Long‐Term Opportunistic Sightings Reveal Shifting Optimal Habitat Locations for Humpback Whales ( Megaptera novaeangliae ) in the Gulf of Maine

Abstract

Models of whale distributions often offer static snapshots that overlook the fluid nature of habitat use. In regions where systematic surveys are infrequent, long‐term observations from tourism vessels provide valuable opportunistic data. In the northern Gulf of Maine, humpback whales ( Megaptera novaeangliae ) have anecdotally been observed shifting from traditional foraging grounds off Maine toward northeastern Canadian waters. Here, we analyzed one‐day movements using an opportunistic dataset of photo‐identified whales to track changes in optimal habitat over time. Movement data were partitioned into 23 overlapping 5‐year windows and fit to models that included both static (bathymetry, distance to shore) and dynamic (tide, chlorophyll ‐a , temperature) environmental variables. Habitat suitability maps generated from model outputs revealed an eastern shift in distribution of optimal habitat over time. While relationships with static features and tide remained stable, associations with other dynamic features weakened and became more variable in recent years. However, these changing relationships tracked changes in environmental conditions (e.g., increasing temperature), suggesting individuals are not changing their inherent habitat preferences. Our findings highlight the value of long‐term opportunistic datasets and the need for adaptive management in marine environments where changing conditions can lead to shifts in locations of optimal habitat for large marine mammals.

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