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Spatiotemporal variations in habitat utilization patterns of four Delphinidae species in the western North Pacific, inferred from carbon and nitrogen stable isotope ratios

Kanaji, Yu, Yoshida, Hideyoshi, Okazaki, Makoto
Marine biology 2017 v.164 no.4 pp. 65
Bayesian theory, Delphinus delphis, Stenella coeruleoalba, biopsy, carbon, coasts, dolphins, habitats, latitude, longitude, nitrogen, nitrogen fixation, seasonal variation, spatial variation, stable isotopes, surface water temperature
Stable isotope ratios of carbon (δ¹³C) and nitrogen (δ¹⁵N) in skin biopsy samples of four species in the Delphinidae family collected in 1993–2015 in the western North Pacific were investigated. Within the four species—common bottlenose, pantropical spotted, striped, and short-beaked common dolphins—δ¹³C and δ¹⁵N were highest in common bottlenose dolphins, and lowest in short-beaked common dolphins. Standard ellipse areas describing the likely range of the δ¹³C and δ¹⁵N, estimated using Bayesian inferences, indicated wider isotopic niche width in common bottlenose and pantropical spotted dolphins. Although spatial distribution patterns have been known to be similar among striped and short-beaked common dolphins, isotopic niche of the two species less overlapped. The stable isotope ratios were then analyzed in relation to space (longitude and latitude) and time (season) using generalized linear mixed models. The δ¹³C and δ¹⁵N values tended to be higher in lower longitudes for all four species, while δ¹⁵N tended to be lower in lower latitudes for common bottlenose and pantropical spotted dolphins, but lowest in higher latitudes for striped dolphins. These variations are considered to relate to north–south and coastal–offshore variations in nitrogen and carbon sources and nitrogen fixation in Kuroshio waters. This theory was further supported by analyzing stable isotope ratios in relation to distance to coast and sea surface temperature. Seasonal variations in δ¹³C and δ¹⁵N values were recognized for pantropical spotted and striped dolphins.