Vaquita Conservation and Abundance
Saving the world's most endangered marine mammal
Abundance and Trends
Historical abundance of the vaquita is unknown, but genetic evidence indicates that the population was never large (Rojas-Bracho et al., 2006). The first precise estimate of abundance was obtained from a cooperative Mexican-American survey conducted in 1997 that sampled the entire geographical range of the species and estimated there were 567 individuals (95% CI 177-1073; (Jaramillo-Legoretta et al., 1999). Early acoustic work between 1997 and 2008 indicated a decline (Jaramillo-Legoretta & Rojas-Bracho, 2008). These data agree with population estimates based on the 1997 visual abundance estimate, combined with the increased number of pangas in the area, the estimated kill rate from bycatch in gillnets and potential vaquita population growth rate (Jaramillo-Legoretta et al., 2007).
A second Mexican-American survey was conducted in 2008 and estimated total vaquita abundance to be 245 animals (CV = 73%, 05% CI 68-884) (Gerrodette et al. 2011). The 2008 estimate was 57% lower than the 1997 estimate, an average rate of decline of 7.6%/year. The 2008 research also gathered data to allow design of a passive acoustic monitoring program using a device that detects vaquita events called a CPOD. The acoustic monitoring program uses a grid of 48 CPODs inside the Vaquita Refuge. The Refuge covers about 50% of vaquitas’ distribution but could not be monitored due to loss of the CPODs to active fishing (both gillnetting and trawling). Results indicated a 67% decline in acoustic activity in the sampled area, for an annual rate of 31% (CIRVA VI Report, in IWC/66/Rep01(2015), Annex L).
A third international survey was conducted in 2015 and estimated total vaquita abundance, based on the combined results of the visual line transect survey and static passive acoustic monitoring, was estimated to be 59 (95% CRI 22-145) (CIRVA VIII Report, 2016). Results of the passive acoustic monitoring program indicate that the vaquita population experienced an average annual decline of 34% (95% CI 21 to 48%) from 2011 to 2015, prior to the emergency gillnet ban which began in May 2015. It is certain (a 100% chance) that the population decreased during this time interval and almost certain (a 98% chance) that it decreased at an annual rate of more than 20%. Overall, the model results indicate that the population decreased by 80% (95% CI 62% - 93%) between 2011 and 2015.
The most current population estimated is based on analysis of the 2016 Acoustic Monitoring Program data which has shows that almost half of the remaining vaquita population were lost between 2015 and 2016 (a 49% annual decline). The average annual rate of decline between 2011 and 2016 is estimated to be 39%, corresponding to a population decline of 90% over this five-year period. CIRVA estimates that, as of November 2016, only approximately 30 vaquitas likely remain and the species is in imminent danger of extinction (CIRVA VIII, 2016).
Interaction with Fisheries
Coincident with the recognition of the vaquita as a new species was the realization that individuals were being incidentally taken in small scale and industrial commercial fisheries (Norris & Prescott, 1961). From around the mid-1930s (Brownell, 1982) to the mid-1970s (Flanagan & Hendrickson, 1976), the most important fishery in terms of vaquita by-catch was the gillnet fishery for totoaba, Totoaba macdonaldi, a large fish up to 2 m in length and can exceed 100 kg in weight that is endemic to the Gulf of California. Despite the closure, many vaquitas continued to die in illegal totoaba nets (Vidal 1995 and see details of the early totoaba fishery in Rojas-Bracho and Taylor 1999). This fishery was officially closed in 1975 because of severe overfishing (the species is on the Mexican Endangered Species list, listed as CITES Appendix I (1976), added to the U.S. Endangered Species list (1979) and is listed (1986) by the IUCN Red List as Critically Endangered). Even following closure of the totoaba fishing, many vaquitas died in both illegal fishing (Vidal 1995) and some in an experimental fishery (see summary of early levels of vaquita kills in totoaba nets in Rojas-Bracho and Taylor 1999). Since that time, and perhaps before, it has become known that vaquita are incidentally caught in gillnets set for shrimp and fish. D’Agrosa et al. (2000) found that some level of vaquita bycatch is known to occur in most, if not all, types of gillnets used in this area. The small scale gillnet fisheries in the northern Gulf of California generally involve the use of boats known as pangas which are (mainly) fiberglass, outboard-powered boats 6-8 meters long crewed by two or three local men (Vidal et al., 1994). The gillnet fishery is highly dynamic due to a combination of environmental variation, market factors and overexploitation (Rojas-Bracho et al., 2006). Much of the market for fish is domestic. Species targeted include corvina (Cynoscion othonopterus), mackerels (sierra, Scomberomorus sierra; also S. concolor), chano (Micropogonias megalops), sharks (including Carcharhinus spp., Sphyrna spp., Rhizoprionodon spp. and Mustelus spp.), and skates and rays (including Myliobatis spp., Rhinobatus spp., Dasyatis brevis, Mobula spp.). The high-value shrimp fishery in the northern Gulf includes a large industrial trawling fleet as well as the pangas that fish with gillnets. The product, especially fresh-frozen shrimp, is consumed locally or exported to the United States (Rojas- Bracho et al., 2006).
Illegal fishing for totoaba has greatly increased in the past few years and is a great menace to the vaquita. As in previous years, vaquitas have died in nets set for totoaba. In addition to the meat, this endangered fish is prized for its swim bladder, which is exported to China where it is used as an ingredient in soup and believed to have medicinal value. Thousands of swim bladders are dried and smuggled out of Mexico, sometimes through the US. Fishermen receive up to $8,500 for each kilogram of totoaba swim bladder, equivalent to half a year’s income from legal fishing activities. Read more: Environmental Investigative Agency 2016 report: Collateral Damage: How illegal trade in totoaba swim bladders is driving the vaquita to extinction and Elephant Action League 2017 report: Operation Fake Gold.
Rojas-Bracho & Taylor (1999) examined whether four hypothesized factors constituted threats that could place the vaquita at risk of extinction. The putative threats and conclusions about their importance are: (1) habitat alteration from reduced flow of the Colorado River does not currently appear to be a threat because ecosystem productivity (nutrient levels and chlorophyll) remains high in vaquita habitat and vaquitas examined after dying in fishing nets appeared to be feeding normally (ie., they were not emaciated); (2) pollutant loads in tissues of bycaught animals are low and available data show that pollutants pose no threat to the survival of the remaining population; (3) reduced fitness from inbreeding depression and loss of genetic variability are unlikely to pose high risk currently, though risk will increase if' vaquitas remain at low abundance over long periods of time; and (4) mortality resulting from fisheries bycatch poses high risk because deaths in nets far exceed possible replacement by births. The authors note that short term management should not be hindered by uncertainty in estimating the magnitude of these threats, and primary conservation efforts should be directed toward immediate elimination of incidental fishery mortality. These conclusions have been repeatedly confirmed by CIRVA, the International Committee for the Recovery of the Vaquita (CIRVA 1997, 1999, 2004, 2012, 2014, 2015, 2017). Recent research focused on vaquita and productivity of the Northern Gulf has corroborated CIRVA´s conclusion: this region has remained a healthy system at the level of primary producers in spite of the possible lack of supply of nutrients by the Colorado River. The small size of the population of vaquitas is not due to the collapse of its ecosystem. Read more: Brusca et al. 2016, Colorado River flow and biological productivity in the Northern Gulf of California, Mexico.
Gillnets for fish and shrimp cause incidental mortality (bycatch) of vaquitas. The only published study that estimates bycatch is from 1993–94 and refers to El Golfo de Santa Clara, one of the three main fishing ports (D’Agrosa et al., 2000). The authors estimated that 39 individuals were killed per year (95% CI 14–93) using combined data from observers and interviews with fishermen. Assuming a similar rate of mortality from the port of San Felipe, the extrapolated estimate of incidental mortality for the two ports was 78 vaquita killed per year in 1993 (D’Agrosa et al., 2000), which is well above what would be sustainable for this species (D’Agrosa et al., 2000; Rojas-Bracho et al., 2006).
Conservation Efforts: Working alongside scientists and non-governmental agencies, the Government of Mexico has taken a number of actions over the years that were intended to eliminate gillnets from the region and to protect the vaquita. To guide these efforts, the Government of Mexico established the International Committee for the Recovery of the Vaquita (CIRVA) in 1996 with a mandate to develop, oversee and promote a recovery plan for the vaquita. CIRVA has developed many recommendations, summarized in 9 reports over the intervening years. The most consistent and important recommendation is to permanently ban the manufacture, possession or use of all gillnets on land or sea throughout the range of vaquitas. Read more: CIRVA reports.
Among the efforts to protect the vaquita adopted by the Government of Mexico are the designation of a Biosphere Reserve (The Upper Gulf of California and Colorado River Delta Biosphere Reserve, a UNESCO World Heritage Site) in 1993 and, in 2005, the establishment of a Vaquita Refuge, where all commercial fishing (including gillnets) is banned in core vaquita habitat. In 2008, the Government introduced the Species Conservation Action Plan for Vaquita (PACE Vaquita), a comprehensive protection and recovery effort which includes a program to encourage fishermen to switch to fishing gear that does not threaten vaquitas. These actions may have slowed, but did not stop, the decline of the species (Rojas-Bracho and Reeves, 2013). In 2013, a new Advisory Commission of the Presidency of Mexico for the Recovery of the Vaquita was established to expedite actions to save the vaquita. Later that year, Mexican Government adopted new regulations (NOM 002) to switch all shrimp gillnetting to small-type trawls over a 3 year period.
Beginning in 2011, the acoustic monitoring program revealed an accelerated decline in the population, due to the resurgence of an illegal fishery for another endangered species - the totoaba (CIRVA V, 2014). With less than 100 individuals remaining, the Government of Mexico responded with a two-year emergency gillnet ban with compensation to the fishermen and related industries and increased enforcement efforts with the Navy in charge. The new program (the Integrated Strategy for the Recovery of the Vaquita) was launched in San Felipe by President Peña Nieto in April of 2015. As part of this program a new survey (Vaquita Expedition 2015) was undertaken to get the most precise abundance estimate possible at the start of this program yet the results only confirmed the continued dramatic decline: the 2015 abundance was estimated to be 59 (Taylor et al. 2016) and the latest population estimate is 30 (CIRVA VIII, 2016).