Dear MARMAM community, My co-authors and I are pleased to announce the publication of the following paper in Marine Mammal Science: Fernández, S. J., M. M.Uhart, A. M.García-Cegarra, V. Falabella, M. P. Heide- Jørgensen, M. Holland, A. Orce, M. Pujana, M. Sironi, F. Sucunza, M. Coscarella, A. N. Zerbini . 2026. “Ocean to Ocean: First Documented Migration of a Southern Right Whale From the Southwest Atlantic to the Southeast Pacific Ocean.” Marine Mammal Science42, no. 3: e70211. [ https://doi.org/10.1111/mms.70211 | https://doi.org/10.1111/mms.70211 ] . ABSTRACT: This study documents the first recorded migration of a southern right whale (Eubalaena australis) from the southwestern South Atlantic to the southeastern South Pacific. On October 25, 2023, an adult female with calf, named “Atenea,” was tagged with a satellite transmitter in Península Valdés, Argentina. During a 24.5-day journey, Atenea traveled 2,767 km, moving southward along the Argentine continental shelf, rounding Cape Horn, and then heading north along the Chilean coast. Mitochondrial DNA and photo-identification analyses revealed no significant genetic differentiation and no previous matches in regional catalogs. The results showed that haplotypes from whales sampled in the Pacific were interspersed among those from the Atlantic, suggesting contemporary or recent genetic and demographic connectivity between populations from both ocean basins. This unprecedented interoceanic movement challenges the notion of strictly segregated populations and provides a new perspective on the migratory plasticity of the species. The findings highlight the importance of continued satellite tracking and genomic studies to improve our understanding of habitat use and to inform conservation strategies for the critically endangered southeastern South Pacific population. Regards Santiago Fernández Laboratorio de Mamíferos Marinos (LAMAMA). Centro para el Estudio de Sistemas Marinos (CESIMAR) Centro Nacional Patagónico, CONICET Blvd. Brown 2915, 9120 Puerto Madryn Chubut, Argentina [ mailto:sfernandez@cenpat-conicet.gob.ar | sfernandez@cenpat-conicet.gob.ar ] / +54 (03401) 15434922