Environmental DNA integrity index is sensitive for species biomass estimation in freshwater

Abstract

Abstract Environmental DNA (eDNA) from aquatic vertebrates has recently been used to estimate the presence of a species. However, the estimation accuracy is affected by the degradation rate of eDNA. In this study, eDNA integrity index (eDI) was introduced to adjust eDNA concentration for carp biomass estimation. The adjusted eDNA concentration was defined as biomass index (BI). The degradation rate of eDNA was studied by simulation experiment, tank and pond experiment successively. The eDNA concentration decreasing slowly after the species was removed while eDI changed rapidly in all experiments. eDI decreased to closely zero in two days while eDNA remained detectable for more than one month. The temperature was found to have no significant effect on eDI. Although the eDNA concentration and BI were both positively correlated with carp biomass in all experiments, BI showed higher correlation (R2>0.95), was more sensitive to biomass changes, and accurate for carp biomass estimation. We used this method to estimate the biomass of carp in a fishpond successfully, which suggested that accurate biomass data can reflect the potential distribution of common carp in the natural environment. It offers a non-invasive, simple, rapid, and accurate method for biomass estimation.