Use of blue whale acoustics for finding the ocean secrets

 Date 21/03/2026
Learning from a webinar

Today on 21st March 2026, in the evening between 7:30–8:45, I got an opportunity to attend a webinar on ‘Movement ecology and conservation of blue whale in the central California current ecosystem’, which was delivered by Dr. John Ryan from Monterey Bay Aquarium Research Institute (MBARI) and organized by the Marine Mammal Research & Conservation Network of India (MMRCNONOI).

  After a long time, I successfully attended this full live webinar from start to end. Overall, this webinar was impressive to listen to and learn inside about blue whale research, which was more focused on a few important topics, including coastal upwelling, low frequency sound, krill, bimodal distribution and their foraging call, D-Call, and bio-logger or tag for blue whale.

  Coastal upwelling is an oceanographic concept which means that because of the wind, the dense, colder and nutrient-rich water from the bottom of the ocean moves from bottom to surface. During this process, less nutrient water from the surface is moved away from that area and nutrient-rich water takes that place. This process stimulates the process of increasing primary productivity of the ocean, such as phytoplankton. During this presentation, the presenter showed a map of sea surface temperature (SST) and chlorophyll value in µg/L, where I could easily understand the correlation between the two graphs: low temperature area has a high number of chlorophyll, which is the main biological material present in phytoplankton to help the process of photosynthesis.

  Second thing which was highlighted during this presentation is the use of ‘passive acoustic sensing’ (PAM), which is used for detecting blue whale calls in this region. PAM is a non-invasive method to collect environmental sound data using a microphone or hydrophone to detect, identify, and localize sound sources without emitting any signal. This research activity was conducted in and around Monterey Bay, California, where scientists collected blue whale low frequency songs which range between 10–80 Hz. During this presentation, the presenter played an acoustic file which was fascinating to listen to. During this presentation, Dr. John Ryan gave insight about the abundant acoustic signal for ecological research — more specifically, huge data about blue whales and fin whales from 2015 to 2024.

  Another important term which was discussed during this presentation is ‘acoustic vector sensing’ (AVS), which is a novel thing they used during this research. In simple words, acoustic vector sensors are different than traditional hydrophones which not only detect and record sound pressure but also detect direction and particle motion of sound waves. Most importantly, this AVS helps to detect direction of arrival of sound, which is more useful for studying particularly low frequency vocalization which ranges between 20–40 Hz, such as for blue whale, fin whale, etc.

  Next important thing which was discussed during this presentation is all about how the tiny creature ‘krill’ is associated with blue whale presence. Because these tiny crustaceans are the primary food source for this giant blue whale. During feeding season, every day a blue whale consumes 4–8 tons of krill. Beyond primary productivity, upwelling drives prey aggregation. Dr. John Ryan showed one slide which shows the relationship between sea surface temperature (SST), water depth in meters ranging from 0–350 meters, and congregation of krill.

  During this presentation, Dr. John Ryan quoted his research article “Oceanic giants dance to atmospheric rhythms: Ephemeral wind‐driven resource tracking by blue whales” which was in the year 2022. After this presentation was over, I downloaded this paper and read it. In simple words, this paper gives us insight about how the blue whales can track tiny krill by following ocean currents stirred up by wind. Using underwater hydrophones and whale tracking tags, scientists discovered that blue whales shift their movements to stay inside these moving plumes of upwelled water. This fantastic trick of blue whales can save their energy during their long migration and provide an opportunity to find a massive amount of food in a short time with minimum energy loss. But another important thing found during this research process is that blue whales cross busy shipping lanes to follow this food-rich current, which highlights the need for smarter ocean management to protect these ocean giants.

  Next paper Dr. John Ryan quoted during this presentation was ‘Animal-borne metrics enable acoustic detection of blue whale migration’ which was published in the year 2020. This research paper gives us insight about change in blue whale singing pattern. During the summer feeding season, blue whales sing mostly during night time because during the day time they are busy feeding on huge numbers of krill. But during their migration to their breeding ground towards the south, they sing mostly in day time. By listening to these daily song patterns, researchers can now tell when the whales have stopped feeding and started migration. This research finding now helps us to slow down large cargo ships on busy shipping lanes during the season of whale migration.

  Next research finding shared by Dr. John Ryan with his research paper ‘Acoustic signature reveals blue whales tune life‐history transitions to oceanographic conditions’, which was published in the year 2022. Based on six-year blue whale acoustic studies, they found out that this species can delay their migration between feeding ground and breeding ground up to four months depending on ocean conditions. If there is more and longer lasting krill as food present, they stay longer time in feeding ground. The timing of their switch off and switch on between these two areas depends on ocean productivity. This flexibility can help them to survive in global environment changes, and this is also a natural sign of ocean health. Another important finding based on this research is to understand how this upwelling modulates blue whale ship strike risk.

Overall, this was a fantastic opportunity for me to know more about blue whales and the factors responsible for their migration. I tried my best to listen carefully to the presentation. And finally, I wrote this article in the way that I understood during the webinar. It is not exactly what the presenter said, but it is more about what I was able to understand. I am thankful to the organiser and presenter for this wonderful opportunity. Please go through the below research articles and spread ocean conservation within your network.

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Pradip Namdeo Chogal

6 April 2026;

Kalyan 

Reference: - 

1. Ryan, J. P., Benoit‐Bird, K. J., Oestreich, W. K., Leary, P., Smith, K. B., Waluk, C. M., ... & Goldbogen, J. A. (2022). Oceanic giants dance to atmospheric rhythms: Ephemeral wind‐driven resource tracking by blue whales. Ecology Letters, 25(11), 2435-2447.
2. Oestreich, W. K., Fahlbusch, J. A., Cade, D. E., Calambokidis, J., Margolina, T., Joseph, J., ... & Ryan, J. P. (2020). Animal-borne metrics enable acoustic detection of blue whale migration. Current Biology, 30(23), 4773-4779.
3. Oestreich, W. K., Abrahms, B., McKenna, M. F., Goldbogen, J. A., Crowder, L. B., & Ryan, J. P. (2022). Acoustic signature reveals blue whales tune life‐history transitions to oceanographic conditions. Functional Ecology, 36(4), 882-895.