The life history and populations of chum salmon (Oncorhynchus keta) in China: An otolith isotopic investigation

摘要

Stable isotope ratios of otoliths (delta C-13 and delta O-18) can be used as a habitat index in anadromous fish, because there are marked differences between freshwater and marine settings. Here we report the results of 84 otoliths of chum salmon (Oncorhynchus keta) collected from three locations (Site-A, Site-B, and Site-C) in China, where all the estuaries for chum salmon ocean entry are located in Russia or North Korea and no biological observation data being obtained. In this study we adopted a blind-test protocol and applied stable isotope analyses in chum salmon otoliths. Two aragonite powder samples were taken from each otolith: one from the nucleus of otoliths; the other from the 2nd summer growth zones. Overall the delta C-13 values of chum salmon otoliths ranged from 10.9 to 4.0 parts per thousand, whereas delta O-18 values of the same samples ranged from 6.4 to +1.9 parts per thousand. Based on delta O-18 values at about 3.5 parts per thousand (the boundary line), two different spawning populations or stocks have been identified (p-value = 0.008). The Site-A samples were collected from the Amur River, while the Site-B samples were collected from the Tumen River. The Suifen River (Site-C) samples had some mixing with the Amur River chum salmon, but they were essentially classified into the Tumen River population. Comparison between our data and the previously reported sockeye salmon and chinook salmon data in North America indicated that the chum salmon in China are anadromous, and have the same life history from freshwater to marine as other populations over the world.