Discard self-sampling of Dutch bottom-trawl fisheries in 2017-2018

In the European Union the collection and management of fisheries data is regulated through the Data Collection Framework (DCF) of the European Commission (EC). Within this context, Wageningen Marine Research (WMR) coordinates a discards monitoring programme in collaboration with the Dutch demersal fishing industry. A ‘reference fleet’ of vessels of which the owners are willing to participate in a self-sampling programme, was recruited in 2009 and has been extended and updated regularly. Annually approximately 160 trips need to be sampled by the reference fleet. Fishermen within the reference fleet are requested to collect discard samples of two separate hauls according to a definite annual sampling plan. In 2017 these trips were in collaboration with the participating vessels evenly divided over the reference fleet. In order to avoid any potential bias in trip selection and to work conform the statistical sound principles as defined in the DCF recast, from 2018 onwards the trips are randomly divided over the reference fleet and any refusals are recorded. After the discard samples are brought to shore, WMR collects and analyses these samples. This report summarizes data that has been collected within this self-sampling monitoring programme in 2017-2018. In 2017-2018 the reference fleet consisted of 19-20 vessels. In total, 159 and 167 were sampled in 2017 and 2018 respectively. All sampled trips were assigned to their respective metiers post sampling, based on gear type, mesh size and species composition of the catch. Seven different metiers were assigned: beamtrawlers with 70-99 (Eurocutters (i.e. engine power ≤300 hp) and large vessels (i.e. engine power > 300 hp)), 100-119, and ≥120 mm meshes, and otter trawlers with 70-99 mm meshes (targeting Nephrops or Demersal fish) and 100-119 mm meshes. Observed discard patterns are quite similar between all metiers; dab and undersized plaice are the most frequently discarded fish species. The majority of the benthic, non-fish, discards consisted of echinoderms and crustaceans. In order to monitor annual discard percentages, it is essential that the sampled trips follow the distribution of the fleet; a mismatch between sampling and the distribution of the fleet could indicate a possible bias in the discard estimate. The results shows that sampling effort of the most-intensely sampled metiers (i.e. TBB_DEF_70-99) indeed follows the fleet through space and time. However, for the less frequently sampled metiers this not always appears to be the case An important element in the reform of the Common Fisheries Policy (CFP) is the obligation to land all catches, i.e. a discard ban. Under this landing obligation all discards of quota regulated species have to be landed. For the demersal fisheries the landing obligation has been phased in over a number years. It is clear that as discarding will continue under various forms of exemptions (high survivability, de minimis, prohibited species), a discards monitoring programme remains necessary under the landing obligation. Furthermore, monitoring of BMS needs to be captured in the sampling programme