ESR prepress abstract   -  DOI: https://doi.org/10.3354/esr01398

ABSTRACT: The seasonality of Critically Endangered eastern North Pacific right whales Eubalaena japonica (NPRWs) is poorly understood in their historical foraging grounds in the eastern Aleutian Island Passes (AIP) and the northern Gulf of Alaska (NGOA). These areas are situated between designated Critical Habitats in the Bering Sea and the GOA. Here we report passive acoustic monitoring results for NPRWs from 6 sites—2 in the AIP (2009–2023) and 4 in the NGOA (2019–2023). All data (64235 h) were manually processed for NPRW vocalizations; results are presented as daily calling activity (CA_Daily; the percentage of 10 min recordings per day with detections). NPRWs occurred at all sites and in the majority (84%) of sampled calendar years. Across sites, variable detections suggest seasonality in occurrence and habitat use. The presence of summer (June–August) peaks in calling at most sites indicates that these areas are contemporary feeding grounds. The greatest, most consistent CA_Daily occurred in the GOA right whale Critical Habitat in fall months (~September–December) concurrent with NPRW presence in the Bering Sea. The timing of overwinter (~December–May) detections at AIP sites relative to the Bering Sea detections support their use as a migratory corridor. Seasonal CA_Daily along the GOA sites does not support a NPRW coastal migratory route, although sampling limitations may obscure underlying migratory trends. Overall, these results offer new seasonal insights into right whale occurrences in 2 key conservation areas.