ORCA Harwich-Esbjerg surveys

A team of up to four trained volunteers including at least one highly experienced observer recorded cetacean sightings using line transect distance sampling methods from a ferry crossing the northern North Sea between Harwich, UK and Esbjerg, Denmark. Two observers searched a 100┬░ area from either side of the ship with a 10┬░ overlap on the trackline to satisfy the assumption that all animals on the trackline are detected while one observer recorded data and the other rested. Effort information including location, vessel speed, course of vessel and environmental conditions (sea state, swell, precipitation, glare and visibility) were recorded every 30 minutes when observers rotate or when conditions change.