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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    Achtergronddocument Rode Lijst Vissen 2011 : zoutwatervissen; analyse en documentatie in 2011 - 2013 publicatie in 2016
    Tien, N.S.H. ; Heessen, H.J.L. ; Kranenbarg, Jan ; Trapman, B.K. - \ 2016
    IJmuiden : IMARES (Rapport / IMARES C021/16) - 85
    vissen - bemonsteren - zout water - bedreigde soorten - zeevissen - fishes - sampling - saline water - endangered species - marine fishes
    In 2011-2013 heeft IMARES als onderaannemer van RAVON, in opdracht van het toenmalige Ministerie van Economie, Landbouw en Innovatie (het hedendaagse Ministerie van Economische Zaken), meegewerkt aan het uitvoeren van analyses om tot een voorstel te komen voor een nieuwe Rode Lijst Vissen. Deze analyses zijn uitgevoerd op basis van een door de Nederlandse overheid vastgestelde methodiek om de mate waarin soorten bedreigd zijn vast te stellen. Hierbij zijn door IMARES 59 zoutwatervissoorten onderzocht die gevangen worden in de wetenschappelijke bemonsteringsprogramma’s IBTS, BTS en DFS. De wetenschappelijke bemonsteringsprogramma’s van IMARES zijn programma’s waarin jaarlijks volgens een vaste methode met boomkortuigen wordt gevist om gegevens te verzamelen over de toestand van Noordzeevisbestanden. Het voorliggende rapport bevat de beschrijving en uitkomst van de analyses zoals uitgevoerd in 2011 en 2012 door IMARES. De tekst is grotendeels in 2011-2013 geschreven, door IMARES en RAVON. Op basis van deze analyses, en de analyses van RAVON (zoetwatersoorten) en stichting ANEMOON en Ecosub (zoutwatersoorten) is een nieuwe Rode Lijst Vissen opgesteld welke sinds 2016 van kracht is.
    Achtergronddocument t.b.v. de uitgave Wadden in Beeld 2015
    Tulp, I.Y.M. ; Cremer, J.S.M. ; Troost, K. ; Glorius, S.T. ; Asjes, J. - \ 2016
    IMARES (Rapport / IMARES C018/16) - 26
    zeevissen - mossels - oesters - zeehonden - kokkels - aquatische wormen - aquatische ecologie - waddenzee - marine fishes - mussels - oysters - seals - clams - aquatic worms - aquatic ecology - wadden sea
    Economic essays on marine invasive species and international fisheries agreements
    Walker, A.N. - \ 2016
    Wageningen University. Promotor(en): Ekko van Ierland, co-promotor(en): Rolf Groeneveld; Hans-Peter Weikard. - Wageningen : Wageningen University - ISBN 9789462576308 - 165
    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.

    Methods for integrated use of fisheries research survey information in understanding marine fish population ecology and better management advice : improving methods for evaluation of research survey information under consideration of survey fish detection and catch efficiency
    Nielsen, J.R. - \ 2015
    Wageningen University. Promotor(en): Adriaan Rijnsdorp. - Wageningen : Wageningen University - ISBN 9789462572553 - 187
    zeevisserij - onderzoek - karteringen - visserijbeheer - zeevissen - populatie-ecologie - evaluatie - methodologie - visvangsten - visbestand - visserijbiologie - marine fisheries - research - surveys - fishery management - marine fishes - population ecology - evaluation - methodology - fish catches - fishery resources - fishery biology


    The thesis developed and improved methods for the integrated analysis of different types of fishery independent research surveys (trawl surveys, acoustic surveys, hydrographical surveys, and gillnet surveys) to study the distribution, density, abundance, migration and biological population dynamic parameters of marine fish species. The topics in the thesis addressed different combinations of trawl, hydro-acoustic, gillnet, and hydrographical data and application of different survey data analysis methods under consideration of factors influencing the survey catch and detection efficiency. Each topic was investigated in one of more case studies.

    One thesis topic has been to provide more precise estimates of fish distribution and density patterns from survey data (Chapter 2). The 1st case study applied advanced statistical methods to Baltic trawl data and hydro-acoustic survey data in combination with survey sampled hydrographical data to estimate distri­bution and density patterns of juvenile 0-group Baltic cod. These patterns were largely unknown. In the 2nd case study new methodology was developed for analyzing trawl research survey data for Baltic cod and whiting including the corre­la­tion in distribution and density according to space, time, size, and species. The more precise density estimates improve the knowledge of the stock-recruitment relationship of Baltic cod and can improve the Baltic multi-species stock assessment. Furthermore, it will enable more precise marine management and spatial planning involving fish stocks and fisheries in the Baltic Sea. In context of Baltic cod stock assessment, the 3rd case study developed a new method for inter-calibration of trawl survey CPUE data by fish size group exemplified by Baltic cod (and flounder) where the concept of disturbance by one trawl haul in relation to the next have been developed and quantified when calibrating new research survey trawl gears with the former ones. These results have been based on introduction of a new international ICES BITS trawl research survey design.

    A second topic was to improve and develop hydroacoustic research survey methods for more precise detection and discrimination of fish species according to fish size and orientation in the water (Chapter 3). Here, the 4th case study focused on more precise acoustic target strength estimation of juvenile cod, while the 5th case study has focused on acoustic discrimination of juvenile gadoid fish in particular juvenile Baltic cod. This enables more efficient research survey estimation of juvenile cod (gadoid) density patterns to be used in stock recruitment estimates and stock assessment.

    The third topic was to estimate more precisely fish mortality, maturity, and growth parameters for small forage fish species using research survey information (Chapter 4). Associated to this, the 5th case study analysed these population dynamic parameters using trawl survey data taking into account spatial variation. This study provided more precise estimates and deeper understanding of Norway pout mortality, maturity, and growth dynamics. The more precise population dynamic parameters have been implemented in and improved the North Sea Norway pout stock assessment, management advice, management, and long term management plan evaluations.

    The fourth topic was to develop methodology to integrate hydroacoustic, gillnet, and hydro­gra­phi­cal research survey data to investigate pelagic fish migration patterns (Chapter 5). The methods were applied in the 6th case study to evaluate Western Baltic herring feeding and spawning migra­tion based on distribution and density estimates in a narrow over-wintering area of the stock. The more precise information on migration patterns gives better possibility for acoustic monitoring of the full stock abundance in different areas and seasons og the year to be used in stock assessment and marine spatial planning. Also, it increases knowledge on biological interactions and mixing with other stocks and species.  

    In the final synthesis Chapter 6, the thesis reviews relevant analysis methods of research survey data and underlying data distributions, survey design and stratification, trawl survey inter-calibration and standardization, as well as estimation procedures and data processing methods in context of the obtained results and methods developed in the thesis. This is done with focus on survey precision and uncertainty (bias, sources of errors) for trawl and acoustic surveys and factors affecting it.





    Quirky patterns in time-series of estimates of recruitment could be artefacts
    Dickey-Collas, M. ; Hintzen, N.T. ; Nash, R.D.M. ; Schoen, P.J. ; Payne, M.R. - \ 2015
    ICES Journal of Marine Science 72 (2015)1. - ISSN 1054-3139 - p. 111 - 116.
    stock-assessment - marine fishes - assessment models - reference points - atlantic - variability - abundance - sea - populations - management
    The accessibility of databases of global or regional stock assessment outputs is leading to an increase in meta-analysis of the dynamics of fish stocks. In most of these analyses, each of the time-series is generally assumed to be directly comparable. However, the approach to stock assessment employed, and the associated modelling assumptions, can have an important influence on the characteristics of each time-series. We explore this idea by investigating recruitment time-series with three different recruitment parameterizations: a stock–recruitment model, a random-walk time-series model, and non-parametric “free” estimation of recruitment. We show that the recruitment time-series is sensitive to model assumptions and this can impact reference points in management, the perception of variability in recruitment and thus undermine meta-analyses. The assumption of the direct comparability of recruitment time-series in databases is therefore not consistent across or within species and stocks. Caution is therefore required as perhaps the characteristics of the time-series of stock dynamics may be determined by the model used to generate them, rather than underlying ecological phenomena. This is especially true when information about cohort abundance is noisy or lacking.
    A genetic linkage map of Sole (Solea solea): A tool for evolutionary and comparative analyses of exploited (flat)fishes
    Diopere, E. ; Maes, G.E. ; Komen, J. ; Volckaert, F.A.M. ; Groenen, M. - \ 2014
    PLoS ONE 9 (2014)12. - ISSN 1932-6203 - 16 p.
    turbot scophthalmus-maximus - common sole - microsatellite markers - comparative genomics - marine fishes - populations - time - divergence - pleuronectiformes - senegalensis
    Linkage maps based on markers derived from genes are essential evolutionary tools for commercial marine fish to help identify genomic regions associated with complex traits and subject to selective forces at play during exploitation or selective breeding. Additionally, they allow the use of genomic information from other related species for which more detailed information is available. Sole (solea solea L.) is a commercially important flatfish species in the North Sea, subject to overexploitation and showing evidence of fisheries-induced evolutionary changes in growth- and maturation-related traits. Sole would definitely benefit from a linkage map to better understand how evolution has shaped its genome structure. This study presents a linkage map of sole based on 423 single nucleotide polymorphisms derived from expressed sequence tags and 8 neutral microsatellite markers. The total map length is 1233.8 cM and consists of 38 linkage groups with a size varying between 0 to 92.1 cM. Being derived from expressed sequence tags allowed us to align the map with the genome of four model fish species, namely medaka (Oryzias latipes), Nile tilapia (Oreochromis niloticus), three-spined stickleback (Gasterosteus aculeatus) and green spotted pufferfish (Tetraodon nigroviridis). This comparison revealed multiple conserved syntenic regions with all four species, and suggested that the linkage groups represent 21 putative sole chromosomes. The map was also compared to the linkage map of turbot (Scophthalmus maximus), another commercially important flatfish species and closely related to sole. For all putative sole chromosomes (except one) a turbot homolog was detected, confirming the even higher degree of synteny between these two flatfish species.
    Vangsten en discards van de pulsvissers GO48 & SL42
    Reijden, K. van der; Rasenberg, M.M.M. - \ 2014
    IJmuiden : IMARES (Rapport / IMARES 14.IMA0354) - 21
    visserij - zeevisserij - zeevissen - samenstelling - pulsvisserij - discards - monitoren - vangstsamenstelling - fisheries - marine fisheries - marine fishes - composition - pulse trawling - discards - monitors - catch composition
    C. Tanis Jaczn. en Zonen C.V. (GO48) en vof Visserijbedrijf C. en J. Brinkman (SL42) zijn in 2012 overgeschakeld naar de pulsvisserij. Vanuit de regeling ‘Duurzame Ontwikkeling Visserijgebieden’ is subsidie toegekend voor de innovatie van de pulskortuigen van beide schepen. Binnen dit project was afgesproken om een document op te leveren met de discard gegevens van beide schepen, deze notitie. Dit betroffen gegevens van twee rnemersreizen en gegevens van twee monitoringsprojecten, afkomstig uit andere projecten. Zo namen beide schepen deel aan het VIP project ‘Praktijknetwerk Netinnovatie’, waaronder de waarnemersreizen vielen. Daarnaast hebben beide schepen deelgenomen aan een monitorprogramma van IMARES; de SL42 nam deel aan de pulskormonitoring, de GO48 aan de discardmonitoring.
    Reisverslag IBTS-Q1 2014
    Hal, R. van - \ 2014
    IJmuiden : IMARES (Rapport / IMARES Wageningen UR C087/14) - 37
    zeevissen - visstand - visbestand - karteringen - noordzee - marine fishes - fish stocks - fishery resources - surveys - north sea
    Het primaire doel van de International Bottom Trawl Survey (IBTS) is het verkrijgen van recruitmentindices van kabeljauw, schelvis, wijting, kever, makreel, koolvis, haring en sprot in de Noordzee, Skagerrak en Kattegat. Daarnaast worden de gegevens gebruikt als “tuning-series” voor de bestandsschattingen van de commerciële soorten.
    Don’t put all your eggs in one basket! : reproductive strategies and fecundity regulation in temperate marine teleosts
    Damme, C.J.G. van - \ 2013
    Wageningen University. Promotor(en): Adriaan Rijnsdorp, co-promotor(en): O.S. Kjesbu; Mark Dickey-Collas. - Wageningen : Wageningen UR - ISBN 9789461736253 - 183
    teleostei - zeevissen - voortplanting - voortplantingspotentieel - oöcytrijping - kuitschieten - biomassa - eierproductie - visstand - visserijbiologie - visserijbeheer - teleostei - marine fishes - reproduction - fecundity - oocyte maturation - spawning - biomass - egg production - fish stocks - fishery biology - fishery management

    In fisheries management the spawning stock biomass (SSB) is an important indicator of the status of exploited fish stocks. Knowledge on the reproductive biology is essential to estimate SSB. A large variety of reproductive strategies is found. In marine fish two extreme strategies are known, capital spawners which have a determinate fecundity (no de novo oocyte recruitment during spawning), and income spawners which have an indeterminate fecundity (de novo oocyte recruitment during spawning). In this thesis fecundity regulating mechanisms are studied in commercial fish species with contrasting life history.

    In capital spawning plaice Pleuronectes platessa and herring Clupea harengus , which spawn in autumn and/or winter, oocyte maturation starts around April when daylight length increases. Both species recruit a high number of oocytes which are down-regulated in the course of time in relation to the available energy. After the summer feeding period, when energy levels are highest, plaice shows a second recruitment phase. In herring, no difference was observed in the oocyte development between autumn and winter spawners, although winter spawners continue developing oocytes and spawn fewer but larger eggs. The income breeding horse mackerel Trachurus trachurus utilises food resources during spawning although the first batch of spawned eggs is developed on stored energy.

    Food availability, through the body condition, is the most important factor regulating fecundity. In situations where food is available during the spawning season traditional determinate spawners may switch to a pseudo-indeterminate fecundity style. In conclusion this thesis shows that fecundity type of marine fish females is not fixed at the species level but represents a plastic response to the environment through food availability and energy allocation.

    Noordzeevissers verkopen hun vis zelf via internet :
    Eijk, H. van; Wubben, R. ; Taal, C. - \ 2013
    Utrecht : InnovatieNetwerk (Rapport / Innovatienetwerk 13.2.318) - ISBN 9789050595025 - 71
    vis - markten - zeevisserij - zeevissen - handel - internet - logistiek - fish - markets - marine fisheries - marine fishes - trade - internet - logistics
    Vissers kunnen via internet, met een eigen ‘webmarket’, een aanzienlijk hogere omzet en een hogere marge per kilogram vis realiseren in vergelijking met de bestaande verkoopmethode via de visafslag. Met deze nieuwe afzetmogelijkheid in de keten voeren de vissers zelf de regie. De directe relatie met de klant die zo wordt gecreëerd, stelt de visser in staat om meer klantgericht te gaan opereren. De in dit rapport kort uitgewerkte businesscase, webmarket “”, verschaft Nederlandse Noordzeevissers inzicht 2 in de rollen, kosten en opbrengsten per ketenschakel. Hiermee is inzichtelijk gemaakt waar mogelijkheden voor vissers liggen om zelf binnen de keten een grotere rol te spelen in het vermarkten van duurzaam gevangen vis, waardoor betere opbrengsten kunnen worden gerealiseerd. Door aan te sluiten op een al opgezette webmarkettool, ’’, zou in samenwerking met de visafslag in Scheveningen (UFA, United Fish Auctions) en andere partijen, een pilot moeten worden gestart om rechtstreeks (via internet) verse vis en garnalen aan consumenten en zakelijke klanten te verkopen.
    Variability and connectivity of plaice populations from the Eastern North Sea to the Western Baltic Sea, and implications for assessment and management
    Ulrich, C. ; Boje, J. ; Cardinale, M. ; Hintzen, N.T. ; Miller, D.C.M. ; Rijnsdorp, A.D. - \ 2013
    Journal of Sea Research 84 (2013). - ISSN 1385-1101 - p. 40 - 48.
    pleuronectes-platessa l. - marine fishes - skagerrak - kattegat - atlantic - flatfish - stocks - size - microsatellites - recruitment
    An essential prerequisite of sustainable fisheries is the match between biologically relevant processes and management action. Various populations may however co-occur on fishing grounds, although they might not belong to the same stock, leading to poor performance of stock assessment and management. Plaice in Kattegat and Skagerrak have traditionally been considered as one stock unit. Current understanding indicates that several plaice components may exist in the transition area between the North Sea and the Baltic Sea. A comprehensive review of all available biological knowledge on plaice in this area is performed, including published and unpublished literature together with the analyses of commercial and survey data and historical tagging data. The results suggest that plaice in Skagerrak is closely associated with plaice in the North Sea, although local populations are present in the area. Plaice in Kattegat, the Belts Sea and the Sound can be considered a stock unit, as is plaice in the Baltic Sea. The analyses revealed great heterogeneity in the dynamics and productivity of the various local components, and suggested for specific action to maintain biodiversity.
    Bio-energetics underpins the spatial of North Sea plaice (Pleuronectes platessa L.) and sole (Solea solea L.) to climate change
    Teal, L.R. ; Hal, R. van; Kooten, T. van; Ruardij, P. ; Rijnsdorp, A.D. - \ 2012
    Global Change Biology 18 (2012). - ISSN 1354-1013 - p. 3291 - 3305.
    ecosystem-model - marine fishes - tagging data - wadden sea - dynamics - growth - population - energy - biodiversity - variability
    Interaction of Streptococcus suis with primary porcine alveolar macrophages was studied using transcriptomics. Transcriptional response of macrophages to two different S. suis strains was studied: wild-type S10 that is resistant to phagocytosis, and its non-encapsulated mutant that is phagocytosed efficiently. The macrophages’ transcriptional response was observed only after 60 min of incubation. Eleven genes were expressed significantly different between macrophages infected with streptococci and control mock-infected macrophages. These genes include IL-1-ß, MIP-2-a and TNF-a. When gene expression was studied as a function of time, transcriptional changes occurred in all macrophages independent of streptococci. The fold induction of induced genes however, was much stronger in macrophages incubated with the non-encapsulated S. suis strain that was phagocytosed. The genes that were higher induced due to S. suis suggest an innate immune response is induced in macrophages. Pathway analysis revealed that genes that are part of the putative MAP-kinase signal transduction system are over-represented among the regulated genes. Using an immortalized alveolar macrophage cell line it was shown that macrophages respond to interaction with S. suis by the translocation of NF-¿B to the nucleus, independent of phagocytosis. This translocation subsequently induced expression of innate immune genes. This strongly suggests besides the MAP-kinase signaling pathway, NF-¿B signaling is also induced upon interaction with S. suis.
    Impact van onderwaterlawaai onderzocht
    Winter, H.V. - \ 2012
    Kennis Online 9 (2012)april. - p. 14 - 15.
    onderwaterakoestiek - geluidshinder - aquatische ecologie - mariene gebieden - landgebruiksplanning - windenergie - zeezoogdieren - zeevissen - noordzee - underwater acoustics - noise pollution - aquatic ecology - marine areas - land use planning - wind power - marine mammals - marine fishes - north sea
    Vroeger was de enige menselijke activiteit op zee de scheepvaart. Maar de Noordzee krijgt steeds meer windmolenparken, pijpleidingen en olieplatforms, en er wordt bijvoorbeeld gebaggerd en seismisch onderzoek gedaan. Over de effecten van geluiden onder water op het leven in zee is echter nog weinig bekend. In samenwerking met de gas- en olie-industrie proberen onderzoekers van onder meer IMARES daar beter zicht op te krijgen.
    Protein and energy nutrition of marine gadoids, Atlantic cod (Gadus morhua L.) and haddock (Melanogrammus aeglefinus L.)
    Tibbetts, S. - \ 2012
    Wageningen University. Promotor(en): S.P. Lall; Johan Verreth, co-promotor(en): Johan Schrama. - [S.l.] : s.n. - ISBN 9789461731357 - 221
    kabeljauw - schelvis - zeevissen - voedingseiwit - energie - visvoeding - diervoeding - verteerbaarheid - ingrediënten - mengvoer - voedingsstoffenbehoeften - visteelt - aquacultuur - cod - haddock - marine fishes - dietary protein - energy - fish feeding - animal nutrition - digestibility - ingredients - compound feeds - nutrient requirements - fish culture - aquaculture

    Primary goals of this thesis were to: 1) examine the in vivo digestion of macronutrients from conventional or alternative feed ingredients used in practical diets of juvenile gadoids (Atlantic cod and haddock), 2) document growth potential of fish at the juvenile grower phase given varying levels of dietary protein and energy and 3) assess the potential of in vitro pH-Stat methods for rapid screening protein quality of feed ingredients, specifically for gadoids. All primary research questions were linked to and built upon one another with the goal of gaining a better understanding of protein and energy utilization of juvenile grower phase gadoids. Studies showed that cod and haddock have a high capacity to utilize a wide range of dietary feed ingredients, such as fish meals, zooplankton meal, soybean products (meal, concentrate and isolate) and wheat gluten meal. New dietary formulations for gadoids may also utilize pulse meals, corn gluten meal, canola protein concentrate and crab meal. Digestibility data in this thesis is currently the only research that examined both in vivo and in vitro macronutrient digestibility of a large number and wide range of individual ingredients, specifically for gadoids. This is essential to gain new knowledge on protein and energy utilization as well as for least-cost ration formulations and effective substitution of ingredients into new formulations. Data has demonstrated a dietary digestible protein/digestible energy (DP/DE)ratio of 30 g DP/MJ DE is required for gadoids during the juvenile phase (<100 g) to ensure maximum somatic tissue growth, high digestibility, maximum nitrogen and energy retention efficiency and minimal excessive liver growth. Preliminary nutrient requirement studies together with an applied nutritional approach has identified that feeds for juveniles farmed in the Western North Atlantic should contain 50-55% crude protein, <12% fat and <17% carbohydrate. Data in this thesis is currently the first aimed at development and application of an in vitro closed-system pH-Stat assay for rapid screening protein quality of test ingredients that is ‘species-specific’ to gadoids. It is demonstrated that in vitro results generally reflected results obtained through conventional in vivo protein digestibility methods. Studies resulted in the first generation of a ‘gadoid-specific’ proteolytic enzyme extraction method and in vitro closed-system pH-Stat assay which may be useful to investigate protein digestion, absorption and metabolism of gadoids and further development of their feeds.

    Comparing demersal fish assemblage between periods of contrasting climate and fishing pressure
    Hofstede, R. ter; Rijnsdorp, A.D. - \ 2011
    ICES Journal of Marine Science 68 (2011)6. - ISSN 1054-3139 - p. 1189 - 1198.
    north-sea - species-richness - community structure - atlantic-ocean - marine fishes - long-term - diversity - trends - temperature - populations
    Fish communities are dynamic and their structure is known to change over time. Traditionally, these changes were considered to be fisheries-induced, but recent analyses also suggest that global warming could affect the distribution, abundance, and assemblage composition of marine fish. However, disentangling the effects of fisheries and those resulting from climate change is difficult, because both potential drivers act simultaneously. In our study, we distinguished between the effects of fisheries and climate change on the fish assemblage of the southern North Sea by comparing survey catch data for that region during four unique periods throughout the past century, characterized by (i) low fishing pressure during a cold period (1902–1908), (ii) low fishing pressure during a warm period (1950–1956), (iii) high fishing pressure during a cold period (1978–1984), and (iv) high fishing pressure during a warm period (2002–2008). Our analysis indicates that the demersal fish community in the southern North Sea has changed in response to changes in both climate and fishing pressure. Our results suggest both a relatively higher richness of Lusitanian (warm-favouring) species compared with boreal (cool-favouring) species, and a lower mean body size of the fish community during times of warming, independent of fishing pressure
    Nine decades of North Sea sole and plaice distribution
    Engelhard, G.H. ; Pinnegar, J.K. ; Kell, L.T. ; Rijnsdorp, A.D. - \ 2011
    ICES Journal of Marine Science 68 (2011)6. - ISSN 1054-3139 - p. 1090 - 1104.
    atlantic shelf seas - climate-change - pleuronectes-platessa - community structure - fish assemblage - bristol channel - marine fishes - trends - oscillation - recruitment
    Recent studies based mainly on research survey data suggest that within the North Sea, sole Solea solea and plaice Pleuronectes platessa have exhibited distribution shifts in recent decades—on average southward for sole and northward to deeper waters for plaice. Various hypotheses may account for such shifts, including climate change effects and more intensive fishing in southern and shallower waters; but the relatively short time-span of datasets analysed so far (~3 decades) has complicated the separation of these two effects. We have made use of a unique dataset of catch and effort data for British North Sea trawlers; these cover nine decades (spanning the period 1913–2007) and are spatially detailed by ICES rectangle (0.5° latitude by 1° longitude). We quantify, for the first time, long-term distribution changes of North Sea sole and plaice over a period approaching a century, and demonstrate that the distribution shift in plaice was attributable to climate change rather than to fishing, but that both climate and fishing played a role in the distribution shift of sole. The discussion also highlights the potential impact of additional factors, including eutrophication, prey availability, and habitat modification
    International survey blauwe wijting. Elke seconde een sample
    Faessler, S.M.M. - \ 2011
    Visserijnieuws 31 (2011)21. - ISSN 1380-5061 - p. 24 - 27.
    wijting - visbestand - visserijbiologie - akoestisch sporen - zeevissen - zeevisserij - whiting - fishery resources - fishery biology - acoustic tracking - marine fishes - marine fisheries
    IJMuiden- in 2011 wordt voor het eerst de jaarlijkse blauwe wijting survey gecoördineerd door Schascha Fässler, geboren Zwitser en sinds 2009 als 'fisheries acoustics' scientist' werkzaam bij IMARES in IJmuiden. In onderstaand artikel gaat Fässler nader in op acoustics in het algemeen en de survey van 2011 door samenwerkende Europese visserijbiologen in het bijzonder. "Het gebruik van onderwater acoustics' in het algemeen en de survey van 2011 door samenwerkende Europese visserijbiologen in het bijzonder. "Het gebruik van onderwater acoustics zal steeds belangrijker worden in de toekomst."
    Regional warming chnages fish species richness in the eastern North Atlantic Ocean
    Hofstede, R. ter; Hiddink, J.G. ; Rijnsdorp, A.D. - \ 2010
    Marine Ecology Progress Series 414 (2010). - ISSN 0171-8630 - p. 1 - 9.
    vissen - soortendiversiteit - klimaatverandering - mariene gebieden - atlantische oceaan - fishes - species diversity - climatic change - marine areas - atlantic ocean - climate-change impacts - long-term changes - assemblage structure - english-channel - marine fishes - celtic sea - diversity - community - shifts - size
    Regional warming causes changes in local communities due to species extinctions and latitudinal range shifts. We show that the species richness of fish in 3 regional seas in the eastern North Atlantic Ocean has changed over time (1997 to 2008), and we relate this to higher water temperatures and the biogeographic affinity of the species. In the North and Celtic Seas, species richness increased due to increases in the number of warm-favouring Lusitanian species. In the area west of Scotland, species richness decreased because the number of cold-favouring Boreal species decreased. Additional analyses of trends in fishing effort imply that the observed changes in species richness are unlikely to have been induced by fisheries in the North and Celtic Seas, thereby strengthening the idea that climate change affects species richness of marine fish. However, in the area west of Scotland, a potential effect of fisheries in addition to temperature change on the observed change in species richness could not be ruled out
    How climate warming impacts the distribution and abundance of two small flatfish species in the North Sea
    Hal, R. van; Smits, K. ; Rijnsdorp, A.D. - \ 2010
    Journal of Sea Research 64 (2010)1-2. - ISSN 1385-1101 - p. 76 - 84.
    vissen - populatiedichtheid - vismigratie - klimaatverandering - noordzee - fishes - population density - fish migration - climatic change - north sea - arnoglossus-laterna walbaum - solenette buglossidium-luteum - long-term trends - marine fishes - west-coast - plaice - scaldfish - growth - sole - assemblage
    Climate change, specifically temperature, affects the distribution and densities of species in marine and terrestrial ecosystems. Here, we looked at the effect of temperature during winter and spawning period on latitudinal range shifts and changes in abundance of two non-commercial North Sea fish species, solenette (Buglossidium luteum) and scaldfish (Arnoglossus laterna). Both species have increased in abundance and moved to the north since the late 1980s, coinciding with a series of mild winters. In 1996, following a very cold winter, the abundance of both species temporarily decreased as they retracted to the south. The shift in temperature affected adult habitat conditions, allowing them to immigrate into new areas where they subsequently reproduced successfully. We can conclude this because recruitment improved following the increase in abundance. The recruitment relates significantly to the higher adult stock and higher temperatures. The predictions of higher average temperatures and milder winters in the North Sea make it likely that these species will increase further in abundance and move northward. The observed increase in abundance of these small flatfish species will affect the North Sea food web and therefore commercial species, e.g. plaice, by predation on juveniles and competition for benthic food resources
    Tarbotkwekerij Franeker zoekt samenwerking : Friese viskweker wil duurzamere en duurdere vis kweken
    Meer, M. van der; Imares, - \ 2009
    Aquacultuur 24 (2009)1. - ISSN 1382-2764 - p. 11 - 16.
    aquacultuur - zeevissen - tarbot - visteelt - viskwekerijen - ecosystemen - innovaties - aquaculture - marine fishes - turbot - fish culture - fish farms - ecosystems - innovations
    Het kweken van zeevis gebeurt in Nederland dicht langs de kust waar zeewater beschikbaar is en het zoute afvalwater weer terug kan naar zee. In Franeker is een tarbotkweker "Frisian Fisch Farms" gevestigd op een tiental kilometers vanaf de Waddenkust. In tegenstelling tot veel andere viskwekers is Floris Sinnema uit op samenwerking met collega's
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