Practical eDNA sampling methods inferred from particle size distribution and comparison of capture techniques for a Critically Endangered elasmobranch

Environmental DNA (eDNA) methods are increasingly applied in the marine environment to identify species and community structure. To establish widely applicable eDNA techniques for elasmobranchs, we used Critically Endangered largetooth sawfish (Pristis pristis Linnaeus, 1758) as a model for: (1) assessing particle size distribution; (2) efficiency of long-term preservation water samples; (3) comparing detection sensitivity filtration precipitation methods. Water samples (1 L) collected from tank containing one specimen were sequentially filtered through five filter membranes decreasing pore (20, 10, 5, 1.2, 0.45 μm). The proportion retained within each class was determined quantitative real-time PCR (qPCR) using species-specific TaqMan probe assay. A linear mixed-effects (lme) showed that 1.2 20 µm filters captured most particles present sampled water. Additionally, whole (0.375 preserved Longmire's buffer, stored at tropical ambient temperatures (26.3°C ± 3.0 SD) extracted time points: immediately, one, two, three months after collection, well frozen later, assess buffer via qPCR analysis. maintained maximal yield least collection storage. Lastly, when methods, more sensitive capture than with or precipitation. However, efficient accounting volume processed. These results provide options best elasmobranch eDNA.