Habitat use of the northern bottlenose whale (Hyperoodon ampullatus) near Jan Mayen, North Atlantic
Data files
Aug 29, 2023 version files 29.23 KB
Abstract
Habitat use of the northern bottlenose whale Hyperoodon ampullatus in the Northeast Atlantic is poorly understood. This study aimed to identify locally utilised habitat features and create predictions of northern bottlenose whale habitat use over a wider area around the island of Jan Mayen, Norway. Bottlenose whales were sighted regularly near Jan Mayen in June 2014–2016 at higher rates than over a wider study region reported in other studies, indicating that the Jan Mayen habitat may be a hotspot of bottlenose whale presence in early boreal summer. Habitat models were created by fitting generalised additive models of selected environmental variables to sighting occurrence and additional whale sightings given a first encounter (total number of sightings – 1) recorded in June 2014–2016. Higher occurrence was estimated at steeper topography and April-average chlorophyll concentration below 0.4 mg m–3. Additional whale sightings given a first encounter were predicted to be higher at water depths (<1000 m) with steep topography, and deeper water (depths between 1300 and 2000 m) with a gentle seafloor slope. Spatial predictions largely corresponded with field observations that indicated high usage around the submarine canyon regions in the east and southeast of Jan Mayen Island. This study highlights the likely importance of steep and deep bathymetric features in shaping patterns of habitat use of this deep-diving species. Predictions of habitat use over a wider area not covered by the analysed surveys require validation; however, these data could inform conservation and management efforts to minimise spatial overlap between potential high-use areas and potentially disruptive anthropogenic activities.
Methods
Visual sighting data of bottlenose whales were collected in June in 2014, 2015, and 2016, with search effort concentrating along the submarine canyon from north to southeast of Jan Mayen Island. Visual surveys were conducted by 2 dedicated observers from the deck whenever weather conditions permitted. Both observers made visual scans from bow to stern, with one observer searching across the starboard and the other across the port of the boat, together covering 360° around the vessel. Binoculars were used to confirm whale species and location once an animal was spotted.
When a sighting was made, the time, whale location (latitude and longitude), estimated sighting distance, bearing, group size, animal heading, and level and duration of seeking (behavioural indication of attractive movement towards the research vessel, as suggested by Whitehead & Hooker 2012) were recorded. Vessel GPS location and speed were automatically logged every 5 s in 2014 and 2015, and every 1 s in 2016.
Following a sighting, the whales were often approached for tagging. If successful, the tagged whale would be tracked for the duration of the tag deployment. Sighting and effort data during tagging and tracking periods were excluded from the analyses.
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