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
Wageningen University. Promotor(en): Simon Bush, co-promotor(en): Hans-Peter Weikard; V. Ram-Bidesi; 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
Valorisation of waste streams from by-product to worm biomass
Laarhoven, Bob - \ 2017
Wageningen University. Promotor(en): Cees Buisman, co-promotor(en): Hardy Temmink; Hellen Elissen. - Wageningen : Wageningen University - ISBN 9789463438117 - 141
biomass - residual streams - animal nutrition - fisheries - organic wastes - helminths - biomassa - reststromen - diervoeding - visserij - organisch afval - wormen

There is a global demand for more feed resources to keep up with the increasing production of livestock. The hunger for resources is most urgent in the aquaculture sector, which to a large degree depends on the non-sustainable use of fish oil/ meal from wild fish. Aquatic macro invertebrates such as the freshwater worm Lumbriculus variegatus (Oligochaeta, Lumbriculidae, common name blackworms, further abbreviated as Lv) are rich in proteins, lipids, vitamins and minerals. When cultivated on safe and low-grade organic wastes they can provide a sustainable fishmeal alternative for most freshwater and marine fish.

Chapter 1 introduces the concept of aquatic worm production on waste streams. Worm biomass composition and relevant research lines are explained. Organic waste sludges from food industries are a rich source of bio-molecules and can be upgraded to (fish) feed when fed to aquatic worms. For valorisation of waste streams by aquatic worms, as proposed in this thesis, these streams preferably are free from contaminants such as organic micro pollutants, heavy metals and pathogens. For example, this would not be the case when sewage (municipal) sludge is used as a substrate for the worms. However, such contaminated sludges may still be applied for non-food applications. Thus, the quality of the waste stream that is used as a substrate for the worms determines the application potential of the worm biomass as well as the options for downstream processing and refinery.

Previous research showed that Lv can be used for reduction and compaction of sewage sludge. The consumption of (suspended) sludge particles results in a dry matter reduction of 25 - 50 % and in worm faeces that are 60 % more compact than the original waste sludge. This contributes to a significant reduction in sludge processing costs. Sludge reduction by aquatic worms is mainly studied by research groups in The Netherlands and in China. Unfortunately, it is generally accepted free swimming worms in full-scale wastewater treatment plants is extremely difficult, mainly because of large (seasonal) population fluctuations. A controlled reactor concept applying the sessile (crawling, sediment dwelling) species Lv already was developed in earlier research. The key characteristic of this reactor is a carrier material for the worms, which also functions as a separation layer between the waste stream (worm food) and a water phase used for aeration, worm harvesting and worm faeces collection. This concept also was the starting point for the development of the improved reactor concept that is described in this thesis.

The two main objectives of this thesis were: (1) to assess the potential of organic waste streams and by-products for Lv production for fish feed and (2) to develop a (cost and resource) effective bioreactor for this purpose.

In Chapter 2 a new, standardized method is described and tested that can be used for a quantitative and qualitative assessment of the effect of different substrates on worm growth. This method not only can be used to select waste streams suitable for worm production, but also is proposed as a tool is ecotoxicology studies.

The test method consists of beaker experiments with a combination of agar and sand to optimize food uptake by and growth of the worms. The effects of agar gel, sand, and food quantity were studied and evaluated for different food sources. Agar gel addition ameliorated growth conditions by reducing microbial food hydrolysis and by improving the sediment structure. This guaranteed that substrate ingestion and worm growth in the first place were the result of the food quality and the effect of other (environmental) factors was reduced. A final test with secondary potato starch sludge demonstrated the test method is appropriate for the evaluation of solid and suspended organic feedstuffs/waste streams.

In Chapter 3 the standardized method of chapter 2 was used for worm growth studies, focussing on the effect of carbon to nitrogen (C/N) ratios of diets on worm growth and reproduction. Growth and reproduction of Lv on different combinations of wheat based derivatives like gluten and gray starch was studied at fixed isoenergetic levels (expressed as chemical oxygen demand (COD) of the food), but at different C/N ratios. Growth and reproduction rates were compared to those on Tetramin, a substrate known to result in excellent worm growth. Growth was mainly controlled by the C/N ratio of the single and mixed wheat fraction diets. Lower C/N ratios of around 6-7 gave a much better performance than high C/N ratios of around 20. This probably was caused by Lv relying on the presence of proteins as carbon and energy source. Although growth and reproduction rates were not as high as on the control diet, the results were promising for development of a worm biomass production reactor, operating on by-products from wheat processing industries.

In Chapter 4 a new reactor concept for Lv cultivation on waste streams was developed and tested. In a vertical tubular reactor a centralized food compartment was surrounded by a gravel layer that mimicked the natural habitat of Lv. Secondary (biological) sludge from a potato starch processing industry was used as a clean and low value food source. The results with respect to worm growth rate, density and production and nutrient recovery were compared to the previous reactor design. Much higher worm densities were achieved (6.0 compared to 1.1 kg ww m-2 carrier material) as well as much faster Lv growth rates (4.4 - 12 compared to 1.2 % d-1). As a result the areal worm production rate was no less than 40 times higher (560 compared to 14 g ww m-2 d-1). The higher worm density, which was found to be independent of gravel size in a range of 2.4 to 8.0 mm, allowed for a significantly shorter food retention time in the reactor (~ 2.2 days compared to > 10 days for the previous reactor design). This restricted microbial mineralization of the food, making high nutrient recoveries from waste to worm biomass possible: 16-30 % COD, 19-22 % N and 9-11 % P. The high biomass density also limited the release of ammonium, which at large concentrations is toxic for the worms. However, even shorter food retention times (e.g. higher loading rates) are not recommended as a minimum microbial activity is needed for conversion of the original substrate into compounds that can be taken up by the worms.

In Chapter 5 worm growth, reproduction and biomass quality were evaluated on several waste streams and by-products of bacterial, animal and plant origin. The effect of 26 different diets, all applied at high food levels, on Lv growth, reproduction and fatty acid (FA) content and profile were investigated. For this purpose the standardized test method of Chapter 2 was used. In addition, it was discussed which diet composition and food sources would be most suitable for large scale production of Lv.

Diets consisting of single cell biomass from bacterial or plant origin with a high protein content (C/N ratio < 8.8), high P content (C/P < 50) and low in total ammonia nitrogen (TAN) (< 20 g N/kg) gave the highest growth rates and vital worms without signs of mortality. Besides the C/P ratio of the diet, worm conditions related with the difference between test and pre-culture conditions. The starting weight of the worms seemed to have an effect on the total fatty acid content of the worms. The growth potential of a diet rich in proteins and P depends on how much TAN is associated with the diet. By blending different food sources these factors to a certain extent can be manipulated. Lv seemed to have a distinct and very stable FA composition, irrespective of the diet’s FA composition. The worms were rich in poly unsaturated FAs (PUFAs), including several w3 and w6 FAs, and contained relatively high levels of C18 and C20 PUFAs. This makes them suitable as fish feed, in particular for freshwater fish.

In order to serve aquaculture feed markets with an attractive alternative to fish meal, such as aquatic worm biomass, a continuous and secure bulk production needs to be realized. In Chapter 6 the performance parameters established in chapter 4 (worm growth rate, density and biomass production rate) were used as the input for a feasibility assessment of large scale worm production on secondary sludge from the potato industry. In addition, in chapter 6 future value chains and lines of research were discussed.

A hypothetical worm production system treating the surplus secondary sludge from a potato processing factory can reduce excess sludge production by 50 % in solids and 62 % in volume. This is accompanied by a daily production of 1.6 metric ton of fresh worm biomass. With a very conservative estimation of the worm density of 1.6 kg ww/m2 carrier material a footprint of the system of 217 m2 can be realized, which is at least two times smaller than with a previous reactor design without a gravel layer. With reduced sludge processing costs and a conservative market price of 1.4 €/kg dry worm biomass, worm production can already be realized at an annual rate of return of 3 years. However, the costs are highly sensitive for worm biomass stocking, reactor construction and operation. A more accurate economic assessment should be based on the results of pilot-scale research.

Two general product types, whole biomass (as fish feed) and refined products can be distinguished and applied in two application areas (feed and non-food), depending on the quality of the organic (waste) sludge that the worms have been produced from. Valorisation for potential bulk markets needs further refinery of crude worm biomass into a lipid (worm oil) and a protein fraction (protein isolate). This can result in several new and unique business models in aquaculture, feed, chemical and agriculture sectors. Obviously, an assessment of economical and legislative boundary conditions needs to be part of such business models.

Worm biomass is a potential high quality fishmeal replacer, with a similar or even better potential than other waste based alternatives such as single cell biomass and insects. A comparison between Lv and fishmeal with respect to crude composition, essential amino acids and FAs learns that Lv is a highly suitable fish feed source. It can provide essential amino acids at sufficiently high levels. Based on its FA composition and (relatively low) fat content, Lv can best be considered a protein source. Still, worm biomass is rich in PUFA, which could be a potential high value product for feed applications. Compared to black soldier fly and bacterial production systems, Lv shows intermediate production efficiencies, while biomass harvesting and processing probably is more easy.

Additional advantages of Lv worm biomass to replace fishmeal are: 1) Lv acts as a strong natural fish attractant, 2) the growth efficiency of fish on worms is high in comparison to regular feeds, 3) the nutritional profile of worms matches that of fishmeal, 4) the worms are a natural feed source for freshwater fish and 5) the worms allow a secure and stable feed production that is independent of natural resources.

Further recommendations for future research as outlined and discussed in chapter 6 are mostly related to the technical upscaling of the reactor technology and obtaining more detailed insight in controlled worm growth in response to food characteristics, reactor design and operational conditions.

Schelpdierbestanden in de Nederlandse kustzone in 2017
Troost, K. ; Perdon, K.J. ; Zwol, J. van; Jol, J. ; Asch, M. van - \ 2017
IJmuiden : Stichting Wageningen Research, Centrum voor Visserijonderzoek (CVO) (CVO rapport 17.014) - 38
schaaldieren - visserij - natura 2000 - noordzee - ensis - spisula - visstand - biodiversiteitsbepaling - shellfish - fisheries - north sea - fish stocks - biodiversity assessment
The exploitation of wild shellfish has developed from free fisheries to a strongly regulated commercial activity, in which economic and ecological objectives are both aimed for. Within the framework of this policy an annual stock estimate is made for the economic important species: razor shell (Ensis directus) and cut-through shell (Spisula subtruncata), and other less economic species. The survey covers the entire Dutch coastal zone, and is commissioned by the Ministry of Economic Affairs. The fieldwork for the 23 th successive survey since 1995 was carried out in spring 2017. The principle objective of this survey is the assessment of the stock sizes of the economically important species Ensis directus and Spisula subtruncata in the Dutch coastal zone, including the Natura-2000 areas: “Noordzeekustzone”, “Voordelta”, “Vlakte van de Raan”, and the mouth of the Westerschelde estuary. In addition to the two most important species, we also report on the occurrence of three species of occasional economic importance: otter shell (Lutraria lutraria), striped venus clam (Chamelea striatula), and banded wedge shell (Donax vittatus). For the Dutch coastal zone the total stock size was estimated at 397.2 million kg fresh weight for razor shells, and 1,281.7 million kg fresh weight of cut-through shells. Stocks of the the other species were estimated at 18.1 million kg fresh weight for striped venus clams, 38.0 million kg fresh weight of banded wedge shells and 4,931 million individuals of otter shells. The stock of razor shells showed a sharp increase and was found to be the highest since 1995. The same can be said for the cut-through shells, where the stock of biomass increased to a level which is the highest since 1995. Also the stock of the otter shell and the banded wedge shell increased where the stock of the striped venus clam showed a slight decrease.
Wettelijke Onderzoek Taken WOT-05 Visserijonderzoek beknopte jaarrapportage 2016
Verver, S.W. - \ 2017
IJmuiden : Wageningen UR, Stichting DLO, Centrum voor Visserijonderzoek (CVO) (CVO rapport 17.003) - 38
visserij - visserijbeheer - wetgeving - jaarverslagen - nederland - fisheries - fishery management - legislation - annual reports - netherlands
Wettelijke Onderzoek Taken WOT-05 Visserijonderzoek Jaarverslag 2016
Verver, S.W. - \ 2017
IJmuiden : Stichting Wageningen Research, Centrum voor Visserijonderzoek (CVO) (CVO rapport 17.002) - 98
visserij - visserijbeheer - wetgeving - jaarverslagen - nederland - fisheries - fishery management - legislation - annual reports - netherlands
The programme WOT-05 Fishery Research is carrying out statutory research tasks related to the management of the fishery and aquaculture in the Netherlands. The programme is developed in consultation with the Ministry of Economic Affairs (EZ). The content and scope of programme has been agreed for the period 2011-2015. In September 2015 it was decided to extend the programme till 31 December 2016. This report is a technical report and summarises the progress made in carrying out the work plan of 2016. Fisheries policy makers and managers are dependent on up-todate information. The aim of this programme is to contribute to the collection of essential data needed for the management of fisheries, fish stocks and aquaculture through sampling programmes in as well marine and inshore areas. The data collection includes sampling programmes on fish species landed in fishing ports, discard and by-catch monitoring programmes on board of commercial vessels and scientific surveys using research vessels. In addition, monitoring programmes on shellfish (bivalves) are carried out in coastal waters to estimate the biomass of these resources. In national fresh waters also the eel stock and the stocks in IJsselmeer and Markermeer are monitored. The data have been used to provide advice which is also part of this programme. The advice for marine stocks and fisheries is based on analyses of international data carried out by working groups. The main frameworks in which this was done were ICES and STECF. These frameworks also play a role in the international co-ordination of the research carried out in this programme. The programme is carried out by the Centre for Fisheries Research (CVO) and the Institute for Marine Resources and Ecosystem Studies (IMARES, since September 2016 Wageningen Marine Research) in IJmuiden. The programme is financed by the Ministry of Economic Affairs and coordinated by Sieto Verver (CVO) CVO rapport 17.002 Jaarverslag WOT visserij 2016 23 of 98 The programme has been executed according to a pre-agreed work plan. It consists of eleven projects, each managed by a project manager. Each project consists of several sub-projects. This document contains two main sections: 1) a report presenting standard information requested by the Ministry discussing the progress made with the research targets set in the pre-agreed working programme and 2) an annex including technical progress reports of the individual projects. Scientific results are not discussed but references are given to the (scientific) products. Also a short version of this progress report is available All the pre-agreed targets in the work plan have been met within the available financial budget. The report format includes a financial summary over 2016. The total cost of the programme in 2016 was 6.6 million Euro. About 0.69 m€ of the 2016 budget was forwarded to 2017 part as a reservation of activities which are planned in 2017.
Overview of the international fishing activities on the Dogger Bank : update with Dutch, British, Danish, German, Belgian, Swedish and French data for 2010-2015
Hamon, Katell G. ; Hintzen, Niels T. ; Oostenbrugge, Hans J.A.E. - \ 2017
Wageningen : Wageningen Economic Research (Wageningen Economic Research memorandum 2017-050) - 35
fisheries - marine animals - fishery management - north sea - population dynamics - europe - cost benefit analysis - visserij - zeedieren - visserijbeheer - noordzee - populatiedynamica - europa - kosten-batenanalyse
This report is an update of the data and analysis on the value of the fishing activities of the Dutch, British, Danish, German, Belgian, Swedish and French fishing fleets on the proposed closed areas on the Dogger Bank. The effort, value and landings are presented for a five-year period (2010-2015) and show large variations over the last years, driven mainly by fishing opportunities for plaice for the Dutch and British fleets and sandeel for the Danish and German fleets.
Waardekaarten van: Haisborough, Hammond & Winterton, North Norfolk Sandbanks & Saturn Reef
Hintzen, N.T. - \ 2017
IJmuiden : Wageningen Marine Research (Wageningen Marine Research rapport C009/17) - 18 p.
vissen - visserij - waarden - kaarten - natura 2000 - groot-brittannië - kustgebieden - fishes - fisheries - values - maps - great britain - coastal areas
Langs de Engelse kust staan een aantal gebieden op de UK Natura 2000 agenda voor sluiting voor de Nederlandse demersale vloot. Wageningen Marine Research bestudeerde in hoeverre de Nederlandse vloot actief was in dit gebied en hoe de voorgenomen te sluiten gebieden overlappen met voor de visserij interessante visgronden. Een grotere opbrengst (factor 3) wordt gehaald uit het North Norfolk Sandbanks & Saturn Reef gebied (dit is één gebied) ten opzichte van het Haisborough, Hammond and Winterton gebied (dit is ook één gebied). Vooral tong word in dit eerste gebied gevangen terwijl scholvangsten groter zijn in het tweede gebied. De voornaamste visgronden die interessant zijn voor de Nederlandse sector zijn niet opgenomen in de voorgenomen te sluiten gebieden, waarbij juist voor de visserij interessante delen van de totale zoekgebieden niet aangemerkt zijn als te sluiten gebied.
International stakeholder dialogue on pulse fisheries : report of the second dialogue meeting, Amsterdam, 20 January 2017
Steins, Nathalie A. ; Smith, Sarah ; Strietman, Wouter Jan ; Kraan, Marloes ; Trapman, B.K. - \ 2017
IJmuiden : Wageningen Marine Research (Wageningen Marine Research rapport C016/17) - 145
pulse trawling - fisheries - fishing methods - fishery policy - stakeholders - pulsvisserij - visserij - vismethoden - visserijbeleid
Frame Survey Curaçao’s fishing fleet 2016
Kraan, Marloes - \ 2017
IJmuiden : Wageningen Marine Research (Wageningen Marine Research rapport C022/17) - 38
fishing vessels - fisheries - curacao - vissersschepen - visserij - curaçao
A brief inventory of the current fishing capacity (frame survey) of the insular fishing fleet of Curacao was conducted. Curacao is part of the Kingdom of the Netherlands. It lies in the southern Caribbean, approximately 60km off the coast of Venezuela.
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
Inspanningsadviezen voor snoekbaars, baars, blankvoorn en brasem in het IJssel-/Markermeer : visseizoen 2017/2018
Tiën, Nicola ; Hammen, Tessa van der; Vries, Pepijn de; Schram, Edward ; Steenbergen, Josien - \ 2017
IJmuiden : Wageningen Marine Research (Wageningen Marine Research rapport C018/17) - 79
snoekbaars - baars - rutilus rutilus - abramis brama - vissen - visserij - visstand - ijsselmeer - pike perch - bass - fishes - fisheries - fish stocks - lake ijssel
Het Ministerie van Economische Zaken wil komen tot wetenschappelijk onderbouwd duurzaam beheer van snoekbaars, baars, blankvoorn en brasem in het IJsselmeer en Markermeer. Voor alle vier bestanden is de beleidsdoelstelling voor visseizoen 2017/2018 geformuleerd in het document “Toekomstbeeld visstand IJsselmeer/Markermeer – synthesedocument’. Hierin wordt in ieder geval gestreefd naar ‘een evenwichtiger lengte-opbouw van de bestanden met meer grotere exemplaren en een groter aantal jaarklassen’, als ook ‘een toename van de (paai)bestanden’. Voor het behalen van deze beleidsdoelstellingen zijn inspanningsadviezen gevraagd over de staandwantvisserij en de zegenvisserij, gecombineerd voor het IJsselmeer en Markermeer.
Report on the eel stock and fishery in the Netherlands 2015/2016
Graaf, Martin de; Bos, Oscar G. - \ 2017
IJmuiden : Wageningen Marine Research (Wageningen Marine Research rapport C003/17) - 59
eels - anguilla - fish stocks - fisheries - netherlands - palingen - visstand - visserij - nederland
Knowledge production at boundaries : an inquiry into collaborations to make management plans for European fisheries
Stange, Kari - \ 2017
Wageningen University. Promotor(en): Jan van Tatenhove, co-promotor(en): Judith van Leeuwen. - Wageningen : Wageningen University - ISBN 9789463430623 - 160
fishery management - european union - stakeholders - european union countries - fishery policy - multi-stakeholder processes - knowledge - knowledge transfer - environmental policy - fisheries - companies - europe - visserijbeheer - europese unie - landen van de europese unie - visserijbeleid - multi-stakeholder processen - kennis - kennisoverdracht - milieubeleid - visserij - kapitaalvennootschappen - europa

This thesis addresses how knowledge is used and produced in stakeholder-led collaborations to make long-term management plans for European fishery management. Boundary object theory is applied and developed to explain how stakeholders from the fishing industry interact with each other, and with fishery scientists and managers, in initiatives to produce management plans. Using a qualitative case study approach, two initiatives were investigated in-depth: the North Sea Advisory Council’s development of a long-term management plan for North Sea Nephrops fisheries, and the Pelagic Advisory Council’s development of a long-term management plan for a new boarfish fishery in the Northeast Atlantic. A conceptual framework with emphasis on boundary spaces was developed to analyse knowledge exchange and the interaction between actors, objects and activities. The findings point to the importance of entry points for actors to become directly involved in knowledge-production processes. Direct stakeholder engagement in management plan production created a sense of ownership of the problems identified and triggered solution-oriented ways of working. The findings highlight the multiple roles played by fishery scientists in the diverse settings where management plans for European fisheries are produced, and draw attention to the need for clear procedures to ensure that different roles are acted out transparently.

Understanding social sustainability of capture fisheries
Veldhuizen, Linda J.L. - \ 2017
Wageningen University. Promotor(en): Imke de Boer, co-promotor(en): Paul Berentsen; Eddy Bokkers. - Wageningen : Wageningen University - ISBN 9789462579644 - 159
fisheries - sustainability - animal welfare - cod - haddock - fishing methods - whitefish - northeast atlantic - visserij - duurzaamheid (sustainability) - dierenwelzijn - kabeljauw - schelvis - vismethoden - houting - noordoost atlantische oceaan

Fishing companies are faced with decreasing profitability and increasing competition. These companies can try to gain a competitive advantage by differentiating their products, e.g. by marketing new product attributes that consumers are interested in such as attributes relating to sustainability. Although consumers could be considerably interested in social sustainability of fish, this sustainability dimension has received little research interest so far. The main objective of this thesis is to understand social sustainability of capture fisheries. Social sustainability can be understood by applying the framework for social sustainability assessment, which consists of stakeholder consultation and issue selection, indicator development and quantification, and interpretation of the results, to the case considered. The case considered in this thesis was capture fisheries in the northeast Atlantic. Stakeholder consultation resulted in the identification of 27 social sustainability issues relevant for capture fisheries in the northeast Atlantic. Overall, social sustainability issues concerning working conditions, employees' job fulfilment and fish welfare were seen as more important than other social sustainability issues. Indicators were defined for the most important social sustainability issues of capture fisheries in the northeast Atlantic. To interpret values for each indicator, rubrics were developed that articulated levels of performance. Application of these indicators and their accompanying rubrics to a Norwegian trawler demonstrated that the indicators and rubrics provide insight into social sustainability at the level of the vessel, which can be used to identify potential room for improvement. To determine whether social sustainability issues can be used for product differentiation, consumer interest in social sustainability issues of whitefish from the northeast Atlantic was studied. Results from a choice modelling survey demonstrated that consumers prefer the issue fish welfare over the issues product quality, worker safety and local employment. Given the lack of overview of the knowledge on fish welfare, the most important social sustainability issue for consumers, the literature on this topic was reviewed to determine how the capture process in capture fisheries affects fish welfare, using the indicators external injuries and mortality. This review showed that scale, skin and fin injuries occur more frequently in trawls, purse seines, gillnets, traps and seines than in hooks, whereas hooking injuries occur in hooks only. Pressure injuries can occur in all gear types when deployed at greater depth. Trawls, purse seines and seines result in higher mortality than gillnets, hooks and traps. Mortality appears to increase with decreasing fish length, and differs across fish species. A greater capture depth and a longer fishing duration were associated with more external injuries and higher mortality, whereas a large change in water temperature, a longer duration of air exposure and a high density in the net were associated with higher mortality only. This thesis shows that application of the framework for social sustainability assessment to capture fisheries in the northeast Atlantic leads to an understanding of social sustainability that fishing companies can use to their advantage. In addition, this thesis shows that fishing companies in the northeast Atlantic need to start paying attention to fish welfare because consumers consider fish welfare the most important social sustainability issue of capture fisheries in the northeast Atlantic.

Ankerkuilmonitoring Westerschelde: resultaten 2016
Boois, I.J. de; Asch, M. van; Couperus, A.S. - \ 2016
IJmuiden : Wageningen Marine Research (Wageningen Marine Research rapport C113/16) - 19
monitoring - visserij - visstand - westerschelde - nederland - fisheries - fish stocks - western scheldt - netherlands
Benthic development around a gas platform in the North Sea -: a small scale closure for fisheries : a trait based approach
Glorius, Sander ; Hal, Ralf van; Kaag, Klaas ; Weide, Babeth van der; Chen, Chun ; Kooten, Tobias van - \ 2016
Den Helder : Wageningen Marine Research (Wageningen Marine Research rapport ) - 42
benthos - aquatic communities - aquatic ecology - fisheries - north sea - aquatische gemeenschappen - aquatische ecologie - visserij - noordzee
This project looked at the effect of closing an area for fisheries on the development of the benthic community. An existing data set of benthic species densities sampled at different distances and angles from a platform was used for this purpose. The particular area was closed due to the installation of a gas production platform, but is likely to function as a marine protected area (MPA), with the expectation that the benthic community develops differently from the benthic community in the surrounding areas as it no longer has to cope with the impact of fisheries. Differences in development might be linked to the impact of fisheries and the effects of closure might provide an expectation for the effect of planned MPAs in similar areas.
Pulse fishing and its effects on the marine ecosystem fisheries : an update of the scientific knowledge
Rijnsdorp, Adriaan ; Haan, Dick de; Smith, Sarah ; Strietman, Wouter Jan - \ 2016
IJmuiden : Wageningen Marine Research (Wageningen Marine Research report C117/16) - 30
pulse trawling - fishing methods - fisheries - aquatic ecology - marine ecology - aquatic ecosystems - pulsvisserij - vismethoden - visserij - aquatische ecologie - mariene ecologie - aquatische ecosystemen
This report summarises the knowledge on the effects of pulse trawls used in the North Sea fishery for flatfish and brown shrimp. The report describes the electrical characteristics of the pulse trawl systems currently used (potential difference over electrode pairs, pulse frequency, pulse width, duty cycle and dimensions of the gear). The shrimp pulse applies a low frequency pulse that invokes a startle response (tailflip) in shrimps. The sole pulse applies a higher frequency that invokes a cramp response that immobilise the fish species facilitating the catching process.
Toestand vis en visserij in de zoete Rijkswateren 2015 : Deel I : Trends
Graaf, M. de; Boois, I.J. de; Bos, O.G. ; Griffioen, A.B. ; Keeken, O. van; Tien, N.S.H. ; Vries, P. de - \ 2016
IJmuiden : Wageningen Marine Research (Wageningen Marine Research rapport C114/16) - 79
vissen - visserij - zoetwaterecologie - monitoring - fishes - fisheries - freshwater ecology
Het rapport “Toestand Vis en Visserij in de Zoete Rijkswateren” bestaat uit drie verschillende delen: Deel I “Trends”, Deel II “Methoden” en Deel III “Data”. In dit rapport (Deel I) worden (i) de trends in commercieel benutte vissoorten per VBC gebied, (ii) de trends in niet-inheemse vissoorten (exoten) en (iii) de trends in ecologische kwaliteitsratio’s vis gerapporteerd. Hiervoor is gebruik gemaakt van de gegevens die binnen de verschillende vismonitoringsprogramma’s op de Zoete Rijkswateren worden verzameld, aangevuld met gegevens over bv. aanlandingen. In de rapportage zijn trendanalyses voor de verschillende commercieel benutte vissoorten en niet-inheemse vissoorten (exoten) gemaakt aan de hand van de beschikbare monitoringsgegevens. De gegevens van deze monitoringsprogramma’s worden gebruikt als indicatoren voor de ontwikkeling van de bestanden van de geanalyseerde soorten over verschillende tijdsperioden. Het rapport concentreert zich op het weergeven van data en trends.
Aanpassing programma monitoring aal ter ondersteuning beleidskader open/gesloten gebieden
Kotterman, Michael - \ 2016
IJmuiden : Wageningen Marine Research (Wageningen Marine Research rapport C084/16) - 34
palingen - monitoring - visserij - toxicologie - visserijbeleid - eels - fisheries - toxicology - fishery policy
Dit rapport beschrijft een aanpassing van het bestaande aalmonitoringsprogramma dat ingezet kan worden voor het te ontwikkelen beleidskader. De aanpassingen zijn op basis van bestaande data. Dit nieuwe protocol is voor het eerst toegepast op het aal monitoringsprogramma in 2016.
Een haalbaarheidsstudie naar integratie van elektrische voortstuwing in de visserijsector : Academic Consultancy Training
Born, Michael van den; Geurts, Joris ; Jong, Hermen de; Langezaal, Hugo ; Dreessen, Sebastiaan - \ 2016
Kenniskringvisserij.nl - 68 p.
fisheries - costs - fuels - electricity - visserij - kosten - brandstoffen - elektriciteit
De visserijsector heeft de laatste jaren te maken gehad met grote fluctuaties in visprijzen en brandstofkosten. Om de sector toekomstbestendig te maken moeten brandstofkosten worden verlaagd om zo minder invloed te hebben op de financiële resultaten. Daarnaast is het terugdringen van emissies en onafhankelijkheid van fossiele brandstoffen een steeds belangrijker thema. Daarom is in dit project onderzocht in hoeverre het mogelijk is om vissersschepen volledig elektrisch aan te drijven. De focus gelegd op drie thema’s: technische haalbaar, ecologisch verantwoord en economisch rendabel. Tevens is er een stakeholderanalyse uitgevoerd. De resultaten zijn samengevat in een sterkte-zwakte analyse.
Cod monitoring : results 2016, quarter 1
Trapman, B.K. ; Machiels, M.A.M. - \ 2016
IJmuiden : Wageningen Marine Research (Wageningen Marine Research rapport C105/16) - 19
cod - fisheries - monitoring - fish catches - north sea - dutch waters - kabeljauw - visserij - visvangsten - noordzee - nederlandse wateren
Monitoring cod catches of the Dutch demersal fleet in 2015
Trapman, B.K. ; Machiels, M.A.M. - \ 2016
IJmuiden : Wageningen Marine Research (Wageningen Marine Research rapport C106/16) - 30
cod - fisheries - fish catches - monitoring - demersal fisheries - netherlands - kabeljauw - visserij - visvangsten - demersale visserij - nederland
Wettelijke Onderzoek Taken WOT-05 Visserijonderzoek : werkafspraken en werkplan 2017
Verver, S.W. - \ 2016
IJmuiden : Stichting Wageningen Research, Centrum voor Visserijonderzoek (CVO) (CVO rapport 16.009) - 103
visserij - onderzoek - wetgeving - planning - nederland - fisheries - research - legislation - netherlands
Dit rapport beschrijft het werkplan voor 2017 voor het Wettelijke taken programma Visserij onderzoek van Wageningen UR. Wageningen UR voert voor het Ministerie van Economische Zaken (EZ) een aantal programma’s met Wettelijke Onderzoek Taken (WOT) uit. Binnen programma WOT- 05 worden Wettelijke Onderzoek Taken uitgevoerd die betrekking hebben op het beheer van de visserij op zee, in Nederlandse kust- en binnenwateren en de aquacultuur. Het werkplan is een uitwerking van de Uitvoeringsovereenkomst en werkafspraken tussen het Ministerie van EZ en de Stichting Wageningen Research, onderdeel van Wageningen UR, voor diensten vanwege wettelijke taken op het terrein van visserijonderzoek voor de periode 2011-2015. In september 2015 is de Uitvoeringsovereenkomst voor WOT-05 met 1 jaar verlengd tot 31 december 2016. Voor 2017 wordt deze Uitvoeringsovereenkomst verlengd of vernieuwd. De Uitvoeringsovereenkomst en de bijbehorende werkafspraken vormen de basis voor de jaarlijkse werkplannen. Daarnaast zijn in deze overeenkomst afspraken gemaakt over de KennisBasis (KB-WOT) die specifiek aan dit programma is gekoppeld. KB-WOT is bedoeld voor het in stand houden en ontwikkelen van de specifieke kennisinfrastructuur die nodig is om het programma te kunnen uitvoeren. Voor de inzet van KB-WOT visserijonderzoek wordt jaarlijks een afzonderlijk werkplan gemaakt. In brede zin heeft de inhoud van het programma betrekking op de advisering van het visserijbeleid en het verzamelen van gegevens die daarvoor nodig zijn. Tevens wordt via de internationale organisaties meegewerkt aan de advisering voor het beheer van de visbestanden in internationale wateren.
Fishing over the sides or over the stern: does it matter : comparison of two fishing methodologies in the Wadden Sea Demersal Fish Survey
Chen, C. ; Bolle, L.J. ; Boois I.J. de, Ingeborg - \ 2016
IJmuiden : Wageningen Marine Research (Wageningen Marine Research report C122/16) - 27
fisheries - fishing methods - fishing gear - demersal fisheries - wadden sea - visserij - vismethoden - vistuig - demersale visserij - waddenzee
Since 1972, the Demersal Fish Survey (DFS) in the Wadden Sea has been carried out with the RV Stern. Within a few years this vessel will be replaced by another vessel as a result of the current ship replacement policy of Rijkswaterstaat Rijksrederij. It is not yet clear which vessel will replace RV Stern. In the search for a new vessel the main question is if fishing over the sides is needed, or if fishing over the stern is possible without a major effect on catch efficiency. Especially in shallow waters, catch efficiency may be affected by fishing over the stern, because of the current created by the ship’s propeller. To be able to continue the use of the long and valuable time-series the shift in vessel should not lead to a different gear efficiency.
Vangstsamenstelling per tuigcategorie : herziening contingentenstelsel visserij in Nederland in het kader van de aanlandplicht
Helmond, A.T.M. ; Steins, N.A. - \ 2016
IJmuiden : IMARES Wageningen UR (IMARES rapport C107/16) - 62
vangstsamenstelling - visvangsten - visserij - quota - vistuig - nederland - catch composition - fish catches - fisheries - quotas - fishing gear - netherlands
In het nieuwe Gemeenschappelijke Visserijbeleid is vastgelegd dat vissers uiterlijk eind 2019 verplicht zijn de volledige vangst van alle soorten waarvoor vangstquota gelden, mee te nemen naar de wal (aanlandplicht). Tot nu moesten vissers soorten waarvoor ze geen vangstrechten hadden of niet marktwaardig waren, juist terug zetten (discarden). Dit betekent dat het huidige Nederlandse co-management systeem voor quotabeheer moet worden afgestemd op de aanlandplicht. In Nederland wordt het Europese quotabeleid sinds eind jaren ’70 ingevuld via een stelsel van individuele contingenten. Een contingent is een (overdraagbaar) aandeel dat een visserijbedrijf heeft in het nationale quotum voor die soort. Op dit moment zijn er contingenten voor schol, tong, kabeljauw, wijting, haring, makreel, horsmakreel, blauwe wijting en grote zilversmelt. Vissers die geen of onvoldoende contingenten voor een soort hebben, mogen deze niet aan boord houden of aanlanden. De nieuwe aanlandplicht verplicht deze groep vissers echter wel tot aanlanden. Het Ministerie van Economische Zaken (EZ) bereidt daarom een herziening van het contingentenstelsel voor. Een van de maatregelen die wordt verkend is een uitvaarverbod. Dit houdt in een visser niet met een specifiek vistuig mag uitvaren als hij geen of onvoldoende contingent heeft voor de soorten die naar verwachting een substantieel onderdeel uitmaken van de vangsten met dat betreffende vistuig.
Fleet dynamics in a changing policy environment
Batsleer, J. - \ 2016
Wageningen University. Promotor(en): Adriaan Rijnsdorp, co-promotor(en): Jan Jaap Poos. - Wageningen : Wageningen University - ISBN 9789462579521 - 171
fleet dynamics - fisheries - fishery policy - fishery management - sustainability - pleuronectiformes - vlootdynamica - visserij - visserijbeleid - visserijbeheer - duurzaamheid (sustainability)

The European Common Fisheries Policy has received much criticism. In the first place for failing to implement effective management measures aimed at rebuilding and maintaining fish stocks at a sustainable level. In addition, it is said current fisheries policy fails to integrate the wider ecosystem effects of fishing into policy making, such as reducing pressure on non-target species and habitats. Especially discarding (i.e. throwing back unwanted catches at sea) in commercial fisheries has received an increased amount of negative attention. Public campaigns stressed discarding is a wasteful and disruptive practice as natural resources are extracted from the ecosystem only to be thrown back to sea dead. In response, the European Commission agreed to enforce a discard ban for European fisheries, obliging all European fishing vessels to retain and land their entire catch, including small sized individuals, of all species subject to quota management.

This thesis explores how management measures can mitigate the adverse effects of fishing to support the development of an ecosystem-based approach to fisheries management. I evaluate how fleet dynamics, i.e. the decision of individual skippers on when and where to fish, while competing for similar resources, may influence the performance of management measures. In particular the thesis focusses on how location choice and discard decisions made by individual fishers in a mixed fishery are influenced by management, resource distribution and technological innovations. Using a generic dynamic state variable model (DSVM), specific applications are built to address the behavioural dynamics for the Dutch North Sea flatfish fisheries and the French mixed demersal fisheries in the Channel in response to new management regulations and economic opportunities.

The first research chapter of this thesis (Chapter 2) explores how a combination of quota management with a discard ban may improve the regulation of fishing mortality for a depleted stock that is exploited in a mixed fishery. Our finding show that under a discard ban, when properly enforced, individual fishers reallocate fishing effort away from areas and weeks with high catch rates of the quota constrained species, reducing over-quota discarding and thus contributes to the conservation of vulnerable species. However, discard reduction measures which coincide with a reduction in the economic performance of the fishery may jeopardise compliance as fishers may trade-off economic gains of non-compliance against the costs.

Fishers will discard marketable fish when quota are exhausted (over-quota discarding) or by trying to optimize their economic return by discarding size or age classes with the lowest economic value (high-grading). In chapter 3 observations of over-quota discarding and high-grading are reviewed to gain insight in the conditions under which discard decisions may occur. The review suggest that high-grading occurs under different management systems for a large variety of fisheries worldwide. In addition, outcomes of the simulation model illustrate fishers have the ability to strategically plan their fishing activities to optimize the composition of their catch taking account of the availability of quota and seasonal price variations. As a result, the size composition of the high-graded catch differs from the landed catch. Difficulties in accounting for this difference may undermine the accuracy of the stock assessments and quality of scientific advice.

Chapter 4 addresses the question how a ban on discarding may promote the transition towards more selective fishing gears. Model results suggest that under a discard ban, fishing activities are restricted and reallocated away from areas and weeks of high catches of small fish constrained by quota. Activities are allocated to areas and weeks where a maximum revenue can be realised landing other species and economically more valuable length classes of the quota restricted species. When using more selective fishing gear, fishing activities will be less restricted. Fewer small fish are landed which would otherwise be counted against the quota, fetching a low price and reduce the economic value of the landings. Hence, there is an economic advantage and fishers can continue fishing for a longer period of time, including areas where a higher density of small fish as well as more economically valuable fish co-occur. As such, if properly enforced, a discard ban can incentivise the use of more selective gear to reduce the catch of undersized fish.

Trawl fisheries targeting demersal fish and shellfish cause mortality on target and non-target species, but impact benthic ecosystems. Fisheries managers mainly resort to technical management measures, such as gear restrictions or spatial measures to mitigate these impacts. Chapter 5 explores the potential of a habitat credit system as an alternative management approach to achieve sustainable exploitation of target species while minimizing the impact on the benthic ecosystem. Results show that a habitat credit system has the potential to reduce the benthic impact and maintain profitable fisheries as vessels can adjust their behaviour by reallocating fishing activities to make optimal use of the available credits.

Fishers can adapt and change their behaviour in relation to imposed constraints, which can lead to unintended and unexpected consequences of fisheries management. To date, the effect of behavioural adaptations of individual fishers on the success of fisheries management is often overlooked by policymakers. The models developed in this thesis provide a strong basis to explore possible unexpected effects of management measures resulting from the adaptive behaviour of fishers to these measures. Outcomes of this thesis draw attention to the importance of making fleet dynamics an integral part of fisheries management and the need to develop innovative analytical methodologies which deliver sufficiently robust insights into complex socioeconomic and ecosystem issues to improve the basis of decision making.

Fishing intensity around the BBL pipeline
Hintzen, Niels - \ 2016
IJmuiden : Wageningen Marine Research (Wageningen Marine Research rapport C102/16) - 27
visserij - vismethoden - pijpleidingen - bescherming - noordzee - fisheries - fishing methods - pipelines - protection - north sea
Wageningen Marine Research was requested by ACRB B.V. to investigate the fishing activities around the BBL pipeline. This gas pipeline crosses the southern North Sea from Balgzand (near Den Helder) in the Netherlands to Bacton in the UK (230km). This pipeline is abbreviated as the BBL pipeline. Part of the activities deployed by the owner of the BBL pipeline is to secure the integrity of the pipeline, which includes checking burial status, detecting free-spans and investigating internal and external threats to the integrity of the pipeline. Fishing is considered as one of the external threats to the pipeline where a collision with fishing gear could damage the pipeline, the fishing gear, the vessel or the crew. Therefore in areas with substantial fishing activity, extra care should be taken. Such a risk inventory becomes more and more common day practice of submarine pipeline and cable owners where discussions now focus on how to best spend effort on protecting pipelines and where to relieve specific burial requirements.
Improving the knowledge basis for advice on North Sea horse mackerel : developing new methods to get insight on stock boundaries and abundance
Brunel, Thomas ; Farrell, Edward D. ; Kotterman, Michiel ; Kwadijk, Christiaan ; Verkempynck, Ruben ; Chen, Chun ; Miller, David - \ 2016
IJmuiden : Wageningen Marine Research (Wageningen Marine Research report C092/16) - 57
trachurus trachurus - fish stocks - fisheries - models - visstand - visserij - modellen
The North Sea horse mackerel stock is currently classified by ICES as a data poor stock, for which the catch advice is based on the trend in an abundance index. The development of an analytical stock assessment, necessary to give more accurate advice, is hampered by a number of limitations on the input data, among which the most important are the poor quality of catch-at-age data and the absence of a targeted survey for North Sea horse mackerel. The aim of this project was to study possibilities to improve the data quality used for an analytical stock assessment model.
Waardekaarten Markham’s Triangle & Hornsea 3
Machiels, Marcel - \ 2016
Wageningen : Wageningen Marine Research (Wageningen Marine Research rapport C085/16) - 15
visserij - waarden - tabellen - gegevensanalyse - fisheries - values - tables - data analysis
Netinnovatie Kottervisserij
Marlen, B. van; Molenaar, P. ; Bol, R.A. ; Dammers, M. ; Groeneveld, K. ; Machiels, M.A.M. ; Heijer, W.M. den - \ 2016
IMARES (Rapport / IMARES C110/15) - 130 p.
visserij - boomkorvisserij - bijvangst - vangstsamenstelling - fisheries - beam trawling - bycatch - catch composition
Als reactie op de aanlandplicht heeft de kottersector via de Coöperatieve Visserij Organisatie (CVO) het initiatief opgepakt om de selectiviteit van de vistuigen te verhogen om zo weinig mogelijk discards te vangen en aan te landen. Na een ontwerpfase met modelonderzoek in de flume tank van SINTEF te Hirtshals, Denemarken, en met ervaringen uit eerdere projecten werden op verscheidene schepen netinnovaties uitgeprobeerd. Er werd onderzoek gedaan op een schip met boomkor, verschillende schepen vissend met pulsvistuigen en op twinriggers. Hierbij werd aanvankelijk gewerkt op ‘trial-and error’ basis met in sommige gevallen zelfmonitoring. Vervolgens werden enkele uitgebreide vangst- en bijvangstvergelijkingen gedaan met medewerkers van IMARES aan boord.
Costs of seabed protection on the Frisian Front and Central Oyster Grounds for the Dutch fishing sector : addendum to LEI report 2015-145
Oostenbrugge, J.A.E. van; Turenhout, M.N.J. ; Hamon, K.G. - \ 2016
Wageningen : LEI Wageningen UR (Memorandum / LEI Wageningen UR 2016-062) - 29 p.
cost benefit analysis - fisheries - aquatic ecosystems - protection - benthos - ecosystems - oyster culture - north sea - kosten-batenanalyse - visserij - aquatische ecosystemen - bescherming - ecosystemen - oesterteelt - noordzee
This memorandum provides an estimation of the costs for four variant closures for the protection of the benthic ecosystem on the Frisian Front and the Central Oyster Grounds for the Dutch fishing sector in addition to the cost-benefit analysis carried out in Van Oostenbrugge et al. (2015). The two preferential variants lead to similar costs for the fisheries sector, whereas the costs of the two alternative combinations are either 20% higher or lower.
Omvang en overleving van schubvis bijvangst in fuikenvisserij nabij kunstwerken
Griffioen, A.B. ; Keeken, O.A. van; Chen, C. ; Blom, E. ; Schram, E. ; Graaf, M. de; Winter, Hendrik V. - \ 2016
IMARES (Rapport / IMARES C140/15) - 53 p.
visserij - bijvangst - vissen - schade - dierenwelzijn - mortaliteit - fisheries - bycatch - fishes - damage - animal welfare - mortality
Deze rapportage geeft een schatting van de omvang van de bijvangst in de beroepsvisserij nabij kunstwerken op basis van fuikvangsten en diverse interviews. Daarnaast is er een experiment uitgevoerd waarbij er gekeken is naar de overleving van schubvis nadat zij in fuiken hebben gezeten. Hierbij zijn de baars en blankvoorn gebruikt om de overleving te testen in relatie tot de volgende variabelen: aanwezigheid aal: geen (0 stuks), weinig aal (7 stuks) en veel aal (50 stuks), staduur van de fuik: 3, 6 of 9 dagen en dichtheid van vis in een fuik: 60 stuks tegenover 240 stuks.
5 years of Industry survey: Does the industry survey improve current stock assessments for plaice and sole?
Reijden, K.J. van der; Poos, J.J. ; Trapman, B.K. ; Verkempynck, R. - \ 2016
IMARES (Rapport / IMARES C039/16) - 31 p.
plaice - dover soles - fish stocks - fishing gear - fisheries - fish industry - schol - tong (vis) - visstand - vistuig - visserij - visverwerkende industrie
This report describes the results of the industry survey; an annual survey targeting sole and plaice on-board of the commercial fishing vessels UK45 and OD1. The survey was set up following the wish of the fishing industry to deliver data for stock assessments themselves, which are collected using commercially representative fishing gears. This survey was expected to make stock assessment results more accurate and to increase trust of the fisheries industry in stock assessments.
Wettelijke Onderzoek Taken WOT-05 Visserijonderzoek : jaarverslag 2015
Verver, S.W. - \ 2016
IJmuiden : Centrum voor Visserijonderzoek (CVO rapport 16.003) - 97 p.
visserij - onderzoek - wetgeving - jaarverslagen - nederland - fisheries - research - legislation - annual reports - netherlands
Wettelijke Onderzoek Taken WOT-05 Visserijonderzoek : beknopte jaarrapportage 2015
Verver, S.W. - \ 2016
IJmuiden : Centrum voor Visserijonderzoek (CVO rapport 16.004) - 34 p.
visserij - onderzoek - wetgeving - jaarverslagen - nederland - fisheries - research - legislation - annual reports - netherlands
Vermindering discards door netinnovatie in de Noorse kreeft visserij
Molenaar, P. ; Steenbergen, J. ; Glorius, S.T. ; Dammers, M. - \ 2016
IJmuiden : IMARES (Rapport / IMARES C027/16) - 119 p.
discards - visserij - nephrops norvegicus - innovaties - vistuig - fisheries - innovations - fishing gear
Dit rapport beschrijft de testen die zijn uitgevoerd binnen het project ‘Sectorale en Ketenintegrale aanpak Langoustines’ in de periode april 2014 – december 2015 dat was gericht op het verminderen van discards binnen de visserij op Noorse kreeft (Nephrops norvegicus). Het project is een initiatief van de Coöperatieve Visserij Organisatie (CVO) en maakte onderdeel uit van breder programma waarin de sector zich voorbereid op de aanlandplicht. De aanlandplicht, als onderdeel van het nieuwe gemeenschappelijke visserijbeleid, is sinds 2015 van kracht en houdt in dat maatse en ondermaatse vissen en schaaldieren van soorten waarvoor vangstbeperkingen gelden niet meer in zee terug mogen worden gezet. Discards in de visserij op Noorse kreeft bestaan o.a. uit kleine Noorse kreeft, schar (Limanda limanda) en ondermaatse schol (Pleuronectes platessa).
VIP Praktijknetwerk Netinnovatie Zuid
Marlen, B. van; Rink, G.J. ; Vandenberghe, C. - \ 2016
IJmuiden : IMARES (Rapport / IMARES C147/14) - 77 p.
visserij - duurzaamheid (sustainability) - pleuronectiformes - netten - noordzee - fisheries - sustainability - nets - north sea
Het VIP project Praktijknetwerk Netinnovatie Zuid beoogde een bijdrage te leveren aan een meer duurzame kottervisserij op platvis op zuidelijke bestekken in de Noordzee door het ontwikkelen van nieuwe netten met een lager brandstofverbruik, en minder netslijtage, bijvangsten en discards.
Verkenning doorvaren passieve vistuigen
Jak, R.G. - \ 2016
IMARES (Rapport / IMARES C014/16) - 20 p.
vistuig - visserij - vuilnis - vismethoden - verontreiniging - nederland - fishing gear - fisheries - refuse - fishing methods - pollution - netherlands
In deze studie is op basis van gesprekken met Nederlandse staandwantvissers en sleepnetvissers verkend in hoeverre het doorvaren van staandwantnetten kan leiden tot het ontstaan van zwerfvuil. Volgens de Nederlandse staandwantvissers zijn de problemen uit voorgaande decennia voorbij door de goede communicatie tussen staandwantvisssers enerzijds en sleepnetvissers anderzijds. Netten worden tegenwoordig nog doorvaren indien niet goed bekend is dat bepaalde activiteiten, zoals baggeren, gaan plaatsvinden. Doorvaren netten worden door de staandwantvissers zoveel mogelijk weer verzameld en eindigen dan niet als zwerfvuil. Door sleepnetvissers wordt aangegeven dat netten van Deense staandwantvissers regelmatig doorvaren worden, vooral gedurende de zomerperiode en binnen de 12-mijlzone. Deze netten worden losgesneden en dan òf als afval meegenomen naar wal, òf achtergelaten indien de netten zijn verankerd. Het is dan onduidelijk of de stukgesneden netten achterblijven als zwerfvuil. Op basis van de bevindingen wordt aanbevolen een betere communicatie te faciliteren tussen staandwantvissers en andere gebruikers van de kustzone.
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 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.

Minimum aanlandingsmaat Brasem (Abramis brama)
Hal, R. van; Miller, D.C.M. - \ 2016
IJmuiden : IMARES (Rapport / IMARES C148/15a) - 17
abramis brama - grootte - visserij - lengte - ijsselmeer - size - fisheries - length - lake ijssel
Ter ondersteuning van een besluit aangaande een minimum aanlandingsmaat voor brasem, primair voor het IJsselmeer en Markermeer, heeft het ministerie van Economische Zaken IMARES verzocht een overzicht te geven van aanlandingsmaten voor brasem in andere landen en waar mogelijk de motivatie achter deze maten te geven. Er blijken in verschillende, voornamelijk oost, Europese landen minimum aanlandingsmaten te zijn ingesteld. Het is echter niet altijd duidelijk of deze voor de commerciële en/of recreatieve visserij gelden. De gegeven maten zijn niet eenduidig, in een deel van de geval gelden de maten voor de gehele vis (puntje neus tot eind staart) voor een ander deel gelden ze voor een kleiner deel van de vis (puntje neus tot begin staart). Het was voor ons niet altijd duidelijk welke meetmethode gebruikt wordt. De gevonden minimum aanlandingsmaten variëren tussen 20 en 45 cm. Er zijn helaas geen gegevens gevonden voor de onderbouwing van deze maten. Een mogelijke methode om een minimum aanlandingsmaat vast te stellen is gebruik te maken van gegevens die per lengte aangegeven welk deel van de populatie volwassen is. Op basis van deze gegevens kan een volwassenheid ogive worden bepaald. Deze was beschikbaar gebaseerd op IMARES survey en afslag gegevens van het IJsselmeer. Met behulp van deze ogive is de lengte waarop 50, 70 en 100% van de populatie brasem volwassen is bepaald. Bij de doelstelling “het zorgdragen van voortplanting” zijn dit maten die indicatief zou kunnen zijn voor een eventuele minimum aanlandingsmaat voor het IJsselmeer en Markermeer.
Flyshoot fishery in relation to sea floor protection of the Frisian front and Central Oyster Ground areas
Rijnsdorp, A.D. - \ 2015
IJmuiden : IMARES Wageningen UR (IMARES rapport C065/15) - 23
fisheries - fishing methods - environmental protection - friesland - visserij - vismethoden - milieubescherming
The Dutch ministries of Infrastructure and Environment and the ministry of Economic Affairs are developing management measures to protect the seafloor in the Frisian Front (FF) and Central Oysterground (CO) areas of the Dutch EEZ. In the consultations with the fishing industry and environmental NGO’s the following questions were raised about the impact of the flyshoot fishery: a. Where do fishermen deploy flyshoot (or other bottom seine gear) and what is the value of the landings taken. b. What are the effects of the flyshoot on the ecology of the benthos in general, and in particular in the areas where this gear is being deployed. What is the recovery potential of the seafloor if there would be no flyshooting. c. How do the effects of the flysoot compare to the effects of the other towed demersal gear in the typical flyshoot grounds.
Voorbereiding van de pulsmonitoring: Vaststellen omvang van bemonsteringsprogramma
Reijden, K.J. van der; Hintzen, N.T. - \ 2015
IMARES (Rapport / IMARES C074/15) - 19 p.
pulsvisserij - demersale visserij - visserij - monitoring - bemonsteren - pulse trawling - demersal fisheries - fisheries - sampling
Toestand vis en visserij in de Zoete Rijkswateren: 2014 Deel I: Trends van de visbestanden, vangsten en ecologische kwaliteit ratio's
Graaf, M. de; Boois, I.J. de; Griffioen, A.B. ; Overzee, H.M.J. van; Tien, N.S.H. ; Tulp, I.Y.M. ; Vries, P. de; Deerenberg, C.M. - \ 2015
IMARES (Rapport / IMARES C199/15) - 102 p.
zoet water - aquatische ecologie - vissen - monitoring - rivieren - inventarisaties - visserij - visvangsten - vistuig - ijsselmeer - visstand - fresh water - aquatic ecology - fishes - rivers - inventories - fisheries - fish catches - fishing gear - lake ijssel - fish stocks
Het rapport “Toestand Vis en Visserij in de Zoete Rijkswateren” bestaat uit drie verschillende delen: “Trends”, “Methoden” en “Data”. In dit rapport (Deel I) worden (i) de trends in commercieel benutte vissoorten per VBC gebied, (ii) de trends in Habitatrichtlijnsoorten en (iii) de ecologische kwaliteitsratio’s vis gerapporteerd. Hiervoor is gebruik gemaakt van de gegevens die binnen de verschillende vismonitoringsprogramma’s op de Zoete Rijkswateren worden verzameld. In de rapportage zijn trendanalyses voor de verschillende commercieel benutte vissoorten en Habitatrichtlijn vissoorten gemaakt aan de hand van de beschikbare monitoringsgegevens. De gegevens van deze monitoringsprogramma’s worden gebruikt als indicatoren voor de ontwikkeling van de bestanden van de geanalyseerde soorten over verschillende tijdsperioden.
Decentraal aalbeheer in Friesland : een economische analyse
Prins, H. ; Zaalmink, W. - \ 2015
LEI Wageningen UR (Report / LEI Wageningen UR 2015-157) - 81 p.
binnenvisserij - palingen - european eels - anguilla - visserij - visvangsten - quota - visserijbeheer - economische ontwikkeling - friesland - nederland - binnenwateren - freshwater fisheries - eels - fisheries - fish catches - quotas - fishery management - economic development - netherlands - inland waters
Within the framework of the eel recovery plan, restrictive measures have been in force in Dutch eel fisheries since 2009. Since 2011, Frisian inland fishers, associated through the Frisian association of inland fishers (Friese Bond van Binnenvissers), have been experimenting with fishing quotas for eel. This approach is also known as 'decentralised eel management' (decentraal aalbeheer). This quota is in lieu of the statutory eel fisheries system, which includes a three-month period in which no eel may be fished. This report will explore the economic development of Frisian inland fisheries since 2007, as well as the question whether fishing quotas are economically viable.
VIP - Pelagic Trawl Innovation
Marlen, B. van; Overzee, H.M.J. van; Helmond, A.T.M. van; Tamis, J.E. ; Vries, P. de; Dammers, M. ; Cuperus, J. - \ 2015
IJmuiden : IMARES (Report / IMARES C109/15) - 33 p.
pelagic fishery - fisheries - size - netherlands - pelagische visserij - visserij - grootte - nederland
In response to the landing obligation for pelagic species, that started in 2015, the Dutch pelagic fishing industry has tested sorting grids with the aim to avoid the capture of undersized and/or unwanted fish.
Langetermijn opties voor het visserij-advies over schubvis op het IJsselmeer en Markermeer
Tien, N.S.H. ; Hammen, T. van der - \ 2015
IJmuiden : IMARES (Rapport / IMARES C163/15) - 22 p.
visserij - visserijbeleid - vissen - visserijbeheer - ijsselmeer - nederland - fisheries - fishery policy - fishes - fishery management - lake ijssel - netherlands
IMARES geeft visserij-advies (vangst-/inspanningsadvies) voor de schubvisbestanden snoekbaars, baars, blankvoorn en brasem op het IJsselmeer en Markermeer. Gezien de lage kwantiteit en kwaliteit van gegevens over de visbestanden en met name de visserij erop, wordt momenteel het advies gebaseerd op een methodiek binnen het ICES-raamwerk, welke is ontwikkeld voor data-gelimiteerde bestanden (‘DLS’). Het ministerie van Economische Zaken (EZ) wil toewerken naar nauwkeuriger advies en wil de relatie tussen beheer en bestandsontwikkelingen kunnen kwantificeren (Kaderbrief 2015). Dit rapport bevat een overzicht van de mogelijkheden en beperkingen voor verbeteringen in de adviezen. Het tijdsgewricht voor deze ontwikkelingen is met name 2017-2019 maar met een doorkijk naar de jaren erna. Dit rapport beschrijft drie aspecten van het advies voor de schubvisbestanden: (1) langetermijn verbeteringen in de toegepaste modellen, (2) beschrijving van hoe de referentieperiode te kiezen in de komende jaren, en (3) beschrijving van mogelijke problemen rond toestaan van verhuur en verkoop van visserijrechten tussen vergunninghouders in de komende jaren.
VIP Rapportage "Steekproef schattingen demersale discards aan boord" : Rapportage Validering en opwerking uitkomsten project "demersale discardverwerking"
Verkempynck, R. ; Machiels, M.A.M. - \ 2015
IJmuiden : IMARES (Rapport / IMARES C166/15) - 23 p.
discards - quota's - visserij - demersale visserij - demersale vissen - quotas - fisheries - demersal fisheries - demersal fishes
Onder de aanlandplicht zullen de discards met het quotum verrekend worden. Daarom is het nodig om het totale gewicht en de samenstelling van de discards te bepalen. In dit rapport worden drie scenario’s voorgesteld waarbij het totale gewicht en de samenstelling van vijf soorten in de discards (schol, tong, roggen, wijting en schar) geschat moet worden voor het boomkorsegment.
Status and trends of St. Eustatius Coral reef ecosystem and fisheries: 2015 report card
Graaf, M. de; Piontek, S. ; Miller, D.C.M. ; Brunel, T.P.A. ; Nagelkerke, L.A.J. - \ 2015
IJmuiden : IMARES (Report / IMARES C167/15) - 41 p.
coral reefs - ecosystems - fisheries - algae - fishery management - pollution - habitat degradation - nature conservation - sint eustatius - koraalriffen - ecosystemen - visserij - algen - visserijbeheer - verontreiniging - habitatdegradatie - natuurbescherming
Toestand vis en visserij in de zoete Rijkswateren : Deel II: Methoden
Sluis, M.T. van der; Tien, N.S.H. ; Griffioen, A.B. ; Keeken, O.A. van; Os-Koomen, E. van; Rippen, A.D. ; Wolfshaar, K.E. van de - \ 2015
IJmuiden : IMARES (Rapport / IMARES C193/15) - 88 p.
zoet water - aquatische ecologie - vissen - monitoring - rivieren - inventarisaties - ijsselmeer - visvangsten - visserij - vistuig - fresh water - aquatic ecology - fishes - rivers - inventories - lake ijssel - fish catches - fisheries - fishing gear
Het rapport “Toestand Vis en Visserij in de Zoete Rijkswateren” bestaat uit drie delen. Dit rapport (Deel II) is een achtergronddocument waarin de gebruikte monitoringsmethodieken in de verschillende vis-monitoringen in de zoete Rijkswateren in detail worden beschreven. Meer informatie over trends en vangsten is te vinden in rapportages Deel I: Trends visbestanden, vangsten en ecologische kwaliteit ratio’s en Deel III: Data).
Toestand vis en visserij in de zoete Rijkswateren: 2014 : Deel III: Data
Boois, I.J. de; Hoek, R. ; Graaf, M. de; Griffioen, A.B. ; Keeken, O.A. van; Lohman, M. ; Os-Koomen, E. van; Westerink, H.J. ; Wiegerinck, J.A.M. - \ 2015
IJmuiden : IMARES (Rapport / IMARES C194/15) - 511 p.
zoet water - aquatische ecologie - vissen - monitoring - rivieren - inventarisaties - ijsselmeer - visvangsten - visserij - vistuig - fresh water - aquatic ecology - fishes - rivers - inventories - lake ijssel - fish catches - fisheries - fishing gear
Dit rapport bevat een overzicht van de gegevens verzameld tijdens de vismonitoringen in de zoete rijkswateren. Het omvat de volgende bemonsteringen: - Open water vismonitoring IJssel- en Markermeer met actieve vistuigen - Oever vismonitoring IJssel- en Markermeer met actieve vistuigen - Vismonitoring in IJssel- en Markermeer met kieuwnetten - Diadrome vis Kornwerderzand Waddenzee op basis van fuikregistraties - Vismonitoring grote rivieren met actieve vistuigen - Vismonitoring zoete rijkswateren op basis van vangstregistratie aalvissers - Diadrome vismonitoring zoete rijkswateren op basis van fuikregistraties (sinds najaar 2012) - Vismonitoring grote rivieren op basis van zalmsteekregistraties - Vismonitoring randmeren met actieve vistuigen - Monitoring glasaal op intreklocaties.
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