New estimate of vaquita status improved through elicitation of expert knowledge

A vaquita being tracked within the Zero Tolerance Area and a panga with a buoy for a set gillnet in the background on 17th October 2019. Credit. Todd Pusser. 

 

The results of a virtual workshop to use expert elicitation to better estimate the number of vaquitas seen in the Zero Tolerance Area are now available here (Final Vaquita Expert Elicitation Report).  Since 2019 acoustic monitoring to assess trends in abundance of the vaquita has not been possible because so much equipment has been stolen.  With so few vaquitas remaining, a two-ship effort in October 2019 was launched in the hope of obtaining sufficient photographically identified vaquita individuals to use mark-recapture methods to estimate vaquita numbers.  Although there were 7 encounters with vaquita groups, surviving vaquitas are so wary and hard to approach that insufficient numbers of high-quality photographs were obtained for the analysis. Therefore, a new approach was adopted, utilizing expert elicitation to obtain the best available estimate of the number of vaquitas seen.  A workshop was held in August, 2020 and included all observers who participated in the vessel-based field survey in October 2019, and was led by researchers at St. Andrews University.  The results of the expert elicitation exercise found the mean estimate for the number of vaquita calves seen was 3 with a 63% belief that there were at least 3 calves.  The mean estimate for the number of unique vaquitas seen in all 7 sightings was 9.4 with a 40% belief that there were at least 10.  Also of note was that tracking vaquitas was difficult because the ships and pangas had to maneuver around illegal fishers with gillnets set.

A female vaquita and her calf next to a panga with a gillnet being set within the Zero Tolerance Area on 17th October 2019. Credit: Museo de la Ballena

Urgent Letter sent from IUCN Species Survival Commission to Mexican Authorities to correct false information about vaquita decline

 

Last week, the IUCN Species Survival Commission sent a letter (see version in Spanish, and English) to the Secretaries of the Mexican Navy, Environment, and Agriculture and Fisheries authorities, to counter false allegations that vaquitas are going extinct because of a change in salinity within the vaquita habitat.  According to the allegations, shark predation and osmoregulation failure are the causes of the vaquita’s precipitous population decline. No scientific evidence (in the form of peer-reviewed scientific articles or data) has been provided to support these allegations and the SSC acted quickly to dispel the rumours, and make clear that the only immediate threat to the species is accidental mortality in gillnets.  The letter’s main objective was to emphasize this, and to do so quickly, as March is the peak of the totoaba poaching season when entanglement risk to vaquitas is greatest. It requests that Mexican authorities take immediate action to reinstate net-removal activities, which are currently on hold, as soon as possible. Scientific evidence to refute the allegations is given in the letter.

2 updated cetacean red list assessments published in March 2021

 

The 2021-1 edition of the Red List, which was published in March 2021, included two updated cetacean assessments. This is in addition to the 22 assessments published in December 2020, 3 earlier in 2020, 6 in December 2019, 2 in July 2019, 5 in March 2019, 35 in November 2018, 10 in July 2018, and 19 in November 2017. A total of 104 updated or new cetacean assessments have now been published in the last 2 ½ years.

 

One of the two 2021-1 updated assessments was of the common dolphin (Delphinus delphis) and it reflects the recent change in taxonomy for this species group (see Committee on Taxonomy), combining all common dolphin forms into a single assessment as Least Concern.  The northern bottlenose whale (Hyperoodon ampullatus) was moved from Data Deficient to Near Threatened in the newly published updated assessment of that species.  Work on the remaining two cetacean species that require updating (sperm whale and Hector’s dolphin), and on some of the more out-of-date subpopulation and subspecies assessments, will continue in 2021.

 

Table 1 – Summary of updated assessments and new assessments published in the 2021-1 edition of the Red List. (NT = Near Threatened, DD = Data Deficient, CR = Critically Endangered, EN = Endangered, LC = Least Concern).

# Species/Subspecies Common name Taxonomic level Category Status change
1 Delphinus delphis Common dolphin Species (global) LC No change
2 Hyperoodon ampullatus Northern Bottlenose whale Species (global) NT DD -> NT

 

The Red List status and documentation for 90 cetacean species as well as 12 subspecies and 28 subpopulations can be found on the IUCN Red List website (redlist.org).  Of the 90 species, 24% are assigned to a threatened category (i.e. CR, EN, VU), 11% are Near Threatened, just over half (54%) are Least Concern, and 10% are considered DD (Table 2). It should also be emphasized that there is strong interest in completing additional assessments of subpopulations that are known or thought to be at higher risk than the species as a whole (e.g. killer whales, belugas, dusky dolphins).

 

Table 2. Summary information on Red List status as of March 2021.

Category Species Subspecies Subpopulations Total
Critically Endangered 4 4 14 22
Endangered 11 4 7 22
Vulnerable 7 4 5 16
Near Threatened 10 0 0 10
Least Concern 49 0 0 49
Data Deficient 9 0 2 11
Total 90 12 28 128

 

 

 

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