Differences in stable isotope ratios of Dall’s porpoises (Phocoenoides dalli) between coastal and oceanic areas of the North Pacific

Carbon and nitrogen stable isotope ratios in the muscle of Dall’s porpoises were measured. Samples were collected from the catches of the hand harpoon fishery, incidental catches of drift net, and scientific research on the use of drift nets. Samples were from the North Pacific, Sea of Japan, Sea of Okhotsk, and Bering Sea. Although no variation in δ¹⁵N was observed, δ¹³C was significantly different between population groups near Japan and the oceanic North Pacific and Bering Sea. The difference may be due not only to local variation in prey species, but also to an overall difference in carbon stable isotope ratios that originate from coastal benthic or oceanic pelagic‐based food webs. We differentiated Dall’s porpoise population groups from both areas using carbon stable isotope ratios with an error rate of <5%. Although further study is needed, our results suggest that carbon stable isotope ratios could possibly be an indicator of whether a Dall’s porpoise belongs to a coastal benthic or oceanic pelagic food web.     

Growth effect on the uptake and elimination of trace metals in the abalones Haliotis

In order to determine trace metal (cadmium, copper, lead, manganese and zinc) levels in muscles in relation to organism growth, abalones Haliotis at various stages from Japanese coastal regions were collected and analyzed. Concentrations of Cd and Pb, two non-essential metals, in the muscles of abalones decreased as the organisms became older. In addition, no significant difference was apparent in Cu, Mn, and Zn concentrations, three essential metals, with increases in shell length (age), although a close negative linear relationship with growth was observed in Zn in one habitat. These results indicate that abalone has an ability to differentiate those metals and develops this ability as the organism became older. This effect appears to be almost consistent, despite habitat variation in the genus Haliotis .