Joint visual and acoustic survey finds vaquitas surviving and reproducing, mostly in and near the sanctuary
By Gustavo Cárdenas-Hinojosa, Lorenzo Rojas-Bracho, Barbara L. Taylor
Major research efforts were made this year to delineate vaquita distribution, estimate abundance, and assess health. The two main elements were (i) an acoustic program to delineate current vaquita distribution and estimate abundance that took place from May through September 2025 and (ii) a joint visual and acoustic survey conducted in September to estimate the number of vaquitas and calves seen using expert elicitation and report on their health using photographs including drone measurements when possible (Final Published Report in Spanish is available here, a draft report in English here – versions in Spanish with English Appendices to be added soon). Regarding the first of these elements, intensive research was conducted using passive detectors deployed throughout the areas where vaquitas had been documented to be present in 2015. This was the first time since 2015 that such range-wide acoustic research had been conducted. More than 8,000 days of acoustic data were acquired between late May and the end of September 2025 and those data will be detailed in a later report. The second element, the visual/acoustic survey, used data from a grid of acoustic detectors that were regularly retrieved to provide locations of vaquita detections allowing the visual survey effort to focus in areas where the chances of seeing and photographing vaquitas were expected to be greatest.
Two Sea Shepherd Conservation Society (SSCS) vessels (Figure 1) were each equipped with 3 pairs of 25-power binoculars and carried an expert team of vaquita observers.
Figure 1. The SSCS vessels Seahorse and Bob Barker
Most vaquita detections were within the Zero Tolerance Area (ZTA) and Extension Area (EA), which in 2022 had been seeded by the Mexican Navy with concrete blocks with 3m-high metal hooks designed to discourage use of the gillnets that have driven vaquitas to very near extinction. We refer to this area protected by the concrete blocks (the ZTA+EA) as the ‘sanctuary area’. The blocks, together with surveillance and enforcement led by the Mexican Navy, in combination with logistical and monitoring support from SSCS, have ensured that since 2022 gillnets have been nearly eliminated from this area. No gillnet fishing was observed during the September ship surveys.
Our greatly expanded research effort in 2025 was prompted by lower-than-expected numbers of vaquita observations within the sanctuary area in 2024 and the possibility that the porpoises were making more use of favored habitat elsewhere within the Vaquita Refuge, which remains heavily fished with gillnets (Figure 2). The 2025 research revealed an unprotected area of high vaquita usage northwest of and adjacent to the EA. Vaquita acoustic detections (not shown in Fig. 2) were also made in favored ridge habitat in the northeastern portion of the Vaquita Refuge, but at much lower levels. During the September ship survey, the vessel was equipped with an advanced sonar system that allowed scientists to determine whether the seafloor was soft or hard. These measurements will help improve understanding of the habitat types that vaquitas use and will contribute to more refined descriptions of preferred habitat within the Refuge. All of the 2025 data will be used to produce a vaquita density distribution map and provide a new abundance estimate that will be released early in 2026.
Figure 2. Acoustic sampling sites without vaquita detections (black dots) and with detections (orange dots) recorded in September 2025, together with the visual survey effort shown by colored tracklines and vaquita sightings by purple dots. Purple stars indicate sightings with calves present.
Other important and very welcome news is that at least one and possibly two calves were seen (Figure 3). In addition, one or two vaquitas measured from drone images were estimated to be 2.5 to 3.5 years old. A drone image taken in 2024 was of a 1.5 year-old vaquita. Therefore, some vaquitas are reproducing and some calves are surviving through their vulnerable early years of life. Since 2017 there have been 93 sightings of vaquitas and none of them appeared to be unhealthy.
Figure 3. A 1.5m vaquita mother with her 1.1m calf. Photograph and measurements by Fabian Rodriguez, SSCS and CONANP.
As in the past two years, a training program for local young people was carried out in 2025, giving them valuable opportunities to participate directly in the research and, for many, the unforgettable experience of seeing a vaquita for the first time. This program not only strengthened local capabilities and engagement but also created a sense of pride and stewardship within the community. The research and training efforts were funded by Mexico’s National Commission for Protected Areas (Comisión Nacional de Áreas Naturales Protegidas -CONANP) and SSCS.
Figure 4. Trainees from San Felipe participating in the vaquita survey.
The 2025 research confirms that vaquitas spend most of their time within the small sanctuary area. However, the research also shows that at least some individuals range outside this area. Waters northwest of the sanctuary area are important vaquita habitat. This area between the EA and the western boundary of the Vaquita Refuge needs immediate protection from gillnets to guarantee the safety of these last vaquita survivors, and especially the critically important females and calves. Expanding the ZTA to encompass the currently known areas of high use would provide the needed protection.