Optimal Conditions to Quantify the Relationship between eDNA Concentration and Biomass in Acanthopagrus latus

Environmental DNA (eDNA) analysis is a useful tool for monitoring the distributions of aquatic species. eDNA can produce quantitative estimates of fish abundance, but its accuracy depends on the species and system. Therefore, its performance must be evaluated and an investigation of how fish biomass affects eDNA dynamics must be conducted on a case-by-case basis. This study evaluates how the biomass of an ecologically and socioeconomically important fish, Acanthopagrus latus, relates to the eDNA concentration in aquariums. We conducted experiments using juvenile individuals and evaluated eDNA and biomass relationships at seven different time points using a previously developed TaqMan assay targeting the cytochrome oxidase I gene to understand the effect of environmental factors on eDNA concentrations. The results from A. latus showed a strong positive linear correlation between eDNA concentration and A. latus biomass (R-2 = 0.72-0.93). The eDNA concentration was negatively correlated with time 20 d after removing A. latus. Salinity significantly affected the eDNA concentration of A. latus at 3 h, and temperature significantly affected the eDNA concentration from 3 to 14 d. The combinations of factors with the greatest effect on the yellowfin seabream eDNA concentration were 35 parts per thousand/30 degrees C/8.5, 35 parts per thousand/30 degrees C/8.0, and 35 parts per thousand/25 degrees C/8.5 (salinity/temperature/pH). This study identified the conditions for detecting A. latus eDNA and provided environmental data to monitor and survey yellowfin seabream biomass resources.