Abstract
Conventional tags applied to individuals have been used to investigate animal movement, but these methods require tagged individuals be recaptured. Maps of regional isotopic variability known as “isoscapes” offer potential for various applications in migration research without tagging wherein isotope values of tissues are compared to environmental isotope values. In this study, we present the spatial variability in oxygen (δ18OH2O) and dissolved inorganic carbon (δ13 CDIC) isotope values of Baltic Sea water. We also provide an example of how these isoscapes can reveal locations of individual animal via spatial probability surface maps, using the high‐resolution salmon otolith isotope data from salmon during their sea‐feeding phase in the Baltic Sea. A clear latitudinal and vertical gradient was found for both δ18OH2O and δ13 CDIC values. The difference between summer and winter in the Baltic Sea δ18OH2O values was only slight, whereas δ13 CDIC values exhibited substantial seasonal variability related to algal productivity. Salmon otolith δ18Ooto and δ13Coto values showed clear differences between feeding areas and seasons. Our example demonstrates that dual isotope approach offers great potential for estimating probable fish habitats once issues in model parameterization have been resolved.
Highlights
Several marking approaches have been employed to address questions in migration ecology
The assignment of an individual to a certain area works by estimating probabilities of occurrence for animal individuals by comparing values obtained from tissue samples to isotopic landscapes
As an example we demonstrate the potential of these isoscapes using two Atlantic salmon individuals from the River Simojoki
Summary
Due to the present size of the tags, the studied fish have to be large and, do not necessarily represent the majority of the population. Intrinsic biochemical markers such as stable isotopes can provide an alternative approach to track individual movements over large geographical distances such as between continents (Hobson & Norris, 2008). Combined with the isotope data from the salmon and spatial probability surface maps, we show probable locations of individual fish in various time points during their sea-feeding migration phase in the Baltic Sea. We demonstrate how parameterization of the models influences on location estimates
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