Oxygen and carbon isoscapes for the Baltic Sea: Testing their applicability in fish migration studies

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 (normalδ18normalOnormalH2O) 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 normalδ18normalOnormalH2O and δ13 CDIC values. The difference between summer and winter in the Baltic Sea normalδ18normalOnormalH2O 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.

Metabolism and foraging strategies of mid‐latitude mesozooplankton during cyanobacterial blooms as revealed by fatty acids, amino acids, and their stable carbon isotopes

“…Potentially, these mesozooplankton δ 13 C isoscapes can be used to identify the commercial fish feeding trails, for example, for herring and sprat in the Baltic Sea (Möllmann & Köster, 2002;Torniainen et al, 2017) from more saline waters in the southwest to the more brackish waters in the EGB (Leppäranta & Myrberg, 2009) and in cyanobacteria-associated food webs.…”

Multidimensional stable isotope analysis illuminates resource partitioning in a sub‐Antarctic island bird community

“…Nitrogen stable isotopes mainly provide information on trophic position (Caut et al 2009), whereas δ 13 C is useful to infer foraging areas. In aquatic ecosystems, oxygen stable isotopes ( 18 O/ 16 O; δ 18 O) have been widely used to reconstruct paleotemperatures from fossilised shells (Burgess et al 2010) and investigate the thermal environments of aquatic animals (Torniainen et al 2017) due to the influence of ambient water temperature on oxygen isotopic fractionation (Kim and O'Neil 1997). In aquatic ecosystems, oxygen stable isotopes ( 18 O/ 16 O; δ 18 O) have been widely used to reconstruct paleotemperatures from fossilised shells (Burgess et al 2010) and investigate the thermal environments of aquatic animals (Torniainen et al 2017) due to the influence of ambient water temperature on oxygen isotopic fractionation (Kim and O'Neil 1997).…”

Validation of otolith δ18O values as effective natural tags for shelf-scale geolocation of migrating fish

“…Surge & Walker 2005, Shephard et al 2007, Rooker et al 2008, Imsland et al 2014, and scientists are increasingly seeking applications for tracking fish geographical movements based on oxygen isoscapes (e.g. Wunder 2010, Trueman et al 2012, Torniainen et al 2017. Individual experience and environmental variation, however, have not previously been considered to any significant extent in fish studies involving otolith δ 18 O (e.g.…”

“…Individual experience and environmental variation, however, have not previously been considered to any significant extent in fish studies involving otolith δ 18 O (e.g. Stephenson 2001, Imsland et al 2014, Torniainen et al 2017). This results primarily from the difficulties in obtaining accurate corresponding positional and environmental data (Begg et al 2005, Tanner et al 2016).…”

“…With few exceptions (e.g. Zazzo et al 2006, Dufour et al 2008, Torniainen et al 2017, previous isotopic studies examining otolith δ 18 O have been based, at best, on results from annual otolith samples. Our results demonstrate, for plaice at least, that geolocation potential is high at a broad spatial scale, but that spatial discrimination based on annual otolith δ 18 O is poor when compared to monthly or even seasonal values.…”