Assessment of fishery resources using environmental DNA: The large yellow croaker (Larimichthys crocea) in the East China Sea

Fisheries management and resource conservation rely upon accurate information on the distribution and abundance of major species. The large yellow croaker (Larimichthys crocea) was once one of the most economically important marine fish in East Asia; however, its wild fishery resource has collapsed since the 1980s. Until recently, the natural resources of L. crocea started to increase due to the practice of stock enhancement and summer fishing moratorium. In this study, we developed the species-specific primers and probe and investigated the distribution and abundance of L. crocea using the environmental DNA (eDNA) approach. We collected 171 samples from 44 stations (190,467 km² sea areas) in the East China Sea and detected 96 positive eDNA samples of L. crocea (56 %) at 29 stations (66 %). We found a significant difference in eDNA concentrations among different stations, indicating a regional distribution in L. crocea. We observed vertical variations in the eDNA concentrations of L. crocea among different water layers and detected the eDNA signals in water depths around 40 m and the bottom at multiple stations. We discovered eDNA hotspots with high concentrations in the Yushan fishing ground, which suggesting an offshore spawning ground might have been established possibly in response to nearshore environmental pollution and overfishing. We evaluated the effect of environmental variables on the distribution of L. crocea, found total depth and temperature were significantly correlated with the eDNA presence and concentration, and built a general linear model for the presence or absence prediction of L. crocea with environmental parameters. This study demonstrates the robustness of the eDNA approach in investigating and monitoring natural resources of a crucial marine fish and thus contributes to the long-term assessment of stocking and other strategies in fisheries enhancement.