Feeding habits of Rhinogobius pflaumi in Jiaozhou Bay, China based on carbon and nitrogen stable isotope analysis

Abstract

Rhinogobius pflaumi is a small-sized, warm-temperate demersal fish species. It is one of the dominant species in fish community, and plays an important role in Jiaozhou Bay ecosystem. The trophic level and feeding habits of R. pflaumi were investigated by carbon and nitrogen stable isotope analysis, based on the data collected from the bottom trawl surveys during May 2011 in Jiaozhou Bay, China in this study. The results showed that the δ15N and δ13C values of R. pflaumi ranged from 11.24‰ to 13.99‰ and -20.67‰ to -18.46‰, respectively. The mean values of δ15N and δ13C were (12.70±0.70)‰ and (-19.08±0.36)‰, respectively. The mean trophic level of R. pflaumi was (3.62±0.21) for all size classes, ranging from 3.49 to 3.76 for different size classes. There was a significant negative correlation between the δ15N values and standard length, while no significant correlation was observed between δ13C values and standard length. The main prey groups of R. pflaumi were polychaeta, decapoda and mollusca. The trophic contributions of zooplankton and particle organic matter (POM) were relatively low. The similarities of prey species composition among different size classes were more than 92%, indicating that there was no significant difference in feeding habits with different standard lengths. R. pflaumi was an intermediate consumer in Jiaozhou Bay ecosystem. The significant negative correlation between trophic level and standard length might be due to variation in the proportion of different prey groups.