Occurrence of Omura’s whale, Balaenoptera omurai (Cetacea: Balaenopteridae), in the Equatorial Atlantic Ocean based on Passive Acoustic Monitoring

Abstract

The current known distribution of Omura’s whale includes the tropical and warm temperate waters of the western Pacific, Indian, and Atlantic Oceans. Evidence of their presence in the Atlantic Ocean is based on beach cast specimens found on the coasts of Mauritania (North Atlantic) and Northeastern Brazil (South Atlantic). The present study characterizes the occurrence of this species in the São Pedro and São Paulo Archipelago (SPSPA), on the mid-Atlantic ridge between South America and Africa, based on autonomous recording systems. Acoustic signals were similar, but not identical, to B. omurai vocalizations recorded off the coast of Madagascar. Although these signals were recorded for only 11 months, there are peaks in vocal activity between May and June in the vicinities of SPSPA, suggesting either a shift in distribution within the Atlantic equatorial waters or seasonality in the species’ vocal behavior in this region. The first acoustic records of Omura’s whales in the Equatorial Atlantic suggest that these animals may also use deep-water habitats, in addition to the shallow-water habitat use observed in other regions.

Overview of Balaenoptera whales strandings in Southern Brazil from 1993 to 2018

“…Most of our knowledge about their distribution and occurrence in Brazilian waters comes from oceanographic cruises (Zerbini et al, 2004;Andriolo et al, 2010;Di Tullio et al, 2016), whaling data, incidental catches (Lucena, 2006), and strandings (Zerbini et al, 1997;Siciliano et al, 2004Siciliano et al, , 2011Cypriano-Souza et al, 2017;Milmann et al, 2020). Acoustic research has also provided new insights into the occurrence and distribution of species such as Omura's and Antarctic minke whales in Brazilian waters (e.g., Moreira et al, 2020, Rossi-Santos et al, 2022.…”