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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New tuna regimes
Yeeting, Agnes David - \ 2017
University. Promotor(en): Simon Bush, co-promotor(en): Hans-Peter Weikard; M. Bailey. - Wageningen : Wageningen University - ISBN 9789463438308 - 154
fisheries - marine fisheries - tuna - sustainability - environmental policy - governance - economic policy - pacific ocean - environmental economics - visserij - zeevisserij - tonijn - duurzaamheid (sustainability) - milieubeleid - economisch beleid - grote oceaan - milieueconomie
governing sustainability and equity in the Western and Central Pacific Ocean
Towards sustainable tuna fishing: understanding the role of private incentive mechanisms
Tolentino-Zondervan, Frazen - \ 2017
University. Promotor(en): Alfons Oude Lansink; Simon Bush, co-promotor(en): Paul Berentsen. - Wageningen : Wageningen University - ISBN 9789463436236 - 205
tuna - fishing - sustainability - sea fishing - marine fisheries - marine animals - environmental protection - value chain analysis - decision making - philippines - south east asia - business economics - tonijn - vis vangen - duurzaamheid (sustainability) - sportzeevisserij - zeevisserij - zeedieren - milieubescherming - waardeketenanalyse - besluitvorming - filippijnen - zuidoost-azië - bedrijfseconomie

Unsustainable fishing practices, including the use of non-selective fishing methods and Illegal Unreported and Unregulated (IUU) fishing, contribute to the decline of tuna fish stocks in the Western and Central Pacific Ocean (WCPO). This has led to emergence of different public and private governance arrangements to foster the sustainable exploitation of tuna stocks. This thesis focuses on the performance of three innovative private incentive mechanisms: Fishery Improvement Projects (FIPs), International Seafood Sustainability Foundation’s Pro-active Vessel Register and eco-FADs, and Marine Stewardship Council (MSC) certification, to deliver economic incentives for improved production. The overall objective of this thesis is to evaluate the extent to which private incentive mechanisms influence Filipino fishers’ decision to improve their fishing practices.

In order to address the overall objective, this thesis first analyses and compares the ways existing private incentive mechanisms influence the upgrading strategies of Filipino tuna fishers in the value chains (in chapter 2). Second, it evaluates the important determinants for small-scale handline fishers’ decisions to participate in two FIPs for yellowfin tuna in the Philippines (in chapter 3). Third, it examines the effect of MSC certification on the allocation of fishing days by Filipino purse seiners operating in Parties to Nauru Agreement (in chapter 4). And finally, it analyses the profitability of investments in measures needed to comply with private incentive mechanisms by Filipino purse seiners (in chapter 5).

The findings show that overall, the incentive mechanisms are able to improve the practices of fishers, however only to a limited extent. The first two chapters (chapters 2 and 3) show that producers first need to have the capabilities to meet the requirements of private incentive mechanisms, so that they can be included in the value chain and that they can realise the incentives offered by these mechanisms. However, being capable does not guarantee that producers will improve their practices. As shown in the last two chapters (chapters 4 and 5), producers must also have the willingness to upgrade, based on their risk attitude and on the ability of the economic incentive to cover the additional costs and to compensate for the increase of the risks of participation of producers. Given that producers have the availability of capabilities to upgrade and that the benefit is sufficient to opt for participation, then producers may decide to improve their practices, which may contribute to the sustainability improvement goal of private incentive mechanisms. As a consequence of this finding, the incentives, inclusiveness, and improvements must be taken into account in both the design and implementation of private incentive mechanisms.

Monitoring cod catches of the Dutch demersal fleet in 2016
Hal, R. van; Machiels, M.A.M. - \ 2017
IJmuiden : Wageningen Marine Research (Wageningen Marine Research Report C056/17) - 29
monitoring - cod - beam trawling - pulse trawling - demersal fisheries - marine fisheries - fish catches - north sea - gadus morhua - kabeljauw - boomkorvisserij - pulsvisserij - demersale visserij - zeevisserij - visvangsten - noordzee
This report presents the results of the cod monitoring program 2016. The research was commissioned by the Dutch Ministry of Economic Affairs within the EZ-program Beleidsondersteunend Onderzoek. Cod catches of the vessels in the fleet segments BT2 (beam trawl and pulse trawl) and TR (otter trawls and seines) need to be monitored yearly, due to the Dutch implementation of the European cod recovery plan. The European cod recovery plan restricts the fishing effort of European fleets catching cod. Fishing effort, based on historical track records, is allocated to different gear groups. Fishing effort can be transferred between gear groups by use of conversion factors. In the Netherlands fishing effort is transferred yearly from the BT2 gear group to the TR group, based on a national conversion factor of 1:3 (BT:TR) kWdays instead of the European conversion factor of 1:16. This is because the cod catches in the Dutch TR fleet are not as high as the European conversion factor implies. In order to substantiate for the national conversion factor, the Dutch government is obliged to report cod catches per unit of effort (CpUE) of the vessels in these gear groups to the European Commission. An overview is provided of the fishing activity, the cod landings and the cod landings per unit of effort of the various gear categories in the BT2 and the TR fleet segments during the year 2016. First the cod Catch per Unit of Effort (CpUE) transition ratio between the BT2 on the one hand and the TR1C plus TR2 fleet segments on the other hand was calculated. And secondly the percentage of cod avoidance trips – trips during which 5% or less cod was caught – in the TR-fleet were calculated. The TR fleet has a higher cod CpUE on average than the BT fleet. When the cod targeted fisheries (TR1AB) are not taken into account, the CpUE effort transition ratio (TR1C+TR2): BT2 of 2016 lies between 4.2:1 and 5.7:1, depending on whether the ratio is calculated on the basis of minimum or maximum cod discards estimation by the Scientific, Technical and Economic Committee for Fisheries (STECF) respectively whereby in the minimum calculation the vessels participating in the CCTV program are excluded. Based on average discards estimations including all vessels, the ratio is 5.1:1. The percentage of cod avoidance trips, fishing trips with 5% cod or less in the total catches, in the TR1C and the TR2 fleets were 94% and 96% in 2016 respectively. These percentages are based on average STECF cod discards estimations. When minimum or maximum discards estimations are used, the calculated percentages of cod avoidance trips does not vary more than 2 or 3% from the percentage based on average estimations.
The KB WOT Fisheries Programme carried out in 2015
Damme, C.J.G. van; Verver, S.W. - \ 2017
IJmuiden : Stichting Wageningen Research, Centre for Fisheries Research (CVO) (CVO report / Centre for Fisheries Research 16.007) - 57
visserijbeheer - zeevisserij - visserijbeleid - visbestand - schaal- en schelpdierenvisserij - discards - onderwaterakoestiek - visstand - vismethoden - fishery management - marine fisheries - fishery policy - fishery resources - shellfish fisheries - underwater acoustics - fish stocks - fishing methods
The KB WOT Fisheries programme is established to maintain and develop the expertise needed to carry out the statutory obligations of the Netherlands in fisheries monitoring and advice. It is also a flexible program which responds to changes over time in WOT requirements, fisheries management and policy needs. While maintaining the core expertise and flexibility, the KB WOT programme also strives to be innovative and participate in the development of fisheries science. The programme operates within the context of the Common Fisheries Policy (CFP), the EU Marine Strategy Framework Directive (MSFD) and the EU Maritime Policy. The KB WOT fisheries programme is established annually and positioned around a number of themes. In 2015 14 projects were originally awarded. However, one project could not meet all the original objectives and with the remaining budget a 15th project was started on the tool development for fish ageing and maturity staging. These 15 projects were successfully completed. The programme focused on the research into the impact of fisheries on the seafloor, development of tools for electronic monitoring, data storage and dissemination and method development for assessment of marine resources. As always the core element of the KB WOT Fisheries was maintaining and developing key expertise for the WOT programme. A large part of the budget was therefore used for projects that standardise fish ageing, provide quality control of discard, ichthyoplankton and shellfish monitoring and development of fisheries acoustics techniques and expertise. These topics are vital for the quality of fish stock assessments and management. Of the 15 projects funded in 2015, seven were carried out in collaboration with institutes outside the Netherlands. As resources and expertise from these other countries contribute to the KB WOT Fisheries programme, these collaborations provided a large amount of added value to the programme. Another large part of the KB WOT resources is specifically dedicated to international collaboration and exchange of science. This ensures that Wageningen Marine Research researchers remain at the centre of scientific developments and international fisheries research. The programme was also very productive in terms of publications, presentations and developing new methods or tools for fisheries research. Over 15 international presentations were given at meetings, workshops and symposia, and 22 international and national reports written. 8 new methods or models were developed, 3 peer reviewed publications published and 5 scientific publications prepared.
KB WOT Fisheries 2017 : maintaining excellence and innovation in fisheries research
Damme, C.J.G. van; Verver, S.W. - \ 2017
IJmuiden : Stichting Wageningen Research, Centre for Fisheries Research (CVO) (CVO report / Centre for Fisheries Research 17.006) - 89
remote sensing - schaal- en schelpdierenvisserij - visserijbeheer - landmeetapparatuur - discards - visvangsten - zeevisserij - shellfish fisheries - fishery management - surveying instruments - fish catches - marine fisheries
The KB WOT Fisheries programme is developed to maintain and advance the expertise needed to carry out the statutory obligations in fisheries monitoring and advice of The Netherlands. The contents of the KB WOT Fisheries programme for 2017 reflects the scientific and management needs of the WOT fisheries programme. The strength of KB WOT Fisheries lies in the top-down development of the programme while allowing bottom-up input, with calls for proposals, to secure innovation. To avoid missing research priorities relevant to WOT and EZ needs, the programme is built from a closed call for proposals to WOT Fisheries project leaders. To keep the innovation WOT project leaders are requested to seek input from other Wageningen Marine Research scientists. The KB WOT Fisheries programme will fund 13 projects in 2017 which will focus on remote sensing of fish and shell fish in the ecosystem, new methods and tools for surveys, discard and catch sampling and investigating the effects of fisheries. International exchange of new expertise and developments, as well as continuous quality assurance, forms a major part of the programme.
The KB WOT Fisheries Programme carried out in 2016
Damme, C.J.G. van; Verver, S.W. - \ 2017
IJmuiden : Stichting Wageningen Research, Centre for Fisheries Research (CVO) (CVO report / Centre for Fisheries Research 17.007) - 63
visserijbeheer - visbestand - visserijbeleid - zeevisserij - schaal- en schelpdierenvisserij - monitoring - onderwaterakoestiek - vis - fishery management - fishery resources - fishery policy - marine fisheries - shellfish fisheries - underwater acoustics - fish
Maintaining and developing the expertises needed to execute the Dutch fisheries monitoring and advice statutory obligations is the core of the KB WOT Fisheries programme. As fisheries management and policy needs, and thus the WOT requirements, change over time, the KB WOT programme needs to be flexible to respond to these changes. The KB WOT programme seeks to be inventive and participate in the fisheries science development, while maintaining the core expertises and flexibility. The programme operates within the context of the Common Fisheries Policy (CFP), the EU Marine Strategy Framework Directive (MSFD) and the EU Maritime Policy. The KB WOT fisheries programme is established annually and positioned around a number of themes. In 2016 17 projects were originally awarded. However, one project could not meet all the original objectives and with the remaining budget a new project was started on the tool development for monitoring catches on board commercial vessels. The 18 projects within the programme were successfully completed. The focus of the programme in 2016 was on research into mapping the seafloor, development of tools and framework for monitoring catches on board commercial vessels, data storage and accessibility and method development for assessment of marine resources. As the basis of the KB WOT Fisheries is maintaining and developing key expertise for the WOT programme, a considerable part of the funds was used for projects that standardise fish ageing, fish and shellfish monitoring and development of fisheries acoustics techniques and expertise. These subjects are essential for ensuring the high quality of fish stock assessments and management. Of the 18 projects funded in 2016, six were carried out in international collaboration with other institutes in- and outside Europe. These partnerships provide a large amount of added value, since resources and expertise from these other countries contribute to the outcomes of the KB WOT Fisheries programme. Also, a large part of the KB WOT resources is specifically dedicated to international collaboration and exchange of science. This ensures that Wageningen Marine Research researchers remain at the centre of scientific developments and international fisheries research. The programme was also very productive in terms of publications, presentations and developing new methods or tools for fisheries research. Over 20 international presentations were given at meetings, workshops and symposia, and 24 international and national reports were written. 9 new methods or models were developed, 4 peer reviewed publications published and 1 scientific publication prepared
Mission report Kenya : scoping Mission Marine Fisheries Kenya
Hoof, Luc van; Steins, Nathalie A. - \ 2017
IJmuiden : Wageningen Marine Research (Wageningen Marine Research report C038/17) - 136
marine fisheries - food security - aquaculture - seaweeds - trade - kenya - zeevisserij - voedselzekerheid - aquacultuur - zeewieren - handel
Mission report Tanzania : scoping mission marine fisheries Tanzania
Hoof, Luc van; Kraan, Marloes - \ 2017
IJmuiden : Wageningen Marine Research (Wageningen Marine Research rapport C004/17) - 66
zeevisserij - visserij - voedselzekerheid - zeewieren - samenwerking - handel - tanzania - marine fisheries - fisheries - food security - seaweeds - cooperation - trade
PMR Monitoring Natuurcompensatie Voordelta-bodemdieren : datarapport campagne bodemschaaf 2015-multivariate analyse 2004-2013
Craeymeersch, J.A. ; Perdon, J. ; Jol, J. ; Brummelhuis, E.B.M. ; Asch, M. van - \ 2017
IJmuiden : IMARES Wageningen UR (IMARES rapport C073.16) - 37
voordelta - bodemarthropoden - bodeminvertebraten - monitoring - gegevensanalyse - zeevisserij - soil arthropods - soil invertebrates - data analysis - marine fisheries
Het voorliggende rapport beschrijft de gewijzigde opzet van de monitoring, alsook de eerste monitoring-resultaten d.m.v. een korte beschrijving van de dataset verkregen met de bodemschaaf (omdat de monsters met de box-corer uit 2015 niet tijdig verwerkt waren om in dit rapport opgenomen te worden). Verder wordt de aanvullende studie nader besproken, qua opzet en resultaten van de multivariate analyses.
Indicatieve impact maatregelen zeebaars : eerste indicatie van de mogelijke impact van zeebaarsbeschermende maatregelen op de Nederlandse zeevisserij
Strietman, W.J. ; Weegh, J.B.M. op de - \ 2016
Wageningen : LEI Wageningen UR (Nota / LEI Wageningen UR 2016-007) - 23 p.
zeebaars - zeevisserij - visserijbeheer - visbestand - bescherming - quota's - milieueffect - nederland - sea bass - marine fisheries - fishery management - fishery resources - protection - quotas - environmental impact - netherlands
Zeebaars paaigebieden en opgroeigebieden in Nederlandse wateren
Tulp, I.Y.M. ; Hal, R. van; Damme, C.J.G. van; Smith, S.R. - \ 2016
IMARES (Rapport / IMARES C060/16) - 35 p.
visserijbeheer - zeevisserij - visserijbeleid - visbestand - habitatbeheer - nederland - het kanaal (english channel) - kuitschieten - waddenzee - zeeuwse eilanden - boomkorvisserij - zeebaars - noordzee - rijpen - fishery management - marine fisheries - fishery policy - fishery resources - habitat management - netherlands - english channel - spawning - wadden sea - beam trawling - sea bass - north sea - maturation
De zeebaarspopulatie neemt sinds 2010 sterk af door een hoge visserij-inspanning en een lage aanwas van jonge zeebaars sinds 2008. Zeebaars is een langlevende soort die zich pas op latere leeftijd gaat voortplanten. Op een leeftijd van ca 4 jaar en met een lengte vanaf ca 42 cm (vrouwtjes) en 32 cm (mannetjes) beginnen ze paairijp te worden. De huidige minimum aanlandingsmaat van 42 cm heeft als gevolg dat veel vrouwtjes al gevangen worden voordat ze voor het eerst hebben kunnen paaien. Naast vangstbeperkende maatregelen wordt gezocht naar maatregelen ter bescherming van paai- en opgroeigebieden. Hiervoor is ecologische kennis nodig, die voor de Nederlandse wateren nog grotendeels ontbreekt. Aanwezigheid van paaiende volwassen zeebaarzen is direct bewijs voor een paaigebied. Het alternatief is om aan paaigebieden vast te stellen aan de hand van de verspreiding van eieren in een vroeg ontwikkelstadium. Een relatief groot aantal larven en juveniele zeebaars kan wijzen op het belang van een gebied als opgroeigebied. Aanbevelingen voor beleid Gezien de huidige staat van onze kennis, kunnen we nu geen steekhoudende aanbevelingen voor maatregelen gericht op bescherming van gebieden of habitats te geven. De evidentie voor paaigebieden is nog erg dun, de opgroeigebieden zijn wel redelijk bekend, maar over het relatieve belang van elk gebied voor de populatie is nog geen inzicht. Het is duidelijk dat overbevissing een probleem is gezien de ontwikkelingen in de aanlandingen en de afname in gemiddelde lengte bij aanlanding. Het is ook duidelijk dat de zeebaars die in Nederland gevangen wordt in ieder geval voor een groot deel afkomstig is uit het Kanaal en dat de visserij daar in het vroege voorjaar van grote invloed is op de hoeveelheid zeebaars, die later in het jaar in onze wateren terechtkomt. Op basis van de huidige gegevens en inzichten is een verdere inperking van de vangsten door zowel commerciële als recreatieve vissers in ieder geval een effectieve maatregel om de zeebaarsstand te vergroten. Of er in aanvulling daarop ook noodzaak is om gericht gebieden of habitats te beschermen of te verbeteren is met de huidige kennis en gegevens niet vast te stellen en kan alleen met aanvullend onderzoek worden vastgesteld.
Economic essays on marine invasive species and international fisheries agreements
Walker, A.N. - \ 2016
University. Promotor(en): Ekko van Ierland, co-promotor(en): Rolf Groeneveld; Hans-Peter Weikard. - Wageningen : Wageningen University - ISBN 9789462576308 - 165 p.
fisheries - fisheries ecology - agreements - biodiversity - invasive species - europe - marine fisheries - marine fishes - visserij - visserij-ecologie - overeenkomsten - biodiversiteit - invasieve soorten - europa - zeevisserij - zeevissen

This thesis is divided into two parts, as explained in Chapter 1, which focus on different aspects of marine ecological change. Part A considers marine Invasive Alien Species (IAS), which are taxa introduced outside of their native range. The detrimental consequences of invasions for human welfare necessitate management of IAS. There are two types of IAS management. These are (i) management of the risks that an invasion will become established, termed “prevention”, and (ii) management of already established invasions, termed “control”. Chapter 2 considers prevention of invasive species with Ballast Water Management (BWM). Vessels transport invasive species in their ballast water. BWM involves treating ballast water to reduce the risk of successful invasion establishment. Chapter 2 studies the determinants of optimal ballast water treatment standards from a theoretical perspective. Chapter 3 considers control of already established invasions from a spatial and dynamic perspective. We model a non-native habitat divided into patches, where each patch may contain a population of the invasive species, and where spread of the invasion between patches is a stochastic process. In this context, we derive optimal management policies.

The second part of this thesis: Part B, considers International Fisheries Agreements (IFAs). IFAs facilitate cooperation in the management of fish stocks. Cooperation is necessary to ensure sustainable management. Part B focuses on two issues which may affect the stability of cooperation within IFAs. These are; in Chapter 4, changes in stock location, which may occur due to climate change, and in Chapter 5, the risk of stock collapse, which may exist due to overfishing. Part B uses game theory to analyse the effects of these two issues on the stability of the Grand Coalition, which is the state of affairs where all parties cooperate to maximize their joint benefit from the fish stock.

The methods and findings of the thesis are summarized as follows: in Chapter 2 (Part A), we construct a model to study optimal BWM standards. The model is built around the assumption that invasions arriving via ballast water are irreversible, i.e. once an invasion has arrived, it is not possible to reduce the size of the invasive population to zero. The hazard rate of invasion establishment can be reduced by setting a BWM standard. The hazard rate is also affected by the Minimum Viable Population (MVPs) of the species and the possibility of an Allee effect. An MVP exists if there is some population size below which there is an insufficient number of invasive individuals to sustain a population. An Allee effect exists if the probability that a population survives increases at an increasing rate in the size of the population. Our analysis focuses on the conditions under which a BWM standard which aims to reduce invasive populations in ballast water to below their MVPs (as is aimed for by the BWM convention) can be optimal. We find that the current aim of the BWM convention can only be optimal in the case that the hazard function (which determines the hazard rate) is not continuously differentiable around the MVP. We find that Allee effects are a requirement for a continuously differentiable hazard function. Therefore, we find that whether or not an Allee effect exists fundamentally affects whether it is optimal to aim to reduce an invasive population in ballast water to marginally below its MVP.

In Chapter 3 (Part A), we combine aspects of previous modelling approaches to provide new generalized management insights for controlling established invasions. We employ a metapopulation network consisting of patches which are arranged one-dimensionally (i.e. in a line), which is relevant, among other cases, for invasive species spreading along coastlines. We allow for the population size of the invasion within patches to be reduced, which we term “removal”, and we allow for the probability of spread between patches to be reduced without affecting the population sizes directly, which we term “containment”. We employ numerical stochastic dynamic programming to explore how these two interventions (removal and containment) can be optimally applied to minimize the sum of damages from the invasion and the costs of removing and containing the invasion. We find that allowing for varying stock sizes within patches facilitates optimal timing of the application of containment. We also identify two novel optimal policies: the combination of containment and removal to stop spread between patches and the application of up to four distinct policies for a single patch depending on the size of the invasion in that patch.

Chapter 4 (Part B) considers how Grand Coalitions can be stabilized in the face of changing stock location. To do so, we employ the Gordon-Schaefer fisheries model. We consider farsightedness as a mechanism by which stability of the Grand Coalition can be increased in the face of changing stock location. Farsightedness allows players to respond to deviations of other players by deviating themselves. This reduces the incentives to leave the Grand Coalition. This is in contrast to shortsightedness, whereby players cannot decide to leave the Grand Coalition in response to such a choice by another player. We begin by modifying the farsightedness concept such that it can be used in games with asymmetric players and transfer payments. We proceed to analyse the modified farsightedness concept in the case where players are symmetric (stock location does not change) in order to identify the properties of the concept in the base case. We find that farsightedness increases Grand Coalition stability with respect to shortsightedness. We proceed to analyse the extent to which farsightedness increases Grand Coalition stability, relative to shortsightedness, as fish stock location changes, using sensitivity analysis. We find that farsightedness increases the stability of the Grand Coalition, but also increases the sensitivity of stability to changes in fish stock location. Thus, for any fish stock location, a Grand Coalition is more likely to be stable if players are farsighted, but shifts between a stable and an unstable Grand Coalition will occur more frequently if players are farsighted.

In Chapter 5 (Part B), we analyse how the stability of Grand Coalitions is affected by an endogenously determined risk of stock collapse. We do so using the Levhari and Mirman (LM) fisheries model, which is adapted such that there is a risk of stock collapse which increases as the fish stock size decreases. We numerically solve the model and calculate the stability of the Grand Coalition. We find that the effect of an endogenously determined risk of stock collapse depends heavily on the assumptions made regarding how payoffs are determined. A common assumption in the literature is that payoffs are determined at the steady state fish stock. Under this assumption, endogenous risk means that for specific discount and growth rates, a Grand Coalition is stable for any number of players. This is a very different result from the original LM model whereby Grand Coalitions can never be sustained. This is because players can essentially follow two strategies in response to the risk. Firstly, they can attempt to maintain the fish stock by fishing less. In doing so they are running the risk of collapse. Secondly, they can avoid the risk by pre-emptively depleting the fish stock, i.e. harvesting the stock to zero immediately to avoid the risk. Grand Coalitions of any number of players are stable for parameterizations for which a Grand Coalition attempts to maintain a non-zero fish stock and if a deviation from the Grand Coalition would result in pre-emptive depletion. We proceed by relaxing the assumption that payoffs are determined in the steady state by allowing for deviators to obtain payoffs in the transition between steady states. In this case, only Grand Coalitions of two players are stable, and then only for certain parameterizations. The reason is that players can now gain payoffs in the process of pre-emptively depleting the stock, i.e. payoffs are received from the process of fishing the stock down to zero. This increases the benefit of deviating from the Grand Coalition. In this case, Grand Coalitions are only stable for two players for specific parameterizations.

Chapter 6 summarises the research questions formulated in Chapter 1 and evaluates the work of the thesis. Regarding Chapter 2, we justify our theoretical approach with the following two points. Firstly, BWM management is a global and complex problem, which means that the information required to formally calculate an optimal standard is prohibitively burdensome. Secondly, we argue that the complexity of BWM necessitates a sound theoretical understanding of the problem in order to evaluate the current BWM standard, and also to aid in future policy formulation. Similarly, in Chapter 3, we focus on deriving generalized management insights which are applicable to a variety of real-world cases, as opposed to deriving an optimal management strategy for a specific case. In addition to the data requirements necessary to derive such a management strategy, the complexity of such applied cases leads to potentially excessive computational burden. Chapter 3 analyses systems of two and three patches, which are likely to be too simple to analyse specific real world cases, but are sufficient to derive generalized management insights.

The game theoretic methodologies in Part B are evaluated principally in terms of the assumptions about changes in stock location in Chapter 4 and the numerical method in Chapter 5. In Chapter 4, the fish stock is conceptualised as existing at a single point in space. The location of this point is determined in relation to fishing nations, which are also conceptualised as single points in space. Changes in stock location result from rises in ocean temperatures due to climate change. Such rises in temperature are likely to lead to other changes in the fish stock such as the size of the area where the fish stock can be found and increases in the maximum fish stock size which the ecosystem can support. These other aspects of changing stock location need to be considered in evaluating Chapter 4, as well as in formulating more applied models. In Chapter 5, a numerical method is adopted to analyse the effects of an endogenous risk of stock collapse. To do so, the utility function in the LM model is adapted such that it can be used in a numerical model. In order to isolate the effect of endogenous risk from changes in the utility function, a validation procedure is carried out by comparing analytically derived results in the deterministic case (without endogenous risk of stock collapse) to numerically derived results in the deterministic case. This reveals that changes to the utility function have a negligible effect and thus the results, in terms of the stability of Grand Coalitions can be attributed solely to endogenous risk of stock collapse.

Overall, Part A of this thesis presents new insights into the determinants of optimal BWM standards. These insights demonstrate the conditions under which the current BWM standard, which aims to eliminate the risk of invasion establishment, may or may not be optimal. Part A therefore provides a novel theoretical framework which aids in the evaluation of current, and the determination of future standards. Part A also provides new insights into the control of established invasions, by extending existing spatially explicit optimal control models. Specifically, dividing space into patches and allowing for varying invasive population sizes within patches facilitates the optimal timing of management interventions and, in general, more detailed, and thus more efficient, management strategies. Part B provides a novel analysis of the effects of changing stock location on Grand Coalitions by explicitly introducing fish stock location in the analysis, and shows how farsightedness can stabilize Grand Coalitions in the face of such changes. Part B also shows how the effects of an endogenous risk of stock collapse on the stability of Grand Coalitions depends vitally on whether transition payoffs are included. These results can form the basis for more interdisciplinary analyses, analyses of different types of marine ecological change, and analyses of these changes in different settings, such as non-European countries.

Overleving van discard platvis: vaststellen en verhogen
Marlen, B. van; Molenaar, P. ; Reijden, K.J. van der; Goudswaard, P.C. ; Bol, R.A. ; Glorius, S.T. ; Theunynck, R. ; Uhlmann, S.S. - \ 2016
IMARES (Rapport / IMARES C180/15) - 116 p.
pleuronectiformes - overleving - discards - zeevisserij - visserijbeheer - nederland - survival - marine fisheries - fishery management - netherlands
On the possibility of RTCs in the Dutch demersal fishery
Verkempynck, R. ; Machiels, M.A.M. - \ 2016
IMARES (Report / IMARES C012/16) - 32 p.
marine fisheries - discards - monitoring - fishery management - netherlands - zeevisserij - visserijbeheer - nederland
VISNED has asked IMARES to do conduct a short feasibility study on the possibility of Real time closures (RTCs) as a tool for the Dutch demersal fishery to cope with the landing obligation (EU regulation 1380/2013). This assignment is part of the EVF-project “Innovatieve discardvermindering in de praktijk” (Innovative discard reduction in practice). In this report we present a short overview of examples of (real time)-closures in Europe. Additionally, known advantages and disadvantages are listed. Next we present discard maps that are based on data from the yearly Dutch discard monitoring and ongoing VIP projects collecting discards. Two sources of data are currently available. We discuss the suitability of these maps and the information they deliver as a driver for a possible RTC system.
VIP report "Use of new broadband echosounder" : Techniques for improved ocean imaging and selectivity in pelagic fisheries
Fassler, S.M.M. ; Scoulding, B.C. ; Burggraaf, D. ; Haan, D. de; Quesson, Benoit ; Sande, Jeroen van de; Beerens, Peter - \ 2015
IMARES (Report / IMARES C171/15) - 100 p.
pelagic fishery - marine fisheries - underwater acoustics - fish stocks - bycatch - fishery resources - fishery management - pelagische visserij - zeevisserij - onderwaterakoestiek - visstand - bijvangst - visbestand - visserijbeheer
Impact Assessment of the Flyshoot fishery in Natura 2000 and MSFD areas of the Dutch continental shelf
Rijnsdorp, A.D. ; Bos, O.G. ; Slijkerman, D.M.E. - \ 2015
IJmuiden : IMARES (Report / IMARES C162/15) - 24 p.
marine fisheries - fishing methods - fishing gear - environmental impact - aquatic ecosystems - north sea - netherlands - zeevisserij - vismethoden - vistuig - milieueffect - aquatische ecosystemen - noordzee - nederland
North Sea Herring and Pelagic Ecosystem Survey (HERAS) report for R/V "TRIDENS" 22 June - 17 July 2015
Couperus, A.S. ; Fassler, S.M.M. ; Scoulding, B.C. - \ 2015
IJmuiden : IMARES (Report / IMARES 15.015) - 30 p.
herrings - surveys - fish stocks - marine fisheries - acoustic tracking - fishery resources - north sea - haringen - karteringen - visstand - zeevisserij - akoestisch sporen - visbestand - noordzee
Fisheries displacement effects related to closed areas : a literature review of relevant aspects
Slijkerman, D.M.E. ; Tamis, J.E. - \ 2015
Den Helder : IMARES (Report / IMARES C170/15) - 51 p.
marine fisheries - fishing grounds - displacement - environmental protection - socioeconomics - fishery management - north sea - netherlands - zeevisserij - visgronden - verplaatsing - milieubescherming - sociale economie - visserijbeheer - noordzee - nederland
VIBEG Monitoring T1 in 2015 - Data Deelrapportage
Goudswaard, P.C. ; Bakker, A.G. ; Asch, M. van; Smith, S.R. ; Weide, B.E. van der; Brummelhuis, E.B.M. ; Cuperus, J. - \ 2015
Yerseke : IMARES (Rapport / IMARES C172/15) - 24 p.
natuurbescherming - zeevisserij - zonering - beschermde gebieden - kustgebieden - bemonsteren - noordzee - nederland - nature conservation - marine fisheries - zoning - reserved areas - coastal areas - sampling - north sea - netherlands
Het ‘VIBEG (Visserij in Beschermde Gebieden) akkoord’ betreft twee Habitat- en Vogelrichtlijngebieden: ‘Noordzeekustzone’ en ‘Vlakte van de Raan’. Het doel van dit akkoord is om de instandhoudingsdoelen te realiseren voor habitattype H1110B en schelpdieretende vogels in het kader van Natura2000, in combinatie met een ecologisch verantwoorde en duurzame visserij in deze gebieden. Om dit doel te bereiken is voor de Noordzeekustzone in december 2011 een zonering ingesteld met verschillende toegangsregels voor de visserij. Om de mogelijke effecten van deze verschillende visserijregimes op het bodemleven te kunnen vaststellen is in 2013 een onderzoeksprogramma opgestart voor benthische organismen en vissen. Met drie verschillende en elkaar aanvullende technieken: boxcorer, bodemschaaf en garnalennet, is in 2013 een eerste bestandsopname (T0) gemaakt op twee locaties in de Noordzeekustzone: Petten en Ameland. In 2015 is een tweede bestandsopname (T1) gemaakt, wederom op de twee locaties in de Noordzeekustzone: Petten en Ameland. In dit rapport worden de resultaten van de bestandsopname in 2015 gepresenteerd. Een vergelijking tussen de data van 2015 en 2013, zoals die gerapporteerd zijn in Goudswaard et al. (2014), zal in een later stadium plaatsvinden.
VIP Report Acoustic Data Collection
Fassler, S.M.M. ; Brunel, T.P.A. ; Couperus, A.S. ; Gastauer, S. ; Burggraaf, D. - \ 2015
IJmuiden : IMARES (Report / IMARES C178/15) - 121 p.
herrings - whiting - marine fisheries - fish stocks - fishery resources - fishery management - fishing vessels - acoustic tracking - surveys - haringen - wijting - zeevisserij - visstand - visbestand - visserijbeheer - vissersschepen - akoestisch sporen - karteringen
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