Viquerat, Sacha; Herr, Helena: Ship based cetacean survey in the Southern Ocean 2023 (MSM115) [dataset]. PANGAEA, https://doi.pangaea.de/10.1594/PANGAEA.984312 (dataset in review)

Distance sampling survey for cetaceans in the Southern Ocean along the Western Antarctic Peninsula conducted on board of Maria S. Merian in March 2023. Effort related sighting data collected during a dedicated survey for cetaceans following distance sampling methodology. We conducted a dedicated line transect distance sampling survey, zig-zagging across the outer shelf-edge from the South Sandwich Islands to the South Orkney Islands. Whenever weather permitted, a team of three observers was placed on the observation deck (at 20 m height ASL) with a starboard and a portside observer scanning the area from the trackline to 90° abeam of the vessel up to the horizon, and a data recorder positioned inside the observation room. The observers reported all sightings, including information on distance (via reticules provided by Fujinon MTRC-SX binoculars that were used for distance estimation only) and horizontal angle to the detected group via radio to the data recorder. Groups of 15 or more individuals were classified as 'aggregations'. Groups with less than 15 animals are henceforth referred to as 'solitary groups' to distinguish them from aggregations. Sighting conditions were assessed and continuously updated, including information on sea-state (Beaufort scale), glare (taking levels from 0: none to 2: intense) and subjective sighting conditions for large whales (good, moderate, poor, or unacceptable as judged by the observers). The data recorder entered all information directly into a computer, logging all sightings and updates of environmental conditions together with position and time stamp. The team members rotated positions every 30 minutes between the three positions. One on-duty team member was replaced every 30 minutes with a fresh observer, so that the maximum duty cycle for a single observer would not surmount 1h 30 minutes.