Site fidelity and movement of humpback whales (Megaptera novaeangliae) in the western Gulf of Alaska as revealed by photo-identification

We describe feeding-site fidelity in terms of the rate of annual return by individual humpback whales (Megaptera novaeangliae (Borowski, 1781)) to Kodiak Archipelago and Shumagin Islands feeding areas and the rate of exchange between these Gulf of Alaska feeding aggregations. Individual whales were photo-identified in both regions between 1999 and 2015 during vessel surveys, either throughout the feeding season (Kodiak region) or in brief 7- to 10-day windows (Shumagin Islands). Feeding-site fidelity was assessed in terms of individuals' annual return rate, sighting interval, total number of years sighted, and movement between feeding areas. We found similarly high degrees of site fidelity in both regions and limited movement of individuals between them, suggesting that the Shumagin Islands and Kodiak Archipelago represent distinct feeding aggregations. Results did not appear affected by temporal differences in sampling strategy in these study areas.