Carbon, nitrogen, and oxygen stable isotope ratios of striped dolphins and short-finned pilot whales stranded in Hokkaido, northern Japan, compared with those of other cetaceans stranded and hunted in Japan

• Published in: Isotopes in environmental and health studies Vol. 59; no. 3; pp. 230 - 247
• Main Authors: Endo, Tetsuya, Kimura, Osamu, Terasaki, Masaru, Nakagun, Shotaro, Kato, Yoshihisa, Fujii, Yukiko, Haraguchi, Koichi, Baker, C. Scott
• Format: Journal Article
• Language: English; German; Russian
• Published: England Taylor & Francis 04.05.2023; Taylor & Francis Ltd
• Subjects: Aquatic mammals; Body length; Carbon 13; Climate change; Coastal waters; Delphinidae; Dolphins; Global warming; isotope ecology; Isotope ratios; Meat products; mercury; migration; Muscles; nitrogen-15; oxygen-18; Prey; short-finned pilot whales (Globicephala macrorhynchus); Stable isotopes; Stenella; Stranding; striped dolphins (Stenella coeruleoalba); Trophic levels; Variability; Whales; Japan; nitrogen-15; stranding; oxygen-18; mercury; isotope ecology; migration; short-finned pilot whales (Globicephala macrorhynchus); Carbon-13; striped dolphins (Stenella coeruleoalba)
• ISSN: 1025-6016; 1477-2639
• DOI: 10.1080/10256016.2023.2234590

Strandings of striped dolphins (SD) and short-finned pilot whales (PW) in Hokkaido, northern Japan, are rare but have recently increased, probably due to global warming. We quantified δ 13 C, δ 15 N, and δ 18 O in muscles of SD (n = 7) and PW (n = 3) stranded in Hokkaido and compared these values with those in muscles (red meat products) of hunted SD and PW in three areas of central and southern Japan. δ 18 O in stranded SD, except for the calf, decreased with increasing body length (BL), whereas δ 13 C increased, with no BL-related changes in δ 15 N. The variability of δ 18 O (range of maximum and minimum) was larger in the stranded SD (7.5 ‰) than of the hunted SD in three areas (0.9, 1.9, and 1.4 ‰), whereas that of δ 15 N was smaller in the stranded SD than in the hunted SD. Similarly, the variability of δ 18 O was larger in the stranded PW in Hokkaido (3.3 ‰) than in the hunted PW in central Japan (1.4 ‰). The larger variability of δ 18 O and smaller variability of δ 15 N in stranded SD imply long-term sojourning in coastal waters and feeding on small amounts of limited prey species at low trophic levels before death.