Seasonal and diel cycles of fin whale acoustic occurrence near Elephant Island, Antarctica

• Published in: Royal Society Open Science
• Main Authors: Elke Burkhardt, Ilse Van Opzeeland, Boris Cisewski, Ramona Mattmüller, Marlene Meister, Elena Schall, Stefanie Spiesecke, Karolin Thomisch, Sarah Zwicker, Olaf Boebel
• Format: Article in Journal/Newspaper
• Language: English
• Published: The Royal Society 2021
• Subjects: fin whale; Balaenoptera physalus; Elephant Island; Antarctica; Scotia Sea; passive acoustic monitoring; Science; Q; Antarc*; Fin whale; Sea ice
• Online Access: https://doi.org/10.1098/rsos.201142; https://doaj.org/article/6e98b56e97844833873c6cfeefd1b20e

This study investigates the relevance of the Elephant Island (EI) region for Southern Hemisphere fin whales (Balaenoptera physalus) in their annual life cycle. We collected 3 years of passive acoustic recordings (January 2013 to February 2016) northwest of EI to calculate time series of fin whale acoustic indices, daily acoustic occurrence, spectrograms, as well as the abundance of their 20 Hz pulses. Acoustic backscatter strength, sea ice concentration and chlorophyll-a composites provided concurrent environmental information for graphic comparisons. Acoustic interannual, seasonal and diel patterns together with visual information and literature resources were used to define the period of occupancy and to infer potential drivers for their behaviour. Spectral results suggest that these fin whales migrate annually to and from offshore central Chile. Acoustic data and visual information reveal their arrival at EI in December to feed without producing their typical 20 Hz pulse. For all 3 years, acoustic activity commences in February, peaks in May and decreases in August, in phase with the onset of their breeding season. Our results emphasize the importance of EI for fin whales throughout most of the year. Our recommendation is to consider EI for establishing a marine protected area to expedite the recovery of this vulnerable species.