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. The tag is equipped with a time-burned wire that corrodes in salt water, releasing after about 12 hours, causing the tag to detach. Once floating, the tag emits a VHF signal in order to be retrieved.
Characterisation of tag data
The data were processed using Igor Pro 64.
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 data, 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