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Rationale: Understanding the migration of marine animals is hindered by the limitations of traditional tracking methods. It is therefore crucial to develop alternative methods. Stable isotope‐based tracking has proven useful for this task, although it requires detailed isoscapes in the focal area. Here, we present predator‐based isoscapes of the coastal zone of the Patagonian Shelf Large Marine Ecosystem (PSLME), which offers a novel tool for geolocation. Methods: Whole‐blood samples from breeding Magellanic penguins nesting at 11 colonies were used to create δ15N and δ13C isoscapes. Isotopic values were assigned to random positions inside their corresponding foraging area. Spatial analysis and data interpolation resulted in δ15N and δ13C isoscapes for the coastal zone of the PSLME, which were validated through cross‐validation. Results: The isoscapes mean standard error ranged from 0.05 to 0.41 for δ15N and from 0.07 to 0.3 for δ13C, similar to the error range of the mass spectrometer used for measuring isotope ratios. Predictive surfaces reflected the latitudinal trends, with δ13C and δ15N values increasing northwards. δ13C values showed a strong latitudinal gradient, while δ15N values had two distinct domains, with higher values in the north. The error surface indicated the highest certainty within 130 km from the shore and within the reported Magellanic penguin foraging areas. Conclusions: Both isoscapes revealed strong spatial variation. The δ13C isoscape showed a latitudinal gradient, consistent with patterns in other oceans. The δ15N isoscape clearly separated northern and southern colonies, likely influenced by nitrogen sources. The error obtained fell within the measurement error ranges, adding credibility to the models. [ABSTRACT FROM AUTHOR]

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Rationale The use of stable isotopes for ecological studies has increased exponentially in recent years. Isotopic trophic studies are based on the assumption that animals are what they eat plus a discrimination factor. The discrimination factor is affected by many variables and can be determined empirically. The Magellanic penguin is a highly abundant marine bird that plays a key role in the southern oceans. This study provides the first estimation of the Magellanic penguin blood discrimination factor for 13C and 15N. Methods A two and a half month feeding experiment was performed, in which ten captive penguins were fed their main natural prey (anchovy Engraulis anchoita). The discrimination factors were estimated by comparing anchovy δ13C and δ15N values (obtained with isotope ratio mass spectrometry using lipid-extracted and bulk anchovy muscle) with penguin blood δ13C and δ15N values. Results Penguin blood was shown to be enriched, compared with anchovies, for 13C and 15N. No changes were observed in the stable isotope ratios of anchovies and discrimination factors during the experiment. The overall discrimination factors were 0.93 ± 0.12 (bulk) and 0.41 ± 0.12 (lipid-free) for 13C; and 2.81 ± 0.17 (bulk) and 2.31 ± 0.17 (lipid-free) for 15N. Conclusions Having an accurate discrimination factor for the studied species is key in any trophic or food web isotopic study. Comparisons of estimated diet-to-blood discrimination factors with published values of aquatic piscivore birds showed that the 13C discrimination factor is particularly variable, and therefore ecologists should be cautious when using a surrogate value from other species. In this study, the Magellanic penguin discrimination factor of a tissue that does not require euthanasia was obtained, a fundamental input for trophic isotopic modeling of the species. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Rationale: Understanding the migration of marine animals is hindered by the limitations of traditional tracking methods. It is therefore crucial to develop alternative methods. Stable isotope-based tracking has proven useful for this task, although it requires detailed isoscapes in the focal area. Here, we present predator-based isoscapes of the coastal zone of the Patagonian Shelf Large Marine Ecosystem (PSLME), which offers a novel tool for geolocation., Methods: Whole-blood samples from breeding Magellanic penguins nesting at 11 colonies were used to create δ 15 N and δ 13 C isoscapes. Isotopic values were assigned to random positions inside their corresponding foraging area. Spatial analysis and data interpolation resulted in δ 15 N and δ 13 C isoscapes for the coastal zone of the PSLME, which were validated through cross-validation., Results: The isoscapes mean standard error ranged from 0.05 to 0.41 for δ 15 N and from 0.07 to 0.3 for δ 13 C, similar to the error range of the mass spectrometer used for measuring isotope ratios. Predictive surfaces reflected the latitudinal trends, with δ 13 C and δ 15 N values increasing northwards. δ 13 C values showed a strong latitudinal gradient, while δ 15 N values had two distinct domains, with higher values in the north. The error surface indicated the highest certainty within 130 km from the shore and within the reported Magellanic penguin foraging areas., Conclusions: Both isoscapes revealed strong spatial variation. The δ 13 C isoscape showed a latitudinal gradient, consistent with patterns in other oceans. The δ 15 N isoscape clearly separated northern and southern colonies, likely influenced by nitrogen sources. The error obtained fell within the measurement error ranges, adding credibility to the models., (© 2024 John Wiley & Sons Ltd.)