Bycatch of Seabirds in the Polish Part of the Southern Baltic Sea in 1970–2018: A Review

Abstract. Bycatch, the unintended capture of animals other than target fish, is one of the most important anthropogenic threats to seabirds worldwide. This problem has been relatively little studied, however. The southern Baltic Sea is one of the three areas worldwide with the highest gillnet bycatch. Forty-eight publications from the years 1982–2021 addressing the problem of seabird bycatch in the Polish Exclusive Economic Zone (PEEZ) of the Baltic Sea were analysed for the purposes of this paper. Twenty-eight bird species were identified in bycatch, 13 of which have threatened or near-threatened status on the European Red Bird List. The magnitude of the annual bycatch was estimated for three periods: 1970s — 47,000 birds, 1980s and 1990s — 39,800 and 2010s — 21,300 birds. The most frequently bycaught species in the 2010s were Long-tailed Duck Clangula hyemalis (9,000 ind. yearly), Greater Scaup Aythya marila (3,500) and Velvet Scoter Melanitta fusca (2,000). Acceptable mortality thresholds calculated using both the Potential Biological Removal (PBR) and the BirdLife International (BLT) methods were found to have been exceeded: for Long-tailed Duck by 175% (PBR) and by 1,061% (BLT); for Greater Scaup by 542% (PBR) and by 3,400% (BLT); for Velvet Scoter by 35% (PBR) and by 495% (BLT). All three species are listed as Vulnerable in Europe. Six distinct bycatch areas have been identified in the PEEZ. Bycatch mitigation is exceedingly difficult to implement: the only effective method currently employed to protect seabirds from bycatch in gillnets involves the temporary closure of bird hotspots to gillnet fishing.