Schubert, Philipp R. , Karez, Rolf and Reusch, Thorsten B. H. (Submitted) Caught on camera: Widespread direct evidence of illegal discards in coastal waters of the Western Baltic Sea. Marine Biology . DOI 10.21203/rs.3.rs-2543245/v1.

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Abstract

Most fish stocks in the European Union (EU) are still being overfished. One recent measure of the EU common fisheries policy to curb overfishing is the introduction of landing obligations that are meant to reduce discards, but the success of landing obligations is controversial, as discards still take place. In the German Western Baltic Sea , discards are currently estimated using ship observer data, but vessels <12 m are not sufficiently controlled. We here use an independent method and document widespread discard of undersized cod and flatfish in late summer 2018 using video transects. Discards along the coastline of the south-western Baltic Sea amount to an extrapolated 14.0 t of cod and 1.0 t of flatfish decomposing on the sea floor in 1-13 m depth in a subarea of Mecklenburg Bight that covers only 2.3% of ICES (International Council for the Exploration of the Sea ) subdivisions 22-24, the habitat of Western Baltic cod. Compared to a similar video-mapping seven years earlier (in 2011), the amount of discard increased markedly, suggesting that the implementation of landing obligations in the time between the two mappings for under-sized catches has not resulted in a decrease but an increase of discards. We suggest that higher observed discards of cod in 2018 are also due to a high percentage of cod coming from the 2016-cohort of the Western Baltic cod stock which are just undersized but nevertheless caught by most passive net gear. Our data complement estimates based on ship observer data, while providing the first direct evidence of the fate of discards in the benthic marine habitat.

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