Ecological habitat characterization of baleen whales in the northern Mozambique Channel: Linking seasonal acoustic detections with environmental drivers

Baleen whales ( Mysticeti ) play vital ecological roles in marine ecosystems, but their habitat use in the southwest Indian Ocean remains poorly understood due to logistical constraints and low population densities. This study analyses five years of passive acoustic monitoring data collected by the REVOSIMA in the northern Mozambique Channel near Mayotte Island. It focuses on three species of baleen whales, including two subspecies of blue whales: the Antarctic blue whale (ANT BW) ( Balaenoptera musculus intermedia ), the Southwestern Indian Ocean pygmy blue whale (SWIO PBW) ( B.m. brevicauda ), the Fin whale (FW) ( B. physalus ) and the Antarctic minke whale (AMW) ( B. bonaerensis ). Acoustic presence was quantified using Daily positive hour (DPH), and Generalized Additive Models assessed relationships between DPH and environmental variables, Sea surface temperature (SST), Sea surface temperature anomaly (SST anomaly), Chlorophyll-a (Chl) concentration, and Significant wave height (SWH). The results reveal species-specific habitat use strategies. ANT BW and AMW use the area as a migratory resting habitat during austral winter and spring; SWIO PBW exhibit bimodal seasonal peaks, consistent with migratory transit; FW show sporadic occurrence related to environmental conditions. SST, SST anomaly, and SWH emerged as key environmental drivers, while Chl showed no consistent effect, indicating limited local feeding activity. These findings identify the northern Mozambique Channel as a multipurpose habitat for baleen whales. Long-term acoustic monitoring provides baseline knowledge supporting conservation within the Indian Ocean Whale Sanctuary under climate change and anthropogenic pressures.