Dear colleagues, Hola, my co-authors, and I are pleased to share with you our latest publication on the sperm whale departure from the central portion of the Gulf of California, particularly in the Midriff Islands Region, which is open access on the section Life and Environment PeerJ journal. Title: The departure of sperm whales (*Physeter macrocephalus*) in response to the declining jumbo squid (*Dosidicus gigas*) population in the central portion of the Gulf of California. Pérez-Puig H, Arias Del Razo A, Ahuatzin Gallardo D, Bolaños J. 2024. The departure of sperm whales (*Physeter macrocephalus*) in response to the declining jumbo squid (*Dosidicus gigas*) population in the central portion of the Gulf of California. PeerJ 12:e18117 https://peerj.com/articles/18117/ Abstract: As sperm whales are important predators that control energy flux in the oceans, changes in their population can be used as a sentinel to measure of ecosystem health. The present study conducted a sperm whale survey of the eastern Midriff Islands Region in the Gulf of California over the course of nine years, recording sightings and collecting photographs of the fluke of sperm whale individuals. A photo-identification catalog was compiled, while individual recapture data were used to estimate the population size in the central portion of the Gulf of California, using a Jolly-Seber POPAN open population model. The results obtained show a yearly population of between 20 and 167 sperm whales, with a super population of 354 sperm whales observed between 2009 and 2015. However, from 2016 to 2018, no sightings of the species were recorded, which coincides with the decline observed in landings of their main prey, the jumbo squid, in the region. General additive model conducted on sperm whale sightings per unit of effort vs jumbo squid landings obtained an adjusted R2 of 0.644 and a deviance explained of 60.3%, indicating a good non-linear relationship between sightings of this odontocete and its prey availability. This evidence suggests that sperm whales departed the region between 2016 and 2018, due to a documented fishery collapse alongside changes of their main prey into its small phenotype, possibly as the result of increase warming conditions in surface and subsurface waters in the Gulf of California in the last three decades. Saludos! -- MC. Héctor Pérez Puig. _______________________________________ Programa de Investigación y Conservación. Centro de Estudios Culturales y Ecológicos. Prescott College A.C. Bahía de Kino, Sonora, México. e-mail: hector.perez@prescott.edu teléfono: (01662) 242-0024. http://www.prescott.edu/kino-bay-center/index.html