Staff Publications

Staff Publications

  • external user (warningwarning)
  • Log in as
  • language uk
  • About

    '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.

    We have a manual that explains all the features 

Current refinement(s):

Records 1 - 20 / 25

  • help
  • print

    Print search results

  • export

    Export search results

  • alert
    We will mail you new results for this query: keywords==fisheries management
Check title to add to marked list
Assessing bottom trawling impacts based on the longevity of benthic invertebrates
Hiddink, Jan Geert ; Jennings, Simon ; Sciberras, Marija ; Bolam, Stefan G. ; Cambiè, Giulia ; McConnaughey, Robert A. ; Mazor, Tessa ; Hilborn, Ray ; Collie, Jeremy S. ; Pitcher, C.R. ; Parma, Ana M. ; Suuronen, Petri ; Kaiser, Michel J. ; Rijnsdorp, Adriaan D. - \ 2019
Journal of Applied Ecology 56 (2019)5. - ISSN 0021-8901 - p. 1075 - 1084.
benthic invertebrates - bottom trawl - fisheries management - impact assessment - life-history meta-analysis - seabed disturbance - systematic review

Bottom trawling is the most widespread human activity directly affecting seabed habitats. Assessment and effective management of the effects of bottom trawling at the scale of fisheries requires an understanding of differences in sensitivity of biota to trawling. Responses to disturbance are expected to depend on the intrinsic rate of increase in populations (r), which is expected to be linearly related to the reciprocal of longevity. We examine the relationship between the longevity of benthic invertebrates and their response to bottom trawling; both in terms of the immediate mortality following a trawl pass and their subsequent rates of recovery. We collate all available data from experimental and comparative trawling studies, and test how longevity influences these aspects of sensitivity. The shortest lived organisms (<1 year) increased in abundance shortly after experimental trawling but showed no response to trawling in long-term comparative studies. Conversely, the abundance of biota with a life span >1 year decreased by ~9% immediately following a trawl pass. The effect of bottom trawling in comparative studies increased with longevity, with a 2–3× larger effect on biota living >10 years than on biota living 1–3 years. We attribute this difference to the slower recovery rates of the long-lived biota. The observed relationship between the intrinsic rate of population increase (r, our metric of recovery rate) and the reciprocal of longevity matches theoretical expectation and predicts that the sensitivity of habitats to bottom trawling is higher in habitats with higher proportions of long-lived organisms. Synthesis and applications. Where the longevity of a species or the longevity distribution of a community is known or can be inferred, our estimates of depletion and intrinsic rate of increase can be combined with high-resolution maps of trawling intensity to assess trawling impacts at the scale of the fishery or other defined unit of assessment. Our estimates of r may also be used to estimate recovery times following other forms of seabed disturbance.

Data from: Assessing bottom-trawling impacts based on the longevity of benthic invertebrates
Hiddink, Jan Geert ; Jennings, Simon ; Sciberras, Marija ; Bolam, Stefan G. ; Cambiè, Giulia ; Mcconnaughey, Robert A. ; Mazor, Tessa ; Hilborn, Ray ; Collie, Jeremy S. ; Pitcher, C.R. ; Parma, Ana M. ; Suuronen, Petri ; Kaiser, Michel J. ; Rijnsdorp, A.D. - \ 2018
fisheries management - bottom trawl - benthic invertebrates - impact assessment - meta-analysis - systematic review - life history - seabed disturbance
Bottom trawling is the most widespread human activity directly affecting seabed habitats. Assessment and effective management of the effects of bottom trawling at the scale of fisheries requires an understanding of differences in sensitivity of biota to trawling. Responses to disturbance are expected to depend on the intrinsic rate of increase of populations (r), which is expected to be linearly related to the reciprocal of longevity. 2. We examine the relationship between the longevity of benthic invertebrates and their response to bottom trawling; both in terms of the immediate mortality following a trawl pass and their subsequent rates of recovery. We collate all available data from experimental and comparative trawling studies, and test how longevity influences these aspects of sensitivity. 3. The shortest-lived organisms (<1yr) increased in abundance shortly after experimental trawling, but showed no response to trawling in longer-term comparative studies. Conversely, the abundance of biota with a life-span >1yr decreased by ~9% immediately following a trawl pass. The effect of bottom trawling in comparative studies increased with longevity, with a 2-3× larger effect on biota living >10yr than on biota living 1-3yr. We attribute this difference to the slower recovery rates of the longer-lived biota. 4. The observed relationship between the intrinsic rate of population increase (r, our metric of recovery rate) and the reciprocal of longevity matches theoretical expectation and predicts that the sensitivity of habitats to bottom trawling is higher in habitats with higher proportions of long-lived organisms. 5. Synthesis and Applications. Where the longevity of a species or the longevity distribution of a community is known or can be inferred, our estimates of depletion and intrinsic rate of increase can be combined with high-resolution maps of trawling intensity to assess trawling impacts at the scale of the fishery or other defined unit of assessment. Our estimates of r may also be used to estimate recovery times following other forms of seabed disturbance.
The commons tragedy in the North Sea brown shrimp fishery: how horizontal institutional interactions inhibit a self-governance structure
Steenbergen, Josien ; Trapman, Brita K. ; Steins, Nathalie A. ; Poos, Jan Jaap - \ 2017
ICES Journal of Marine Science 74 (2017)7. - ISSN 1054-3139 - p. 2004 - 2011.
brown shrimp fisheries - fisheries management - growth overfishing - institutional analysis - tragedy of the commons
Self-regulation is now widely regarded as an effective mechanism for collective action aimed at sustainable management of common pool resources. The brown shrimp (Crangon crangon) fishing industry in the Netherlands has been working on the implementation of a self-management strategy since 2007, as part of its ambition to get certified to the Marine Stewardship Council standard. Part of the self-management strategy is the development of a harvest control rule for reducing fishing effort when catches are low. Until recently, these attempts failed. The failure of the initiatives for self-management is examined within Ostrom’s nested framework for understanding institutions for managing resource use. This framework emphasises the importance of strong vertical embeddedness of institutional arrangements for resource (co)management. Our analysis shows that, despite a strong vertical embeddedness, mismatches between different institutional frameworks at the same level (horizontal interaction) affect the performance of self-management at the organizational level. This inhibits the resource users’ collective actions to self-manage their brown shrimp fishery, leading to a potential commons tragedy.
Identifying marine pelagic ecoystem management objectives and indicators
Trenkel, V.M. ; Hintzen, N.T. ; Farnsworth, K. ; Olesen, C. ; Reid, D. ; Rindorf, A. ; Shephard, S. ; Dickey-Collas, M. - \ 2015
Marine Policy 55 (2015). - ISSN 0308-597X - p. 23 - 32.
north-sea - fisheries management - celtic sea - continental-shelf - functional-groups - fish communities - forage fish - atlantic - seabirds - impacts
International policy frameworks such as the Common Fisheries Policy and the European Marine Strategy Framework Directive define high-level strategic goals for marine ecosystems. Strategic goals are addressed via general and operational management objectives. To add credibility and legitimacy to the development of objectives, for this study stakeholders explored intermediate level ecological, economic and social management objectives for Northeast Atlantic pelagic ecosystems. Stakeholder workshops were undertaken with participants being free to identify objectives based on their own insights and needs. Overall 26 objectives were proposed, with 58% agreement in proposed objectives between two workshops. Based on published evidence for pressure-state links, examples of operational objectives and suitable indicators for each of the 26 objectives were then selected. It is argued that given the strong species-specific links of pelagic species with the environment and the large geographic scale of their life cycles, which contrast to demersal systems, pelagic indicators are needed at the level of species (or stocks) independent of legislative region. Pelagic community indicators may be set at regional scale in some cases. In the evidence-based approach used in this study, the selection of species or region specific operational objectives and indicators was based on demonstrated pressure-state links. Hence observed changes in indicators can reliably inform on appropriate management measures.
Profit fluctuations signal eroding resilience of natural resources
Richter, A.P. ; Dakos, V. - \ 2015
Ecological Economics 117 (2015). - ISSN 0921-8009 - p. 12 - 21.
social-ecological systems - early-warning signals - regime shifts - fisheries management - ecosystem services - tipping point - slowing-down - fish stocks - extinction - indicators
A common pattern of environmental crises is a vicious cycle between environmental degradation and socio-economic disturbances. Here we show that while such feedbacks may give rise to critical transitions in social-ecological systems, at the same time they can offer novel o0pportunities for anticipating them. We model a community that has joint access to the harvest grounds of a resource that is prone to collapse. Individuals are tempted to overexploit the resource, while a cooperative harvesting norm spreads through the community via interprersonal relations. Both social and ecological collapses can be induced by environmental or socio-economic driving forces. Regardless of the type and cause of collapse we find that upcoming transitions may be detected using simple socio-economic response variables, such as individual profits. Our findings suggest that such alternative sources of information can be used to detect upcoming critical transitions in social-ecological systems. However, we also find that robust detection of critical transitions may be confounded by recovery attempts undertaken by resource users in the vicinity of an upcoming collapse, which may be falsely interpreted as a stabilization of the social-ecological system.
An exposure-effect approach for evaluating ecosystem-wide risks from human activities
Knights, A.M. ; Piet, G.J. ; Jongbloed, R.H. ; Tamis, J.E. ; Robinson, L.A. - \ 2015
ICES Journal of Marine Science 72 (2015)3. - ISSN 1054-3139 - p. 1105 - 1115.
baltic sea - fisheries management - environmental-change - coastal ecosystems - marine ecosystems - human impact - new-zealand - food webs - support - climate
Ecosystem-based management (EBM) is promoted as the solution for sustainable use. An ecosystem-wide assessment methodology is therefore required. In this paper, we present an approach to assess the risk to ecosystem components from human activities common to marine and coastal ecosystems. We build on: (i) a linkage framework that describes how human activities can impact the ecosystem through pressures, and (ii) a qualitative expert judgement assessment of impact chains describing the exposure and sensitivity of ecological components to those activities. Using case study examples applied at European regional sea scale, we evaluate the risk of an adverse ecological impact from current human activities to a suite of ecological components and, once impacted, the time required for recovery to pre-impact conditions should those activities subside. Grouping impact chains by sectors, pressure type, or ecological components enabled impact risks and recovery times to be identified, supporting resource managers in their efforts to prioritize threats for management, identify most at-risk components, and generate time frames for ecosystem recovery.
Evaluation of ecosystem-based marine management strategies based on risk assessment
Piet, G.J. ; Jongbloed, R.H. ; Knights, A.M. ; Tamis, J.E. ; Paijmans, A.J. ; Sluis, M.T. van der; Vries, P. de; Robinson, L.A. - \ 2015
Biological Conservation 186 (2015). - ISSN 0006-3207 - p. 158 - 166.
fisheries management - new-zealand - vulnerability - support - areas - south - pressure - context - threats - number
This study presents a comprehensive and generic framework that provides a typology for the identification and selection of consistently defined ecosystem-based management measures and allows a coherent evaluation of these measures based on their performance to achieve policy objectives. The performance is expressed in terms of their reduction of risk of an adverse impact on the marine ecosystem. This typology consists of two interlinked aspects of a measure, i.e. the “Focus” and the “Type”. The “Focus” is determined by the part of the impact chain (Driver–Pressure–State) the measure is supposed to mitigate or counteract. The “Type” represents the physical measure itself in terms of how it affects the impact chain directly; we distinguish Spatio-temporal distribution controls, Input and Output controls, Remediation and Restoration measures. The performance of these measures in terms of their reduction in risk of adverse impacts was assessed based on an explicit consideration of three time horizons: past, present and future. Application of the framework in an integrated management strategy evaluation of a suite of measures, shows that depending on the time horizon, different measures perform best. “Past” points to measures targeting persistent pressures (e.g. marine litter) from past activities. “Present” favors measures targeting a driver (e.g. fisheries) that has a high likelihood of causing adverse impacts. “Future” involves impacts that both have a high likelihood of an adverse impact, as well as a long time to return to pre-impacted condition after the implementation of appropriate management, e.g. those caused by permanent infrastructure or persistent pressures such as marine litter or specific types of pollution.
The interaction triangle as a tool for understanding stakeholder interactions in marine ecosystem based management
Rockmann, C. ; Leeuwen, J. van; Goldsborough, D.G. ; Kraan, M.L. ; Piet, G.J. - \ 2015
Marine Policy 52 (2015). - ISSN 0308-597X - p. 155 - 162.
traditional ecological knowledge - fisheries management - environmental assessment - citizen participation - resource-management - risk communication - uncertainty - governance - framework - science
Expectations about ecosystem based management (EBM) differ due to diverging perspectives about what EBM should be and how it should work. While EBM by its nature requires trade-offs to be made between ecological, economic and social sustainability criteria, the diversity of cross-sectoral perspectives, values, stakes, and the specificity of each individual situation determine the outcome of these trade-offs. The authors strive to raise awareness of the importance of interaction between three stakeholder groups (decision makers, scientists, and other actors) and argue that choosing appropriate degrees of interaction between them in a transparent way can make EBM more effective in terms of the three effectiveness criteria salience, legitimacy, and credibility. This article therefore presents an interaction triangle in which three crucial dimensions of stakeholder interactions are discussed: (A) between decision makers and scientists, who engage in framing to foster salience of scientific input to decision making, (B) between decision makers and other actors, to shape participation processes to foster legitimacy of EBM processes, and (C) between scientists and other actors, who collaborate to foster credibility of knowledge production. Due to the complexity of EBM, there is not one optimal interaction approach; rather, finding the optimal degrees of interaction for each dimension depends on the context in which EBM is implemented, i.e. the EBM objectives, the EBM initiator’s willingness for transparency and interaction, and other context-specific factors, such as resources, trust, and state of knowledge.
Why the complex nature of integrated ecosystem assessments requires a flexible and adaptive approach
Dickey-Collas, M. - \ 2014
ICES Journal of Marine Science 71 (2014)5. - ISSN 1054-3139 - p. 1174 - 1182.
fisheries management - ecological indicators - mixed-fisheries - framework - implementation - policy - uncertainty - thresholds - scientists - support
This article considers the approach taken by the ICES to integrated ecosystem assessments (IEAs) in the context of the wider evolution of IEAs and the science/policy landscape within the ICES region. It looks forward and considers the challenges facing the development of IEAs, specifically those of scoping for objectives, participatory engagement, developing indicators and targets, risk analysis, and creating tools to evaluate management measures for marine anthropogenic activities. It concludes that expectations that the implementation of IEAs will take an ordered, stepwise approach will lead to disappointment and frustration. This is a consequence of the need to operate in an adaptive manner in a complex system. The ecosystem, the science support infrastructure, and the governance systems are all complex. Plus when engaged in a debate about societal objectives, we expect to encounter a complex and changing landscape. As a community, the challenge is to find leverage mechanisms to encourage IEA efforts to provide insights and tools within resources. We will need to innovate and be responsive to the complexity of the ecosystem and governance structures encountered when performing IEA.
Fluctuating quota and management costs under multiannual adjustment of fish quota
Dijk, D. van; Haijema, R. ; Hendrix, E.M.T. ; Groeneveld, R.A. ; Ierland, E.C. van - \ 2013
Ecological Modelling 265 (2013). - ISSN 0304-3800 - p. 230 - 238.
north-sea plaice - pleuronectes-platessa l. - fisheries management - stock - uncertainty - sustainability - maturation - failure - trends - growth
North Sea fisheries are managed by the European Union (EU) through a system of annual quota. Due to uncertainty about future fish stocks, yearly revisions of these policies lead to fluctuation in quota, which in turn affects harvest and investment decisions of fishermen. Determination of quota requires high management costs in terms of obtaining information and negotiations between experts and policy makers. To reduce both quota fluctuation and management costs, the EU has proposed a system of multiannual quota. In this paper we study the effect of multiannual quota on quota volatility and resource rents, while accounting for management costs. We develop a bi-level stochastic dynamic programming model, where at level one, the EU determines the quota that maximizes resource rents. At level two, fishermen decide myopically on their harvest and investment levels, subject to the quota. Results show that policy makers can reduce quota volatility and improve resource rents from the fishery with multiannual quota. Important trade-offs are involved in the accomplishment of these objectives: fish stock and investments become more volatile, which leads to more overcapacity.
Administrative Co-management: The Case of Special-Use Forest Conservation in Vietnam
Nguyen, T.K.D. ; Bush, S.R. ; Mol, A.P.J. - \ 2013
Environmental Management 51 (2013)3. - ISSN 0364-152X - p. 616 - 630.
fisheries management - interests
Special-use forests (SUFs) are nature protected areas in Vietnam used to conserve nature and its biodiversity. While the Vietnamese government has managed to increase the size and number of SUFs, biodiversity within these areas continues to decline. To improve protection of these SUFs, co-management has been advocated in Vietnam. Successfully implementing co-management requires decentralization of authority and a certain extent of public involvement in management activities. This paper assesses how and to what extent the governance of Vietnam’s SUFs have taken up the challenge of shifting from conventional government-based management to co-management. Current practices of (co-) management were investigated in 105 of the 143 SUFs. The results show that the type of co-management varies little between different categories of SUFs. Nevertheless, a national ‘style’ of Vietnamese co-management could be identified, labelled ‘administrative’ co-management; fostering interaction between a variety of actors, but final decision-making power on management remaining strongly in the hands of the provincial government.
How to turn the tide: Developing legitimate marine governance arrangements at the level of the regional seas
Tatenhove, J. van - \ 2013
Ocean & Coastal Management 71 (2013). - ISSN 0964-5691 - p. 296 - 304.
fisheries management - ocean governance - european-union - institutionalism - framework - governability - perspectives - ecosystems - coastal - systems
Competing spatial claims and conflicts between maritime economic activities and biodiversity in Europe's seas continue to challenge governments and non-governmental actors. Responses to these problems have resulted in a fragmented patchwork of EU policies, private initiatives, and regulations on different levels. It is clear that the different sets of problems in each sea and the existing institutional arrangements (often created in an ad hoc fashion) require different responses and that a regional approach to marine governance is more flexible than a pan-European one. This paper explores whether and how it is possible to develop integrated maritime governance arrangements for Europe's regional seas. It explores the sui generis institutional setting of the EU – a fragmented system in constant flux – and the roles of the Regional Sea Commissions, Member States and other stakeholders. This, together with Wallace's concept of the swinging pendulum of governance, provides us with the basis to identify the conditions for more effective and legitimate EU marine governance arrangements and examine whether it is possible to turn the tide of marine governance to the level of the regional sea? Using concepts from institutional theory, such as institutional ambiguity, institutional layering and conversion and institutional capacity building, this paper develops six building blocks that could help to turn the tide, help to develop legitimate regional-level marine governance arrangements and strengthen the capacity of marine institutions and governance.
Monitoring and evaluation of spatially managed areas: A generic framework for implementation of ecoystem based marine management and its application
Stelzenmueller, V. ; Breen, P. ; Stamford, T. ; Dankers, N.M.J.A. ; Jak, R.G. ; Hofstede, R. ter - \ 2013
Marine Policy 37 (2013). - ISSN 0308-597X - p. 149 - 164.
sea use management - fisheries management - methodological approach - offshore waters - indicators - conservation - uncertainty - habitats - objectives - strategies
This study introduces a framework for the monitoring and evaluation of spatially managed areas (SMAs), which is currently being tested by nine European case studies. The framework provides guidance on the selection, mapping, and assessment of ecosystem components and human pressures, the evaluation of management effectiveness and potential adaptations to management. Moreover, it provides a structured approach with advice on spatially explicit tools for practical tasks like the assessment of cumulative impacts of human pressures or pressure-state relationships. The case studies revealed emerging challenges, such as the lack of operational objectives within SMAs, particularly for transnational cases, data access, and stakeholder involvement. Furthermore, the emerging challenges of integrating the framework assessment using scientific information with a structured governance research analysis based mainly on qualitative information are addressed. The lessons learned will provide a better insight into the full range of methods and approaches required to support the implementation of the ecosystem approach to marine spatial management in Europe and elsewhere.
Editorial: Global in scope and regionally rich: an IndiSeas workshop helps shape the future of marine ecosystem indicators
Shin, Y.J. ; Bundy, A. ; Piet, G.J. - \ 2012
Reviews in Fish Biology and Fisheries 22 (2012)3. - ISSN 0960-3166 - p. 835 - 845.
size-based indicators - cusum control charts - to-end models - fisheries management - community structure - ecological status - climate-change - fuzzy-logic - food webs - catch
This report summarizes the outcomes of an IndiSeas workshop aimed at using ecosystem indicators to evaluate the status of the world’s exploited marine ecosystems in support of an ecosystem approach to fisheries, and global policy drivers such as the 2020 targets of the Convention on Biological Diversity. Key issues covered relate to the selection and integration of multi-disciplinary indicators, including climate, biodiversity and human dimension indicators, and to the development of data- and model-based methods to test the performance of ecosystem indicators in providing support for fisheries management. To enhance the robustness of our cross-system comparison, unprecedented effort was put in gathering regional experts from developed and developing countries, working together on multi-institutional survey datasets, and using the most up-to-date ecosystem models.
Permeable Boundries: Outsiders and Acces to Fishing Grounds in the Berau Marine Protected Ares
Gunawan, B. ; Visser, L.E. - \ 2012
Anthropological Forum : a journal of social anthropology and comparative sociology 22 (2012)1. - ISSN 0066-4677 - p. 187 - 202.
fisheries management
The designation of Marine Protected Areas (MPAs) in Indonesia has been accelerated over the past two decades in line with international biodiversity conservation commitments and to secure a basis for decentralised fisheries resources management. The Berau MPA of northeast Kalimantan is one of them. This paper shows how the establishment of the park boundaries and zoning affects local fishers' livelihoods. Particular attention is paid to the position of outsider fishers or andon, who have a legal right to access the resource rich fishing grounds. Decentralised district government legitimises outsider fisheries activities because andon fishing permits bring in fees as a contribution to the regional income (PAD or pendapatan asli daerah), while international environmental organisations and local fishers regard the outsider fishers as illegitimately entering the MPA to access resources they regard as their own. Thus, MPA boundaries appear to be highly permeable, with both local fishers and environmental NGOs seeing the presence of andon as illegitimate and illicit, despite being legal.
The durability of private sector-led marine conservation: A case study of two entrepreneurial marine protected areas in Indonesia
Bottema, M.J.M. ; Bush, S.R. - \ 2012
Ocean & Coastal Management 61 (2012). - ISSN 0964-5691 - p. 38 - 48.
coral-reef management - fisheries management - community - displacement - philippines - environment - governance - resources - sociology - reserves
This paper investigates the durability of entrepreneurial marine protected areas (EMPAs) by exploring the role of the private sector in marine conservation. Set within a wider set of social science questions around the marine protected areas as negotiated interventions, we focus on whether and how tourism entrepreneurs can instill a long-term vision for marine conservation, funding and management, thereby overcoming commonly cited implementation and enforcement failures in state-led marine parks. The analysis is based on an empirical comparison of the Yayasan Karang Lestari coral restoration project in Pemuteran on the Northwest coast of Bali, and the marine tourism park around the island of Gili Trawangan off the west coast of Lombok in Indonesia. Our results show that the private sector is able to increase awareness of conservation amongst tourists and coastal communities, provide new income alternatives, and provide financial capacity to support marine conservation activities. It does not, however, appear to have the capacity to create durable, institutionalised arrangements without state support. These findings feed into a wider discussion on the formation of EMPAs, the role of alternative organisational structures and technologies in facilitating change in coastal areas, and how traditionally economic concepts such as entrepreneurship can contribute to a wider understanding of marine conservation governance.
The tower of Babel: Different perceptions and controversies on change and status of North Sea fish stocks in multi-stakeholder settings
Verweij, M.C. ; Densen, W.L.T. van; Mol, A.P.J. - \ 2010
Marine Policy 34 (2010)3. - ISSN 0308-597X - p. 522 - 533.
fisheries management - mixed fisheries - information - knowledge - anecdotes - advice - risk
Fishermen, scientists, national policy makers, and staff of environmental NGOs (ENGOs) hold different perceptions about temporal patterns in fish stocks. Perception differences are problematic in multi-stakeholder settings, because they elicit controversies and unbalanced disputes. These hinder effective participation, a prerequisite for ‘good governance’ and effective management of sustainable fisheries. This study shows that perceptions of change (‘does the stock increase or decrease?’) and of current status of a fish stock (‘is it doing well or not?’) are influenced by the capturing and processing of information, rather than by interests alone. We focused on the Dutch North Sea fishery on plaice and sole and examined (1) availability and accessibility of information on temporal patterns of these stocks and (2) perception differences between all parties. A first explanation for these differences is the use of different parameters as a measure for stock size. Fishermen focus on catch rates or catch-per-unit-effort (relative stock size), whereas scientists, policy makers, and ENGO-staff mainly use scientific assessments of spawning stock biomass (absolute stock size). Between-group perception differences are further explained by spatial aggregation levels of information, lengths of time series evaluated, and by modes of comparison to qualify the current status of fish stocks. Awareness of information differences and the development of shared information use and processing may release some of the tensions in multi-stakeholder settings debating fisheries management. However, comprehension problems amongst all parties on how spawning stock biomass is reconstructed and how it relates to catch rates in the fishery may pose an enduring barrier
Co-management: an alternative to enforcement?
Hoof, L.J.W. van - \ 2010
ICES Journal of Marine Science 67 (2010). - ISSN 1054-3139 - p. 395 - 401.
fisheries management - user participation - lessons - governance - framework
The decline in fish stocks worldwide has often been attributed to problems inherent with resources being treated as common property. Government is usually called upon to define and implement solutions, but the issues society face today cannot be dealt with by the classical, state-centred system of the industrial society. In this article, the Dutch case of fisheries management is used to demonstrate how a government-orientated solution, such as the recently inaugurated EU Community Fisheries Control Agency, and a governance-type solution, such as co-management, relate to each other and whether a partnership between government and the market, such as co-management, can serve as an alternative to direct government enforcement. Although the Dutch case is not a true-bred form of co-management, but rather a case of co-enforcement, it can be used to service a theoretical assessment of the possibilities of co-enforcement at a European scale.
Selecting MPAs to conserve ground fish biodiversity: the consequences of failing to account for catchability in survey trawls
Fraser, H.M. ; Greenstreet, S.P.R. ; Piet, G.J. - \ 2009
ICES Journal of Marine Science 66 (2009)1. - ISSN 1054-3139 - p. 82 - 89.
marine protected areas - north-sea fish - fisheries management - community structure - ecosystem approach - species-diversity - adjacent fishery - reef fishes - long-term - reserves
Fishing has affected North Sea ground fish species diversity. De. ning Marine Protected Areas (MPAs) to address this will rely on ground fish surveys. Species-specific catch efficiencies vary between trawl gears, and apparent species diversity distributions are influenced by the type of gear used in each survey. It may be that no single survey depicts actual diversity distributions. Two MPA scenarios designed to protect ground fish species diversity are described, the first based on unadjusted International Bottom Trawl Survey data and the second based on the same data adjusted to take account of catchability. Spatial overlap between these scenarios is low. Assuming that the adjusted data best describe the actual species diversity distribution, the level of diversity safeguarded by MPAs, based on unadjusted data, is determined. A fishing effort redistribution model is used to estimate the increase in fishing activity that is likely to occur in MPAs that take catchability into account, if closed areas based solely on the unadjusted ground fish data were implemented. Our results highlight the need to take survey-gear catchability into account when designating MPAs to address fish-species diversity issues
Comprehensive discard reconstruction and abundance estimation using flexible selectivity functions
Aarts, G.M. ; Poos, J.J. - \ 2009
ICES Journal of Marine Science 66 (2009)4. - ISSN 1054-3139 - p. 763 - 771.
north-sea plaice - pleuronectes-platessa - fisheries management - stock assessment - mixed fisheries - beam-trawl - age data - catch - survival - flatfish
The additional mortality caused by discarding may hamper the sustainable use of marine resources, especially if it is not accounted for in stock assessment and fisheries management. Generally, long and precise time-series on age-structured landings exist, but historical discard estimates are often lacking or imprecise. The flatfish fishery in the North Sea is a mixed fishery targeting mainly sole and plaice. Owing to the gear characteristics and a minimum landing size for these species, considerable discarding occurs, especially for juvenile plaice. Discard samples collected by on-board observers are available since 1999 from a limited number of commercial fishing trips. Here, we develop a statistical catch-at-age model with flexible selectivity functions to reconstruct historical discards and estimate stock abundance. We do not rely on simple predefined selectivity ogives, but use spline smoothers to capture the unknown non-linear selectivity and discard patterns, and allow these to vary in time. The model is fitted to the age-structured landings, discards, and survey data, the most appropriate model is selected, and estimates of uncertainty are obtained
Check title to add to marked list
<< previous | next >>

Show 20 50 100 records per page

 
Please log in to use this service. Login as Wageningen University & Research user or guest user in upper right hand corner of this page.