FIELD OPS · CONTROLLED DOCUMENT
AE-SOP-0240 — eDNA & Acoustic Survey
To survey species presence and abundance across a range using environmental-DNA water sampling and passive and active acoustics, so that the League maps populations without ever handling the animals. The procedure guarantees that eDNA samples are filtered and preserved before degradation, that acoustic coverage and detection thresholds are set before the survey runs, and that field blanks prove no cross-site contamination — because a survey that cannot distinguish a real detection from a carried-over trace tells the fleet nothing.
ActiveField OpsRev C
Doc Control AE-SOP-0240Revision CEffective 2090-05-04Next Review 2091-05-04Owner Marine ScienceApprover Marine ScienceStatus ActiveClass RESTRICTED // TIDEWATER-EYES-ONLY
1. Purpose
To survey species presence and abundance across a range using environmental-DNA water sampling and passive and active acoustics, so that the League maps populations without ever handling the animals. The procedure guarantees that eDNA samples are filtered and preserved before degradation, that acoustic coverage and detection thresholds are set before the survey runs, and that field blanks prove no cross-site contamination — because a survey that cannot distinguish a real detection from a carried-over trace tells the fleet nothing.
2. Scope
All non-invasive eDNA and acoustic surveys across field ranges.
- In scope: Survey design, eDNA water filtration and preservation, passive and active acoustic recording, contamination control, and detection processing.
- Out of scope: Forensic-grade sampling intended for prosecution, which follows AE-SOP-0312; acoustic tagging of resident cetaceans, which follows AE-SOP-0405.
3. Definitions
| Term | Definition |
|---|
| eDNA | Trace genetic material shed into the water, filtered and sequenced to detect species without capture. |
| Filter Blank | A clean filter carried through the full process to prove no cross-site or gear contamination. |
| Passive Acoustics | Recording ambient sound to detect vocalising species without emitting any signal. |
| Detection Threshold | The minimum read count or signal-to-noise level that counts as a confirmed detection. |
| Acoustic Coverage | The fraction of the survey range within effective hydrophone or sonar range. |
4. Responsibilities
| Role | Responsibility |
|---|
| Marine Science (Owner) | Owns survey design; sets detection thresholds and signs the survey report. |
| Survey Operator | Runs eDNA filtration and acoustic recording in the field and maintains contamination control. |
| Bioinformatics Analyst | Processes sequences and acoustic detections against thresholds and resolves ambiguous reads. |
| NEREID | Geotags samples and recordings, maps acoustic coverage against the survey plan, and flags coverage gaps for re-survey. |
5. Survey Method Parameters
| Method | Sample / Coverage | Preservation / Window | Detection Threshold |
|---|
| eDNA water filtration | ≥ 2 L per station | Preserve ≤ 30 min, freeze ≤ 24 h | ≥ 3 positive replicates |
| Passive acoustic | ≥ 80 % range coverage | Continuous record | SNR ≥ 6 dB confirmed call |
| Active acoustic / sonar | Planned transect lines | Per-pass calibration | Target strength in band |
| Filter / field blank | 1 per site minimum | Carried through full process | Zero target reads |
Note. A site with any positive filter-blank read is discarded and re-surveyed; a detection is confirmed only on the replicate or SNR threshold, never on a single ambiguous read.
6. Materials & Equipment
- eDNA filtration rig with single-use filter cartridges
- Sample preservation buffer and chilled transport
- Hydrophone array for passive acoustics
- Calibrated active-acoustic / sonar transducer
- Filter and field blanks for every site
- Geotag-synced survey logging device
7. Procedure
7.1 Plan & Deploy
- Lay out eDNA stations and acoustic transects to meet the coverage target.
- Set detection thresholds and calibrate transducers before the first pass.
- Carry a filter blank for every site.
7.2 Collect
- Filter the station water volume and preserve within the window.
- Record passive and active acoustics across the planned coverage.
- Process a field blank at each site to prove no cross-site contamination.
7.3 Process & Report
- Sequence eDNA and score acoustic detections against thresholds.
- Discard and re-survey any site with a positive blank read.
- Compile the survey report and flag coverage gaps for re-survey.
8. Records
- Survey design and station/transect plan (retained 3 years)
- eDNA filtration and preservation log
- Acoustic recording and calibration logs
- Filter and field blank results
- Detection report with thresholds applied
9. References
10. Revision History
| Rev | Date | Author | Summary |
|---|
| A | 2088-09-12 | Marine Science | Initial issue; eDNA filtration and passive-acoustic survey established. |
| B | 2089-10-08 | Marine Science | Added filter blanks and replicate detection thresholds. |
| C | 2090-05-04 | Marine Science | NEREID coverage mapping and active-acoustic transect calibration added. |