Six-year Monterey Bay hydrophone reveals humpbacks rise, blue whales lag after marine heat wave

A single hydrophone 891 meters deep in Monterey Canyon collected six years of continuous whale-song data, showing humpback songs climbed from 34% to 76% of days while blue whale songs dipped during and after a marine heat wave—reflecting prey-driven, species-specific foraging responses and illustrating how long-term acoustic monitoring can serve as an ocean-health indicator.