New Findings Reveal Vaquitas Outside Protected Areas Following May 2024 Survey

Barbara Taylor and Lorenzo Rojas-Bracho

Given the 45% annual decline estimated in 2018, most people expected Mexico’s vaquita porpoise to be extinct by now. As vaquita numbers declined, the distribution of vaquita acoustic activity in the Vaquita Refuge shrank to the area currently known as Zero Tolerance Area (ZTA) (Jaramillo-Legorreta et. al. 2019). Between August 2022 and September 2024 the Mexican Navy deployed more than 400 concrete blocks with 3m high metal hooks designed to entangle gillnets within the ZTA and an extension area adjacent to the ZTA. Since then, the Navy and Sea Shepherd Conservation Society (SSCS) have collaborated to monitor fishing activity. Deployment of the gillnet-entanglement devices, which resulted in a 90% decrease in gillnetting within the ZTA, is probably the most significant recent step toward buying precious time for the new Government to take additional vaquita-protection actions.

In May 2023 scientists saw about the same number of vaquitas they had seen in 2019 and 2021 in the ZTA (read the full report here in English and here in Spanish plus the Appendices in English only). The May 2023 vaquita survey observed gillnets just outside the ZTA boundary, including in an area where a mother and calf were seen. This prompted the government to designate an Extension Area (EA) that was later seeded with more concrete blocks.

Figure 1. The Seahorse with crew on the bow and observation team on the bridge deck in the foreground and the Sirena de la Noche with the observation team on the bow in the background.

The May surveys in 2023 and 2024 were designed to be comparable using the same 2 ships, the Seahorse and the Sirena de la Noche (Figure 1), the same observers and the same methods (both surveys funded by CONANP and SSCS). Weather was also comparable with a bit more coverage in good sea states in 2024 than in 2023. In May 2024, there were 9 sightings of vaquitas within the ZTA and the Extension Area (read the full report here in English and here in Spanish plus the Appendices here in English only) (Figure 2) compared to 16 sightings in 2023. Results from Expert Elicitation of the 2024 survey data indicated that it was highly likely that no calves were seen, one yearling was seen and there was a 75% probability that the total number of vaquitas seen was between 6 and 8 individuals. 6-8 is considered a minimum estimate of the number of vaquitas left. The 2024 estimate is less than the 10-13 that were seen in 2023 within a similar area. All the animals looked healthy and they were apparently feeding.

Figure 2. Summary of vaquita acoustic and visual detections during the May survey. The ZTA is within the yellow corner dots. Corners of the Extension Area (EA) are indicated by red dots. Black dots are positions for survey navigation some of which correspond to locations of acoustic detectors. Sites with acoustic detections are green dots. Sightings (purple dots) 3, 4, 5 and 7 were in the EA and sighting 6 was along the boundary of the ZTA. Tracklines of the Seahorse are in red and the Sirena de la Noche in blue. San Felipe harbor is the small square at the bottom of the figure.

The authors of the 2024 Report cautioned that the reduced number of vaquitas detected within the ZTA plus EA doesn’t necessarily represent a further decline since the surveyed area represents only 12% of the species’ range in 2015 (Rojas-Bracho et al. 2024). Following recommendations within the survey report, acoustic research outside the ZTA was conducted (acoustic report here in English and here in Spanish). In late August and early September passive acoustic detectors had vaquita detections both within the ZTA and in areas within the Vaquita Refuge that were previous high vaquita use areas. Finding that vaquitas are using their former range gives hope that the reduced numbers seen in the May 2024 survey may not represent reduced numbers of vaquitas remaining. However, given that there is no evidence of reduced levels of gillnetting except within the ZTA and part of the Extension Area, additional protective measures will be needed for vaquitas found outside these areas in the Vaquita Refuge.

Citations:

Rojas-Bracho et al. 2024. Mexico must save the vaquita from gill nets. Science Vol 385, Issue 6708, p 504. DOI: 10.1126/science.adp5382.

Jaramillo-Legorreta, A.M., G. Cardenas-Hinojosa, E. Nieto-Garcia, L. Rojas-Bracho, L. Thomas, J.M. Ver Hoef, J. Moore, B. Taylor, J. Barlow, N. Tregenza. 2019. Decline towards extinction of Mexico’s vaquita porpoise (Phocoena sinus). R. Soc. Open sci. 6: 190598.