Material & Methods

Study area

Two humpback whales were tagged. The first set of data was collected from a tag deployed in Eyjafjörður off Akureyri on the 30th of April 2024, while the second set of data was collected from a tag deployed in Skjálfandi Bay off Húsavík starting on the 26th of June.

Tag deployment

The whale was approached at a 45-degree angle using a Zodiac inflatable boat to ensure parallel positioning and enable a quick retreat if needed. An 8-meter pole was used to deploy the suction-cup tag between the blowhole and dorsal fin when the whale surfaced to breathe. The tag was equipped with a time-burned wire that corrodes in salt water, causing the tag to detach after about 12 hours. Once floating, the tag emitted a VHF signal to be retrieved.

Characterisation of tag data

The data were processed using Igor Pro 64 and following the methods employed by Iwata et al. (2021; 2024).

A dive was defined as being ≥ 10 seconds and > 3 meters. For each dive, data on duration, depth, post-dive surface time, number of lunge feeding events, and fluke stroke rate were extracted.

Using dive depth and fluke stroke rate, dives were categorized into four types:

  • Feeding: presence of at least 1 feeding event 
  • Resting: Shallow depth (between 3 and 20 m), slow fluke stroke rate (≤ 2 strokes min-1)
  • Shallow active: Shallow depth (between 3 and 20 m), higher fluke stroke rate (> 2 strokes min-1)
  • Transit: Deeper dives (> 20 m), regardless stroke rate

Surface resting was defined as surface time (depth <3 m) between consecutive resting dives or as surface periods exceeding the average duration between resting dives.

BACKGROUND and Aims
RESULTS
References

Iwata, T., Aoki, K., Miller, P. J. O., Biuw, M., Williamson, M. J., & Sato, K. (2024). Non‐lunge feeding behaviour of humpback whales associated with fishing boats in Norway. Ethology, 130(2), e13419.

Iwata, T., Biuw, M., Aoki, K., Miller, P. J. O., & Sato, K. (2021). Using an omnidirectional video logger to observe the underwater life of marine animals: Humpback whale resting behaviour. Behavioural Processes, 186, 104369.