Stable isotope composition and parasitic infections of harbor seal young‐of‐the‐year used as prey‐based diet indicators

• Published in: Marine mammal science Vol. 34; no. 1; pp. 7 - 26
• Main Authors: Vega, Camille, Lebreton, Benoit, Lehnert, Kristina, Asmus, Ragnhild, Siebert, Ursula, Asmus, Harald
• Format: Journal Article
• Language: English
• Published: Beaufort Wiley Subscription Services, Inc 01.01.2018; Wiley
• Subjects: Adults; Animal tissues; Chemical composition; Diet; Environmental Sciences; Fish; Fish diets; Forage; Foraging; Infections; Isotope composition; Isotopes; Lactation; Marine mammals; Milk; Muscles; Nitrogen isotopes; Nursing; Phoca vitulina; postweaning fast; Prey; prey‐based diet; Puppies; Seals; Stable isotopes; Temporal variations; Tissue; Tissues; trophically transmitted parasites; Vibrissae; Wadden Sea; young‐of‐the‐year; δ13C and δ15N; Pey-based diet; Trophically transmitted parasites; δ13C and δ15N; Postweaning fast; Lactation; Young-of-the-year; Wadden Sea; Phoca vitulina
• ISSN: 0824-0469; 1748-7692
• DOI: 10.1111/mms.12433

The stable isotope composition (δ13C and δ15N values) of harbor seals (Phoca vitulina) is influenced by their diet. Young‐of‐the‐year during lactation and postweaning fast are expected be enriched in 15N compared to foraging seals. We studied the temporal variation of stable isotope composition of young‐of‐the‐year and adults to determine from which point in time the young‐of‐the‐year tissues (i.e., muscles and vibrissae) are influenced by independent foraging only. These results were compared with the development of trophically transmitted parasitic infections. The δ15N values in young‐of‐the‐year muscles decreased from June (20.3‰ ± 0.5‰) to October (18.5‰ ± 0.4‰), while those of foraging seals were all year long below 19.2‰. This decrease coincides with the increase of parasitic infections in young‐of‐the‐year, reflecting a shift to fish diet. Together these results suggest that the muscles of the young‐of‐the‐year older than 5–6 mo reflect independent foraging and that they can therefore be used in community diet studies. The nursing signal in vibrissae was unclear, as the δ15N values of young‐of‐the‐year were stable over time, whereas those of adults varied seasonally. However, δ15N values of nursing pups were significantly higher than those of adults in May and June, maybe due to their reliance on milk.