; how can engagement with fishers’ ecological knowledge be improved; and how integration of scientific disciplines advances understanding of coastal habitat dynamics? Methods included ecological surveys, isotope analysis of archaeological fish remains, and semi-structured interviews with fishers using photo elicitation. Results showed that SAV vertical structure increased overall epifauna abundance, whereas filamentous algae favoured only gastropod grazers (Paper I). Juvenile sticklebacks increased with all vegetation variables, while adults showed no associations (Paper II). These results suggest that shifts to filamentous algae could alter epifaunal communities and grazing dynamics, while providing nursery habitat for sticklebacks. Paper III reconstructed millennia of coastal and inland vegetated fishing habitats use, and demonstrated long-standing importance of these habitats for supporting humans. Paper IV showed that photo elicitation accesses explicit and tacit dimensions of fishers’ ecological knowledge, revealing rich understandings of habitat dynamics. A final reflection highlighted epistemological agility, effective communication, role clarity, and time allocation as key to interdisciplinary work. By linking present-day ecological patterns with historical human use and methods to engage with fishers’ knowledge, the thesis provides an integrated perspective to inform management and conservation of coastal vegetated habitats.