European Ocean Biodiversity Information System

The study area comprised the waters of the Valencia and Murcia Regions (central Spanish Mediterranean), from the coastline to between 30 to 80 km offshore, with depths ranging from 10 m to 2800 m. Seasonal line transect surveys were conducted from June 2000 to March 2003. Transects followed a systematic saw-tooth pattern that covered the area representatively (Buckland et al. 2001). The fieldwork platform was a high-wing aircraft (“push-pull” Cessna 337) flying at an altitude of 152 m (500 ft) and at a groundspeed of approximately 166 km/h (90 knots). Two observers, positioned on each side of the aircraft, scanned the sea surface and a recorder took note of data reported: species, number of animals, location (obtained from a GPS), time, and environmental conditions, including Beaufort sea state. Environmental conditions were updated whenever changes occurred and GPS provided a continuous record of position (updated every few seconds). Surveys were conducted only in good sighting conditions of Beaufort sea state less than 3.