IUCN Red List Assessment
Red List Category
Red List Criteria
The generation time for the vaquita is estimated as 10 years (Rojas-Bracho and Taylor 1999, Taylor and Rojas-Bracho 1999), therefore three generations is approximately 30 years.
Criterion A4d: Given what is known about fishing history in the northern Gulf of California and the vaquita?s vulnerability to entanglement in gillnets, it is reasonable to assume that the porpoise population has been declining since the 1940s when gillnet fisheries became widespread in the region. The best estimate of total population size is from 1997: 567 (95% CI: 177, 1,073) (Jaramillo-Legorreta et al. 1999). The estimated annual level of mortality in the early 1990s for one of the three main fishing communities, based on reports from onboard observers (Method 1) and those observer reports combined with information from interviews with fishermen (Method 2), was 84 (95% CI: 14, 155) (Method 1) or 39 (95% CI: 14, 93) (Method 2) (Rojas-Bracho and Taylor 1999, D?Agrosa et al. 2000). Using the 1997 abundance estimate, the range of bycatch estimates for a single community in the early 1990s, and plausible potential rates of population increase for phocoenids, Rojas-Bracho and Taylor (1999) estimated that the vaquita population was declining rapidly, possibly by as much as 15% per year. Using the lower of their plausible decline rates (0.05), the population size would be reduced by more than 80% over three generations (i.e., 30 years), including both the past and the future (Rojas-Bracho and Taylor 1999). The cause of the reduction (incidental mortality in fisheries) has not ceased and may even have increased over the last 10 years based on fishing effort (ca. 1,000 gillnet boats might operate in vaquita habitat each year; Rojas-Bracho et al. 2006).
Criterion C2a(ii): The mature and reproductively active component of the census population is estimated as 0.55 (Woodley and Read 1991), or 311 in 1997. Given the inferred decline in abundance due to fishery bycatch during the nine years since 1997 (possibly at a rate of 0.05 to 0.15/yr according to Taylor and Rojas-Bracho 1999), there are now plausibly far fewer than 250 mature individuals (criterion C). From available data on fishery activities (types and effort) and vaquita bycatch rate, a continuing decline in number of mature individuals is projected and inferred (C2). It is assumed that the species population is not divided into subpopulations and therefore 100% of mature individuals are in a single population (C2aii).
- 2007Critically Endangered
- 1996Critically Endangered
- 1994Endangered(Groombridge 1994)
- 1990Endangered(IUCN 1990)
- 1988Vulnerable(IUCN Conservation Monitoring Centre 1988)
- 1986Vulnerable(IUCN Conservation Monitoring Centre 1986)
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