Summary
This report describes the vaquita survey of 10 to 26 May 2023, with 17 days of visual search from two ships in and around the Zero Tolerance Area. The team made 16 sightings and 61 acoustic encounters. Expert elicitation gave a 76% probability that between 8 and 13 vaquitas were seen, including 1 to 2 calves.
Why it matters
It was the first visual survey in May rather than October, and it found more calm days and more sightings than the 2019 and 2021 surveys. It also reported close to no gillnetting inside the Zero Tolerance Area after the Navy placed concrete blocks with hooks there.
Key findings
- 17 days of visual search between 10 and 26 May 2023 produced 16 sightings and 61 acoustic encounters.
- Expert elicitation: a 76% probability that 8 to 13 vaquitas were seen (mean 10.6) and a 65% confidence that at least 10 were seen.
- Calves: 1 or 2 judged about equally likely, with a 10% chance of more than 2. One mother and calf were photographed on 3 consecutive days.
- Winds were low enough to sight vaquitas on 11 days, against 4 and 5 days in 2019 and 2021; all animals appeared healthy.
- No gillnetting was seen inside the Zero Tolerance Area, but it was regularly seen northwest of it, where vaquitas were also seen.
Caveats
The 8 to 13 range is a minimum count of animals seen in a small part of the vaquita's range and not a population estimate. The authors say that, given the precision of the 2019 to 2023 results, no conclusion can be drawn about whether vaquitas are increasing or decreasing, and that the move to May makes comparison with earlier surveys harder.