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ESR prepress abstract   -  DOI:

More vaquita porpoises survive than expected

Lorenzo Rojas-Bracho, Barbara Taylor*, Cormac Booth, Len Thomas, Armando Jaramillo-Legorreta, Edwyna Nieto García, Gustavo Cárdenas Hinojosa, Jay Barlow, Sarah L. Mesnick, Tim Gerrodette, Paula Olson, Annette Henry, Henoch Rizo, Eva Hidalgo-Pla, Andrea Bonilla-Garzón

*Corresponding author:

ABSTRACT: In 2018 it was estimated that fewer than 20 of Mexico’s endemic vaquita porpoise Phocoena sinus remained and the species was declining by 47% yr-1. Entanglement in gillnets is the sole threat, and gillnetting has increased in the small area where most vaquitas remain since the last population size estimate. We conducted research efforts in 2019 and 2021 in that area to estimate the minimum numbers seen, to estimate the numbers of calves, and to look for any signs that vaquitas are unhealthy. Through expert elicitation, we estimated between 7 and 15 unique individuals were seen in 2019 and between 5 and 13 were seen in 2021. Calves were seen in both years and all vaquitas appeared healthy. Population projections from the last full survey indicated that more vaquitas have survived than expected. We suggest that these surviving adult vaquitas may have learned to avoid entanglement in gillnets. These vaquitas and their calves provide hope that the species can survive. High levels of illegal gillnetting and theft of equipment hindered our monitoring efforts in vaquita habitat. With around 10 individuals remaining, survival can only be assured if their habitat is made gillnet free.