Using long-term passive acoustic monitoring to examine blue whale migration in a changing world

• Main Author: Truong, Gary
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: UNSW, Sydney 2023
• Subjects: blue whales; Antarctic krill; Antarctic sea ice; climate change; passive acoustic monitoring; pygmy blue whale; Southern Hemisphere; El Nino Southern Oscillation; La Nina; El Nino; Satellite data; sea surface temperature; chlorophyll; migration; environmental modelling; anzsrc-for: 310305 Marine and estuarine ecology (incl. marine ichthyology); Antarctic; Austral; Indian; Pacific; The Antarctic; Antarc*; Antarctic Krill; baleen whale; Blue whale; Sea ice
• Online Access: http://hdl.handle.net/1959.4/101663; https://doi.org/10.26190/unsworks/25370

Blue whales, like many other baleen whale species, are threatened by anthropogenic activities and climate change. In the previous century, blue whales were hunted to the brink of extinction and their numbers remain at a fraction of their original population. Studying blue whales can be difficult due to their low numbers and often remote habitat where they are found. To identify how climate change is affecting blue whales, long term data is needed. However long-term studies can be logistically difficult and financially costly. Passive acoustic monitoring (PAM) provides a cost-effective and non-invasive way for collecting long-term data on vocal species. PAM is a suitable tool for studying blue whales as they produce highly stereotypical songs. In this thesis, I examined the acoustic presence of several blue whale populations across the Southern Hemisphere. I examined the degree of overlap between Antarctic blue whales and subantarctic blue whales in the Southeast Pacific Ocean and the Southeast Indian Ocean. I found that Antarctic blue whales were sympatric with both the Chilean blue whale and the Southeast Indian Ocean blue whale during the austral autumn/winter. However, the peak in acoustic detection occurred later for the Antarctic blue whales. I modelled the interannual variability of the SEIO pygmy blue whale with environmental data and found a strong correlation with El Niño Southern Oscillation (ENSO) and the number of whale call detections. I also modelled the Antarctic blue whale presence across four sites in the Southern Hemisphere and found that ENSO, the Southern Annular Mode, Antarctic sea-ice extent, and Antarctic krill abundance were correlated with the acoustic detections of Antarctic blue whales. These results show that blue whale migration is influenced by environmental conditions likely due to changing availability of their prey such as krill. This highlights that climate change will impact blue whales in the future by altering productivity in their primary feeding areas with the potential to ...