| Studies of the food web are an important inlet to carry out integrative research on sustainable marine ecosystems. These investigations further highlight the main food chain in the study of end-to-end food webs, and the research is conducted at each trophic level (TL). Under multiple pressures of human activities and climatic change, coastal sea ecosystems have undergone significant changes. Therefore, it is very important to clarify the food contact and its present variation in the Bohai Sea ecosystem. In this study, we analyzed 27 different fish species with 10156 stomachs, collected from bottom trawl surveys during 2010~2011 in the Bohai Sea. The percentage frequencies of occurrence, number, and weight of different prey categories were calculated to describe the diet composition. The Shannon–Wiener diversity index was used to evaluate the dietary breadth of each fish. The TL of each fish was calculated, and then the fish were classified as low, medium, and high TL (≤3.8, 3.9~4.4, and ≥4.5, respectively). The results showed that the 27 fish species, including 12 low TL species (Clupanodon punctatus, Sardinella zunasi, Enedrias fangi, Thrissa kammalensis, Callionymus beniteguri, Cynoglossus joyneri, Cynoglossus lighti, Setipinna taty, Enchelyopus elongates, Chaeturichthys stigmatias, Trichiurus muticus, and Chaeturichthys hexanema), 12 medium TL species (Scomberomorus niphonius, Pseudosciaena polyactis, Hexagrammos otakii, Johnius belangerii, Sebastiscus marmoratus, Sebastodes fuscescens, Liparis tanakae, Platycephalus indicus, Hemitripterus villosus, Argyrosomus argentatus, Chelidonichthys kumu, and Lateolabrax japonicus) and three high TL species (Saurida elongate, Lophius litulon, and Sphyraena pinguis), were classified into omnivores, zooplanktivores, benthivores, mixed animal predators, and piscivores. Compared to that in the 1990s, the TL of each fish has not changed much. Three kinds of high TL fish belonged to the piscivores fish category, and their dietary breadth was very low, and so they were stenophagous fish. Finespot goby and small yellow croaker had the highest dietary breadth and were the most important prey species in the food web of the Bohai Sea ecosystem; therefore, their euryphage was beneficial to the material and energy flow of each trophic hierarchy in the food web. Presently, the food chain “zooplankton–anchovy–large piscivores fish” was basically destroyed, and so, the main food chains changed to “plants, organic detritus–Alpheidae– fishes” and “benthic animals–goby fish, small yellow croaker–large commercial fishes” in the food web of the Bohai Sea. The weakening of the pelagic food chain is not conducive to the carbon sink of the marine ecosystem and the material and energy flow of the food web. Therefore, studies of the end-to-end food web and the main food chain of the Bohai Sea should change accordingly. |
