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

Evaluating fibre orientation dispersion in white matter: comparison of diffusion MRI, histology and polarized light imaging

Diffusion MRI is an exquisitely sensitive probe of tissue microstructure, and is currently the only non-invasive measure of the brain’s fibre architecture. As this technique becomes more sophisticated and microstructurally informative, there is increasing value in comparing diffusion MRI with microscopic imaging in the same tissue samples. This study compared estimates of fibre orientation dispersion in white matter derived from diffusion MRI to reference measures of dispersion obtained from polarized light imaging and histology. Three post-mortem brain specimens were scanned with diffusion MRI and analyzed with a two-compartment dispersion model. The specimens were then sectioned for microscopy, including polarized light imaging estimates of fibre orientation and histological quantitative estimates of myelin and astrocytes. Dispersion estimates were correlated on region – and voxel-wise levels in the corpus callosum, the centrum semiovale and the corticospinal tract. The region-wise analysis yielded correlation coefficients of r=0.79 for the diffusion MRI and histology comparison, while r=0.60 was reported for the comparison with polarized light imaging. In the corpus callosum, we observed a pattern of higher dispersion at the midline compared to its lateral aspects. This pattern was present in all modalities and the dispersion profiles from microscopy and diffusion MRI were highly correlated. The astrocytes appeared to have minor contribution to dispersion observed with diffusion MRI. These results demonstrate that fibre orientation dispersion estimates from diffusion MRI represents the tissue architecture well. Dispersion models might be improved by more faithfully incorporating an informed mapping based on microscopy data

Discard self-sampling of Dutch bottom-trawl and seine fisheries in 2014-2016

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. Fishermen within the reference fleet are requested to collect discard samples according to a definite annual sampling plan. After the discard samples are brought to shore, WMR collects and analyses these samples. This report summarizes data that has been collected within this monitoring programme in 2014-2016.In 2014-2016 the reference fleet consisted of 20-22 vessels. In total, 160, 172 and 157 trips were sampled in 2014, 2015 and 2016 respectively. All sampled trips were assigned to their respective metiers, based on gear type, mesh size and species composition of the catch. Within a trip, the crew retained a sample during two separate hauls, thus constructing two independent samples. Sampling was conducted on board vessels from eleven different metiers: 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, Scottish seiners with 70-99, 100-119 mm, and ≥120 mm meshes, and otter trawlers with 70-99 mm meshes, 100-119 and ≥120 mm meshes.Discard patterns are quite similar between all metiers; dab and undersized plaice are the most frequently discarded species. In addition, the flyshoot trips frequently discarded grey gurnard, whiting and horse mackerel. The majority of the benthos discards within the beamtrawl and otter trawl metiers consisted of echinoderms and crustaceans. In comparison, flyshooters discarded almost no benthos.An important element in the reform of the Common Fishery 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 will be phased in over a number of years. The landing obligation will have a particular strong impact on the Dutch demersal fishing industry as this is a mixed fishery where catches can contain many different quota species

Discard self-sampling of the Dutch bottom-trawl fisheries in 2019

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 selfsampling 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 2019. In 2019 the reference fleet consisted of 21 vessels. In total, 158 trips were sampled in 2019. All sampled trips were assigned to their respective metiers post sampling, based on gear type, mesh size and species composition of the catch. Eight different metiers were assigned: beam trawlers with 80 (engine power > 300 hp and engine power ≤ 300 hp), 100-119 and ≥120 mm mesh size, and otter trawlers with 70-99 mm mesh size (targeting Nephrops, mixed crustaceans and demersal species, or demersal fish) 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 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 does not always appear 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. From 2016 onwards, monitoring of the catch fraction Below Minimum Size (BMS) has been included in the sampling protocol of the discards monitoring programme. So far, BMS has observed and registered sporadically in the self-sampling trips. 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. From 2016 onwards, monitoring of the catch fraction Below Minimum Size (BMS) has been included in the sampling protocol of the discards monitoring programme. So far, BMS has observed and registered sporadically in the self-sampling trips

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

Aanvullend onderzoek aan de biologie en visserij van snoekbaars, baars, blankvoorn en brasem : Gericht op de beheerstrategieëvaluatie voor de visserij op het IJsselmeer/Markermeer

Voor het visserijbeheer van snoekbaars, baars, blankvoorn en brasem op het IJssel-/Markermeer zal in 2023 een zogenaamde beheerstrategieëvaluatie uitgevoerd worden. In een beheerstrategieëvaluatie wordt een virtuele wereld gecreëerd, waarbij de geschiedenis van een visbestand wordt nagebootst. In deze virtuele wereld worden vervolgens verschillende beheerplannen van de overheid getest. In de simulatie worden de vissen per cohort gevolgd; een cohort wordt geboren, groeit, en sterft via visserij, vogelpredatie of andere vormen van mortaliteit. De daadwerkelijke geschiedenis van het bestand wordt zo nauwkeurig mogelijk nagebootst, op basis van historische gegevens uit visserij- en surveyvangsten, aangevuld met biologische kennis van het systeem en de soort. Vooruitlopend op deze evaluatie is geprobeerd om de beschikbare modellen, gegevens en kennis te verbreden en verdiepen. Dit betreft drie onderdelen van doorontwikkeling; van de modellen zelf (Mosqueira et al. 2022), en van de gegevens die de modellen voeden. Deze gegevens betreffen ecologische informatie (de Leeuw et al. 2022) en informatie over de biologie en visserij (het‘aanvullend onderzoek’ in dit rapport).De belangrijkste gegevens in dit type modellen zijn visserijgegevens: hoeveel vis wordt door de visserij onttrokken? Een groot gemis momenteel is een betrouwbare tijdserie van de historische aanlandingen van brasem en blankvoorn. Er is uitvoerig met vissers overlegd en ondanks ruime medewerking is het niet gelukt om de tijdserie van de vangst op deze manier te verbeteren. Wel is door deze gesprekken het beeld van de historische zegenvisserij op blankvoorn en brasem verbeterd en is de onzekerheid rondom de historische vangsten iets verkleind. Ook gesprekken met SportvisserijNederland en PO IJsselmeer hebben niet tot verbeterde tijdreeksen geleid. Een andere vorm vanvisserijonttrekking die meer duidelijkheid heeft gekregen is de discarding in de fuikenvisserij. De schattingen zijn met grote onzekerheid omgeven, maar de inschatting is dat met name discarding van baars (maar ook andere bestanden) een grote bron van visserijsterfte kan zijn. Deze vorm van visserijsterfte wordt tot nu toe niet meegenomen in de tijdserie van visserijvangsten. Er wordt sterk aangeraden meer onderzoek te doen naar de vangstsamenstelling en discardsterfte van de fuikenvisserij. Een derde vorm van visserijonttrekking die verder is onderzocht is de recreatieve visserij. De hoeveelheid onttrekking door de traditionele recreatieve visserij vanaf de oevers isonderzocht, als ook de nieuw opgekomen hengelsportvisserij met geavanceerde sonarapparatuur vanaf boten. De voorzichtige conclusie hierbij blijft dat de recreatieve visserij tot een verwaarloosbare visserijonttrekking leidt, in vergelijking met de beroepsvisserij. Ook is gewerkt aan een meer representatieve schatting van de lengtesamenstelling van de commerciële vangsten en van de selectiviteitcurves van de surveytuigen.Van de vier soorten zijn er sterke aanwijzingen dat de groeisnelheid van baars, blankvoorn en brasem is toegenomen sinds de jaren 90. Alleen voor snoekbaars is geen indicatie voor een toename in groeisnelheid gevonden door de decennia heen. Snoekbaars vertoonde ook in een andere analyse afwijkende resultaten van de andere drie bestanden: in de surveyvangsten zijn nieuwe cohorten van baars, blankvoorn en brasem goed terug te vinden in het jaar erna, maar van snoekbaars niet. Dit gebrek aan volgbaarheid was gerelateerd aan afwijkende processen in de twee meren: in het Markermeer zijn cohorten wel te volgen in de survey, maar in het IJsselmeer niet. Dit gebrek aan volgbaarheid in het IJsselmeer hangt waarschijnlijk samen met een sterk afgenomen overleving vannieuwe jaarklassen in het IJsselmeer. Deze afgenomen overleving valt weer samen met een sterke toename in het aantal aalscholvers dat in het IJsselmeer jaagt. Mogelijke verklaringen zijn dat toegenomen vogelpredatie heeft bijgedragen aan de afgenomen overleving in het IJsselmeer, en/of dat beide trends veroorzaakt zijn door de toegenomen waterhelderheid op het IJsselmeer.Alle resultaten zullen in 2023 op gepaste wijze worden meegenomen in de beheerstrategieëvaluatie. Deze wijze wordt ook in dit rapport zover als mogelijk uitgelegd

New perspectives for urbanizing deltas : a complex adaptive systems approach to planning and design : Integrated Planning and Design in the Delta (IPDD)

The delta region between Rotterdam and Antwerp is a prime example of an area where spatial developments face increasing complexity. Local initiatives for developing urban expansions, recreation areas, nature and industrial complexes must harmonize with measures such as adequate flood protection, sufficient freshwater supply, restoration of ecosystems and large-scale infrastructure over the long term. This complexity demans a new approach to spatial planning and design. This book is the result of a research project that aimed to develop such a new planning practice. The research was carried out in collaboration by a consortium of universities, centres of expertise, and engineering and design firms. The research conceived of the Southwest Delta of the Netherlands as a laboratory for the new approach, which has nonetheless also proven relevant to other regions dealing with a similar level of complexity

New perspectives for urbanizing deltas : a complex adaptive systems approach to planning and design : Integrated Planning and Design in the Delta (IPDD)

The delta region between Rotterdam and Antwerp is a prime example of an area where spatial developments face increasing complexity. Local initiatives for developing urban expansions, recreation areas, nature and industrial complexes must harmonize with measures such as adequate flood protection, sufficient freshwater supply, restoration of ecosystems and large-scale infrastructure over the long term. This complexity demans a new approach to spatial planning and design. This book is the result of a research project that aimed to develop such a new planning practice. The research was carried out in collaboration by a consortium of universities, centres of expertise, and engineering and design firms. The research conceived of the Southwest Delta of the Netherlands as a laboratory for the new approach, which has nonetheless also proven relevant to other regions dealing with a similar level of complexity