Spatio-temporal patterns of blue and fin whale sound production identified in National Oceanic Atmospheric Administration-National Park Service Ocean Noise Reference Station Network recording sites in the Pacific Ocean

Abstract

The ability of sound to travel long distances, especially in lower frequencies, makes it an effective way for organisms to communicate in marine environments. Passive acoustic monitoring (PAM) is an essential method to study low-frequency sound in marine ecosystems. The NOAA-NPS Ocean Noise Reference Station Network (NRS) project is a long-term study that utilizes PAM to monitor low-frequency (<2kHz) soundscapes throughout the U.S. exclusive economic zone. While these data have been analyzed to understand large scale patterns, assessment of specific sound sources is an area where these datasets can provide new insights. This study used a call energy index (CEI) to assess blue whale and fin whale sound production from three NRS recording sites in the Gulf of Alaska, off the Olympic coast, and near the Channel Islands between 2014 and 2020. We present the diel and seasonal patterns detected for both species and compare them to the decidecade bands assessed for the recording sites. Understanding the song production and migration patterns for endangered blue whales and fin whales is essential for effective conservation efforts. By utilizing PAM and efficient detection methods such as CEI, researchers gain the ability to process large amounts of bioacoustic data and better understand the migratory behaviors of endangered marine species.