By Barbara Taylor and Lorenzo Rojas-Bracho
Given the 45% annual decline estimated in 2018, most people expected Mexico’s vaquita porpoise to already be extinct. Scientists have just seen (May 2023) about the same number of vaquitas they saw in 2019 and 2021 in a small area in the far northern Gulf of California near San Felipe, Mexico (read the full report here in English and here in Spanish plus the Appendices in English only). The visual research, including both ships and contracted professional observers, was funded by Sea Shepherd Conservation Society. Around ten individuals, including at least one calf, were seen. All the animals looked healthy and they were feeding. Given the precision of estimates between 2019 and 2023 no conclusion can be drawn as to whether vaquitas are increasing or decreasing. One reason the team was able to obtain photographs and drone footage is that there was very little fishing activity in the area at the time of the survey. Intense fishing activity had interfered with survey efforts in previous years, which had always been in the autumn shrimping season.
In August 2022 the Mexican Navy deployed 193 concrete blocks with 3m high metal hooks designed to entangle gillnets. Blocks were set within the vaquitas’ last stronghold: a 12 x 24 km area called the Zero Tolerance Area (ZTA). The Navy and Sea Shepherd Conservation Society (SSCS) have collaborated to monitor fishing activity over the past 9 months. The apparent 90%+ decrease in gillnetting within the last stronghold of vaquitas is probably the most significant step taken to date toward saving the species. When gillnetting within the ZTA is observed, SSCS reports to the Navy and the Navy is expected to ensure that the gillnets are removed and the fishermen relocate to fish outside the ZTA. Sometimes nets are confiscated, despite the fact that all gillnets should be banned in the vaquita’s area of distribution.
May is a low fishing season, so the two survey ships were able to work outside the ZTA for the first time in recent years. Acoustic research, funded by the Government of Mexico and the Cetacean Action Treasury, had already made many acoustic detections of vaquitas along the northwestern border of the ZTA (Figure 1).
Figure 1. Summary of vaquita acoustic detections during the May survey period with the days of recording depicted by the size of the dots and the color indicating the number of acoustic encounters. The small yellow dots are locations where vaquitas were seen. Clusters of yellow dots represent multiple locations of the same individuals tracked over time. The ZTA is outlined in green and the San Felipe harbor is the small square at the bottom of the figure.
This year’s survey recorded visual sightings of both vaquitas (Figure 2) and gillnetting (Figure 3) in the area.
Figure 2. Tracklines followed by Seahorse (blue lines) and Sirena de la Noche (red lines) during Vaquita Survey May 2023. The small dots are locations where vaquitas were seen: green for confirmed cow/calf locations and black for all other vaquita locations. Clusters of dots represent multiple locations of the same individuals tracked over time. The ZTA is outlined in green and San Felipe harbor is the small square at the bottom of the figure.
The concrete blocks together with enforcement within the ZTA seem to constitute an effective way to prevent gillnetting. The SSCS ship has advanced side-scan sonar and has found only one net entangled on the blocks and hooks (Figure 4). Based on this year’s results, expansion of the concrete block-and-hook approach to other areas where vaquitas are known to be feeding is an urgent priority.
Figure 3. Gillnetters with panga tied up to the ZTA border buoy at the northern-most corner. Their gillnets were set just outside the ZTA in the area where vaquitas were observed. Photo: Barbara Taylor.
Figure 4. Red lines show where side-scan sonar was used. The area of the ZTA is completely covered because of the focus to search for ghost nets entangled on the concrete block hooks. The yellow rectangle depicts a buffer zone used to quantify fishing effort near the ZTA. The blue line shows the boundary of the Vaquita Refuge.
