The Small Cetacean Abundance in the North Sea and Adjacent waters (SCANS) survey was conducted in July 1994. The survey was carried out by teams of observers onboard research ships and small aircraft in the North Sea, Kattegat, Skagerrak, western Baltic, English Channel and Celtic Sea. The ships and aircraft used line transect methods to collect distance sampling data to estimate the number of animals in the area.
The map shows the area surveyed and species
encountered (place cursor over names to display data, click
here to display the map in a new window).
There are many threats to small cetaceans in European waters. Incidental captures, or bycatch, in fishing nets is of particular concern and thousands of small cetaceans are taken annually in European waters. The number of dolphins and porpoises being caught has been estimated in certain fisheries by placing observers on fishing vessels to record bycatch events. In other cases we know very little of how many cetaceans are being taken but evidence from stranded animals confirms that it is occurring.
Ultimately, the long-term aim is to have zero bycatch in all fisheries. The complete closure of fisheries in most cases is not a viable option. Therefore, the number of dolphins and porpoises being captured needs to be assessed against the size of the population to determine whether it’s sustainable. The Agreement on the Conservation of Small Cetaceans in the Baltic and North Seas (ASCOBANS) advised that the maximum annual bycatch for harbour porpoises should not exceed 1.7% of the population size in that year. The International Whaling Commission (IWC) has stated that if the number of small cetaceans captured is greater than 1% of their total population size then this should raise the flag of concern. Therefore, estimates of abundance are essential to assessment and management of bycatch.
SCANS generated the first large-scale abundance estimates for the harbour porpoise, white-beaked dolphin and minke whale throughout the North Sea, Kattegat, Skagerrak and Celtic Sea. The estimates were also precise and unbiased due to the extensive survey coverage and methodological developments designed for surveying harbour porpoises and other small cetaceans. Using the abundance estimates for harbour porpoise, known bycatch levels in the North Sea and Celtic Sea were considered unsustainable by the above IWC criteria. Bycatch of harbour porpoises in these areas has decreased, due to a combination of reduced fishing effort and the use of acoustic "pingers" (Pingers are acoustic devices which emit ultrasonic signals at varying intervals to warn cetaceans that nets are present). SCANS was the first, and currently the only, large-scale survey to estimate cetacean abundance in these waters.
Estimates from SCANS