Bycatch of seabirds in Norwegian coastal fisheries – comparison of estimation methods with regards to bias

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Decline in sea-bird populations in the North-East Atlantic increases the need to understand and reduce anthropogenic mortality factors that can be controlled. One such factor is unintentional bycatch in marine fisheries. The aim of this study was to improve knowledge about bycatch of seabirds in Norwegian coastal gillnet and longline fisheries. A key objective was to try out different methods for collecting and analyzing data on seabird bycatch. We assess two methods for collecting data; 1) An in situ survey with personal interviews with 133 fishermen (2009 – 2010) from vessels less than 15 m; and 2) analyzing data on seabird bycatch from 2006 to 2009 from 21 vessels in the coastal reference fleet program managed by the Norwegian Institute of Marine Research (IMR). We used several statistical approaches to estimate and compare bycatch from five different fisheries. Northern fulmars (Fulmarus glacialis), cormorants (Phalacrocorax spp.), black guillemots (Cepphus grille), Atlantic puffins (Fratercula arctica) and razorbills (Alca torda) are the species most often killed in long-lines and gill-nets used in the coastal fishery in Norway. The methods and findings are discussed with regards to future sampling design and estimation procedures.