Humpback whales migrate seasonally from high latitude feeding areas to lower latitude breeding areas for mating and calving. In 2004-2006, a North Pacific basin-wide study called SPLASH was conducted as an international collaboration among various groups of researchers. The Russian Far East consists of multiple high latitude feeding areas and during SPLASH, 102 whales were identified and compared to catalogs from breeding areas. Our goal in this study was to further investigate the migratory destinations of whales from the Russian Far East using a total of 1,459 photographs of whales identified from 2004 to 2014. We compared the latest Russian catalog with the SPLASH catalog from wintering areas (2004)(2005)(2006) and with two additional regional catalogs from Okinawa (1989Okinawa ( -2006 and the northern Philippines (2000Philippines ( -2006. We found a total of 152 matches: 106 with Asian, 35 with Hawaiian, and 11 with Mexican breeding grounds. The match rate was higher in mainland Kamchatka and consisted mostly of whales from the Asian breeding ground. In the Commander Islands, the proportion of whales from Asia was twice that of Hawaii and six times higher than Mexico. The total match rate was low, supporting the hypothesis of some undiscovered humpback whale breeding location in the North Pacific.

Mitochondrial DNA (mtDNA) differences between humpback whales on different feeding grounds can reflect the cultural transmission of migration destinations over generations, and therefore represent one of the very few cases of gene-culture coevolution identified in the animal kingdom. In Russian Pacific waters, photo-identification (photo-ID) studies have shown minimal interchange between whales feeding off the Commander Islands and those feeding in the Karaginsky Gulf, regions that are separated by only 500 km and have previously been lumped together as a single Russian feeding ground. Here, we assessed whether genetic differentiation exists between these 2 groups of humpback whales. We discovered a strong mtDNA differentiation between the 2 feeding sites (FST = 0.18, ΦST = 0.14, P < 0.001). In contrast, nuclear DNA (nuDNA) polymorphisms, determined at 8 microsatellite loci, did not reveal any differentiation. Comparing our mtDNA results with those from a previous ocean-basin study reinforced the differences between the 2 feeding sites. Humpback whales from the Commanders appeared most similar to those of the western Gulf of Alaska and the Aleutian feeding grounds, whereas Karaginsky differed from all other North Pacific feeding grounds. Comparison to breeding grounds suggests mixed origins for the 2 feeding sites; there are likely connections between Karaginsky and the Philippines and to a lesser extent to Okinawa, Japan, whereas the Commanders are linked to the Mexican breeding grounds. The mtDNA differentiation between the Commander Islands and Karaginsky Gulf suggests a case of gene-culture coevolution, correlated to fidelity to a specific feeding site within a particular feeding ground. From a conservation perspective, our findings emphasize the importance of considering these 2 feeding sites as separate management units.

We present an ocean-basin-scale dataset that includes tail fluke photographic identification (photo-ID) and encounter data for most living individual humpback whales (Megaptera novaeangliae) in the North Pacific Ocean. The dataset was built through a broad collaboration combining 39 separate curated photo-ID catalogs, supplemented with community science data. Data from throughout the North Pacific were aggregated into 13 regions, including six breeding regions, six feeding regions, and one migratory corridor. All images were compared with minimal pre-processing using a recently developed image recognition algorithm based on machine learning through artificial intelligence; this system is capable of rapidly detecting matches between individuals with an estimated 97–99% accuracy. For the 2001–2021 study period, a total of 27,956 unique individuals were documented in 157,350 encounters. Each individual was encountered, on average, in 5.6 sampling periods (i.e., breeding and feeding seasons), with an annual average of 87% of whales encountered in more than one season. The combined dataset and image recognition tool represents a living and accessible resource for collaborative, basin-wide studies of a keystone marine mammal in a time of rapid ecological change.

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