To explore the feasibility of using pectoral fin rays instead of otoliths as? sample detection material in strontium markinging of fish, and establish a microchemical marking method for fish that could simultaneously meet the requirements of obtaining the detection material without causing lethal harm to the fish and achieving large-number marking of small-sized fish. For this purpose, the juveniles of Lateolabrax maculatus were used as the experimental animals, and the strontium marking "fingerprints" of the otoliths and pectoral fin rays of L. maculatus under different Sr2+concentrations and marking durations were compared. The juveniles of L. maculatus were respectively immersed in seawater with Sr2+ concentrations of 50, 100, 200 and 400 mg·L-1 for 48 hours or be respectively immersed in seawater with Sr2+ concentrations of 50 mg·L-1 for 48, 72, 96, 120 and 144 hours. Then, the juveniles in each group were respectively transferred to normal seawater for breeding. From the beginning of the experiment, the number of death juveniles was observed and recorded daily. On the 30th day of the experiment, five juveniles were randomly selected from each group to extract their otoliths and pectoral fin rays for EMPA analysis. A significant peak was observed in EPMA line transect analysis and a "high strontium marking ring" appeared in EPMA mapping analysis of L. maculatus otoliths in all the marked groups. These results indicated that the otoliths of L. maculatus were sensitive to the variations of trace elements in their habitats. The changes of Sr2+ in the habitat can be recorded by the deposition of elements in the otoliths. The otoliths strontium marking technique can also be applied to L. maculatus. Fish fin rays and otoliths both belong to the metabolically inert hard tissues of the fish body. Therefore, there is a possibility that fish fin rays could instead of otoliths for microchemical fingerprinting research. In our study, the significant peak in EPMA line transect analysis and the "high strontium marking ring" in EPMA mapping analysis of pectoral fin rays were also observed in L. maculatus, whom were immersed in seawater with Sr2+ concentrations of 200 and 400 mg·L-1 for 48 hours or be immersed in seawater with Sr2+ concentrations of 50 mg·L-1 for 96, 120 and 144 hours. This result indicated that it was also feasible to microchemically marking the pectoral fin rays of L. maculatus by artificially adding a certain concentration of strontium ions to seawater. No death was observed in the L. maculatus juveniles during the entire marking experiment and the survival rates of the L. maculatus juveniles in each group were basically the same during the culturing period after marking experiment. These results indicated that the strontium marking technique was safe to be used as a large-scale marking method for small-sized L. maculatus juveniles. The peak value of Sr/Ca ratio in otoliths increased significantly with the increase of the Sr2+ concentrations of seawater in marking experiment. Similarly, the peak value of Sr/Ca ratio in the pectoral fin rays of the L. maculatus juveniles that were successfully marked significantly increased with the increase of the Sr2+ concentrations of seawater. The consistency between the Sr/Ca ratios in the pectoral fin rays or otoliths of the L. maculatus juveniles and those in the ambient water environment is further demonstrated by the effects of varying marking durations on Sr/Ca incorporation. In this study, no significant differences were observed in the peak value of Sr/Ca ratios in either otoliths or pectoral fin rays among the 96h, 120h, and 144h groups whom both detection materials were successfully marked (P>0.05). However, within the otolith successfully marked groups, the peak values of Sr/Ca ratio in the 48h and 72h groups were significantly lower than those in the 96h, 120h, and 144h groups (P<0.05). These results indicated that although the effect of marking duration on strontium accumulation in otoliths and pectoral rays was significantly lower than the Sr2+ concentration, as the markling time of fish in a high-strontium environment increases, the accumulation of strontium in otoliths and pectoral rays also increases, and the Sr/Ca ratio also increases. Compared with the otoliths, the peak value of Sr/Ca ratios in pectoral fin rays was significantly lower than that in otoliths in each group whom both detection materials were successfully marked, the pectoral fin rays required a fourfold increase in Sr2+ concentration or a twofold increase in marking time to form "high-strontium marking rings", and thus the cost of marking was higher. For common fish, using otoliths as the detection material for microchemical marking of fish was more economical. In conclusion, this study revealed that when the concentration of strontium ions in seawater is increased to a specific level, "high-strontium marking rings" can be formed on both the otoliths and pectoral fin rays of the L. maculatus, successfully marking fishes. The pectoral fin rays could be used as detection materials for microchemical marking of fish, which could achieve large-number marking of small-sized fish without causing lethal harm to the sampled fish. This has important application value for the research on the marking and release of protected fish and cartilaginous fish.