Assessing incidental bycatch of seabirds in Norwegian coastal commercial fisheries: Empirical and methodological lessons

With diminishing seabird populations and little knowledge on incidental bycatch in fisheries in the Northeast Atlantic, this study aimed to screen seabird bycatch in Norwegian coastal fisheries in 2009. The purpose was to 1) quantify magnitude of seabird bycatch rates and estimate total bycatch from the entire fleet by different estimators 2) evaluate data from an access point survey against monitoring data from a reference fleet as methods for collecting data on bycatch mortality of seabirds and 3) give advice on further bycatch studies. The study focused on three small-vessel fisheries (<15 m LOA) outside Northern Norway; the coastal cod (gillnet and manual longline) and lumpfish (gillnet) fisheries and the more offshore Greenland halibut longline fishery. We found no correlation between landed catch and bycatch and upscaling was made based on number of fishing trips. In these fisheries, northern fulmars Fulmarus glacialis outnumbered the other species and constituted almost half of the overall bycatch, totalling about 5500 (mostly on longlines) of the >11 000 birds estimated caught. The black guillemot Cepphus gryllealso stood out as a numerous victim, constituting almost two thirds of the >3000 birds estimated to have drowned in lumpfish gillnets. The two methods were both considered to hold merit and yielded approximately similar estimates of the bycatch in the coastal cod fisheries, however BPUE differs. Further studies are recommended especially on the lumpfish gillnet and Greenland halibut longline fisheries and on temporal and spatial variations in bycatch. More studies are also needed to model effects on seabirds at the population level.