Year‐Round Passive Acoustic Detection of Sperm Whales in the Cerralvo Channel Within the Gulf of California, Mexico

ABSTRACT

Historically, sperm whales have been consistently observed in the Gulf of California (GoC). However, recent research has documented a reduction in sperm whale sightings around the centre of the GoC, which may be representative of a population decline, prompting concerns about their conservation status in the entire gulf. In this study, using passive acoustic monitoring, the presence of sperm whales in the southern region of the GoC (Cerralvo Channel) is demonstrated. Sperm whales were acoustically detected in eight deployments of a moored hydrophone system from November 2022 to December 2023. Higher detection event rates were found during the day; however, event duration did not differ between day and night. Group composition estimates from call analysis indicated a predominance of immature individuals and adult females/juveniles, with adult males less frequently detected. Recent claims have suggested sperm whale decline in the central area; however, our findings suggest year‐round presence in the southern region. These results highlight the relevance of passive acoustic monitoring to study sperm whales in the GoC. Obtaining accurate data is fundamental to establish conservation efforts for the population in the GoC, a priority region for cetacean protection.