Detection of an invasive species through an environmental DNA approach: The example of the red drum Sciaenops ocellatus in the East China Sea.

Biological invasions are among the most critical threats to local species diversity and ecosystem ecology. The red drum was introduced for marine aquaculture circa 1991 and has become a commercially important maricultural fish species in China and was widely cultured across the coastal areas in mainland China. However, after two decades of maricultural activities, the red drum has been consecutively recorded as escapees along the entire coastal waters of China. Due to the lack of effective monitoring methods, there are not many reports on its distribution in natural seas. In current study, the environmental DNA (eDNA) method was applied. A set of red drum-specific primers and probe were designed, and the distribution and biomass of the red drum were conducted in the East China Sea. The results showed that a total of 47 samples (26.40% of 178 samples) in 27 stations (61.36%) were found to be positive for red drum eDNA. The hotspot was found around the central areas of the East China Sea, especially around the Jiaojiang Estuary and Sanmen Bay area. Significant eDNA concentration differences were found among different stations. Moreover, the presence/absence was also found significantly different among stations. Vertical distribution differences of eDNA presence/absence and concentrations were also found. This study can provide technical support for the monitoring, evaluation, and eradication of invasive species in the future.