Report using expert elicitation to estimate total unique vaquitas and calves seen in the Zero Tolerance Area during the 2021 survey
Lorenzo Rojas-Bracho, Cormac Booth, Barbara Taylor, Len Thomas, Armando Jaramillo-Legorreta, Sarah Mesnick, Tim Gerrodette, Annette Henry
There were no photographs taken of the quality needed to identify individuals and hence to estimate population size within the study area using mark-recapture; instead expert elicitation was used to estimate the number of unique calves and unique vaquitas (including calves) seen during the survey. Note that the target quantity is different ? the number seen is an estimate of minimum population size and does not attempt to account for animals missed during the survey. This report summarizes results from the expert elicitation, which used the Rational Impartial Observer method (EE-RIO). The EE-RIO exercise required all experts to take 3 hours of online training and to read the evidence dossier covering the 8 vaquita sightings. Elicitation was facilitated over a 2-day period using video-conferencing for a total of 6 hours.