The Marine Strategy Framework Directive (MSFD) requires EU Member States to develop programmes of measures that aim to achieve or maintain Good Environmental Status (GES) in European seas. In order to be able to evaluate the quality status of marine waters on a regular basis and the effects of the measures taken, monitoring programs for MSFD descriptors and indicators have been established by the Member States. The Dutch monitoring program for Marine Litter (Descriptor 10) includes the collection of data on the abundance, composition and distribution of macro litter on the seafloor. According to the Dutch program, the data on seafloor litter must be collected during statutory task fish surveys using a standardised Grand Ouverture Verticale (GOV) fishing net as part of the International Bottom Trawl Survey (IBTS), which is carried out yearly in the North Sea. Anthropogenic pollution of the oceans, including marine litter, threatens wildlife, hinders human activities and reduces the recreational value of our coasts. Marine litter affects all groups of marine wildlife through effects such as entanglement and ingestion. Various initiatives to reduce litter in the (marine) environment are running or are currently under discussion. Despite management measures to decrease the input of litter and to remove litter from the environment, litter is still found in monitoring of the seafloor. This report presents the seafloor litter composition, abundance and spatial distribution based upon catches of the regular fish surveys, the IBTS and the Dutch Beam Trawl Survey (BTS). Only the catches on the Dutch Continental Shelf (DCS) are used for data analysis. To assess the status of seafloor litter on the DCS, the Dutch data are supplemented with those from international partners surveying the DCS within the IBTS. The seafloor litter catches on the DCS consisted mainly of plastic items: 90% (IBTS) and 89% (BTS) of the litter items found were made of plastic. Monofilaments, plastic sheets and various types of (plastic) ropes/lines were the most commonly caught litter types. A mean density of 74 litter items per km 2 over the years 2021-2023 was calculated for the IBTS on the DCS, whereby for the BTS a mean density of 185 litter items per km 2 over the last two years (2020-2022) was calculated on the DCS. It should be noted that the nets used during the IBTS (GOV) and BTS (beam trawl) are not designed to catch litter. For the GOV, the catchability of many benthic species (e.g. Asteroidea) is assumed to be less than 5% compared to a beam trawl (Piet et al., 2009), therefore the chance of catching a litter item when it is present in the trawl path is likely to be even smaller than 5%. The fact that these items are caught despite the suggested low catchability thus indicates that it is plausible that there are many more litter items in the trawl path and that current values are a large underestimation of the actual amount of litter present. In a recent study from Wageningen University, the beam trawl appears to catch seven times more litter than the GOV net at the North Sea level (Van Rossum & Boer, 2023). This is reflected by the fact that hardly any (small) single-use plastics, such as cutleries, straws and stirrers, were caught while these items are commonly found on beaches (Boonstra & Hougee, 2021). The inclusion of the BTS data in recent years has improved the picture of the litter types present on the seafloor. The BTS catches a wider range of litter types and roughly three times more items per swept area then the IBTS according to the data presented in this report. Yet, the abundance and density estimations of seafloor litter presented in this report have to be considered as a very low estimation of the total amount of a selection of litter types present on the DCS, rather than its actual status. This has been demonstrated in a new Dutch study using a benthic dredge for seafloor litter sampling (Roos et al., 2023), which shows much higher seafloor litter densities.

Sampling protocol: Survey_dem Sampling objective(s): data collection for fishery-independent timeseries for by trawling Start of sampling: 1969 (Sole Net survey SNS_NLD), 1970 (International bottom trawl survey IBTS_Q1, Demersal Young fish survey DYFS), 1985 (Beam trawl survey BTS) Sampling ongoing: yes Data use Primary data use: data from commercial fish species as well as elasmobranchs is used as tuning series in single stock assessments.The data users are stock coordinators in ICES Herring assessment working group (HAWG) and ICES Working Group on the Assessment of Demersal Stocks in the North Sea and Skagerrak (WGNSSK), as well as ICES Working Group on Elasmobranch Fishes (WGEF).The main target species can be found in Table 1 in http://data.europa.eu/eli/dec_impl/2021/1168/oj.It should however be noted that survey data of more species is used in stock assessments.The most up to date data use can be found in the advice sheets per species.

This report contains an outline of a working plan for the monitoring of small pelagic fish on the Dutch Continental Shelf. Pelagic fish include species that are not connected to the bottom and live large parts of their life in schools in midwater. Stakeholders within the North Sea Counsel (Noordzeeoverleg) discussed what kind of research is required in the context of sustainable economic use of the North Sea. This resulted in the North Sea Agreement (Noordzeeakkoord - NZA). Part of the North Sea Agreement is the Monitoring-Research- Nature Restoration-Species Protection (Monitoring-Onderzoek-Natuurherstel-Soortbescherming - MONS). A commission has defined the research questions that are at stake and the sort of research that is required to answer these questions from 2022 onwards. Part of this research has received priority - labelled “No regret studies” - of which the monitoring of small pelagic fish is one. The MONS commission has asked Wageningen Marine Research (WMR) to make a proposal for the monitoring of small pelagic fish in the next five years. The first year is a pilot year meant for testing (parts) of proposed methods. The key questions of the client are “What is the distribution of small pelagic fish species in Dutch waters, by season and from year to year?” and “How can these geographical and temporal distributions be explained by the known natural history of the species involved, in terms of known behaviour and habitat requirements?”. This information is required to describe the starting situation for future impact assessments of windfarms construction and other offshore infrastructural building. In addition, the client asks that the plan consists of the following components: (1) A year-round beach sampling of the shallow surf zone and (2) A year-round and annual sampling of small pelagic fish. A summary is given of existing and innovative survey methods. Followed by an overview of historic research on small pelagic fish and of coordinated international surveys in the (Dutch) North Sea. Potential monitoring techniques are briefly described, including both standard and innovative techniques. Furthermore, a limited inventory is made of wishes and requirements of the MONS monitoring proposals for other animal groups. This is followed by practical considerations and the actual monitoring proposal. The proposal consists of two hydro acoustic surveys per year along the Dutch coast in a zone of 20 nautical miles, which includes the (proposed) near coast locations of wind farms. Each of these surveys covers approximately 750 nm with a duration of 3 weeks. One survey is proposed to take place in January/February simultaneous with the International Bottom Trawl Survey (IBTS). The other survey is proposed to take place in June immediately preceding the international Hydro Acoustic Survey for Herring and Sprat (HERAS). The proposed surveys will provide a small-scale distribution map of pelagic fish species in the Dutch coastal zone and will thus give relative distributions of all pelagic species in the Dutch coastal zone. The international data from the IBTS and HERAS are publicly available. HERAS is an acoustic survey and will provide biomasses for sprat and herring on predefined areas in the North Sea (strata) for comparison. For the IBTS – a trawl survey - it is proposed to collect acoustic data during the Dutch part of the survey. This requires some additional effort and training of personal involved. The gathering of acoustic data from foreign vessels in the IBTS, requires consultation with international partners and will therefore take longer than one year. After five years comparison of indexes of the acoustic surveys with the IBTS and HERAS indexes will give answer to the questions (1) “Can abundance changes from year to year in the Dutch coastal zone be explained by shifts in distribution or can it be explained by changes in abundance in the North Sea?”, which contributes to the description of the starting situation mentioned above. It is proposed to fill the temporal gaps between these two surveys without running into extensive costs using standalone hydro acoustic stations (Wbat). For this two methods are being tested during the pilot year: (1) two standalone echosounders in a frame on the bottom, pointing upwards to the surface and (2) a drone that sails repeated transects in a windfarm. As a third supportive method (3) qualitative fish information will be collected by means of gill net sampling. Measurements will be carried out simultaneous during the month of June. In order to get additional temporal reference data over time it is proposed to deploy the Wbat and the gill nets at least in the period during and between the acoustic surveys, preferably the whole year. For the sampling of small pelagic fish in the surf zone, a proposal is made, containing a two weekly sampling scheme running for a large part of the year with a hand towed beam trawl from the beach and sampling with a gill net. It is expected that this sampling scheme – although not tailored to sample pelagic fish – will contribute to a better understanding of pelagic fish distribution, by direct comparison of the gill net catches with the offshore sampling and by providing information on the seasonal occurrence of species and their lengths. The second key question “How can these geographical and temporal distributions be explained by the known natural history of the species involved, in terms of known behaviour and habitat requirements?” is harder to be answered by monitoring. The monitoring data might provide some insight into habitat use and possibly even into schooling behaviour. However, additional studies will have to be initiated in the future, focusing on life history questions and accessory behaviour of the small pelagic fish species in the Dutch coastal zone. For these studies and for studies addressing the impact of offshore constructions on the DCP, the proposed monitoring will provide the necessary baseline information.

The Marine Strategy Framework Directive (MSFD) requires EU Member States to develop programmes of measures that aim to achieve or maintain Good Environmental Status(GES) in European seas. In order to be able to evaluate the quality status of marine waters on a regular basis and the effects of the measures taken, monitoring programs for MSFD descriptors and indicators have been established by the Member States. The Dutch monitoring program for Marine Litter (Descriptor 10) includes the collection of data on the presence, abundance and distribution of macro litter on the seafloor. According to the Dutch program, the data on seafloor litter must be collected during statutory task fish surveys using a standardised Grand Ouverture Verticale (GOV) fishing net as part of the International Bottom Trawl Survey (IBTS), which is carried out yearly in the North Sea. Anthropogenic pollution of our oceans, including marine litter, threatens wildlife, hindershuman activities and reduces the recreational value of our coasts. Marine litter affects all groups of marine wildlife through effects such as entanglement and ingestion. Various initiatives to reduce litter in the (marine) environment have recently been started or are currently under discussion. Despite management measures to decrease the input of litter and to remove litter from the environment, litter is still found in monitoring of the seafloor.This report presents the seafloor litter composition, abundance and spatial distribution based upon catches of the regular fish surveys, the IBTS and the Dutch Beam Trawl Survey(BTS). Only the catches on the Dutch Continental Shelf (DCS) are used for data analysis.To assess the status of seafloor litter on the DCS, the Dutch data are supplemented with those from international partners surveying the DCS within the IBTS.The seafloor litter catches on the DCS consisted mainly of plastic items: 93% (IBTS) and 88% (BTS) of the litter items found were made of plastic. Monofilaments, plastic sheets and various types of (plastic) ropes/lines were the most commonly caught litter types. A mean density of 88 litter items per km2 over the years 2020-2022 was calculated for the IBTS on the DCS, whereby for the BTS a mean density of 198 litter items per km2 over the last two years (2020-2021) was calculated on the DCS. It should be noted that the net used during the IBTS (GOV) and BTS (beam trawl) is not designed to catch litter. For the GOV, the catchability of many benthic species is assumed to be less than 5% compared to a beam trawl, therefore the chance of catching a litter item when it is present in the trawl path is likely to be even smaller than 5%. The fact that these items are caught despite the suggested low catchability thus indicates that it is plausible that there are many more litter items in the trawl path and that current values are a large under estimation of the actual amount of litter present. On top of that, due to the selectivity of the fishing gears used in the surveys, only a selection of the types of litter items present retain in the net. This is reflected by the fact that hardly any (small) single-use plastics, such as cutleries, strawsand stirrers, were caught. However, by including the BTS survey a slightly better picture of the litter types present on the seafloor is provided since two times more items werecollected and a wider range of litter items was caught. Therefore, the BTS data will be included in this report the coming years. Yet, the abundance and density estimations of seafloor litter presented in this report have to be considered a minimum estimation of the total amount of a selection of litter types present on the DCS, rather than its actual status.

This study is done as part of the permit requirements for TenneT to investigate whether and to what extent there are effects of electromagnetic fields on marine mammals and fish. In this study we assess if there are possible indications that EMFs around the cables of offshore windfarms influence the behaviour and presences of several commercial benthic fish species. In addition, it is also analyzed if there are indications of influence on the behaviour and presence of elasmobranchs and several commercial round fish species. Estimations of fish abundance are based on the catch of a beam trawl fished over the cable route and are compared to adjacent reference sites with no cables, parallel to the cable route, of the Borssele wind area. In order to ensure the catches came from the cable route being within the EMF, the beam trawls were equipped with EMF-sensors that were tested beforehand. Results of this study indicate that there was no significant difference between the catches of the target flatfish species in the vicinity of the cable and in the reference areas. For some of the assessed non-target species, it was shown that there is a difference between the cable route and the reference, specifically for dragonet and whiting. In these cases, the species showed higher abundance on the cable than in the reference area, suggesting some attraction by the cable. It remains however difficult to disentangle the impact of the EMF from other (indirect) factors. In conclusion, the results show that under the current circumstances there is no basis for any negative impact of the cable on the abundance of the species found. Furthermore, there is no solid indication of impact of the EMF at all, which is in line with recent literature where little effect on fish behaviour in relation to EMF is found and that there is no significant effect to be expected.

The Marine Strategy Framework Directive (MSFD) requires EU Member States to develop programmes of measures that aim to achieve or maintain Good Environmental Status (GES) in European seas. In order to be able to evaluate the quality status of marine waters on a regular basis and the effects of the measures taken, monitoring programs for MSFD descriptors and indicators have been established by the Member States. The Dutch monitoring program for Marine Litter (D10) includes the collection of data on the presence, abundance and distribution of macro litter on the seafloor. According to the Dutch program, the data on seafloor litter must be collected during statutory task fish surveys using a standardised GOV (Grand Ouverture Verticale) fishing net as part of the International Bottom Trawl Survey (IBTS), which is carried out yearly in the North Sea. Anthropogenic pollution of our oceans, including marine litter, threatens wildlife, hinders human activities and reduces the recreational value of our coasts. Marine litter affects all groups of marine wildlife through effects such as entanglement and ingestion. Various initiatives to reduce litter in the (marine) environment have recently been started or are currently under discussion. Despite management measures to decrease the input of litter and to remove litter from the environment, litter remains on the seafloor. This report presents the seafloor litter composition, abundance and spatial distribution based upon catches of the regular fish surveys, the International Bottom Trawl Survey (IBTS) and the Dutch Beam Trawl Survey (BTS). Only the catches on the Dutch Continental Shelf (DCS) are used. To assess the status of seafloor litter on the DCS, the Dutch data are supplemented with those from international partners surveying the DCS within the IBTS. The seafloor litter catches on the DCS consisted mainly of plastic items: 88% (BTS) and 95% (IBTS) of the litter items found were made of plastic. Monofilaments, plastic sheets and various types of (plastic) ropes/lines were the most commonly caught litter types. A mean density of 165 (IBTS) and 201 (BTS) litter items per km2 was calculated on the DCS, with mean values per ICES rectangle exceeding 200 items per km2. It should be noted that the net used during the IBTS (GOV) and BTS (beam trawl) is not designed to catch litter. For the GOV, the catchability of many benthic species is assumed to be less than 5%, the chance of catching a litter item when it is present in the trawl path is likely to be even smaller than 5%. The fact that these items are caught thus indicates that it is plausible that there are many more litter items in the trawl path and that current values are a large underestimation of the actual litter present. On top of that, due to the selectivity of the fishing gears used in the surveys, only a selection of the types of litter items present retain in the net. This is reflected by the fact that hardly any (small) single-use plastics were caught. However, by including the BTS survey a slightly more representative picture of the litter types present on the seafloor is given since a wider range of litter items was caught, therefore the BTS data will be included in the coming years. Yet, the abundance and density estimations have to be considered as a minimum estimation of the amount of a select part of the litter present on the DCS, rather than the actual status of it.

European eel,Anguilla anguilla(L.), migrating to sea encounter many man-made structures that can hamper and delay migration or induce mortality. Three pumping stations in Friesland, the Netherlands, were covered with acoustic receivers. Ninety-three silver eels tagged with acoustic transmitters were released in the polders upstream of the stations and 89% were detected passing a pumping station. The majority of silver eels passed the stations within a day after arriving at the station. Four silver eels stayed for longer than 2 weeks before passage, and 18 were detected at the receiver downstream the pumping station for more than one day, with detections up to several weeks. These detections probably indicated a dead eel, but could also indicate a live eel remaining at the site. Most of the silver eels passed the pumping stations within a day after release, so fish-friendly pumps will benefit the migrating population most. In the Netherlands, there are several thousand pumping stations. Installing fish passages near these stations is not feasible due to high costs. Prioritising all these sites in relation to the degree of blockage, mortality rates and its relative importance for migratory fish, can maximise the effectiveness of measures and mitigation taken.

In de periode van 16 tot 23 juni 2020 heeft Wageningen Marine Research in opdracht van Rijkswaterstaat in het kader van Natuurlijk Veilig opnieuw een kustlangse survey uitgevoerd in de vooroever. Dit jaar is bemonsterd vanaf IJmuiden tot aan Texel en aanvullend in de westelijke Waddenzee (Balgzand). De survey is opgezet om de verspreiding en abundantie van (plat)vis in de vooroever te bepalen en gegevens te verzamelen over (a)biotische factoren die deze verspreiding bepalen. Het doel van de bemonstering is om mogelijke effecten van zandsuppleties in de vooroever op vis in kaart te brengen. De dit jaar uitgevoerde bemonsteringen zijn, ondanks een gedeeltelijk andere opzet, bedoeld als aanvulling op eerdere werkzaamheden binnen het Natuurlijk Veilig project, welke zijn uitgevoerd in 2017, 2018 en 2019. Vanaf IJmuiden naar het noorden toe en in de westelijke Waddenzee zijn er om de paar kilometer op verschillende waterdieptes in totaal 81 locaties succesvol bemonsterd. Iedere locatie is bemonsterd voor vis met een 3 meter boomkor (het DFS-tuig). Daarnaast is op iedere locatie (m.u.v. 3 locaties) een sedimentmonster genomen en zijn er gegevens verzameld over doorzicht, watertemperatuur en saliniteit. In totaal zijn in de 81 vistrekken 90.796 vissen gevangen verdeeld over 36 soorten. Daarnaast zijn er 37 overige soorten (o.a. benthos) geregistreerd. De meest gevangen vissoorten waren haring (incl. clupeidae), zandspiering en schol en voor de overige soorten waren dit gewone garnaal, gewone zwemkrab en strandkrab.

The Marine Strategy Framework Directive (MSFD) requires EU Member States to develop programmes of measures that aim to achieve or maintain Good Environmental Status (GES) in European Seas. In order to be able to evaluate the quality state of marine waters on a regular basis and the effects of the measures taken, monitoring programs for MSFD descriptors and indicators have been established by the Member States. GES is defined by 11 descriptors, including Marine Litter (D10). The Dutch monitoring program for this descriptor includes the collection of data on the presence, abundance and distribution of macro litter on the seafloor. According to the Dutch program, the data on seafloor litter must be collected during statutory task fish surveys using a standardised GOV (Grand Ouverture Verticale) fishing net as part of the International Bottom Trawl Survey (IBTS), which is carried out yearly in the North Sea. This report presents the results of the seafloor litter monitoring during the IBTS of Quarter 1, 2020. Seafloor litter data have been collected annually since 2013, and the new data are presented and compared to the data collected in previous years. This is done for both the composition and the spatial distribution of the seafloor litter. The allocation of rectangles was the same as in 2019, however owing to permit issues of participating countries and extremely bad weather conditions during the survey period, the area covered by the Dutch IBTS 2020 was not as planned and deviates from the covered area in 2019 and earlier years. These deviations in the spatial coverage hampers comparisons over the years. In 2020, litter was caught in 83% of the hauls. The composition of this litter was similar to that of previous years, more than 90% of the 155 items recorded was plastic and these were mainly monofilament lines and plastic sheets. The majority of these items was, as in previous years, small (<25 cm2). The haul with the highest amount of litter items was in the south-east part of the North Sea towards the Dutch coast, with 19 separate items recorded. Due to the spatial deviation of the surveyed area in each year, and the semi-random sampling in a grid cell, it is difficult to compare the data between years. Bearing this in mind, mean and median values from this year were nearly the same as those of the previous two years, but lower than those of earlier years since recording began in 2013. It should be noted that the net used during the IBTS (GOV) is not designed to catch litter, therefore, it probably has a small chance of catching a litter item when it is present in the trawl path. Thus, the fact that these items are caught indicates that it is likely that there are many more items in the trawl path and that current values are a large underestimation of the actual litter present. Consequently, the degree of litter pollution on the seafloor is probably much larger than presented in this report. The Dutch seafloor litter monitoring results are uploaded to the ICES DATRAS database, and are used in OSPAR assessments of seafloor litter in the North Sea. Due to this aggregation of many ICES seafloor litter surveys of the North Sea, an assessment of the presence/absence and total count of seafloor litter items can probably be made in the near future for the whole North Sea area.

In de nacht van 1 op 2 januari 2019 raakte het containerschip MSC Zoe ter hoogte van Terschelling de zeebodem waardoor in totaal 342 containers overboord geslagen zijn en verspreid geraakt over het gebied tussen Terschelling en Schiermonnikoog. Rijkswaterstaat heeft Wageningen University & Research opdracht gegeven onderzoek te doen naar de mogelijke gevolgen van de containerramp op het ecosysteem van de Noordzee en Waddenzee. De doelstelling van dit onderzoek is het in 2019 geregistreerd verzamelen van plastics en organismen die plastics kunnen hebben ingenomen, aansluitend bij bestaande monitoringprogramma’s. In 2019 is in het kader van deze opdracht zwerfvuil verzameld bij monitoring, en daarnaast zijn vissen, vismagen en vogels verzameld en veiliggesteld voor analyse op aanwezigheid van (micro)plastics. Zwerfvuil: Het registreren van zwerfvuil van de zeebodem is een reguliere activiteit tijdens visbestandsopnames met bodemtrawl netten in het IBTS-programma. Volgens hetzelfde protocol is aanvullend zwerfvuil op de zeebodem geregistreerd tijdens twee andere vissurveys en tijdens schelpdierinventarisaties. Ook is er een analyse gedaan naar zwerfvuil verzameld op Griend. Het zwerfvuilonderzoek richt zich op grotere objecten dan microplastics. Vogels: er zijn ten minste 43 dood gevonden Noordse Stormvogels verzameld, waarvan verreweg het grootste deel op de Waddeneilanden en de Fries-Groninger waddenkust. Daarnaast zijn ten minste 14 Zwarte Zee-eenden, 1 Grote Zee-eend en 4 Drieteenmeeuwen verzameld, allen dood aangetroffen in het Waddengebied. Vissen: er zijn tijdens reguliere visbestandsopnames in het gebied boven de Nederlandse eilanden tot aan Helgoland 211 magen van vissen uit de vangsten verzameld, en 4856 vissen uit de gehele Noordzee tijdens het reguliere onderzoek naar bijvangsten van de visserij. Begin 2020 gaf RWS opdracht aan WMR om (een deel van) de biologische monsters in 2020 te analyseren.

The North Sea International Bottom Trawl Survey (NS-IBTS) is an internationally coordinated survey. The fisheries-independent indices for young herring, sprat, whiting, cod, haddock, Norway pout and other commercial fish species from the survey are used in fisheries management. As the complete catch is processed, the survey also provides marine ecosystem information. The survey is coordinated by the IBTS Working Group (IBTSWG) of the International Council for Exploration of the Seas (ICES). The survey setup, including the gear -Grande Ouverture Verticale (GOV)-, is standardised and written down in a manual. The results of an intensive evaluation of the GOV-gear used in the NS-IBTS by different institutes, indicated that all gears differed, and none of them matched the manual exactly. This, together with a wish for a new gear that would be using modern materials, would be cheaper, and able to fish in rougher areas, formed the start of the development of a new gear for the IBTS. Two new gears have been developed, one by the Marine Institute, Ireland (MI) and one by Marine Scotland Science (MS Science). Both gears have a very similar design, their main difference is the ratio in which the mesh sizes are attached to each other. The main differences with the current GOV are the netting materials used, and the removal of the lower wings. To test the two gears, MS Science organized a gear trial experiment, for two weeks in November 2019 on board of the Scottish research vessel Scotia. Other members of the IBTSWG were invited to participate, and the Netherlands accepted this, so the WMR gear technician and the RWS boatswain joined the field trial. This report provides the preliminary results of the trials, along with the observations of the Dutch participants. The preliminary results indicate that both new gears are fishing properly, and both target at least the same fish community as the GOV. There are differences observed in spreading and height of the net, that directly translate into differences in catch composition. The overall conclusion after the trials still is that both new gears would be suitable to replace the GOV. Having seen both gears operational, it is clear that both nets could be handled on board of the Dutch research vessel Tridens without real adjustments. The Dutch participants had a slight preference for the Irish net, because it is simpler to handle. However, in their opinion the Irish gear should be made of stronger materials to make it more durable and the smallest mesh-size (80 mm) should be made smaller (50 mm). The Scottish gear is currently too heavy for the sandy areas in the southern North Sea if the rigging used during the trials is being used, and should be made lighter. Both gear developers indicated that such adjustments are still possible. In the IBTSWG in April 2020, the preliminary results of the trials were discussed and it was concluded to continue the current road with the two new gears. Terms of reference were developed for a workshop with gear technicians end of 2020, early 2021 to discuss the materials, the rigging and further development of the gears into a single new gear for the North Sea IBTS. After this workshop a final net should be made, which can then be used on trial fisheries by each institute involved in the IBTS. The further roadmap for implementing the new gear in the near future, was drafted by the ICES Workshop on impacts of planned changes in the North Sea IBTS (WKNSIMP) in 2019, and includes a transition period in which both gears, the current GOV and the new gear, will be used in the NS-IBTS.

European eel, Anguilla anguilla L., migrating to the sea encounter many man-made structures that can hamper and delay migration or induce mortality. Studying small-scale behavioural movements in front of these man-made structures could provide insight in further mitigating adverse effects. The behaviour of eel approaching a trash rack in front of a large pumping station was investigated using a dual-frequency identification sonar (DIDSON). Eels approaching the trash rack swam through the rack (40.5%) but also showed turning behaviour at (44.7%) or in front of the rack (14.7%). Eels approaching the rack had varying body positions, predominantly head or tail first, but also curled up into a ball or drifted sideways. After turning in front or at the trash rack, eels showed upstream and downwards swimming towards the canal bottom. The results suggest a stepwise response to potential cues, when firstly the body position is changed in such a way that secondly, later on, enhances eventual fast upstream escapement when perceived necessary. Implications for management of these behavioural observations are discussed.

Nederland heeft onder verordening 605/2013, de zogenoemde ‘Shark Finning Regulation’, een rapportageplicht wat betreft het aanvoeren van haaien. Hiervoor zijn gegevens over de aanvoer (2009 – 2019) en discards (2011 – 2019) van haaien en roggen door de Nederlandse visserij ontsloten. Aan de hand van EU-logboek gegevens uit VISSTAT is een overzicht te maken van de aanvoer van haaien en roggen per aanvoerhaven. Ook zijn gegevens vanuit de jaarlijkse marktbemonstering gebruikt om de lengte-frequentie verdeling van bemonsterde aanvoer van haaien en roggen te tonen. De totale discards haaien en roggen zijn opgewerkt vanuit het discard zelfbemonstering programma. De aanvoer van roggen door de Nederlandse visserij varieert door de jaren heen, zonder een duidelijke trend te tonen. Den Helder en IJmuiden zijn de belangrijkste aanvoerhavens voor roggen. Er is een toename in aanvoer van haaien, met name hondshaai, en Harlingen en Vlissingen zijn de voornaamste Nederlandse aanvoerhavens. Haaien worden ook regelmatig in havens in Frankrijk en het Verenigd Koninkrijk aangevoerd. In de marktbemonstering worden voornamelijk stekelrog, gevlekte rog en blonde rog bemonsterd. Echter, de marktbemonstering van haaien, met name hondshaai, is in 2015 stop gezet. Sinds 2017 neemt de hoeveelheid discards aan haaien en roggen toe waarbij een groot aandeel van de discards uit de belangrijkste commerciële soorten bestaat. Voor doornhaai, ruwe haai, sterrog en koekoeksrog zijn slechts voor een beperkt aantal jaren gegevens beschikbaar. Het is belangrijk te weten dat de opwerking van discardgegevens uit zelfbemonsteringsreizen sterk afhankelijk is van het aantal bemonsterde reizen en het voorkomen van een soorten in een specifiek vlootsegment. Mogelijk zijn de in dit rapport gepresenteerde discardgegevens dan ook een over- of onderschatting van totale discardaantallen voor haaien en roggen in de vloot. Naast de commerciële vangstgegevens zijn ook (inter)nationale vis- en visserijsurveys ontsloten uit Frisbe (1980 – 2019) en de DATRAS database van ICES. Deze gegevens zijn geanalyseerd op basis van aantallen, lengte en ruimtelijke verspreiding, waarbij ook de inzet van Nederlandse monitoring in kaart is gebracht. Uit de analyse blijkt dat het samenvoegen van gegevens uit deze programma’s een waardevolle gegevensbron voor bestandsschattingen of biologische gegevens zijn, maar ook een belangrijke rol vervullen in het detecteren van ruimtelijke verspreidingspatronen zoals bijvoorbeeld het waarnemen van verschillen in de ruimtelijke verspreidingspatronen van verschillende grootte van stekelrog. Uit de analyse blijkt ook dat Nederland een breed scala aan vis en visserij bemonsteringsprogrammas uitvoert. Deze programma’s variëren van langlopende internationaal gecoördineerde surveys tot kortlopende nationale projecten zoals impactstudies. Deze surveys hebben een waardevolle rol bij de monitoring en zijn een cruciaal onderdeel van veel bestandsschattingen. Als laatste is binnen dit rapport een review gemaakt met betrekking tot overlevingsstudies naar roggen in de Noordzee en is een overzicht met afgeronde en lopende projecten met haaien en roggen sinds 2015 opgenomen. De informatie ontsloten in dit rapport moeten richting geven de effectiviteit en de kansen op het behalen van de doelstellingen gespecificeerd onder het in 2009 aangenomen European Union Action Plan for the Conservation and Management of Sharks en de in 2008 uitgevaardigde Europese Kaderrichtlijn Mariene Strategie (KRM). Aanbevelingen over aanvullend onderzoek met betrekking tot het verbeteren van educatie en communicatie, het terugdringen van ongewenste bijvangst en het verhogen van de overleving van soorten zijn in de conclusies van dit rapport opgenomen.

Suppleties van zand op vooroever of strand worden in opdracht van Rijkswaterstaat uitgevoerd om de Nederlandse kust tegen erosie te beschermen en om voldoende zand in het kustfundament te houden. Een groot deel van de suppleties vindt plaats in of nabij de kuststrook die binnen de Natura2000 regelgeving wordt beschermd, de Noordzeekustzone. Het is dus van belang de eventuele effecten van deze praktijk op de natuur zorgvuldig te bestuderen, zodat dit effect kan worden afgezet tegenover het algemene nut voor de maatschappij. Betere kennis van de effecten kan leiden tot beperking van eventuele schade aan- en mogelijk zelfs tot versterking van- gewenste natuurwaarden en ecosysteemdiensten. Tot nog toe is er in vergelijking met benthos relatief weinig aandacht geweest voor de gevolgen van suppleren op vispopulaties, terwijl de kinderkamerfunctie van de ondiepe kustzone voor vis een zeer belangrijke economische ecosysteemdienst levert. Kennis van de omgevingsfactoren die het voorkomen van juveniele vis in de ondiepe kustzone bepalen, leidt tot een verbeterd inzicht in de gevolgen van suppleties op vispopulaties en daarvan afhankelijk overig zeeleven. In overleg met natuurorganisaties en de kennisinstituten Deltares en Wageningen Marine Research is in 2016 het document `Ecologische effecten van zandsuppleties’ (Herman et al., 2016) geschreven met als doel onderzoek te formuleren naar ecologische effecten van zandsuppleties. In het onderdeel ‘uitvoeringsplan’ (deel C in Herman et al. 2016) zijn 3 onderzoekslijnen (ook wel Krachtlijnen genoemd) gedefinieerd, te weten: Vooroever, Duinen en Waddenzee. Het hier beschreven meetplan voor een survey in 2020 valt onder de onderzoekslijn Vooroever. De onderzoeksvraag luidt: “Wat zijn de cumulatieve gevolgen van reguliere suppleties op samenstelling en functioneren van het ecosysteem van de ondiepe vooroever van de Nederlandse kust?” Deze volgt uit de prioritering van de krachtlijn Vooroever: (cumulatieve) gevolgen van reguliere suppleties op samenstelling en functioneren van het ecosysteem van de vooroever. Het onderdeel dat in onze monitoring de hoogste prioriteit heeft gekregen is vis en dan met name de bodemgebonden (plat)vis omdat hier het meest directe effect van een verandering in sedimentsamenstelling door suppleties is te verwachten. Om de verspreiding en abundantie van deze vis in relatie tot omgevingsvariabelen zoals sedimentsamenstelling beter te begrijpen is er in 2017, 2018 en 2019 bemonsterd in de ondiepe vooroever (<10m) waarbij verschillende omgevings-variabelen zijn bepaald. In 2017 en 2018 is dit gedaan voor specifieke gebieden met een experimentele opzet. Vanwege de beperkt beschikbare tijd (en de noodzaak van goede weersomstandigheden binnen dit tijdsbestek) leverde dit minder resultaten op dan vooraf verwacht. Vandaar dat in 2019 besloten is een andere opzet te kiezen waarbij de experimentele opzet minder van belang was. Er werd toen uitgebreider gekeken naar het ruimtelijke beeld langs de gehele Nederlandse kustzone. In navolging van 2019 wordt er voor 2020 opnieuw een kustlangse survey voorgesteld. Gedurende een week wordt er vanaf het onderzoeksschip de Luctor met een 3 m boomkor gevist en wordt er op dezelfde locaties een sedimentmonster genomen. Voorlopige analyses van de eerder verzamelde gegevens laten zien dat de vangsten van schol in de kustzone vele malen lager zijn dan die in publicaties over de Waddenzee. Dit zou een werkelijk verschil in aanwezigheid van schol kunnen zijn, maar waarschijnlijk speelt de vangstefficiëntie van de gebruikte vistuigen hierin ook een rol. Om hier zicht op te krijgen, is er voor 2020 voorgesteld om in beide gebieden te bemonsteren met hetzelfde tuig. Om deze aanpassing op de kustlangse bemonstering zoals uitgevoerd in 2019 mogelijk te maken, is ervoor gekozen om het meest zuidelijke transect, langs de Zandmotor, uit de 2019 bemonstering te laten vervallen. Hiervoor in de plaats wordt een dag gebruikt om een transect op het Balgzand in de Waddenzee te bemonsteren. In 2020 gaat er vanuit IJmuiden tot aan Texel langs de kust op een diepte tussen 4-5 m bemonsterd worden, aangevuld met bemonsteringen op het Balgzand. In 2019 zijn twee raaien naar dieper water (12m) bemonsterd om inzicht te krijgen of de verspreiding van jonge schol zich enkel beperkt tot de 4-5m diepte zone, of dat ze in het voorjaar ook al aanwezig zijn in diepere wateren. Om meer inzicht op deze ruimtelijke verspreiding te krijgen zal er langs de kust in 2020 opnieuw geprobeerd worden een aantal raaien naar dieper water (12m) te bemonsteren.

Beam trawls are criticized for their negative impact on benthic ecosystems. Pulse trawls may be an environmental more friendly alternative. In addition to the environmental benefits, the pulse trawl is expected to improve the catch efficiency for the main target species (sole Solea solea). Here, we report on an opportunistic comparison between a pulse and traditional tickler chain beam trawl (TCBT). Catch efficiency for sole and plaice was determined in 39 paired hauls, during which both vessels fished parallel, and by comparing average landings during commercial hauls in which the vessels fished in close proximity of each other. Additionally, total catch quantity and composition and benthos composition were compared between both gears. Unfortunately, the TCBT fished with a smaller mesh size than the pulse trawl (67mm versus 80mm). To take account of the differences in mesh-size, plaice and sole catches for the comparative hauls were corrected using selection ogives of recent mesh-size selection experiments. The current study found a 23% higher catch efficiency for market sized sole and a non-significant 3% lower catch efficiency in market sized plaice. The improved size selectivity observed in a similar experiment in 2011, when pulse fishing was just introduced, could not be corroborated. With the exception of Norway lobster and spider crabs, all benthic invertebrate species showed lower catch rates in the pulse-trawl. Due to the difference in cod-end mesh-size, the results of the experiment should be interpreted with caution.