Discard self-sampling of Dutch bottom-trawl and seine fisheries in 2013
In the European Union, the collection of discard data is enforced through the Data Collection Regulation Framework (DCF) of the European Commission (EC). To comply with these requirements, the Institute for Marine Resources and Ecosystem Studies (IMARES, part of Wageningen University and Research) coordinates a discards monitoring programme in collaboration with the Dutch fishing industry. Within this project, a ‘reference fleet’ of vessel owners, willing to participate in a self-sampling programme, has been recruited. Fishermen are requested to collect discard samples for a definite number of trips per year. After the discard samples are brought to shore, IMARES collects and analyses these samples. This report summarizes data from this monitoring programme of Dutch demersal fisheries operating in the North Sea (ICES subarea IV) in 2013.
In 2013, the reference fleet consisted of 23 vessels. In total, 140 trips were sampled, of which 8 (5.7 %) were considered invalid due to missing or incomplete information. During the 132 valid self-sampling trips 263 hauls were sampled, typically two hauls per trip. While the majority of observations (57 trips) were done on-board beamtrawl vessels with mesh sizes ranging between 70 and 99 mm (>300hp), data were collected from additional metiers as well. These metiers included beamtrawlers with larger mesh sizes, seines (100-119mm and >=120mm), otter-trawlers (100-119mm, >=120mm) and otter trawlers (70-99mm) with a different target species assemblages (i.e. mixed crustaceans (MCD) in stead of demersal fish (DEF)).
For all metiers with mesh sizes of 70-99mm, combined fish and benthos discards exceeded the landings. In contrast, large meshed beam, otter and seine trawls (>100mm) landed on average more than they discarded. The majority of discards comprised of fish, consisting of commercially valuable species like common dab (Limanda limanda) and European plaice (Pleuronectes platessa) and non-commercially valuable species like dragonet (Callionymus lyra), grey gurnard (Eutrigla gurnardus), scaldfish (Arnoglossus laterna), solenette (Buglossidium luteum) and lemon sole (Microstomus kitt). Most frequently discarded benthos (invertebrate) species included several starfish and brittle star species (Asteria rubens, Ophiura ophiura, Astropecten irregularis, Ophiothrix fragilis), swimming crab species (Liocarcinus sp.), hermit crab (Pagurus bernhardus), sea potato (Echinocardium cordatum) and helmet crabs (Corystes cassivelaunus).