A comparative study on eDNA-based detection of Siamese bat catfish (Oreoglanis siamensis) in wet and dry conditions

Abstract

The use of environmental DNA (eDNA) analysis has demonstrated notable efficacy in detecting the existence of freshwater species, including those that are endangered or uncommon. This application holds significant potential for enhancing environmental monitoring and management efforts. However, the efficacy of eDNA-based detection relies on several factors. In this study, we assessed the impact of rainfall on the detection of eDNA for the Siamese bat catfish (Oreoglanis siamensis). Quantitative polymerase chain reaction (qPCR) analysis indicated that samples from days with average rainfall exceeding 35 mm (classified as heavy and very heavy rain) yielded negative results. While eDNA detection remains feasible on light or moderate rainy days, a noteworthy reduction in eDNA concentration and qPCR-positive likelihood was observed. Analysis across 12 sampling sites established a statistically significant negative relationship (p < 0.001) between eDNA detection and rainfall. Specifically, for each 1 mm increase in rainfall, there was an observed drop in eDNA concentration of 0.19 copies/mL (±0.14). The findings of this study provide definitive evidence that precipitation has a significant impact on the detection of eDNA in Siamese bat catfish. However, in the case of adverse weather conditions occurring on the day of sampling, our research indicates that it is acceptable to continue with the task, as long as the rainfall is not heavy or very heavy. To enhance the effectiveness of an eDNA survey, it is crucial to consider many factors related to climatic conditions. The aforementioned factor holds significant importance not only for the specific species under scrutiny but also for the broader dynamics of the climate.

Keywords: Endemic species; Freshwater species detection; Rainfall influence; Siamese bat catfish; eDNA analysis.

Figure 1

eDNA concentration of Siamese bat catfish detected at each site on every sampling day, along with the corresponding rainfall data.

Figure 2

Plotted data graphs obtained from regression analysis, which were used to assess the correlation between the concentration of eDNA measured in copies per millilitre (copies/mL) and the amount of rainfall recorded in millimetres (mm). The outcomes of site 1 to 12 are represented by the letters A to L, respectively. In each graph, a linear regression line has been incorporated, accompanied by the inclusion of a light grey stripe encircling the line, which represents the standard error of the estimate.