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.





    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.
    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.

    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."
    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
    Market Sampling of Landings of Commercial Fish Species in the Netherlands in 2007
    Verver, S.W. ; Overzee, H.M.J. van - \ 2008
    IJmuiden : Centrum voor Visserijonderzoek (CVO report 08.005) - 115
    visserij - visserijbeheer - zeevissen - vis vangen - bemonsteren - monitoring - beoordeling - visbestand - visserijbeleid - nederland - vismethoden - visstand - fisheries - fishery management - marine fishes - fishing - sampling - monitoring - assessment - fishery resources - fishery policy - netherlands - fishing methods - fish stocks
    Dit rapport geeft een overzicht van alle door IMARES afgenomen monsters in 2007 van de belangrijkste commerciele vissoorten zoals haring, makreel, horsmakreel, (blauwe) wijting, schol, tong, tarbot en kabeljauw. Daarnaast is er aandacht voor de bemonsteringsprocedure van de aanvoer van commerciële vissoorten in Nederland. Welke soorten zijn bemonsterd, op welke wijze zijn de vissen gevangen, waar en wanneer zijn de monsters genomen, hoeveel vissen zijn gemeten, van hoeveel vissen is de leeftijd bepaald enz.
    Designing a decision support system for marine reserves management: an economic analysis for the Dutch North Sea
    Ding, Hongyu ; Ruijs, A.J.W. ; Ierland, E.C. van - \ 2007
    Milano : Fondazione Eni Enrico Mattei (Working Papers / Fondazione Eni Enrico Mattei paper 47) - 27
    marien milieu - visserij - biodiversiteit - zeevissen - soortendiversiteit - milieubescherming - noordzee - nederland - milieueconomie - zeevisserij - beslissingsondersteunende systemen - marine environment - fisheries - biodiversity - marine fishes - species diversity - environmental protection - north sea - netherlands - environmental economics - marine fisheries - decision support systems
    The authors explore how a Decision Support System (DSS) for managing the marine environment can be set up. They use the Driving force-Pressure-State- Impact-Respond (DPSIR) framework to analyze which are the major driving forces impacting upon the marine environment in the North Sea. Moreover, a number of potential responses are identified. Furthermore, a preliminary and simplified optimization model has been set up and can be used in a DSS to decide on the best location of marine reserves for the protection of species. The model is based on a bio-economic metapopulation model that can be used to decide which parts of the sea should be opened for fisheries and which should be protected as marine reserve. It accounts for the dispersal of fish and considers both the economic returns from fisheries and the ecological value of marine biodiversity. A number of suggestions are given on how to extend and improve the DSS.
    Market Sampling of Landings of Commercial Fish Species in the Netherlands in 2006
    Verver, S.W. ; Overzee, H.M.J. van - \ 2007
    IJmuiden : Centrum voor Visserijonderzoek (CVO report intern 07.007) - 109
    visserij - visserijbeheer - zeevissen - vis vangen - bemonsteren - monitoring - beoordeling - visbestand - visserijbeleid - nederland - vismethoden - visstand - fisheries - fishery management - marine fishes - fishing - sampling - monitoring - assessment - fishery resources - fishery policy - netherlands - fishing methods - fish stocks
    Dit rapport geeft een overzicht van alle door IMARES afgenomen monsters in 2006 van de belangrijkste commerciele vissoorten zoals haring, makreel, horsmakreel, (blauwe) wijting, schol, tong, tarbot en kabeljauw. Daarnaast is er aandacht voor de bemonsteringsprocedure van de aanvoer van commerciële vissoorten in Nederland. Welke soorten zijn bemonsterd, op welke wijze zijn de vissen gevangen, waar en wanneer zijn de monsters genomen, hoeveel vissen zijn gemeten, van hoeveel vissen is de leeftijd bepaald enz.
    Market Sampling of Landings of Commercial Fish Species in the Netherlands in 2005
    Verver, S.W. ; Overzee, H.M.J. van - \ 2007
    IJmuiden : Centrum voor Visserijonderzoek (CVO report intern 07.009) - 190
    visserij - visserijbeheer - zeevissen - vis vangen - bemonsteren - monitoring - beoordeling - visbestand - visserijbeleid - nederland - vismethoden - visstand - fisheries - fishery management - marine fishes - fishing - sampling - monitoring - assessment - fishery resources - fishery policy - netherlands - fishing methods - fish stocks
    Dit rapport geeft een overzicht van alle door IMARES afgenomen monsters in 2005 van de belangrijkste commerciele vissoorten zoals haring, makreel, horsmakreel, (blauwe) wijting, schol, tong, tarbot en kabeljauw. Daarnaast is er aandacht voor de bemonsteringsprocedure van de aanvoer van commerciële vissoorten in Nederland. Welke soorten zijn bemonsterd, op welke wijze zijn de vissen gevangen, waar en wanneer zijn de monsters genomen, hoeveel vissen zijn gemeten, van hoeveel vissen is de leeftijd bepaald enz.
    An integrated approach to map ecologically vulnerable areas in marine waters in the Netherlands (V-maps)
    Offringa, H.R. ; Lahr, J. - \ 2007
    The Hague : RIKZ (Report / RIKZ no. A09) - 93
    waterverontreiniging - mariene gebieden - noordzee - milieueffect - olieverontreinigingen - cartografie - vogels - zeezoogdieren - benthos - zeevissen - schaaldieren - nederland - ecologische risicoschatting - water pollution - marine areas - north sea - environmental impact - oil spills - mapping - birds - marine mammals - benthos - marine fishes - shellfish - netherlands - ecological risk assessment
    Ecologische basiskaarten voor de Nederlandse mariene wateren ten behoeve van advisering bij crisismanagement : selectie vissen
    Mesel, I.G. de; Zweeden, C. van; Hofstede, R. ter - \ 2007
    IJmuiden : IMARES (Rapport / Wageningen IMARES nr. C085/07) - 33
    zeevissen - kustwateren - crises - noodgevallen - mariene ecologie - zoögeografie - nederland - noordzee - waddenzee - oosterschelde - westerschelde - marine fishes - coastal water - crises - emergencies - marine ecology - zoogeography - netherlands - north sea - wadden sea - eastern scheldt - western scheldt
    Bij dreigende calamiteiten wil men over kennis beschikken van de verspreiding van onder andere de visfauna op het Nederlands Continentaal Plat en de Nederlandse kustwateren om effectief te kunnen ingrijpen bij rampen en milieucalamiteiten. Het doel van dit project is het toekennen van kwetsbaarheidscores aan een aantal vissoorten in viier deelgebieden binnen de Nederlandse wateren. Per vissoort is de beschermingsstatus bepaald en het relatieve belang van het deelgebied als paaigebied, opgroeigebied of leefgebied
    Fosfaatbemesting Noordzee: een kritische beschouwing
    Lindeboom, H.J. ; Rijnsdorp, A.D. - \ 2007
    Visionair : het vakblad van sportvisserij Nederland 1 (2007)4. - ISSN 1569-7533 - p. 30 - 33.
    visserij - visproductie - visbestand - voedingsstoffengehalte - voedingsstoffentekorten - noordzee - fosfaat - mariene ecologie - eutrofiëring - zeevissen - voedingsstoffenbeschikbaarheid - temperatuur - groei - visstand - bemesting - fisheries - fish production - fishery resources - nutrient content - nutrient deficiencies - north sea - phosphate - marine ecology - eutrophication - marine fishes - nutrient availability - temperature - growth - fish stocks - fertilizer application
    Door de introductie van fosfaatvrije wasmiddelen en betere afvalwaterzuivering zit er volgens de beroepsvisserij onvoldoende voedsel in het Noordzeewater. Dit zou de oorzaak zijn van het teruglopen van de visproductie. De sector pleit daarom voor bemesting. Het Wageningse onderzoeksinstituut IMARES kreeg van voormalig minister Veerman de opdracht het mogelijke verband tussen fosfaatconcentratie en visproductie nader te onderzoeken. In dit artikel worden de resultaten samengevat
    Managing fisheries to conserve North Sea groundfish and benthic invertebrate species diversity
    Greenstreet, S.P.R. ; Robinson, L. ; Callaway, R. ; Reiss, H. ; Ehrich, S. ; Piet, G.J. ; Kroncke, I. ; Craeymeersch, J.A.M. - \ 2007
    Aberdeen : Fisheries Research Services Marine Laboratory (Fisheries research services collaborative report no. 05/07) - 136
    visserij - vissen - soortendiversiteit - zeevissen - zeedieren - natuurbescherming - noordzee - fisheries - fishes - species diversity - marine fishes - marine animals - nature conservation - north sea
    Concerns over man’s impact on the environment and ecosystems of the world have resulted in a shift in emphasis in the management of marine natural resources. Consequently, an ecosystem approach to management (EAM) is in the process of being developed and implemented for the North Sea
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