Discard self-sampling of the Dutch bottom-trawlfisheries in 2020

Bleeker, K.; Overzee, H.M.J. van; Dammers, M.


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 hauls according to a definite annual sampling plan. 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 2020. In 2020 the reference fleet consisted of 21 vessels. The COVID-19 pandemic, which arrived in Europe at the end of January 2020, had minimal impact on the execution of the self-sampling programme. In total 164 trips, out of the planned 160 trips, were sampled correctly in 2020. 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: beam trawlers with 80 mm mesh size (engine power > 300 hp and engine power ≤ 300 hp), 100-119 mm mesh size and ≥120 mm mesh size, and otter trawlers with 70-99 mm mesh size (targeting Nephrops or mixed crustaceans and demersal species) and 100-119 mm mesh size. 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 both in space and time; a mismatch between sampling and the distribution of the fleet could indicate a possible bias in the discard estimate. The results show that sampling effort of the most intensely sampled metiers (i.e. TBB_DEF_70-99, OTB_CRU-70-99) indeed follows the fleet through space and time. However, for the less frequently sampled metiers this does not always appear to be the case. An important element in the reform of the Common Fisheries Policy (CFP) 2014-2020 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 of years (starting in 2016 and full implementation in January 2019). It is clear that discarding will continue under various forms of exemptions (high survivability, de minimis, prohibited species). Therefore, a discards monitoring programme remains necessary under the landing obligation. From 2016 onwards, monitoring of the catch fraction Below Minimum Size (BMS) has been included in the sampling protocol of the discards monitoring programme. Similar to previous years, BMS has been observed and registered sporadically in the self-sampling trips in 2020.