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

View Article: PubMed Central - PubMed

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 (δ13CDIC) 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 δ13CDIC values. The difference between summer and winter in the Baltic Sea δ18OH2O values was only slight, whereas δ13CDIC 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.

No MeSH data available.


Probability surfaces of locations for two example River Simojoki Atlantic salmons (FISH 1 and 2) during their feeding phase of first sea winter (1SW; a and d, respectively), second sea summer (2SS; b and e, respectively) and second sea winter (2SW; c and f, respectively) in the Baltic Sea. Calculations are based on salmon otolith and Baltic Sea water δ18O and δ13C values. White and high‐saturation colors indicate that all value surfaces used in the calculation of probabilities (temperature, δ18OH2O, δ13CDIC and prey isotope values) are reliable in contrast to low confidence probabilities indicated in gray and grayish colors. Probability surface results indicated in red represent high probability of presence according to the used model of Hanson et al. (2013) (Model 1), green color indicates high probability or presence with the average model of all four used models in this study (Model 2; Godiksen et al., 2010; Hanson et al., 2013; Patterson et al., 1993; Storm‐Suke et al., 2007) and blue color represents high probability or presence on the model probabilities of Patterson et al. (1993) (Model 3)
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ece32841-fig-0007: Probability surfaces of locations for two example River Simojoki Atlantic salmons (FISH 1 and 2) during their feeding phase of first sea winter (1SW; a and d, respectively), second sea summer (2SS; b and e, respectively) and second sea winter (2SW; c and f, respectively) in the Baltic Sea. Calculations are based on salmon otolith and Baltic Sea water δ18O and δ13C values. White and high‐saturation colors indicate that all value surfaces used in the calculation of probabilities (temperature, δ18OH2O, δ13CDIC and prey isotope values) are reliable in contrast to low confidence probabilities indicated in gray and grayish colors. Probability surface results indicated in red represent high probability of presence according to the used model of Hanson et al. (2013) (Model 1), green color indicates high probability or presence with the average model of all four used models in this study (Model 2; Godiksen et al., 2010; Hanson et al., 2013; Patterson et al., 1993; Storm‐Suke et al., 2007) and blue color represents high probability or presence on the model probabilities of Patterson et al. (1993) (Model 3)

Mentions: Based on the Model 1 (Hanson et al., 2013) assignments, the most probable first sea winter location of FISH 1 was in the Baltic Proper (Figure 7a). During the next summer and the second winter, FISH 1 appeared to occupy waters close to the Gulf of Riga, and the areas of the southwest and northern Baltic Proper, respectively (Figure 7b,c). The results for FISH 2 were very similar, except that in the first winter it appeared to be located in the Bothnian Sea or in the Gulf of Riga (Figure 7d–f). Compared to the Model 1, assignments of the Model 3 (Patterson et al., 1993) were located more northern and also colder areas or to areas with lower salinity (the Gulf of Finland; Figure 7). Model 2 (the average model of four models used in the study) salmon assignments were between Hanson et al. (2013) and Patterson et al. (1993) models (Figure 7). Some of the assignments of the models 2 and 3 were confined to such a small area that results of the models were not very visible in the assignment maps (Figure 7).


Oxygen and carbon isoscapes for the Baltic Sea: Testing their applicability in fish migration studies
Probability surfaces of locations for two example River Simojoki Atlantic salmons (FISH 1 and 2) during their feeding phase of first sea winter (1SW; a and d, respectively), second sea summer (2SS; b and e, respectively) and second sea winter (2SW; c and f, respectively) in the Baltic Sea. Calculations are based on salmon otolith and Baltic Sea water δ18O and δ13C values. White and high‐saturation colors indicate that all value surfaces used in the calculation of probabilities (temperature, δ18OH2O, δ13CDIC and prey isotope values) are reliable in contrast to low confidence probabilities indicated in gray and grayish colors. Probability surface results indicated in red represent high probability of presence according to the used model of Hanson et al. (2013) (Model 1), green color indicates high probability or presence with the average model of all four used models in this study (Model 2; Godiksen et al., 2010; Hanson et al., 2013; Patterson et al., 1993; Storm‐Suke et al., 2007) and blue color represents high probability or presence on the model probabilities of Patterson et al. (1993) (Model 3)
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ece32841-fig-0007: Probability surfaces of locations for two example River Simojoki Atlantic salmons (FISH 1 and 2) during their feeding phase of first sea winter (1SW; a and d, respectively), second sea summer (2SS; b and e, respectively) and second sea winter (2SW; c and f, respectively) in the Baltic Sea. Calculations are based on salmon otolith and Baltic Sea water δ18O and δ13C values. White and high‐saturation colors indicate that all value surfaces used in the calculation of probabilities (temperature, δ18OH2O, δ13CDIC and prey isotope values) are reliable in contrast to low confidence probabilities indicated in gray and grayish colors. Probability surface results indicated in red represent high probability of presence according to the used model of Hanson et al. (2013) (Model 1), green color indicates high probability or presence with the average model of all four used models in this study (Model 2; Godiksen et al., 2010; Hanson et al., 2013; Patterson et al., 1993; Storm‐Suke et al., 2007) and blue color represents high probability or presence on the model probabilities of Patterson et al. (1993) (Model 3)
Mentions: Based on the Model 1 (Hanson et al., 2013) assignments, the most probable first sea winter location of FISH 1 was in the Baltic Proper (Figure 7a). During the next summer and the second winter, FISH 1 appeared to occupy waters close to the Gulf of Riga, and the areas of the southwest and northern Baltic Proper, respectively (Figure 7b,c). The results for FISH 2 were very similar, except that in the first winter it appeared to be located in the Bothnian Sea or in the Gulf of Riga (Figure 7d–f). Compared to the Model 1, assignments of the Model 3 (Patterson et al., 1993) were located more northern and also colder areas or to areas with lower salinity (the Gulf of Finland; Figure 7). Model 2 (the average model of four models used in the study) salmon assignments were between Hanson et al. (2013) and Patterson et al. (1993) models (Figure 7). Some of the assignments of the models 2 and 3 were confined to such a small area that results of the models were not very visible in the assignment maps (Figure 7).

View Article: PubMed Central - PubMed

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 (δ13CDIC) 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 δ13CDIC values. The difference between summer and winter in the Baltic Sea δ18OH2O values was only slight, whereas δ13CDIC 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.

No MeSH data available.