Does the efficiency of PAL to reduce harbor porpoise bycatch persist?

Background and Objective

Special warning devices (Porpoise ALert, PAL) that reduce the bycatch of harbor porpoises (Phocoena phocoena) in set nets have been used by fishers in Schleswig-Holstein on a voluntary basis since 2017. However, it is unclear whether the effect of the PAL, as demonstrated by the Thünen Institute of Baltic Sea Fisheries, persists over long periods of time, or whether it might diminish as harbor porpoises become accustomed to the warning signals. The third-party funded project "PAL use in German waters - Current efficiency and mode of operation" (PAL-CE), led by the Deutsches Meeresmuseum Stralsund and funded by the Federan Agency for Nature Conservation (Bundesamt für Naturschutz), will contribute to clarifying these questions over the next three years. Additional partners to this project are the Thünen Institute of Baltic Sea Fisheries (project leader Dr. C. von Dorrien), the Aarhus University (Denmark), the Naturhistoriska Riksmuseet Stockholm (Sweden) and the Ostsee Info Center Eckernförde (Germany).

Approach

While the Deutsches Meeresmuseum will experimentally study the reaction of harbor porpoises to the PAL, one of the activities of the Thünen Institute of Baltic Sea Fisheries will be to record potential acoustic reactions of harbour porpoise to PAL that is attached to the set nets of comercial fishermen over long time periods off the coasts of Schleswig-Holstein and Denmark.