Qualitative and quantitative detection using eDNA technology: A case study of Fenneropenaeus chinensis in the Bohai Sea

Accurate knowledge of species distributions and population dynamics is the basis for conservation biology.However, for certain species with unique life histories and very small populations, monitoring species distributions and population dynamics is extremely difficult. Recently, newly developed eDNA technology has been widely used in species monitoring, biodiversity assessments, and biomass assessments. In this research, we studied Fenneropenaeus chinensis in the Bohai Sea. We used a 0.45 μm glass fiber filter combined with a vacuum to filter 2 L seawater samples for eDNA enrichment from 54 stations in June and 60 stations in August. A DNeasy Blood and Tissue kit was used to extract the eDNA. After DNA extraction, the specific primers and probes of the mitochondrial DNA COI gene of F. chinensis were designed. Real-time quantitative PCR was used to qualitatively and quantitatively analyze the eDNA in the Bohai Sea. The temporal and spatial distribution of F. chinensis was detected by the eDNA technique. The relationship between the eDNA copy number and trawl-netted F. chinensis biomass was explored. The applicability and sensitivity of eDNA technology in marine crustacean research were verified. The results showed that the mtDNA COI gene of F. chinensis was successfully amplified in the 54 water samples collected in June, and the detection rate reached 100%. Detections occurred in only 23 of the 60 stations sampled in August. F. chinensis had a detection rate of only 38%. The copy number of eDNA obtained by realtime PCR was fitted to the density of F. chinensis captured by bottom trawling. There was not a significant positive correlation between copy number and biomass. The results obtained through this research will provide a method and theoretical basis for the application of eDNA technology in marine crustacean research.