Factors Affecting Detection Probability of Fishes and Amphibians Using Environmental DNA Sampling

Effective conservation programs require monitoring techniques that are both accurate and efficient. The use of environmental DNA (eDNA) to detect aquatic species has the potential to greatly increase our ability to detect endangered and invasive species and can be highly cost-effective compared with standard field survey methods. We are working across systems to better understand the effects of sun exposure, pH, and water temperature on detection probability of eDNA for aquatic species. In the lab, we conducted a full factorial experiment to better understand the impacts of each of these factors on eDNA persistence. In the field, we sampled in coordination with field crews to directly compare standard field and eDNA techniques for fishes and amphibians and to model the relationships between environmental factors and detection probabilities. We collected eDNA using cellulose nitrate filters, analyzed samples with quantitative PCR, and interpreted results using occupancy modeling. Preliminary data indicate high detection probabilities for Arizona treefrogs (Hyla wrightorum; 1.0 for 250 mL samples) and lower detection probabilities for Chiricahua leopard frogs (Lithobates [Rana] chiricahuensis; 0.65 for 250 mL samples). Better understanding of the relationship between environmental factors and eDNA detection can help inform the sampling design of cost-effective survey and monitoring efforts.