Seasonal variation in trophic structure of fish community in Minjiang Estuary based on stable isotope technique

To study the trophic structure of fish community in Minjiang Estuary, we measured the carbon and nitrogen stable isotope ratios (δ¹³C and δ¹⁵N) of common fish species sampled in winter (January), spring (May), summer (August) and autumn (November) of 2015 by trawling, as well as seven quantitative metrics (ratios range of δ¹⁵N, NR; ratios range of δ¹³C, CR; total area, TA; standard ellipse area, SEAc; average distance of centroid, CD; mean nearest neighbor distance, MNND; standard deviation of nearest neighbor distance, SDNND). The results showed significant differences of δ¹³C values among all the seasons except between summer and autumn. There were significant differences of δ¹⁵N values between spring and other three seasons but no significant difference among summer, autumn, and winter. According to the results of the seven quantitative metrics, trophic structure of common fish community remarkably varied among the four seasons, as TA, SEAc, CR, NR, CD and MNND increased in succession from summer, autumn, winter to spring. Our results indicated that seasonal differences in trophic structure of common fish community were related to the fish spawning migration and the diversity of food source.