The aim of this study is to investigate isotopic variability in archaeological (n=85) and modern (n=29) freshwater fish specimens from Switzerland. Here, carbon (δ13C) and nitrogen (δ15N) stable isotope ratio analysiswas performed on bone collagen samples of pike (Esox lucius), perch (Perca fluviatilis), barbel (Barbus barbus), roach (Rutilus rutilus) and carp (Cyprinus carpio) fromeleven archaeological (11th to 18/19th centuries CE) andmodern sites. The archaeological vs. modern fish data revealed significant isotopic differences for pike, perch and barbel (δ13Cp≤ 0.03; δ15Np≤ 0.008), and provides possible evidence for a temporal change in Swiss aquatic ecosystems from Medieval to modern times. In comparison to archaeological fish (δ13C mean ± SD; −23.3 ± 1.6‰; δ15N mean ± SD; 8.3 ± 1.8‰), the modern fish samples show decreased δ13C and increased δ15N values (δ13C mean± SD; −27.4 ± 2.3‰; δ15N mean± SD; 12.5± 4.1‰) that can be associated with anthropogenic effects: fossil fuel combustion, deforestation and organic waste in the form of sewage and fertilizers. The isotopic signatures of archaeological fish remains indicate a local fishery practice, but also the exploitation of distant fishing grounds and freshwater fish transportation. Furthermore, a diachronic isotopic trend is observed in young perch from sites in Basel, dating between the 12th and 15/16th centuries CE, and the isotopic data from the Rhine freshwater fish (18/19th century CE) suggests that a significant shift in the river's trophic state was possibly caused by organic pollution fromurban and industrial wastewater. This retrospective research illustrates possible natural processes and human activitieswhich can cause differences in fish stable isotope data and highlights the ability to elucidate changes in past bodies of water. Furthermore, this study provides an interpretative framework for additional palaeoenvironmental studies and modern restoration projects focused on freshwater ecosystems.
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RBINS Staff Publications 2016
Carbon and nitrogen stable isotope ratios were measured in 157 fish bone collagen samples from 15 different archaeological sites in Belgium which ranged in ages from the 3rd to the 18th c. AD. Due to diagenetic contamination of the burial environment, only 63 specimens produced results with suitable C:N ratios (2.9-3.6). The selected bones encompass a wide spectrum of freshwater, brackish, and marine taxa (N = 18), and this is reflected in the d13C results (-28.2‰ to -12.9‰). The freshwater fish have d13C values that range from -28.2‰ to -20.2‰, while the marine fish cluster between -15.4‰ to -13.0‰. Eel, a catadromous species (mostly living in freshwater but migrating into the sea to spawn), plots between -24.1‰ to -17.7‰, and the anadromous fish (living in marine environments but migrating into freshwater to spawn) show a mix of freshwater and marine isotopic signatures. The d15N results also have a large range (7.2‰ to 16.7‰) indicating that these fish were feeding at many different trophic levels in these diverse aquatic environments. The aim of this research is the isotopic characterization of archaeological fish species (ecology, trophic level, migration patterns) and to determine intra-species variation within and between fish populations differing in time and location. Due to the previous lack of archaeological fish isotope data from Northern Europe and Belgium in particular, these results serve as an important ecological backdrop for the future isotopic reconstruction of the diet of human populations dating from the historical period (1st and 2nd millennium AD), where there is zooarchaeological and historical evidence for an increased consumption of marine fish.
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