Trophic interactions of reef-associated predatory fishes (Hexagrammos otakii and Sebastes schlegelii) in natural and artificial reefs along the coast of North Yellow Sea, China

Large reef-associated predatory fishes play important roles in aquatic ecosystem along coast because of their ecological functions and economic values to recreational and commercial fisheries. This study was carried out to assess the function of artificial reefs as alternative habitats for two common reef-associated predatory fishes in the north of Yellow Sea, China, Fat Greenling Hexagrammos otakii and Korean rockfish Sebastes schlegelii. According to the catch per unit effort (CPUE), the biomass of predatory fishes at the artificial reef was comparable (H. otakii) to or higher (S. schlegelii) than the natural reef, highlighting the environmental fitness of the artificial reef. Gut content analysis (GCA) showed that H. otakii preyed primarily on Decapod and Amphipoda, while S. schlegelii exhibited higher dependence on fish (Blinniidae and Gobiidae) and Decapod. Collectively, prey richness and diversity were greater at the natural reef relative to the artificial reef, and prey availability may be different between the two reef types. Stable isotopic analysis (SIA) in conjunction with the Bayesian mixing model (MixSIAR) revealed spatial and interspecific difference on the diet composition of H. otakii and S. schlegelii as well. Based on GCA and MixSIAR result, the habitat-specific effect on the prey availability was confirmed. Additionally, comparisons on trophic niche breadth and niche overlap indicated higher trophic diversity but relatively lower food resources partitioning degree for both species at the natural reef than at the artificial reef. Our results suggest that artificial reefs may harbor a different prey assemblage comparing to natural reef but can support large populations of predatory reef-associated fishes and accommodate their coexistence.