SCANS II cetacean sightings on primary platform of vessel surveys 2005

Original provider: Sea Mammal Research Unit, University of St. Andrews Dataset credits: Sea Mammal Research Unit, University of St. Andrews Abstract: The European Union (EU) Habitats Directive requires Member States to monitor and maintain at favourable conservation status those species identified to be in need of protection, including all cetaceans. In July 2005 we surveyed the entire EU Atlantic continental shelf to generate robust estimates of abundance for harbour porpoise and other cetacean species. The survey used line transect sampling methods and purpose built data collection equipment designed to minimise bias in estimates of abundance. Shipboard transects covered 19,725 km in sea conditions <= Beaufort 4 in an area of 1,005,743 km2. Aerial transects covered 15,802 km in good/moderate conditions (<= Beaufort 3) in an area of 364,371 km2. Thirteen cetacean species were recorded; abundance was estimated for harbour porpoise (375,358; CV = 0.197), bottlenose dolphin (16,485; CV = 0.422), white-beaked dolphin (16,536; CV = 0.303), short-beaked common dolphin (56,221; CV = 0.234) and minke whale (18,958; CV = 0.347). Abundance in 2005 was similar to that estimated in July 1994 for harbour porpoise, white-beaked dolphin and minke whale in a comparable area. However, model-based density surfaces showed a marked difference in harbour porpoise distribution between 1994 and 2005. Our results allow EU Member States to discharge their responsibilities under the Habitats Directive and inform other international organisations concerning the assessment of conservation status of cetaceans and the impact of bycatch at a large spatial scale. The lack of evidence for a change in harbour porpoise abundance in EU waters as a whole does not exclude the possibility of an impact of bycatch in some areas. Monitoring bycatch and estimation of abundance continue to be essential. Supplemental information: Surveys from seven different vessels were merged. Each vessel contained two sightings platforms running concurrently – primary and tracker. This dataset includes sightings from the primary platform. Sightings from the tracker platform are registered in SCANS II cetacean sightings on tracker platform of vessel surveys 2005. Effort or vessel tracks for these surveys are provided with this dataset. Survey conditions such as sea state, glare, swell, wind are found in the effort data. In the primary platform, normal binoculars were used and distance and angle were estimated by observer on the vessel with raditional bearing board and range finder-stick.