Background The incidental capture and killing of small cetaceans during fishing activities is a major threat to their conservation. The species considered most at risk in northwest European waters are the harbour porpoise (Phocoena phocoena), which can be trapped in bottom-set gillnet fisheries, and the common dolphin (Delphinus delphis), which can be trapped in pelagic trawl fisheries. Results from a number of studies indicate that the current levels of bycatch are unsustainable, but there is a lack of up-to-date estimates of overall abundance of the cetacean species affected. The first comprehensive survey (LIFE92NAT/UK/027), Small Cetacean Abundance in the North Sea and adjacent waters (SCANS), was completed in 1994, and the results have been widely used by the international community. However, it is important to repeat such estimates of overall abundance at ten-year intervals and for this reason, an application was made for a LIFE-Nature project to carry out a SCANS II survey. Objectives The principal objective of the project was to update the current scientific estimates of small cetacean abundance in European Atlantic waters and feed this information into policy decisions about permissible bycatch levels. The development of improved methods for monitoring and of a robust management framework, should also help define a clear course of action to allow populations to recover and to maintain favourable conservation status. The project would use both airborne and shipboard survey methods to cover all Atlantic shelf waters under European jurisdiction. It would involve a pilot phase to test equipment and methodologies, before undertaking a full survey in July 2005. The key species to be surveyed were harbour porpoise, common dolphin and bottle-nosed dolphin (Tursiops truncatus). In addition to providing up-to-date reliable estimates of the overall abundance of a number of cetacean species, the project would also develop the methodologies for more frequent monitoring activities to be undertaken between major surveys. Results The project followed the SCANS project and provided an opportunity to observe how distribution and abundance has changed in the intervening decade. It produced several key deliverables including: A review and development of visual and acoustic methods for collecting and analysing data from surveys. Fieldwork manuals for data collection. Trained visual and acoustic observers from many European countries. The completion of shipboard and aerial surveys in the North Sea and European Atlantic. Robust estimates of abundance for harbour porpoise, white-beaked, bottlenose and common dolphin, and minke whale for the entire European Atlantic continental shelf. Recommendations for monitoring small cetacean populations, including an analysis to investigate the power of different methods to detect population trends and to assess the cost-effectiveness of these methods to achieve given power. A management framework for determining safe limits of bycatch of small cetaceans including an application for the harbour porpoise. Results were made available on the project website as well as at a final project conference and via other media. As well as estimating abundance and developing methods for future monitoring, the project also developed a management model for determining safe limits for bycatch. While the latter tool is highly appropriate for achieving conservation objectives required for the Member States under the Habitats Directive, in order to progress this agenda the policymakers need to agree on the conservation and management objects for the species in question. The project outlines the steps that will be necessary to achieve compliance with the Habitats Directive in a comprehensive After Life Conservation Plan that recognises the difficulties involved in resolving possible conflicts of interest between fisheries and environmental stakeholders. Further information on the project can be found in the project's layman report (see "Read more" section).