Details of Status Assessment for the Vaquita

The vaquita (Phocoena sinus) is found only in the waters of the northern Gulf of California, Mexico (see map), and recent surveys within the area now most favoured by vaquitas have observed only about ten individuals remaining over the period from 2019 to 2023. 

The IWC Scientific Committee has not conducted its own status assessment modelling for vaquitas, but published research on vaquita status (including modelling conducted by outside agencies) has been regularly reported to and reviewed by the Scientific Committee.

Recent survey abundances are tabled below. Some of these surveys have used different methods and therefore can be difficult to compare.

In 1975, the IWC Scientific Committee (SC) first expressed its concerns about bycatch of vaquita in gillnets and since 1991 the SC has recognised that the low population size and relatively high rate of mortalities in fisheries was unsustainable.  By 2015 a monitoring programme estimated a total abundance for the species of 22 to 145 individuals with a best estimate of 59 (Taylor et al. 2016), a rate of decline of 18.5% per year.  In 2018, acoustic monitoring found that there were only about 10 individuals remaining (uncertainty range 6-19; Jaramillo-Legorreta et al. 2019).

Although historical abundance is highly uncertain, Jaramillo Legorreta (2008) estimated that it might have been around five thousand animals, which suggests that the current depletion level is severe, perhaps less than 1%.

Vaquita abundance declined by a cumulative 99% (95% confidence interval from nearly 100% to 92.1%) from 1998 to 2018. This extends the estimated 92% decrease over the 18-year period 1997-2015 estimated by Taylor et al. (2016).  However, the rate of decrease has not been constant over recent decades.  The cumulative total decline reflects both a 8% annual rate of decline during 1997-2008 and a 45% annual rate of decline during 2011-2018.  Since 2018, the decline has likely slowed, as a continuation of the prior rate of decline would have almost surely led to extinction by now, although recent detection rates continue to decline (Jaramillo-Legorreta, 2023).

From 2019 to 2022, acoustic monitoring was reduced and targeted to the Vaquita Protection Refuge, and then the smaller ‘Zero Tolerance Area’, due to the continuing contraction of the area where vaquita were detected and because illegal fishers removed the acoustic detectors.  However, the adults and calves observed visually during this period appeared healthy and there was a higher rate of survival than expected (Rojas-Bracho et al. 2022). 

Recent acoustic surveys from April to December 2022, identified 77 acoustic encounters of vaquitas in 17 of the 42 sampling sites inside the ‘Zero Tolerance Area’, showing that vaquitas still exist in at least a small portion of their previous habitat (Jaramillo-Legorreta et al. 2023).  However, illegal fishing remained rampant, even in the designated “Zero Tolerance Area” until that year (Taylor et al. 2022).

Incidental mortality in gillnets is the only documented threat to the vaquita.  Vaquitas become entangled in all types of gillnets, including those set for shrimp and finfish, but the highest mortality rate has been from nets set for totoaba (Vidal 1995), a fish similar in size to vaquita, which has skyrocketed in value due to the black-market demand for totoaba swim bladders in China (EAL 2018, EIA 2017).  Totoaba fishing is not the sole concern, however, as between 1997 and 2008 about 400 vaquitas died in nets that were not totoaba nets. The rapid decline of the vaquita toward extinction is deeply concerning and exemplifies the challenge facing other dolphin and porpoise species living in coastal waters and struggling to survive alongside human activities, particularly fishing. The involvement of organised crime in the totoaba fishery (Felbab-Brown 2022) makes the decline particularly difficult and dangerous to address.

Regulations established by the government of Mexico banning all gillnets have so far proved unenforceable, and in August 2022 concrete blocks with entangling hooks were installed throughout the ‘Zero Tolerance Area’ where remaining vaquitas appear to spend most of their time.  A dramatic reduction of gillnetting within that area followed.  However, gillnetting outside this refuge remains rampant and there is no evidence of fishing practices moving towards vaquita-safe gear.

The precipitous decline from 2011 to at least 2018, if projected to today, would most likely have resulted in extinction (Rojas-Bracho et al. 2022).  Against all odds, at least 6 - 19 vaquitas remained within the ‘Zero Tolerance Area’ from 2019-2023 and appear to be healthy and have healthy calves. Due to the natural rarity of vaquitas, data examining the full genome found evidence that the species is likely to be robust to inbreeding depression (Robinson et al. 2022).  Thus, the vaquita is not doomed to extinction due to inbreeding alone, and could recover, even from such a low current population size, if bycatch mortality is immediately halted.

Given that perhaps only 10 individuals remain, and efforts to save the species have mostly been ineffective, it is clear that the vaquita is in immediate danger of extinction. The species is listed as Critically Endangered in the IUCN Red List and is the first species for which the IWC has issued an Extinction Alert.

The assessment date for vaquitas is 2018.

References 

CIRVA (2019). Report of the Eleventh Meeting of the Comité Internacional para la Recuperación de la Vaquita (CIRVA). 35pp. http://www.iucn-csg.org/wp-content/uploads/2019/03/CIRVA-11-Final-Report-6-March.pdf

D'Agrosa, C., Lennert‐Cody, C.E., Vidal, O. (2000) Vaquita bycatch in Mexico's artisanal gillnet fisheries: driving a small population to extinction. Conserv Biol 14: 1110-9

Elephant Action League (EAL). 2018. ‘Operation Fake Gold’. [online report, 100 pp.] Available at: https://earthleagueinternational.org/wp-content/uploads/2018/07/EAL-Operation-Fake-Gold-Final.pdf (Accessed on 06 March, 2023.)

Environmental Investigation Agency (EIA) 2017. ‘Facing Extinction: Survival of the vaquita depends on eliminating the illegal trade in totoaba’ [online report, 20 pp.] Available at: https://eia-international.org/wp-content/uploads/EIA_Ocean_report_briefing_Vaquita_Final.pdf (Accessed on 06 March, 2023.)

Felbab-Brown, V. 2022. China-Linked Wildlife Poaching And Trafficking In Mexico. Foreign Policy at Brookings. The Brookings Institution,1775 Massachusetts Ave., NW Washington, D.C. 20036 brookings.edu. 50 pp. Available at: https://www.brookings.edu/research/china-linked-wildlife-poaching-and-trafficking-in-mexico/ (Accessed on 06 April, 2023.)

Gerrodette, T., Taylor, B.L., Swift, R., Rankin, S., Jaramillo-Legorreta, A.M., and Rojas-Bracho, L. 2011. A combined visual and acoustic estimate of 2008 abundance, and change in abundance since 1997, for the vaquita, Phocoena sinus. Marine Mammal Science 27:E790-E100. https://doi.org/10.1111/j.1748-7692.2010.00438.x

International Whaling Commission. 1991. Report of the Scientific Committee, pg. 78, and Annex G. Report of the sub-committee on small cetaceans. Rep. Int. Whal. Comm. 41:172-90.

International Whaling Commission. 2022. Scientific Committee Report. Section 16.3.3 Vaquita (Phocoena sinus), pp. 132-135 and Annex Q, pp. 321-329. J. Cetacean Res. Manage. (Supplement). 24:1-406.

Jaramillo-Legorreta, A. M., Rojas-Bracho, L ,and Gerrodette, T. 1999. A new abundance estimate for vaquitas: first step for recovery. Mar. Mamm. Sci. 15, 957–973. (doi:10.1111/j.1748-7692. 1999.tb00872.x)

Jaramillo-Legorreta A. M., Cardenas-Hinojosa, G., Nieto-Garcia, E., Rojas-Bracho, L.R., Thomas, L., Ver Hoef, J.M., Moore, J., Taylor, B., Barlow, J. and Tregenza, N. 2019. Decline towards extinction of Mexico’s vaquita porpoise (Phocoena sinus). R. Soc. open sci. 6: 190598. http://dx.doi.org/10.1098/rsos.190598

Jaramillo-Legorreta, A.M. 2008. Estatus actual de una especie en peligro de extinción, la vaquita

(Phocoena sinus): una aproximación poblacional con métodos acústicos y bayesianos. PhD dissertation. Facultad de Ciencias Marinas. Universidad Autónoma de Baja California. Ensenada, B.C., México. 108 pp. + appendices.

Jaramillo Legorreta, A.M., Nieto García, E., Cárdenas Hinojosa, G. and Rojas Bracho, L. 2023. Acoustic monitoring and status of vaquita population in 2022. Report SC/69A/SM01 presented to the Scientific Committee, International Whaling Commission. 24 April - 6 May 2023. 11 pp.

Rojas-Bracho, L., Taylor, B.L. & Jaramillo-Legorreta, A. (2022). Phocoena sinus. The IUCN Red List of Threatened Species 2022: e.T17028A214541137. https://dx.doi.org/10.2305/IUCN.UK.2022-1.RLTS.T17028A214541137.en.

Lorenzo Rojas-Bracho^1*, Barbara Taylor², Cormac Booth³, Len Thomas⁴, Armando Jaramillo-Legorreta⁵, Edwyna Nieto García⁵, Gustavo Cárdenas Hinojosa⁵, Jay Barlow², Sarah L. Mesnick², Tim Gerrodette², Paula Olson², Annette Henry², Henoch Rizo⁶, Eva Hidalgo-Pla⁷, Andrea Bonilla-Garzón⁸ 2022. Benefits of monitoring very small populations: more vaquita porpoises survive than expected. Endangered Species Research 48: 225-234.

Robinson, J.A., Kyriazis, C.C., Nigenda-Morales, S.F. Beichman, A.C., Rojas-Bracho, L., Robertson, K.M., Fontaine, M.C., Wayne, R.K., Lohmueller, K.E., Taylor, B.L., Morin P.A. 2022. The critically endangered vaquita is not doomed to extinction by inbreeding depression. Science 376: 635–639.

Taylor, B., Rojas-Bracho, L., Moore, A.M., Jaramillo-Legorreta, A., Ver Hoef, J., Cardenas-Hinojosa, G., Nieto-Garcia, E., Barlow, J., Gerrodette, T., Tregenza, N., Thomas, L. and Hammond, P. 2016. Extinction is imminent for Mexico’s endemic porpoise unless fishery bycatch is eliminated. Cons. Lett. 10(5): 588-95. [Available at: https://doi.org/10.1111/conl.12331].

Taylor, B.L., Barlow, J., Breese, D. Gerrodette, T. , ... & Yin, S. (2022). Illegal gillnetting remains a serious threat to vaquitas. Report SC/68D/SM09 presented to the Scientific Committee, International Whaling Commission. 25 April - 13 May 2022. 9pp.

Thomas L., Jaramillo-Legorreta, A., Cardenas-Hinojosa, G., Nieto-Garcia, E., Rojas-Bracho, L., Ver Hoef, J.M., Moore, J., Taylor, B., Barlow, J., Tregenza, N. 2017. Last call: Passive acoustic monitoring shows continued rapid decline of critically endangered vaquita. J. Acoust. Soc. Am. 142(5):EL512. doi: 10.1121/1.5011673. PMID: 29195434.

Vidal O (1995) Population biology and incidental mortality of the vaquita, Phocoena sinus. Report International Whaling Commission Special Issue 16: 247–272.