Chilean Blue Whales: Fidelity to Feeding Areas and Migratory Connectivity With the Eastern Tropical Pacific ¹

In the Eastern South Pacific (ESP), blue whale ( Balaenoptera musculus subsp.) aggregations have been described for two feeding areas (in northern and southern Chile) and in the Eastern Tropical Pacific (ETP). However, despite the knowledge of these areas, little is known about the seasonal movements of blue whales between them. Comparisons of 1074 individual blue whales, photographed across these regions from 1992 to 2019, resulted in re‐sightings of 107 individuals. Photo‐identification comparisons were conducted using the Southern Hemisphere Blue Whale Catalog, a collaborative platform for sharing photo‐identification data among 21 research groups from 7 nations. A total of 92 matches were found within the southern Chile feeding area and 13 matches within the northern Chile feeding area. High site fidelity was found for the southern Chile feeding area (return rates ≥ 43%). The longest interval between the first and last sighting was 17 years. There was no exchange between northern and southern Chile feeding areas. Two matches revealed long‐distance connectivity and migration of blue whales from southern Chile to the Galápagos Islands in the southern ETP. There were no matches between Chile and the Costa Rica Dome, farther north in the ETP, a location known for the year‐round presence of blue whales. The results highlight the importance of collaboration to understand blue whale movements and migration patterns. Our results provide valuable ESP and ETP region‐wide data toward understanding population structure and informing conservation and management strategies, population assessments, and/or delineating biologically important areas.