Discrimination of nursery locations of juvenile Japanese flounder Paralichthys olivaceus on the Pacific coast of northern Japan based on carbon and nitrogen stable isotope ratios

To test whether stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) can be used to understand the ecological connectivity of Japanese flounder Paralichthys olivaceus, we evaluated the isotopic signatures of juvenile P. olivaceus from the Pacific coast of northern Japan (i.e., from Aomori to Ibaraki Prefectures). We measured δ13C and δ15N in muscle and collagen extracted from vertebrae and found that isotope ratios were strongly correlated in both. The discrimination models we developed for muscle and collagen proved useful in distinguishing among juvenile P. olivaceus collected from the five prefectures (Aomori, Iwate, Miyagi, Fukushima, and Ibaraki). Juveniles collected in Aomori in particular showed significantly lower values of δ13C and δ15N than those from the other prefectures, which likely reflects the greater influence of the Tsugaru Warm Current in that region. Because collagen in the vertebral centrum can be used to reconstruct annual isotopic records, our results may also assist in developing migration tracking procedures for adult P. olivaceus along the Pacific coast of northern Japan.