Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Classifying fisher behaviour in The Netherlands: the potential of integrating fishing styles analysis into fleet behaviour models
Schadeberg, Amanda - \ 2019
Beyond metier analysis: using fishing styles to understand social heterogeneity in the Dutch demersal fleet
Schadeberg, Amanda - \ 2019
Fishing activity near Wintershall offshore pipelines
Hintzen, Niels - \ 2019
IJmuiden : Wageningen Marine Research (Wageningen Marine Research report C073/19) - 22
On the North Sea bottom lie numerous pipelines to link oil- or gas offshore units, - platforms and processing stations on land. Although pipeline tubes are coated and covered with protective layers (Concrete Weight Coating), the pipelines risk being damaged through man-made threats like fishing activities with bottom trawls (trawling interference), anchoring and dropped objects. IRM Systems performs integrated risk assessments of pipelines for amongst others Wintershall. Spatial maps of fishing activity would contribute to this risk assessment. Therefore, WMR was tasked to quantify the amount of fishing activity in the vicinity of Wintershall pipelines. Fishing activity has been quantified at a spatial scale of approximate 2500 m2 blocks (50m by 50m) using fishing Vessel Monitoring System (VMS) data for 2016 and 2018. In total, for each year 69 shapefiles specifying the fishing intensity in a buffer area of 100m either side of the pipeline, were delivered. The overall total trawl fishing intensity in 2016 and 2018 along the pipeline trajectories ranges from 0 - 18.83 times per grid cell per year and is the result of combining all beam-trawl fleet activities, though split by large beam trawls and shrimp trawls. There is substantial difference in effort between 2016 and 2018 which varies up to 200% for some pipeline segments. Though, at the North Sea scale, fishing has been relatively stable over the past 10 years. Highest fishing intensities are recorded within the 12nm zone where the effort of the shrimp trawlers is most abundant and has increased almost 5-fold in some areas from 2010 and has not come to a halt yet. At the spatial scale relevant in this study, small spatial differences make for substantial differences though.
Review of the evidence regarding the use of antenatal multiple micronutrient supplementation in low- and middle-income countries
Bourassa, Megan W. ; Osendarp, Saskia J.M. ; Adu-Afarwuah, Seth ; Ahmed, Saima ; Ajello, Clayton ; Bergeron, Gilles ; Black, Robert ; Christian, Parul ; Cousens, Simon ; Pee, Saskia de; Dewey, Kathryn G. ; Arifeen, Shams El ; Engle-Stone, Reina ; Fleet, Alison ; Gernand, Alison D. ; Hoddinott, John ; Klemm, Rolf ; Kraemer, Klaus ; Kupka, Roland ; McLean, Erin ; Moore, Sophie E. ; Neufeld, Lynnette M. ; Persson, Lars Åke ; Rasmussen, Kathleen M. ; Shankar, Anuraj H. ; Smith, Emily ; Sudfeld, Christopher R. ; Udomkesmalee, Emorn ; Vosti, Stephen A. - \ 2019
Annals of the New York Academy Of Sciences 1444 (2019)1. - ISSN 0077-8923 - p. 6 - 21.
LMICs - micronutrient - pregnancy - supplements

Inadequate micronutrient intakes are relatively common in low- and middle-income countries (LMICs), especially among pregnant women, who have increased micronutrient requirements. This can lead to an increase in adverse pregnancy and birth outcomes. This review presents the conclusions of a task force that set out to assess the prevalence of inadequate micronutrient intakes and adverse birth outcomes in LMICs; the data from trials comparing multiple micronutrient supplements (MMS) that contain iron and folic acid (IFA) with IFA supplements alone; the risks of reaching the upper intake levels with MMS; and the cost-effectiveness of MMS compared with IFA. Recent meta-analyses demonstrate that MMS can reduce the risks of preterm birth, low birth weight, and small for gestational age in comparison with IFA alone. An individual-participant data meta-analysis also revealed even greater benefits for anemic and underweight women and female infants. Importantly, there was no increased risk of harm for the pregnant women or their infants with MMS. These data suggest that countries with inadequate micronutrient intakes should consider supplementing pregnant women with MMS as a cost-effective method to reduce the risk of adverse birth outcomes.

Baseline and power analyses for the assessment of beach litter reductions in the European OSPAR region
Schulz, Marcus ; Walvoort, Dennis J.J. ; Barry, Jon ; Fleet, David M. ; Loon, Willem M.G.M. van - \ 2019
Environmental Pollution 248 (2019). - ISSN 0269-7491 - p. 555 - 564.
Baseline value - Beach litter - litteR - Non-parametrical power analysis - Reduction target

Marine litter pollution is a global environmental problem. Beach litter is a part of this problem, and is widely monitored in Europe. The European Marine Strategy Framework Directive (MSFD) requires a reduction of beach litter. A reduction of 30% has been proposed in the European Plastics Strategy. The aims of this study are to develop (a) a method to calculate sufficiently stable and precise baseline values for beach litter, and (b) to derive a method of power analysis to estimate the number of beach litter surveys, necessary to detect a given reduction, using these baseline values. Beach litter data from the OSPAR (Oslo Paris Convention) region were used, and tailor-made statistical methods were implemented in open source software, litteR. Descriptive statistics and Theil-Sen and Mann-Kendall trend analyses were calculated for the most abundant beach litter types, for 14 survey sites. The length of a baseline period necessary to obtain a specified precision of the mean baseline value, expressed as Coefficient of Variation (CV), was calculated. Power analyses were performed using Monte Carlo simulations combined with Wilcoxon tests to determine significant deviations of the simulated datasets from the baseline mean values. For most survey sites, the mean length of monitoring periods necessary to achieve a CV < 10% amounts to four to five years with four surveys a year. The mean number of surveys necessary to detect a statistically significant reduction of 30% with 80% power ranges from 14 to 20. Power analyses show that a reduction of 10% is difficult to detect, because more than 24 surveys are needed. In contrary, a reduction of 40–50% can be detected easily with a small (<12) number of surveys. The new methods could also be applied to other areas where similar beach litter surveys are performed.

Best practices II : Effect on future development of sole and plaice of changing mesh size from 80mm to 90mm in the beam trawl fishery
Brunel, Thomas ; Verkempynck, Ruben ; Chen, Chun ; Batsleer, Jurgen - \ 2019
IJmuiden : Wageningen Marine Research (Wageningen Marine Research rapport C016/19) - 35
This study investigates the consequence for future development of stock size, catches, landings and discards of sole and plaice of changing the mesh size of the cod-end from 80mm to 90mm for the Dutch beam trawlers in theTBB 70-99 fleet currently fishing with 80 mm.This study investigates the consequence for future development of stock size, catches, landings and discards of sole and plaice of changing the mesh size of the cod-end from 80mm to 90mm for the Dutch beam trawlers in theTBB 70-99 fleet currently fishing with 80 mm. The question is addressed by means of long term stochastic simulations. Using the simulation framework developed to test the effect of implementing the landing obligation, the future fishery selection pattern (how the fishing mortality is distributed across ages) is modified based on the results of the selectivity experiment to represent the consequence of changing mesh size. Simulations were then run for the next 50 years for different assumptions on the survival rate for both stocks: a 0% survival rate, and the lower and upper bounds of the current estimates of survival for each species. The differences in the effect on sole and plaice of using a 90mm net are related to both the direct effect of exploiting the stock with a different selection pattern and of applying different Fmsy values. The effects of changing mesh size are larger for sole than for plaice, because the share of the landings taken by the Dutch beam trawlers currently fishing with 80 mm is much larger for sole than for plaice. For sole, fishing with the 90mm net results in lower discards (10 to 16%). Landings are also lower (up to 4%) in the short term, but the situation reverses and landings become higher in the medium and long term (up to 3% after 5 years). These results are explained by the fact that when the 90mm net is used, the cohorts are exploited at a slightly later age combined with a stronger targeting of the older ages. This exploitation patterns leads in the medium and long term to a larger stock (by 3 to 13%), which explains the higher landings. Those benefits (in the medium and long term) of using the 90mm net are largest for the 0% and 10% survival assumptions, but are smaller (especially for the landings) for the assumption with 30% survival: the higher the chance for a discarded fish to survive, the less it pays to increase the selectivity of the gear because fish caught and discarded have still a chance to join the stock and further grow and reproduce. For plaice, in the scenarios with 0% and 10% survival, the Fmsy value for the 90mm net is higher than for the 80mm net. As a result, stock size is lower and catches, landings and (despite the improved selectivity of the net) discards are higher if the 90mm net is used. For the scenario with 20% survival rate, Fmsy values are similar for the 80mm and 90mm mesh size and the improved selectivity of the 90mm net indeed results in slightly lower discards, which in the medium and long term result in a slightly larger stock with slightly higher landings. One important assumption in these simulations is that the stocks are exploited at Fmsy in the future. However, if the beam trawl fleet switches to the 90mm net, its catchability (at least for sole) will decrease, meaning that a higher fishing effort will be necessary to achieve a same fishing mortality on the stock. The present study does not model explicitly catchability and effort, and therefore cannot quantify the change in effort implied if the stocks were to be exploited at Fmsy with the 90mm net.
Best practices II : spatial distribution of the discards of the Dutch beam trawler fleet
Brunel, Thomas ; Verkempynck, Ruben ; Batsleer, Jurgen - \ 2019
IJmuiden : Wageningen Marine Research (Wageningen Marine Research rapport C015/19) - 43
This study aims at describing the spatial distribution – and its temporal variations - of discarding intensity (i.e. expected weight of discards for a standard trawl haul) for the 6 main species discarded by the Dutch beam trawl fisheries. For each species, the spatial distribution (quarterly maps for the period 2013 to 2017) is estimated using statistical models that take spatial and temporal correlation into account, which also allowed to test for the effect of a number of factors related to geography, environment, fishing practices and operational aspects on discarding. The data used to fit those models came from the observer trips and self-sampling program conducted at Wageningen Marine Research and from discards sampling trips conducted by the fishing industry. As by-product, the models provide descriptors of the temporal and spatial scales at which the discards of a given species are structured. The distribution of the expected discards per haul for dab was highly variable from quarter to quarter, with generally high discarding intensity in front of the southern coast of the Netherlands in quarter 1, a discarding intensity which is high on the German bight and low in front of the Dutch coast in quarter 3, and variable distributions for quarter 2 and 4. For plaice, the distribution was more stable, with high values consistently observed in the south of the area (between the south of the Netherlands and England), with occasional hot spots on the German bight. For sole, discards were not observed on the north-western part of the area, and a hotspot of sole discarding was found consistently in front of the southern coast of the Netherlands, occasionally expanding towards England or to the northern coast of the Netherlands. Discarding of turbot first occurred with a low intensity along the coast from Belgium to Germany. After the fourth quarter of 2015, high discarding started to occur, first limited to the small area in the southern North Sea, but progressively expanding to a larger area in the southern and central part of the North Sea, while discarding intensity remained low in the northern part of the area and in front of England. The distribution discarding intensity for whiting was highly variably, characterised by hotspots suddenly appearing for most years in the fourth quarter, and disappear in the following first quarter. Discarding of rays occurred mainly in the western part of the area, especially in front of southern England, with an increasing level since the fourth quarter of 2016. The distributions observed and their variability were further discussed in the light the available information on the distribution and migration of the species and on the management measures potentially influencing discarding.
Declining catch rates of small scale fishers in the southern North Sea in relation to the pulse transition in the beam trawl fleet
Rijnsdorp, Adriaan D. ; Rijssel, Jacco van; Hintzen, Niels - \ 2018
IJmuiden : Wageningen Marine Research (Wageningen Marine Research rapport 051/18) - 26
Alternative harvest control rules for multi-fleet and multi-species fisheries under data-poor conditions in Eastern Indonesia
Yuniarta, S. ; Groeneveld, R.A. ; Zwieten, P.A.M. van - \ 2018
In: Book of Abstracts 2018 Biennial Conference of the International Institute of Fisheries Economics and Trade. - - p. 415 - 415.
Variations in North Sea sole distribution : variation in North Sea sole distribution with respect to the 56°N parallel perceived through scientific survey and commercial fisheries
Brunel, Thomas ; Verkempynck, Ruben - \ 2018
IJmuiden : Wageningen Marine Research (Wageningen Marine Research rapport C087/18) - 27
The Dutch commercial fisheries report that sole (Solea solea) catches in the north of the North Sea have been increasing over the past years. While the large majority of North Sea sole catches are taken by beam trawl with 80mm mesh size, fishing with this gear is currently not allowed north of 56°N. In order to be able to get permission for a dedicated sole fishery (80 mm) in that area, scientific proof is needed for the increase in sole in the area north of 56°N. This study analyses data collected during the Beam Trawl Survey and STECF landing and effort data to investigate whether the spatial distribution of North Sea sole has changed over the last two decades. The study focusses in particular on the part of the North Sea to the north of the 56°N parallel where the main sole targeting fishery (beam trawl with 80mm mesh size) is currently not allowed to fish. Results based on the survey data show that the abundance and the extent of the distribution of sole in the area north of 56°N has increased (nearly doubled) since 2010. The proportion of the stock distributed north of 56°N also increased, but remains overall low (less than 7.5%). Over the same period, the centre of gravity of the stock has remained at a similar location. The only fleet operating at a scale large enough to provide information on sole at the scale of the North Sea was the Danish gillnet fishery. The proportion of landings of this fleet taken north of 56oN (in front of northern Denmark) has increased markedly since 2012, even when potential changes in the spatial distribution of the effort are taken into account. These results suggest an expansion of the stock at the margin of the distribution, while the core of the distribution of the stock has remained in the southern and central part of the North Sea (south of 54°N).
The importance of the Banda Sea for tuna conservation area : A review of studies on the biology and the ecology of tuna
Satrioajie, W.N. ; Suyadi, ; Syahailatua, A. ; Wouthuyzen, S. - \ 2018
In: International Symposium on Banda Sea Ecosystem (ISBSE) 2017 23 October 2018, Balai Kartini Convention Center, Jakarta, Indonesia. - IOP Publishing (IOP Conference Series: Earth and Environmental Science ) - 12 p.
Banda Sea - study - tuna

Tuna exploitation in the Banda Sea was started when the Indonesian government gave access to the Japanese fleet under the bilateral cooperation of the Banda Sea Agreement (BSA) in 1975-1980. Several studies were conducted afterward in revealing the magnitude of tuna resources in the Banda Sea. In this paper, we reviewed the tuna studies that were done in the Banda Sea over the periods of 1980-2017 to improve our understanding on the biology and ecology of tuna in the region as the basis for future studies. Overall, we reviewed 29 publications consisted of eight research themes; biodiversity (5), catch composition (8), fish aggregating device (FAD) (2), fishing ground (2), growth-population (3), harvest-effort strategy (4), reproduction (4), and tagging (1). The Snellius II expedition in 1984-1985 was a remarkable study covering almost whole area of the Banda Sea. The study of catch composition and biodiversity were dominant in recent decade indicating there was urgent need to manage the tuna fisheries in the Banda Sea to preserve the tuna stock. Since the Banda Sea is considered as a tuna conservation area, the future studies should be focussed on the scientific findings to support the regulation.

Discard self-sampling of Dutch bottom-trawl and seine fisheries in 2014-2016
Verkempynck, Ruben ; Overzee, Harriet van; Dammers, Michiel - \ 2018
IJmuiden : Stichting Wageningen Research, Centre for Fisheries Research (CVO) (CVO report 18.007) - 102
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.---In de Europese Unie wordt het verzamelen en beheren van visserijgegevens gereguleerd doormiddel van de Data Collectie Verordening (DCF) van de Europese Commissie (EC). Binnen deze regulatie, coördinatie Wageningen Marine Research (WMR) een discards monitoring programma in samenwerking met de Nederlandse demersale visserij. In dit project wordt gebruik gemaakt van een ‘referentie vloot’, bestaande uit een groep Nederlandse commerciële vissers die zich willen inzetten voor het onderzoek. Deze vissers wordt gevraagd om voor specifieke visreizen, die aan het begin van het jaar zijn vastgesteld, een deel van de discards aan boord te houden, waarna dit wordt opgehaald en geanalyseerd door WMR. Voorliggend rapport presenteert de resultaten van het zelfbemonsteringproject van de Nederlandse demersale vloot opererend inde Noordzee (ICES deelgebied IV) in 2014-2016.In 2014-2016 bestond de referentievloot uit 20-22 schepen. In totaal zijn 160, 172 en 157 visreizen bemonsterd in respectievelijk 2014, 2015 en 2016. Voor de zelfbemonstering neemt de referentievloot volgens een door WMR opgezet bemonsteringsschema gedurende een vis reis op gezette tijden van twee vistrekken steekproeven van de vangst die anders overboord zou zijn gegaan (d.w.z. discards) De monsters met bijbehorende gegevens over de totale vangst per trek, visserij-inspanning en vispositie worden aangeland en aan WMR overgedragen. WMR zorgt voor de verdere verwerking van de monsters. Op basis van vistuig, maaswijdte en soorten samenstelling van de vangst zijn alle bemonsterde visreizen aan een metier groep toegekend. In 2014-2017 zijn 11 verschillende metiers bemonsterd: boomkorschepen vissend met 70-99 (waarbij onderscheid gemaakt wordt tussen Eurokotters (d.w.z. vissend met een motorvermogen ≤ 300 pk) en grote kotters (d.w.z. vissend met een motorvermogen > 300 pk)), 100-119, en ≥120 mm maaswijdte, flyshooters vissend met 70-99, 100-119 mm, en ≥120 mm maaswijdte, en otter trawlers vissend met 70-99 (waarbij onderscheid gemaakt wordt tussen schepen die voornamelijk Noorse kreeft vangen en schepen die voornamelijk demersale vis vangen), 100-119, en ≥120 mm maaswijdte.De waargenomen discards patronen blijken vergelijkbaar tussen de verschillende metiers; schar en ondermaatste schol zijn de meest voorkomende soorten in de visdiscards. Daarbij werden grauwe poon, wijting en horsmakreel frequent gediscard binnen de flyshoot reizen. De meerderheid van de benthos discards binnen de boomkor en otter trawlers bestonden uit stekelhuiden (verschillende zeestersoorten) en kreeftachtigen (zoals zwemkrabben en Noorse kreeft).Een belangrijk element in de herziening van het Gemeenschappelijk Visserij Beleid (GVB) is de verplichting om alle vangsten aan land te brengen. Onder de aanlandplicht moeten alle discards van commerciële soorten die gereguleerd worden door quota aangeland worden. Binnen de demersale visserij wordt de aanlandplicht tussen 1 januari 2016 en 1 januari 2019 ingevoerd. De aanlandplicht zal met name voor de Nederlandse demersale visserij een effect hebben aangezien dit een gemengde visserij is waar de vangsten uit tal van verschillende soorten bestaan
Disentangling the complexity of tropical small-scale fisheries dynamics using supervised Self-Organizing Maps
Mendoza-Carranza, Manuel ; Ejarque, Elisabet ; Nagelkerke, Leopold A.J. - \ 2018
PLoS ONE 13 (2018)5. - ISSN 1932-6203

Tropical small-scale fisheries are typical for providing complex multivariate data, due to their diversity in fishing techniques and highly diverse species composition. In this paper we used for the first time a supervised Self-Organizing Map (xyf-SOM), to recognize and understand the internal heterogeneity of a tropical marine small-scale fishery, using as model the fishery fleet of San Pedro port, Tabasco, Mexico. We used multivariate data from commercial logbooks, including the following four factors: fish species (47), gear types (bottom longline, vertical line+shark longline and vertical line), season (cold, warm), and inter-annual variation (2007–2012). The size of the xyf-SOM, a fundamental characteristic to improve its predictive quality, was optimized for the minimum distance between objects and the maximum prediction rate. The xyf-SOM successfully classified individual fishing trips in relation to the four factors included in the model. Prediction percentages were high (80–100%) for bottom longline and vertical line + shark longline, but lower prediction values were obtained for vertical line (51–74%) fishery. A confusion matrix indicated that classification errors occurred within the same fishing gear. Prediction rates were validated by generating confidence interval using bootstrap. The xyf-SOM showed that not all the fishing trips were targeting the most abundant species and the catch rates were not symmetrically distributed around the mean. Also, the species composition is not homogeneous among fishing trips. Despite the complexity of the data, the xyf-SOM proved to be an excellent tool to identify trends in complex scenarios, emphasizing the diverse and complex patterns that characterize tropical small scale-fishery fleets.

Optimizing air flow distribution in maritime refrigerated containers
Lukasse, L.J.S. ; Staal, M.G. - \ 2018
In: 8th International Postharvest Symposium. - International Society for Horticultural Science (Acta Horticulturae ) - ISBN 9789462611900 - p. 1391 - 1398.
Cover - Gradient - Homogeneity - Reefer - T-bar - Temperature - Uniformity
Ever more intercontinental fruit transport takes place in reefer containers. The global installed fleet of 40 ft high cube reefer containers counts approximately 1,000,000 units. The reefer market has generally realized a compound annual growth (CAGR) of 5%. Product temperature requirements are very tight for highly temperature-sensitive fruit like grape and kiwi. Another application where temperature requirements are particularly tight is in cold treatment shipments, required as a quarantine measure by authorities of importing countries. In cold treatment shipments it is often hard to maintain the warmest product temperature below the regulatory imposed treatment limit, without causing chilling injury in the cold spots. Temperature gradients are reduced by good air flow distribution. T-bars make up the air ducts of reefer containers. Unfortunately most air escapes from the ducts before reaching the container door-end if no further measures are taken. An appropriate T-floor cover could help to guide more air to the locations where it is needed most. This paper reports on an experimental study with the aim to design an optimised T-floor cover and assess its effect on fruit temperature distribution. In a series of climate chamber tests it is investigated how temperature gradients are affected by four different T-bar cover designs. During the tests the container is stuffed with palletized empty cartons, with zero autonomous heat production. The results show clear positive effects of T-bar covers. The best of the four covers is non-perforated, of a trapezoidal-like shape, installed in the container with the narrowest end towards the door-end. It reduces the temperature difference between warmest and coldest measurement location by nearly 50%, and also accelerates temperature recovery after a power off period. In view of the promising results it is recommended to follow-up with real transport tests.
Likely status and changes in the main economic and fishery indicators under the landing obligation : A case study of the Basque trawl fishery
Alzorriz, Nekane ; Jardim, Ernesto ; Poos, Jan Jaap - \ 2018
Fisheries Research 205 (2018). - ISSN 0165-7836 - p. 86 - 95.
Basque trawl mixed fishery - Bay of Biscay - Discards - Effort allocation - Fleet dynamics - Landing obligation
We modelled fleet dynamics and the economic impact of three implementations of the EU landing obligation for fisheries, and contrasted the results with those obtained under a scenario of no landing obligation. Simulations were performed using a dynamic state variable model of effort allocation for the Basque trawl fleet, assuming that the landing obligation had been implemented in 2012. The three implementations of the landing obligation involved different policy arrangements: (i) quota increases; (ii) international swapping of quotas; and (iii) inter-species quota flexibility. All three scenarios resulted in changes to fishing patterns caused by choke species and improved selectivity of harvest, but also resulted in a negative short-term impact on the economic performance of the fleet. We report average reductions in net revenue of up to 60% when compared with results obtained under a no landing obligation scenario. Our model results suggested that these negative short-term impacts could be alleviated by incorporation of inter-species quota flexibility in the implementation of the landing obligation. Our results indicate that there will be a strong incentive to use this policy arrangement to alleviate the choke effect problem where species with limiting quotas constrain the fishery.
Impact of fisheries on seabed bottom habitat : fisheries from The Netherlands, Germany, Denmark and Sweden
Piet, Gerjan ; Hintzen, Niels ; Quirijns, Floor - \ 2018
IJmuiden : Wageningen Marine Research (Wageningen Marine Research rapport C012/18) - 51
The Marine Stewardship Council (MSC) released new certification requirements in 2014. The new requirements come with new guidelines for scoring fisheries for several Performance Indicators (PIs). One of the adjusted PIs is PI 2.4.1: the Habitats outcome indicator:“The Unit of Assessment (UoA) does not cause serious or irreversible harm to habitat structure and function, considered on the basis of the area(s) covered by the governance body(s) responsible for fisheries management.”Up to now, the new guidelines for this PI have not yet been translated into an operational performance indicator. An international group of fisheries organisations, from the Netherlands, Denmark, Germany and Sweden, is interested in applying for MSC accreditation or for renewal of existing accreditation. For them it is relevant to know how the new guidelines for PI 2.4.1 translate into a scoring of their fisheries. Therefore, the fisheries organisations requested WMR to develop a methodology for assessing fisheries’ impact on the North Sea seabed which could be used in assessments for MSC accreditation.WMR combined the MSC guidelines with a methodology for assessing fisheries’ impact on the seabed developed in collaboration with partners in the International Council for Exploration of the Sea (ICES). A so-called ‘Population Dynamic’ method was applied, which indicates how bottom trawling affects the biomass of the benthic community relative to an undisturbed situation. Recovery of a habitat is an important aspect in determining whether serious or irreversible harm is caused by a fishery. The benthic invertebrate community consists of many different taxa that differ in their sensitivity to fishing disturbance. This difference in sensitivity is reflected in the parameterisation which distinguishes between an average sensitivity (sensitivity I) and a high sensitivity (sensitivity II). Recovery of Seabed Integrity (SI) is used as an indicator for serious or irreversible harm. This methodology was applied for habitats with status type ‘commonly encountered’. Data that were used are satellite (VMS) and logbook data giving information on the spatial distribution and intensity of the fisheries. Information on North Sea habitats was obtained from EMODnet EU Sea Map and data on recovery rates and gear specific impact rates were obtained from an EU project called ‘BENTHIS’. The methods were applied to 11 UoAs for four different countries, in four different management areas (North Sea, Skagerrak, Kattegat and Eastern English Channel).The analysis comprised of a definition of the current state of seabed integrity (SI), based on historic fishing intensity. For each UoA a study area or ‘footprint’ was defined by gear and management area. Next, for each grid cell (1-minute longitude by 1-minute latitude) the fishing intensity was calculated from VMS data for three different gear groups: Beam Trawl (BT), Demersal Otter Trawls (TR) and Danish Seine (SDN). It was then possible to assess recovery rates for each grid cell (relative increase of biomass per year). The SI was calculated for the moment right after fishing impact and then for respectively 1, 5, 10 and 20 years after ceased fishing. Two indicators were used to assess whether recovery of the habitat to 80% of its unimpacted structure was achieved:- T80% > 0.95K: the top 80% of least impacted grid cells have an SI of at least 0.95 K, meaning that biomass is at more than 95% of the carrying capacity (K).- 100% > 0.80K: all grid cells in the study area have an SI of at least 0.80 K, so biomass is more than 80% of K.For habitats with status type ‘Vulnerable Marine Ecosystem’ (VME) we did not apply the methodology. In order not to cause any serious or irreversible harm to VMEs, the VMEs should not be fished at all. If that is taken into account during assessments for MSC accreditation, it is not relevant whether the VME habitat recovers. We did overlay maps of fishing by UoA with maps of vulnerable habitats (based on either ICES or OSPAR data) in order to see whether VMEs may be a relevant theme during assessments for MSC accreditation.Habitats with status type ‘minor’ were not considered, as with our interpretation these are insignificant in the North Sea and data for carrying out the above (or any) methodology is lacking.The analyses show that for the scenario with Sensitivity I (average recovery rates) none of the UoAs causes serious or irreversible harm to the commonly encountered habitats. I.e. recovery up to 80% is achieved within 20 years for both indicators. If the other Sensitivity is applied (II, with lowest recovery rates), the results are different. The ‘T80% > 0.95K’ indicator always reaches the threshold value within 20 years, but the ‘100% > 0.80K’ indicator does not reach the threshold value for 6 UoA. The 6 UoAs are the TR groups from Denmark (North Sea and Skagerrak), Germany (North Sea), the Netherlands (North Sea) and Sweden (Skagerrak) and the BT group from the Netherlands (North Sea). This may mean – dependant on whether both indicators should reach the threshold value or not – that for these 6 UoA it could be concluded that they do cause serious or irreversible harm to the habitat.Overlaying fishing activities by UoA with VMEs in the North Sea show us that there may be an issue for the German TR unit on the North Sea. This UoA has a minimal overlap with VMEs according to the ICES database. However, if data on threatened and/or declining species and habitats from OSPAR are used, a larger overlap is found. The methodology developed in this study can be a useful starting point for assessing the impact of fishing on the sea bed. It is not yet fully developed to be used in the framework of MSC accreditation: there are still several issues to be dealt with. First of all, a decision needs to be made on which performance indicator(s) to use: the ‘T80% > 0.95K’ indicator or the ‘100% > 0.80K’ indicator, or both. Second, a choice needs to be made about the sensitivity to be used.Another issue that needs to be considered concerns the UoAs. Each UoA may have a negligible impact on the seabed compared to the whole fleet. However, all UoAs together may cause serious or irreversible harm to the seabed. It is therefore important to be aware of the context in which the UoA is practicing the fishery.
Exploring habitat credits to manage the benthic impact in a mixed fishery
Batsleer, J. ; Marchal, P. ; Vaz, S. ; Vermard, V. ; Rijnsdorp, Ad ; Poos, J.J. - \ 2018
Marine Ecology Progress Series 586 (2018). - ISSN 0171-8630 - p. 167 - 179.
Fleet dynamics - Dynamic state variable modelling - TAC - Total allowable catch - Mixed fisheries - Eastern English Channel - Plaice - Cod
The performance of a combined catch quota and habitat credit system was explored to manage the sustainable exploitation of a mix of demersal fish species and reduce the benthic impacts of bottom trawl fisheries using a dynamic state variable model approach. The model was parameterised for the Eastern English Channel demersal mixed fishery using otter trawls or
dredges. Target species differed in their association with habitat types. Restricting catch quota for plaice and cod had a limited effect on benthic impact, except when reduced to very low values, forcing the vessels to stay in port. Quota management had a minimal influence on fishing behaviour and hence resulted in a minimal reduction of benthic impact. Habitat credits may reduce the
benthic impacts of the trawl fisheries at a minimal loss of landings and revenue, as vessels are still able to reallocate their effort to less vulnerable fishing grounds, while allowing the fishery to catch their catch quota and maintain their revenue. Only if they are reduced to extremely low levels can habitat credits potentially constrain fishing activities to levels that prevent the fisheries from using up the catch quota for the target species.
Optimal Management Under Institutional Constraints : Determining a Total Allowable Catch for Different Fleet Segments in the Northeast Arctic Cod Fishery
Richter, Andries ; Eikeset, Anne Maria ; Soest, Daan van; Diekert, Florian Klaus ; Stenseth, Nils Chr - \ 2018
Environmental and Resource Economics 69 (2018)4. - ISSN 0924-6460 - p. 811 - 835.
Dynamic optimization - Fleet segments - Group quota - ITQs - Second-best policy - Tradable permits
Many real world fisheries have an individual vessel quota system with restrictions on transferability of quota or entrance of new vessels into the fishery. While the standard economic reasoning is that these institutional constraints lead to welfare losses, the size of those losses and optimal second-best policies are usually unknown. We develop a dynamic bioeconomic model, in which a scientific body provides an optimal TAC given restrictions on (i) transferability between vessel segments and (ii) entrance of new vessels. Further, we also quantify welfare losses arising from not maximizing economic welfare, but physical yield—which is actually the case in many fisheries. We apply the model to the Northeast Arctic cod fishery, and estimate not only the cost and harvesting functions of the various vessel types, but also the parameters of the biological model as well as those of the demand function. This allows us to determine optimal second-best policies and quantify corresponding welfare effects for our case study fishery.
Marine litter
Fleet, D.M. ; Dau, K. ; Gutow, L. ; Schulz, M. ; Unger, Bianca ; Franeker, J.A. van - \ 2017
Wilhelmshaven : Common Wadden Sea Secretariat (Wadden Sea Quality Status Report ) - 22 p.
The results from the various investigations and monitoring programmes presented in this report demonstrate the continuous and widespread occurrence of litter in the Wadden Sea and adjacent offshore waters. Marine litter of different sizes and from diverse sources occurs on dunes and beaches, in and on inter- to subtidal sediments and in marine organisms, including protected seabirds and mammals. The OSPAR Beach Litter Monitoring and Monitoring on Litter in Fulmars’ Stomachs provide an evaluation of the temporal development of litter abundance in the southern North Sea. Both programmes clearly show that litter densities have not declined since the last Wadden Sea QSR in 2009, indicating that large amounts of litter are still entering the marine environment either directly within the Wadden Sea or from adjacent waters. The amount of litter entering the marine environment is continuously increasing
(Jambeck et al., 2015). This increase is, however, not apparent in the results of the two monitoring programmes. Litter degrades in the marine environment and breaks down into ever smaller fragments. The fragmentation of plastic objects produces microplastics, which are not sufficiently assessed by current monitoring programmes. Densities of microplastics are expected to increase substantially in the future in all marine habitats. Accordingly, scientifically sound monitoring of these synthetic particles with standardized methods that allow for the comparison of results from different programmes will be indispensable.
Marine litter is not restricted to specific habitats but occurs in all compartments of the marine environment with a constant exchange between them. Accordingly, monitoring litter densities in both coastal and offshore habitats is essential for a sound evaluation of litter pollution of the Wadden Sea. Many of the investigations presented in this report are on-off events, which do not provide information on temporal trends. However, they do demonstrate that the Wadden Sea is contaminated with marine litter and that litter densities in the Wadden Sea are not lower than in other coastal regions. The litter densities presented in this report provide a valuable baseline for future evaluations of temporal trends. The monitoring of litter in fulmars’ stomachs and the examinations of carcasses of harbour porpoise, harbour seals and eider ducks revealed that litter does not simply occur in the marine environment but actually interacts in a potentially harmful way with the marine biota. It is well established that the ingestion of litter can have deleterious and often lethal effects on marine organisms. It is yet unknown whether marine litter has demographically relevant implications for marine species. For evaluating this, the effects of marine litter must not be considered in isolation but always together with the effects of other environmental stressors such as ocean warming and acidification, eutrophication and the exploitation of natural stocks (see reports on climate change, geomorphology, eutrophication and fisheries). Several
Wadden Sea Plan targets are compromised by the continuous pollution of the North Sea with marine litter. A proper management of the marine litter problem will require appropriate reduction measures and extended and optimized monitoring programmes in order to evaluate future developments.
A model for optimal fleet composition of vessels for offshore wind farm maintenance
Alcoba, A.G. ; Ortega, G. ; Hendrix, E.M.T. ; Halvorsen-Waere, E.E. ; Haugland, Dag - \ 2017
Procedia Computer Science 108 (2017). - ISSN 1877-0509 - p. 1512 - 1521.
We present a discrete optimisation model that chooses an optimal fleet of vessels to support maintenance operations at Offshore Wind Farms (OFWs). The model is presented as a bi-level problem. On the first (tactical) level, decisions are made on the fleet composition for a certain time horizon. On the second (operational) level, the fleet is used to optimise the schedule of operations needed at the OWF, given events of failures and weather conditions.
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