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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    Mitigating seafloor disturbance of bottom trawl fisheries for North Sea sole Solea solea by replacing mechanical with electrical stimulation
    Rijnsdorp, A.D. ; Depestele, J. ; Eigaard, O.R. ; Hintzen, N.T. ; Ivanovic, A. ; Molenaar, P. ; O’Neill, F.G. ; Polet, H. ; Poos, J.J. ; Kooten, T. van - \ 2020
    PLoS ONE 15 (2020)11. - ISSN 1932-6203
    Ecosystem effects of bottom trawl fisheries are of major concern. Although it is prohibited to catch fish using electricity in European Union waters, a number of beam trawlers obtained a derogation and switched to pulse trawling to explore the potential to reduce impacts. Here we analyse whether using electrical rather than mechanical stimulation results in an overall reduction in physical disturbance of the seafloor in the beam-trawl fishery for sole Solea solea. We extend and apply a recently developed assessment framework to the Dutch beam-trawl fleet and show that the switch to pulse trawling substantially reduced benthic impacts when exploiting the total allowable catch of sole in the North Sea. Using Vessel Monitoring by Satellite and logbook data from 2009 to 2017, we estimate that the trawling footprint decreased by 23%, the precautionary impact indicator of the benthic community decreased by 39%, the impact on median longevity of the benthic community decreased by 20%, the impact on benthic biomass decreased by 61%, and the amount of sediment mobilised decreased by 39%. The decrease in impact is due to the replacement of tickler chains by electrode arrays, a lower towing speed and higher catch efficiency for sole. The effort and benthic physical disturbance of the beam-trawl fishery targeting plaice Pleuronectes platessa in the central North Sea increased with the recovery of the plaice stock. Our study illustrates the utility of a standardized methodological framework to assess the differences in time trends and physical disturbance between gears.
    A blockchain-based configuration for balancing the electricity grid with distributed assets
    Alskaif, Tarek ; Holthuizen, Bart ; Schram, Wouter ; Lampropoulos, Ioannis ; Sark, Wilfried Van - \ 2020
    World Electric Vehicle Journal 11 (2020)4. - ISSN 2032-6653 - p. 1 - 17.
    Automatic frequency restoration reserve - Balancing market - Blockchain - Demand side management - Distributed assets - Electric vehicles - Flexibility
    This paper explores a future perspective to foster the provision of balancing services to the electricity grid by distributed assets. One recent test case, initiated by the Dutch Transmission System Operator (TSO), was to operate an Electric Vehicle (EV) fleet on the automatic Frequency Restoration Reserve (aFRR) market, which entails fast and automated reserves. To achieve that in a decentralised, automated and transparent manner, the role of blockchain technology for this specific application is explored. We propose a novel configuration that can serve as a basis for deploying distributed assets for aFRR markets using blockchain or any alternative Distributed Ledger Technology (DLT). Automation can be achieved via the deployment of smart contracts, which also results in transparency in the system. The blockchain configurations are designed for three phases in the aFRR market, namely: (i) Operational planning and scheduling by a balancing service provider (i.e., formulation and submission of aFRR bid), (ii) Real-time operations (i.e., activation and measurements), and (iii) Verification and settlement (i.e., imbalance correction and financial settlement). The paper concludes that the scalability of distributed assets that can participate in the system, combined with the large transaction times and energy consumption of some consensus mechanisms, could put limitations on the proposed architecture. Future research should address benchmarking studies of other alternatives (e.g., DLTs, such as the ones based on directed acyclic graphs, and non-DLT solutions) with the proposed blockchain solution.
    Seine fishing on the Dutch and German parts of the Dogger Bank, 2013-2019 : Overview of the economic importance and the ecologic impact of the Belgian, British, Danish, Dutch, French, German and Swedish fleets
    Hamon, Katell G. ; Glorius, Sander ; Klok, Arie ; Tamis, Jacqueline ; Jongbloed, Ruud - \ 2020
    Wageningen : Wageningen Economic Research (Wageningen Economic Research report 2020-105) - ISBN 9789463955973 - 43
    The effort, value and landings by the Dutch, UK, Danish, German, Belgian, Swedish and French fishing seine fleets on the Dutch and German part of the Dogger Bank show low and irregular activity over the 2013-2019 period, driven mainly by fishing opportunities for plaice. The ban of pulse fishing is unlikely to lead to an increase of flyshoot vessels in the Dutch fleet given the financial, technical, regulatory and knowledge barriers to transition. Ecological impact of seines alone is complex to assess and while uncertain, the impact on relative benthic biomass is considered low at the past and current level of fishing.
    To Fish or Not to Fish – Economic Perspectives of the Pelagic Northeast Atlantic Mackerel and Herring Fishery
    Rybicki, Sandra ; Hamon, Katell G. ; Simons, Sarah ; Temming, Axel - \ 2020
    Frontiers in Marine Science 7 (2020). - ISSN 2296-7745
    bio-economic model - herring - mackerel - Northeast Atlantic - pelagic fishery

    Environmental, political, and economic conditions influence fishermen’s decisions, which in turn have consequences on the profitability of fishing fleets. We applied the bio-economic model FishRent to understand the response of eight fleets operating in the Northeast Atlantic mackerel and North Sea autumn spawning herring fishery to a number of scenarios, including changes in recruitment, the quota allocation key, and disruptions in fish and fuel prices. In all scenarios, both the Irish and German fleets were close to the break-even point, making them more vulnerable to additional disturbances than other fleets. Yet, these events are expected to occur simultaneously and a larger margin between costs and revenue would enhance the fleets resilience. The replacement of the historical quota allocation key to countries by an allocation according to biomass distribution negatively affected the German fleet most (−450% profitable within 1 year from 2020 to 2021), followed by the Dutch and Danish fleets (−175% profitable on average among those fleets), while the United Kingdom and Ireland increased their profitability by more than 250%. The differences among fleets highlights the sensitivity of a historical allocation key revision. In case of a continued herring recruitment failure, the profitability of most fleets targeting herring decreased but none of the fleets had to disinvest. Declines in fish prices (16% for frozen mackerel and herring, 81% for fresh herring, and 105% for fresh mackerel on average) and increases in fuel prices (17% on average) forced the United Kingdom, Icelandic, and large-scale (>40 m) Irish fleets to reduce their number of vessels by up to 40%.

    Data underlying the publication: Mitigating ecosystem impacts of bottom trawl fisheries for North Sea sole Solea solea by replacing mechanical with electrical stimulation
    Rijnsdorp, Adriaan ; Depestele, J. ; Eigaard, O.R. ; Hintzen, Niels ; Ivanovic, A. ; Molenaar, Pieke ; O'Neill, F. ; Polet, H. ; Poos, Jan Jaap ; Kooten, Tobias van - \ 2020
    Wageningen University & Research
    beam trawl - Dutch fleet - habitat - North Sea - pulse trawl
    The csv data file “SAR_TBB.csv” contains data on habitat characteristics and fishing effort of the Dutch beam trawl fleet by grid cells of 1 minute longitude * 1 minute latitude in the North Sea used to study the changes in trawling impact on the benthic ecosystem due to the transition from conventional beam trawling to pulse trawling. Habitat variables include %sand, %gravel, %mud, bed shear stress (N.m-2) and level 3 EUNIS habitat type. Fishing effort, expressed as the annual swept area ratio (area swept by the gear in km2 / surface area of the grid cell (km2)), is given for the total Dutch beam trawl fleet and for a subset of vessels holding a pulse license (PLH) when fishing with the conventional beam trawl gear (PLH.T.year) or with the innovative pulse trawl (PLH.P.year).
    Indicators of the balance between fleet capacity and fishing opportunities: discrepancies between the Dutch national fleet report and STECF
    Beukhof, Esther ; Hamon, Katell - \ 2020
    IJmuiden : Wageningen Marine Research (Wageningen Marine Research report C045/20) - 29
    The 2019 report of the Balance Expert Working Group, STECF-19-13, paid particular attention to the discrepancy in indicators values between the national fleet reports and their own calculations for the year 2017. They observed that the Netherlands used a different fleet segmentation, thereby making comparisons difficult. Furthermore, they found large differences in the two biological indicators and some small differences in the economic indicators, which in some cases even indicated a different state of balance compared to what the Dutch national fleet report concluded. This report therefore investigated the discrepancy in balance indicator values from 2017, with the aim to explain the observed differences and to re-calculate the indicators for the national fleet report for the 2017 data with the same fleet segmentation and methods as STECF-19-13. For the biological indicators, differences in indicator values were caused by a wrong interpretation in the Dutch national fleet report of the equations in the 2014 Commission guidelines. Furthermore, not all stocks that were fished upon by fleet segments were included in the analysis of the fleet report, thereby excluding stocks that were still overexploited. Different procedures on how to divide the landings data by species over the stocks may also have led to the discrepancy in biological indicators. Differences in the economic indicators were small compared to the biological indicators, and both the fleet report and STECF-19-13 came to the same conclusions regarding the balance of the fleet from an economic point of view. The small discrepancies were caused using different interest rates and real values. No difference in technical indicators was observed for the pelagic fleet segment. Redoing the calculations for the national fleet report with the 2017 data and the same fleet segmentation as STECF led to the same or very similar values for most indicators. Future work is needed in close cooperation with the Balance EWG to make sure that the methods are aligned with both the Commission guidelines and STECF. This is particularly applies to the biological indicators, for which some small differences with the STECF values were still observed after improving the methods. Based on the findings in this report, it is recommended to become more actively involved in the Balance EWG, preferably by having somebody with biological expertise attending future EWG meetings who can solve the remaining issues in the national fleet report calculations and avoid any discrepancies in the future. Furthermore, the biological section of the national fleet report should include time series of the biological indicators, as management measures may take time before the desired state and balance are reached. Future fleet reports should also use a landings data splitting procedure tailored to the year of interest and to the Dutch landings. Regarding the economic and technical indicators, it is recommended to use both the STECF fleet segmentation (to allow for comparison with the EWG) and the clustered segmentation to ensure that local knowledge and context of the fleet is provided, as the data of particularly the small-scale fleet segment, and therefore also its indicators, need to be interpreted with caution.
    Antenatal multiple micronutrient supplementation: call to action for change in recommendation
    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, L. ; Rasmussen, Kathleen M. ; Shankar, Anuraj H. ; Smith, Emily ; Sudfeld, Christopher R. ; Udomkesmalee, Emorn ; Vosti, Stephen A. - \ 2020
    Annals of the New York Academy Of Sciences 1465 (2020)1. - ISSN 0077-8923 - p. 5 - 7.
    Condition and survival of discards in tickler chain beam trawl fisheries
    Schram, Edward ; Molenaar, Pieke ; Kleppe, Raoul ; Rijnsdorp, Adriaan - \ 2020
    IJmuiden : Wageningen Marine Research (Wageningen Marine Research report C034/20) - 31
    Dutch demersal fisheries in the North Sea is a mixed fishery that mainly targets Dover sole (Solea solea) with plaice (Pleuronectes platessa), turbot (Scophthalmus maximus), brill (Scophthalmus rhombus) and other species as valuable bycatches. The fleet currently uses two gear types: pulse beam trawls and conventional tickler chain beam trawls. Pulse beam trawlers operate with a temporary exemption from the EU prohibition to use electric stimulation in fishing gears, of which the last exemptions will expire in June 2021.To assess the consequences of transitions between pulse and tickler chain beam trawling for discards mortality, knowledge on the discards survival probabilities as well as the amount of discards is required for both gear types. The objective of the current study was to estimate discards survival probabilities for undersized plaice, sole, turbot, brill and thornback ray discarded by tickler chain beam trawl fisheries using fish condition as a proxy for survival probability. To this end the condition and reflex impairment of undersized fish in the catches of tickler chain beam trawlers were assessed and compared to similar data collected from pulse trawl fisheries. For spotted ray we assessed fish condition in tickler chain beam trawling but could not estimate its discards survival probability because a relation between survival probability and fish condition is lacking for this species. In this study direct mortality imposed by the tickler chain beam trawling ranged between 10 and 32% in flatfish species and was between 2-4 times higher than in pulse beam trawling. Direct mortality in ray species was lowest among the investigated species (2-8%) and did not differ between the two gear types. Differences in direct mortality were reflected in the condition scores. Direct mortality of sole was higher in tickler chain beam trawling (17%) than in pulse beam trawling (8%). Brill, turbot and plaice discarded by pulse beam trawling are in better condition than when discarded by tickler chain beam trawl fisheries. For sole no effect of gear type on fish condition could be detected. We consider the lower fish condition scores of brill, plaice and turbot from tickler chain beam trawling a direct reflection of the higher mechanical impact of this gear on the fish. For thornback ray and spotted ray no effect of gear type on fish condition could be detected. The predicted survival of plaice, brill and turbot discards indicate that discards survival could indeed be lower in tickler chain beam trawl fisheries compared to pulse beam trawl fisheries. For sole and thornback ray discards we found no evidence for such difference between gear types. The discards survival probabilities for tickler chain beam trawling as presented in this study should be considered as predictions based on the currently best available information instead of definite values. Actual measurements of discards survival at sea are needed to confirm and quantify survival probabilities in tickler chain beam trawling.
    Catch sampling of the pelagic freezer trawler fishery operating in European waters in 2017-2018: joint report of the Dutch and German national sampling programmes
    Overzee, H.M.J. ; Ulleweit, J. ; Helmond, A.T.M. van; Bangma, T. - \ 2020
    IJmuiden : Stichting Wageningen Research, Centre for Fisheries Research (CVO) (CVO report 20.004) - 53
    The pelagic freezer trawler fishery targets small pelagic species. The economically most important species are: herring (Clupea harengus), blue whiting (Micromesistius poutassou), horse mackerel (Trachurus trachurus), mackerel (Scomber scombrus), greater argentine (Argentina silus) and pilchard (Sardina pilchardus). The annual landings of this fishery follow seasonal patterns; different species are targeted during different parts of the year. The total landings of these target species by the Dutch fleet operating in European waters of were about 245,000 tonnes in 2017 and about 303,000 tonnes in 2018. The total landings of these target species by the German fleet operating in European waters were about 124,000 tonnes in 2017 and about 129,000 tonnes in 2018. Herring, blue whiting, mackerel and horse mackerel were the most abundant landed species. 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, from 2002 onwards catches of the European freezer trawler fleet are sampled by the Netherlands and Germany through two separate observer programmes. A process to harmonize the pelagic on board sampling programmes has started a few years ago and is still continuing. This report presents a summary of the data collected in the two monitoring programmes in European waters during the period 2017 and 2018. The two programmes together correspond with a sampling coverage of around 15% and 11% of the total Dutch and German flagged pelagic freezer trawler fleet effort (expressed in number of trips) in European waters in 2017-2018, respectively. An important element in the reform of the Common Fisheries Policy (CFP) is the obligation to land all catches, i.e. the landing obligation. Consequently, from 2015 onwards the European pelagic freezer trawler fishery is in principle obliged to keep catches of quota regulated species on board. This has affected the sampling protocols and procedures; sampling has shifted from discards monitoring towards catch monitoring. Furthermore, the CFP also introduced the concept of regionalisation, meaning that Member States which share a fishing area should work together in collecting, managing and making the data available for scientific advice. Regionalisation of data collection was established during the recast of the Council Regulation describing the DCF (EU 2017/1004). Ultimately, under regional sampling, the Dutch and German pelagic sampling programmes are expected to merge together or at least be completely harmonised and thus interchangeable. Currently, the EU regional coordination group for the North Sea/Eastern Arctic & North Atlantic is working on a regional sampling plan for the freezer trawler fleet exploiting pelagic fisheries in the Northeast Atlantic.
    Highly resolved spatiotemporal simulations for exploring mixed fishery dynamics
    Dolder, Paul J. ; Minto, Cóilín ; Guarini, Jean Marc ; Poos, Jan Jaap - \ 2020
    Ecological Modelling 424 (2020). - ISSN 0304-3800
    Bycatch avoidance - Heterogeneity - Individual based - Mixed fisheries - Spatial management - Spatiotemporal

    To understand how data resolution impacts inference on mixed fisheries interactions we developed a highly resolved spatiotemporal discrete-event simulation model MixFishSim incorporating: i) delay-difference population dynamics, ii) population movement using Gaussian Random Fields to simulate patchy, heterogeneously distributed and moving fish populations, and iii) fishery dynamics for multiple fleet characteristics based on population targeting under an explore-exploit strategy. We applied MixFishSim to infer community structure when using data generated from: commercial catch, a fixed-site sampling survey design and the true (simulated) underlying populations. In doing so we thereby establish the potential limitations of fishery-dependent data in providing a robust characterisation of spatiotemporal distributions. Different spatial patterns were evident and the effectiveness of a simulated spatial closure was reduced when data were aggregated across larger spatial areas. The simulated area closure showed that aggregation across time periods has less of a negative impact on the closure success than aggregation over space. While not as effective as when based on the true population, closures based on high catch rates observed in commercial data were still able to reduce fishing on a protected species. Our framework allows users to explore the assumptions in modelling observational data and evaluate the underlying dynamics of such approaches at fine spatial and temporal resolutions. From our application we conclude that commercial data, while containing bias, provides a useful tool for managing catches in mixed fisheries if applied at the correct spatiotemporal scale.

    Implementing the Landing Obligation. An Analysis of the Gap Between Fishers and Policy Makers in the Netherlands
    Kraan, Marloes ; Verweij, Marieke - \ 2020
    In: Collaborative Research in Fisheries / Holm, P., Hadjimichael, M., Linke, S., Mackinson, S., Springer (MARE Publication Series ) - ISBN 9783030267834 - p. 231 - 248.
    perceptions - landing obligation - discards - trust - collaborative research
    The introduction of the landing obligation is a radical change of the European fisheries policy that has widened the gap between fishers and policy officers in the Netherlands. Especially the mixed demersal trawl fisheries have to adjust to this new measure, which requires a concerted effort between ministry, fleet and research institutions. This chapter describes the implementation process of the landing obligation in the Netherlands (between 2013–2015) and how it has been met with strong opposition by Dutch fishers. This chapter argues that such opposition stems not only from interests, but also from strongly held perceptions about the (ecological) consequences of the measure, as was clear from observing meetings and interviewing key actors. Although several meetings had been organised by the ministry to discuss the landing obligation with fishers, perception differences were not discussed explicitly. Discussions rather seemed to be parallel monologues where parties failed to meet a shared understanding. This situation jeopardises real cooperation in the preparation for full implementation of the landing obligation. The chapter ends with a discussion on possible ways to bridge the gap between fishers and policy officers
    Electronic monitoring in fisheries: Lessons from global experiences and future opportunities
    Helmond, Aloysius T.M. ; Mortensen, Lars O. ; Plet‐hansen, Kristian S. ; Ulrich, Clara ; Needle, Coby L. ; Oesterwind, Daniel ; Kindt‐Larsen, Lotte ; Catchpole, Thomas ; Mangi, Stephen ; Zimmermann, Christopher ; Olesen, Hans Jakob ; Bailey, Nick ; Bergsson, Heidrikur ; Dalskov, Jørgen ; Elson, Jon ; Hosken, Malo ; Peterson, Lisa ; Mcelderry, Howard ; Ruiz, Jon ; Pierre, Johanna P. ; Dykstra, Claude ; Poos, Jan Jaap - \ 2020
    Fish and Fisheries 21 (2020)1. - ISSN 1467-2960 - p. 162 - 189.
    catch documnetation - discard monitoring - electronic monitoring - fully documented fisheries - video-based monitoring
    Since the beginning of the 21st century, electronic monitoring (EM) has emerged as a cost‐efficient supplement to existing catch monitoring programmes in fisheries. An EM system consists of various activity sensors and cameras positioned on vessels to remotely record fishing activity and catches. The first objective of this review was to describe the state of play of EM in fisheries worldwide and to present the insights gained on this technology based on 100 EM trials and 12 fully implemented programmes. Despite its advantages, and its global use for monitoring, progresses in implementation in some important fishing regions are slow. Within this context, the second objective was to discuss more specifically the European experiences gained through 16 trials. Findings show that the three major benefits of EM were as follows: (a) cost‐efficiency, (b) the potential to provide more representative coverage of the fleet than any observer programme and (c) the enhanced registration of fishing activity and location. Electronic monitoring can incentivize better compliance and discard
    reduction, but the fishing managers and industry are often reluctant to its uptake. Improved understanding of the fisher's concerns, for example intrusion of privacy, liability and costs, and better exploration of EM benefits, for example increased traceability, sustainability claims and market access, may enhance implementation on a larger scale. In conclusion, EM as a monitoring tool embodies various solid strengths that are not diminished by its weaknesses. Electronic monitoring has the opportunity to be a powerful tool in the future monitoring of fisheries, particularly when integrated within existing monitoring programmes.
    Discard self-sampling of Dutch bottom-trawl fisheries in 2017-2018
    Overzee, Harriet van; Dammers, Michiel ; Bleeker, Katinka - \ 2019
    IJmuiden : Stichting Wageningen Research, Centre for Fisheries Research (CVO) (CVO report 19.024) - 56
    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.
    On offshore wind farm maintenance scheduling for decision support on vessel fleet composition
    Alcoba, A.G. ; Hendrix, E.M.T. ; Ortega, G. ; Halvorsen-Waere, E.E. ; Haugland, D. - \ 2019
    European Journal of Operational Research 279 (2019)1. - ISSN 0377-2217 - p. 124 - 131.
    Scheduling; Offshore Wind Farm; Heuristic; Fleet composition; Maintenance planning
    Maintenance costs account for a large part of the total cost of an offshore wind farm. Several models have been presented in the literature to optimize the fleet composition of the required vessels to support maintenance tasks. We provide a mixed integer linear programming (MILP) description of such a model, where on the higher level, the fleet composition is decided and on the lower level the maintenance operations are scheduled for a set of weather and breakdown scenarios. A drawback of deciding an a priori information schedule for the coming year is that, the weather outcomes and breakdowns are not known in advance. Consequently, given a fleet composition, its corresponding maintenance costs are underestimated compared to what can be realised in practice under incomplete information. Therefore, we present a heuristic that simulates the practical scheduling and may provide a better cost estimate. The latter method is used to evaluate a fleet composition based on available information and it is compared with the MILP solution based on a priori information.
    Evaluation and implementation of discards policies under catch-based fisheries management regimes
    Alzorriz Gamiz, Nekane - \ 2019
    Wageningen University. Promotor(en): A.D. Rijnsdorp, co-promotor(en): J.J. Poos; I. Mosqueira. - Wageningen : Wageningen University - ISBN 9789463806206 - 204

    This thesis brings a contribution to the debate, formally recognising fishers as an integral part of the ecosystem, by investigating the implications of applying a policy of limiting discards at sea in complex mixed fisheries that are managed under catch limits for the well-being of both the ecosystem and humans.

    Discard restrictions and discard management regimes have been implemented to different extents in a number of fisheries around the world (e.g., Chile, Norway, Faroe Islands, Iceland, New Zealand, Namibia, Canada, and the US). The implementation, monitoring and control of the landing obligation generates some new challenges. In particular, the focus of monitoring and control shifts from landing to activities at sea leading to potentially higher costs of enforcement as it might require, for successful implementation, full observer coverage or electronic video monitoring to validate a self-reporting system. In chapter 2, experiences from fisheries around the world show that choosing the right measures is not a simple process and therefore, management authorities need to simultaneously implement complementary measures which will support implementation and encourage compliance with discarding rules.

    The need to adapt the regulatory framework does not just concern enforcement systems. Other measures, including adaptations to the technical measure’s framework, also need to be considered. Improved selectivity of fishing gears remains a primary and important tool to avoid discards. In chapter 3 I studied the selective properties of a bottom trawl fitted with a 70 mm diamond mesh codend and a 100 mm top square mesh panel (SMP) in the commercial Basque bottom otter trawlers in the Bay of Biscay. Results suggested that a 100 mm SMP potentially enable undersized and immature individuals to escape through the meshes. However, the selectivity cruises demonstrated that in practice, the SMP was largely ineffective at releasing undersized and the release potential for the diamond mesh codend was found to be significantly lower than the length-at-maturity and the legal minimum conservation reference size for hake, pouting and red mullet. The introduction of the obligation to land all catches will create new challenges for this trawl fleet and thereby an incentive to improve selectivity to avoid unwanted catches of undersized individuals.

    Moving to using more selective gears (bigger mesh size codend) may provide a partial solution to mitigate the potential impact of the landing obligation. However, such a measure may also lead to losses in marketable catch and reductions in revenue that make the fishery unviable in the short-term and perhaps in the long-term. Hence, dynamic state variable models allow studying how fishers may respond to changing policies and what consequences this adaptive response may have for the economic and social performance of the fishery. The 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. The 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. To study the possible consequences on a longer time horizon, an MSE approach can be applied to evaluate the long-term consequences of the changes in exploitation pattern on the productivity of the exploited stocks. Combining the main CFP objectives: exploiting at MSY and no discarding allowance, the

    MSE showed that quota species brought risk of changing exploitation patterns also for non-quota stocks. Fishing effort was constrained by one or two quota stocks, resulting in drastic reductions of effort over the short-term and mid-term.

    Classifying fisher behaviour in The Netherlands: the potential of integrating fishing styles analysis into fleet behaviour models
    Schadeberg, Amanda ; Kraan, M.L. ; Hamon, K.G. ; Poos, J.J. ; Batsleer, J. - \ 2019
    Beyond metier analysis: using fishing styles to understand social heterogeneity in the Dutch demersal fleet
    Schadeberg, Amanda ; Kraan, M.L. ; Hamon, K.G. ; Poos, J.J. ; Batsleer, J. - \ 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.

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