Advances in Scale Assessment of Seabird Bycatch: A New Methodological Framework

This paper presents a methodology for indirectly estimating the scale of seabird bycatch using existing data. The study focuses on five key species ducks that winter in Polish waters Baltic Sea and are highly susceptible to bycatch: Long-tailed Duck, Velvet Scoter, Common Greater Scaup, Tufted Duck. evaluation units used divided into Bornholm (BS) Gotland Subdivisions (GS) within Exclusive Economic Zone (PEEZ). analysis acknowledges lack data certain areas known have high concentrations diving birds fishing activity. population sizes waterbirds were assessed ship-based surveys distance sampling approach. Fishing effort from seasons between 2015/2016 2019/2020 analyzed. Bycatch rates estimated based conducted previous seasons, threshold values established concept “small numbers” defined EU directives. results show GS PEEZ, average abundance all was 174,800 individuals, with an annual 7921 (4.5% total). Scoter most abundant species, followed by In BS, 624,600 5056 (0.8% Duck numerous Scoter. Acceptable thresholds exceeded both subdivisions despite much smaller BS. findings highlight need effective management conservation measures address mortality seabirds due bycatch. presented this offers valuable approach can support efforts minimize impact populations.