Fishery Resource Assessment with eDNA Metabarcoding and Acoustic Survey in Xiangyun Bay, Bohai Sea

Xiangyun Bay Marine Ranch, in the Bohai Sea, China, is an important fishery resource area but has long been affected by eutrophication, habitat destruction, and overfishing. To support resource conservation and management, this study combined environmental DNA (eDNA) metabarcoding, acoustic survey, and a traditional net survey to assess fish resources. The traditional net survey collected 18 fish species (2143 individuals), with Speartailed goby (Chaeturichthys stigmatias) and Indian flathead (Platycephalus indicus) as the dominant species (~70% of total). An acoustic survey revealed that fish resource density in the reef area ranged from 6.05 × 10−5 to 9.38 × 10−5 ind/m2, with vertical distribution concentrated in the 1–3 m water layer; strong scatterers (−47 to −42 dB) at 3 m depth indicated benthic large individuals. The eDNA analysis generated 1,091,731 high-quality sequences assigned to 39 fish species, with dominant species including Kammal thryssa (Thryssa kammalensis), Yellow-spotted slipmouth (Nuchequula flavaxilla), and Large-mouth naked goby (Gymnoglobus macrognathos). In conclusion, the acoustic survey demonstrates unique advantages in assessing spatial distribution of fishery resources, while eDNA technology serves as an effective supplement to traditional net surveys. Their combined application provides more accurate scientific evidence for the production management and sustainable utilization of marine ranches.