[Identification of released population of Japanese flounder based on stable isotopes analysis]

Japanese flounder (Paralichthys olivaceus) is an important releasing fish in the Yellow and Bohai Seas of China. The identification of wild and releasing population is the premise to evaluate the enhancement effects. In order to study the application of stable isotope in the identification of released P. olivaceus population, captured juveniles in the offshore releasing area of Qinhuangdao were distinguished into wild and released population using previous method (combination of morphology and molecular). Then, the contents of carbon and nitrogen stable isotope in muscle and otoliths (including the whole and the core region) were measured. The cultured population was set as control. The results showed that δ¹³C values (wild population: -17.19‰±0.73‰; released population: -17.10‰±0.61‰; cultured population: -20.75‰±0.07‰) and δ¹⁵N values (wild population: 11.81‰±0.38‰; released population: 11.62‰±0.48‰; cultured population: 8.64‰±0.60‰) of muscle and δ¹³C value (wild popu-lation: -4.47‰±0.35‰; released population: -4.63‰±0.29‰; cultured population: -6.59‰±0.58‰) of the whole otolith could be used to identify the cultured population, but could not be used to distinguish the wild from the released population. The δ¹³C value (wild population: -4.66‰±0.30‰; released population: -5.41‰±0.21‰; cultured population: -5.37‰±0.19‰) of the core region of otolith could be used to identify the wild popu-lation. The δ¹⁸O values of the whole and the core region of otolith from these three groups were overlapped and could not be used to distinguish different populations. Our results indicated that the δ¹³C value of the core area of otolith could be used to identify wild and released population, with application prospect in the identification of broodstocks participating in spawning migration. This study provided basic data and technical methods for evaluating early resources replenishment and the effects of Japanese flounder enhancement.