Vaquitas continue to surprise the world with their tenacity

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).  Around ten individuals, including at least one calf, were seen. All the animals looked healthy and they were feeding.  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 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. The ZTA is outlined by the grey dashed line, 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 by 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.

Good News from the Zero Tolerance Area in late 2022: Less illegal gillnetting and more evidence of vaquita survival

by Kristin Nowell, Cetacean Action Treasury

In 2022 there was a major new development in the Zero Tolerance Area (ZTA), the 225 km² polygon inside Mexico’s Vaquita Refuge in the Upper Gulf of California.  The ZTA, which was delineated to encompass all recent vaquita sightings and acoustic detections, has been designated as a no-fishing and no-entry zone since September 2020.  However, there is strong evidence of lax enforcement: fishing skiffs (pangas) were observed inside the ZTA on 88% of observation days from October 2021 to May 2022. In response to persistent violations, the Mexican Navy developed a radical proposal to deter the use of illegal gillnets which have driven the precipitous decline of the Critically Endangered vaquita population.  Between July 8 and September 30 (normally a season of low fishing activity), a grid of 193 gillnet-deterrent structures was installed on the ZTA seabed.  They were lowered by crane into the water and placed in a grid about 1.1 km apart.  The structures are concrete blocks a meter square, with two 3.5 m tall, 1 ½ inch diameter iron rebar hooks protruding from the top, intended to entangle gillnets as they drift with the tides (Figure 1).

Figure 1 – Gillnet deterrent structures being deployed in the Zero Tolerance Area

Anti-trawl structures have been used by other countries to stop trawl nets from operating in protected areas (such nets are dragged along the seafloor), but this approach has never been tried against gillnets outside of shallow waters (ZTA depths range from 10-30 m).  Counts of fishing pangas in the ZTA from Sea Shepherd Conservation Society (SSCS) and scientific vaquita surveys were used to determine if there were any initial deterrent impacts (see full report for details).

The highest-ever recorded count of pangas in the ZTA in recent years (117) was in the fall 2021 shrimp season.  To try to prevent a repeat in the fall 2022 shrimp season, Cetacean Action Treasury’s Mexican partner organization, Pesca ABC, with support from the International Conservation Fund of Canada, made five posts on its Facebook page in September through October, providing the ZTA coordinates and offering to assist fishers to input them into their GPS.  Over a dozen fishers came to Pesca ABS’s office in San Felipe for assistance, and overall the posts garnered nearly 18,000 views.

It is well known locally that gillnetters prefer to work in spring tides (strong tidal fluctuations associated with the full and new moons, with approximately two such tidal periods per month).  Maximum daily panga count data for 2021 and 2022 were grouped and averaged for consecutive spring tides (days when the difference between consecutive tide peaks – high or low – are over 350 cm).  Although panga counts were not available for all spring tide days due to occasional absence of SSCS ships from the area, comparing consecutive tides for the two years suggests a significant reduction in gillnetting in the ZTA in 2022 subsequent to the first major fishing effort in the second October spring tide (Table 1). In other words, many fishers with gillnets apparently began to avoid the area.

Table 1. Reduction in average maximum daily count of pangas in the ZTA over consecutive bi-monthly spring tides in 2022 compared to 2021

On November 16, Pesca ABC warned the community in its social media that they knew of fishers getting their nets stuck on the structures.  On January 11 2023, another San Felipe CAT partner organization (MAREM) asked fishers on Facebook to share coordinates of lost nets to aid in their removal. Although the only public comment on the post was “Nobody wants to cooperate” (which is illustrative of local non-compliance with the December 8 2021 requirement to report lost fishing gear within 24 hours), ultimately eight sets of coordinates were provided by fishers.  Two sets were outside the ZTA, but all six sets reported inside the ZTA coincided with coordinates of deterrent structures, suggesting that the structures had been at least partially effective at snagging gillnets.

Active deterrence actions by the Mexican Navy increased significantly in fall 2022 compared to the previous year.  SSCS ships assisted compliance monitoring by sending situation reports (SITREPs) of gillnetting in the ZTA; Navy actions are described in SSCS daily Scientist reports.  The Navy was generally responsive to SSCS SITREPs during the spring tides of 2022, and was observed to “drive pangas out of the ZTA” on multiple occasions, with several instances where gillnets were seized or fishers were directed to remove them.  In contrast, although Navy patrol boats were present during the 2021 fall vaquita survey (first two spring tides in Table 1), no interaction with pangas was observed.

The reduction of illegal gillnetting may have contributed to an observed increase in the rate of vaquita acoustic encounters after installation of the deterrent structures (Armando Jaramillo-Legorreta, pers. comm.). Eight acoustic sampling exercises (see here for background on Mexico’s acoustic monitoring program), supported by CICESE and CONANP and facilitated by community fishers associated with Pesca ABC and MAREM, were carried out in neap tide periods in 2022 (when few gillnetters would be expected to be present, thus minimizing the potential for loss of or tampering with monitoring equipment). Vaquitas were detected in every sampling exercise, indicating that at least some individuals were consistently present in the ZTA. Based on distance between encounters and maximum potential swimming speeds, 11.7% of 77 total encounters in 2022 were considered likely to have been detections of different individuals or groups of individuals.  Comparing five exercises with comparable sampling effort, the number of vaquita encounters per day (number of acoustic detections >30 minutes apart) increased noticeably after installation of the deterrent structures was completed (Table 2).  An increased acoustic encounter rate could reflect a change in vaquita behavior (vaquitas generally echolocate when hunting prey) associated with reduced gillnetting in the ZTA, but does not signify a change in population trend, which is still declining (A. Jaramillo-Legorreta, pers. comm.).

Table 2. Rate of vaquita acoustic encounters/day in the ZTA increased in late 2022

Source: A. Jaramillo-Legorreta pers. comm., research supported by CICESE/CONANP

The Navy and CONANP had been warned in advance that pangas with gillnets would likely concentrate around the ZTA, creating an edge effect and increasing the risk to vaquitas that move outside the ZTA, which they certainly do.  Since early February 2023, SSCS has been conducting panga counts in a one nautical mile buffer zone around the ZTA, and hopefully the Mexican Navy will be as responsive to reports of illegal gillnetting around the ZTA as inside it. Time-bound compliance processes in 2023 under CITES and the USMCA will further increase the pressure on Mexico to enforce its gillnet ban more effectively in the Upper Gulf of California. Unfortunately, a program to frequently inspect and clean the deterrent structures of entrapped or snagged net material, which could pose an entanglement risk to vaquitas, has not yet been implemented.  There will be continued urgency to prevent fishers with other types of gillnets from entering the ZTA as the fishing seasons change in spring from shrimp to commercial finfish fishing and totoaba poaching.  Some types of finfish and totoaba gillnetting usually do not involve setting on the bottom, as shrimp gillnets are, and these other types of gillnetting may not be deterred by the seabed concrete structures. Therefore, security for vaquitas during the coming months will depend on increased voluntary compliance by the fishing community and enforcement actions by authorities.