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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Response of benthic fauna to experimental bottom fishing : A global meta-analysis
Sciberras, Marija ; Hiddink, Jan Geert ; Jennings, Simon ; Szostek, Claire L. ; Hughes, Kathryn M. ; Kneafsey, Brian ; Clarke, Leo J. ; Ellis, Nick ; Rijnsdorp, Adriaan D. ; Mcconnaughey, Robert A. ; Hilborn, Ray ; Collie, Jeremy S. ; Pitcher, C.R. ; Amoroso, Ricardo O. ; Parma, Ana M. ; Suuronen, Petri ; Kaiser, Michel J. - \ 2018
Fish and Fisheries 19 (2018)4. - ISSN 1467-2960 - p. 698 - 715.
Dredging - Effects of trawling - Fishing impacts - Invertebrate communities - Systematic review - Taxonomic analysis
Bottom-contact fishing gears are globally the most widespread anthropogenic sources of direct disturbance to the seabed and associated biota. Managing these fishing disturbances requires quantification of gear impacts on biota and the rate of recovery following disturbance. We undertook a systematic review and meta-analysis of 122 experiments on the effects-of-bottom fishing to quantify the removal of benthos in the path of the fishing gear and to estimate rates of recovery following disturbance. A gear pass reduced benthic invertebrate abundance by 26% and species richness by 19%. The effect was strongly gear-specific, with gears that penetrate deeper into the sediment having a significantly larger impact than those that penetrate less. Sediment composition (% mud and presence of biogenic habitat) and the history of fishing disturbance prior to an experimental fishing event were also important predictors of depletion, with communities in areas that were not previously fished, predominantly muddy or biogenic habitats being more strongly affected by fishing. Sessile and low mobility biota with longer life-spans such as sponges, soft corals and bivalves took much longer to recover after fishing (>3 year) than mobile biota with shorter life-spans such as polychaetes and malacostracans (<1 year). This meta-analysis provides insights into the dynamics of recovery. Our estimates of depletion along with estimates of recovery rates and large-scale, high-resolution maps of fishing frequency and habitat will support more rigorous assessment of the environmental impacts of bottom-contact gears, thus supporting better informed choices in trade-offs between environmental impacts and fish production.
Effect of the NU-AGE Diet on Cognitive Functioning in Older Adults : A Randomized Controlled Trial
Marseglia, Anna ; Xu, W. ; Fratiglioni, Laura ; Fabbri, Cristina ; Berendsen, A.M. ; Bialecka-Debek, Agata ; Jennings, A. ; Gillings, Rachel ; Meunier, N. ; Caumon, E. ; Fairweather-Tait, S. ; Pietruszka, B. ; Groot, C.P.G.M. de; Santoro, A. ; Franceschi, Claudio - \ 2018
Frontiers in Physiology 9 (2018). - ISSN 1664-042X
Background: Findings from animal and epidemiological research support the potential neuroprotective benefits from healthy diets. However, to establish diet-neuroprotective causal relations, evidence from dietary intervention studies is needed. NU-AGE is the first multicenter intervention assessing whether a diet targeting health in aging can counteract the age-related physiological changes in different organs, including the brain. In this study, we specifically investigated the effects of NU-AGE’s dietary intervention on age-related cognitive decline.
Materials and Methods: NU-AGE randomized trial (NCT01754012, included 1279 relatively healthy older-adults, aged 65–79 years, from five European centers. Participants were randomly allocated into two groups: “control” (n = 638), following a habitual diet; and, “intervention” (n = 641), given individually tailored dietary advice (NU-AGE diet). Adherence to the NU-AGE diet was measured over follow-up, and categorized into tertiles (low, moderate, high). Cognitive function was ascertained at baseline and at 1-year follow-up with the Consortium to Establish a Registry for Alzheimer’s Disease (CERAD)-Neuropsychological Battery and five additional domain-specific single cognitive tests. The raw scores from the CERAD subtests [excluding the Mini-Mental State Examination (MMSE)] and the single tests were standardized into Z-scores. Global cognition (measured with MMSE and CERAD-total score), and five cognitive domains (perceptual speed, executive function, episodic
memory, verbal abilities, and constructional praxis) were created. Cognitive changes as a function of the intervention were analyzed with multivariable mixed-effects models.
Results: After the 1-year follow-up, 571 (89.1%) controls and 573 (89.8%) from
the intervention group participated in the post-intervention assessment. Both control and intervention groups showed improvements in global cognition and in all cognitive domains after 1 year, but differences in cognitive changes between the two groups were not statistically significant. However, participants with higher adherence to the NU-AGE diet showed statistically significant improvements in global cognition [b 0.20 (95%CI 0.004, 0.39), p-value = 0.046] and episodic memory [b 0.15 (95%CI 0.02, 0.28), p-value = 0.025] after 1 year, compared to those adults with lower adherence.
Discussion: High adherence to the culturally adapted, individually tailored, NU-AGE diet could slow down age-related cognitive decline, helping to prevent cognitive impairment and dementia.
Acoustic dose-behavioral response relationship in sea bass (Dicentrarchus labrax) exposed to playbacks of pile driving sounds
Kastelein, Ronald A. ; Jennings, Nancy ; Kommeren, Aimée ; Helder-Hoek, Lean ; Schop, Jessica - \ 2017
Marine Environmental Research 130 (2017). - ISSN 0141-1136 - p. 315 - 324.
Acoustics - Behavior - Marine fish - Offshore industry - Pile driving - Sea bass - Startle response - Wind park

The foundations of offshore wind turbines are attached to the sea bed by percussion pile driving. Pile driving sounds may affect the behavior of fish. Acoustic dose-behavioral response relationships were determined for sea bass in a pool exposed for 20 min to pile driving sounds at seven mean received root-mean-square sound pressure levels [SPLrms; range: 130-166 dB re 1 μPa; single strike sound exposure level (SELss) range: 122-158; 6 dB steps]. Initial responses (sudden, short-lived changes in swimming speed and direction) and sustained responses (changes in school cohesion, swimming depth, and speed) were quantified. The 50% initial response threshold occurred at an SELss of 131 dB re 1 μPa2 s for 31 cm fish and 141 dB re 1 μPa2 s for 44 cm fish; the small fish thus reacted to lower SELss than the large fish. Analysis showed that there is no evidence, even at the highest sound level, for any consistent sustained response to sound exposure by the study animals. If wild sea bass are exposed to pile driving sounds at the levels used in the present study, there are unlikely to be any adverse effects on their ecology, because the initial responses after the onset of the piling sound observed in this study were short-lived.

Global analysis of depletion and recovery of seabed biota after bottom trawling disturbance
Hiddink, Jan Geert ; Jennings, Simon ; Sciberras, Marija ; Szostek, Claire L. ; Hughes, Kathryn M. ; Ellis, Nick ; Rijnsdorp, Adriaan D. ; Mcconnaughey, Robert A. ; Mazor, Tessa ; Hilborn, Ray ; Collie, Jeremy S. ; Pitcher, C.R. ; Amoroso, Ricardo O. ; Parma, Ana M. ; Suuronen, Petri ; Kaiser, Michel J. - \ 2017
Proceedings of the National Academy of Sciences of the United States of America 114 (2017)31. - ISSN 0027-8424 - p. 8301 - 8306.
logistic recovery model - systematic review - metaanalysis - impacts - trawling
Bottom trawling is the most widespread human activity affecting seabed habitats. Here, we collate all available data for experimental and comparative studies of trawling impacts on whole communities of seabed macroinvertebrates on sedimentary habitats and develop widely applicable methods to estimate depletion and recovery rates of biota after trawling. Depletion of biota and trawl penetration into the seabed are highly correlated. Otter trawls caused the least depletion, removing 6% of biota per pass and penetrating the seabed on average down to 2.4 cm, whereas hydraulic dredges caused the most depletion, removing 41% of biota and penetrating the seabed on average 16.1 cm. Median recovery times posttrawling (from 50 to 95% of unimpacted biomass) ranged between 1.9 and 6.4 y. By accounting for the effects of penetration depth, environmental variation, and uncertainty, the models explained much of the variability of depletion and recovery estimates from single studies. Coupled with
large-scale, high-resolution maps of trawling frequency and habitat, our estimates of depletion and recovery rates enable the assessment of trawling impacts on unprecedented spatial scales.
Effect Of The NU-AGE Individually Tailored Diet On Cognitive Function: A Randomized Control Trial
Marseglia, Anna ; Xu, Weili ; Santoro, A. ; Scurti, M. ; Berendsen, A.M. ; Pietruszka, B. ; Jennings, A. ; Meunier, N. ; Caumon, E. ; Fairweather-Tait, S. ; Brzozowska, A. ; Groot, C.P.G.M. de; Franceschi, C. - \ 2017
Corrigendum to : Modelling marine community responses to climate-driven species redistribution to guide monitoring and adaptive ecosystem-based management (Global Change Biology, (2016), 22, 7, (2462-2474), 10.1111/gcb.13285)
Marzloff, Martin Pierre ; Melbourne-Thomas, Jessica ; Hamon, Katell G. ; Hoshino, Eriko ; Jennings, Sarah ; Putten, Ingrid E. van; Pecl, Gretta T. - \ 2017
Global Change Biology 23 (2017)3. - ISSN 1354-1013 - p. 1360 - 1360.

This article was published in GCB (2016/22:2462–2474). The authors of the paper ‘Modelling marine community responses to climate-driven species redistribution to guide monitoring and adaptive ecosystem-based management’ would like to inform readers that the R code supplied as online Supporting Information (SI2), includes an error that affects the colour scaling of the response signs of model variables to long-term perturbations, as shown in Figures 4 and 5. Specifically, in both the figures, a greater proportion of predicted responses ought to be interpreted as ‘ambiguous’ (shown in grey). The overall message of the paper and the general interpretation of the results remain unchanged, as only the visualisation of predicting ambiguity is affected by this error and not the direction and overall patterns of predicted model responses. The authors would like to apologize for the erroneous R code, and for any confusion it may have caused.

Estimating the sustainability of towed fishing-gear impacts on seabed habitats: a simple quantitative risk assessment method applicable to data-limited fisheries
Pitcher, C.R. ; Ellis, Nick ; Jennings, Simon ; Hiddink, Jan G. ; Mazor, Tessa ; Kaiser, Michel J. ; Kangas, Mervi I. ; Mcconnaughey, Robert A. ; Parma, Ana M. ; Rijnsdorp, Adriaan D. ; Suuronen, Petri ; Collie, Jeremy S. ; Amoroso, Ricardo ; Hughes, Kathryn M. ; Hilborn, Ray ; Freckleton, Robert - \ 2017
Methods in Ecology and Evolution 8 (2017). - ISSN 2041-210X - p. 472 - 480.
benthic fauna - depletion - ecological risk assessment - ecoystem-based fishery management - effects of trawling - recovery - resilience - sensivity - trawl footprints - vulnerability indicators
1. Impacts of bottom fishing, particularly trawling and dredging, on seabed (benthic) habitats are commonly perceived to pose serious environmental risks. Quantitative ecological risk assessment can be used to evaluate actual risks and to help guide the choice of management measures needed to meet sustainability objectives. 2. We develop and apply a quantitative method for assessing the risks to benthic habitats by towed bottom-fishing gears. The meth od is based on a simple eq uation for relative benthic status (RBS), derived by solving the logistic population growth equation for the equilibrium state. Estimating RBS requires only maps of fishing intensity and habitat type – and parameters for impact and recovery rates, which may be taken from meta-analyses of multiple experimental studies of towed-gear impacts. The aggregate status of habitats in an assessed region is indicated by the distribution of RBS values for the region. The application of RBS is illustrated for a tropical shrimp-trawl fishery. 3. The status of trawled habitats and their RBS value depend on impact rate (depletion per trawl), recovery rate and exposure to tra wling. In the shrimp-trawl fishery region, gravel habitat was most sensitive, and though less exposed than sand or mudd y-sand, was most affected overall (regional RBS = 91% relative to un-trawled RBS = 100%). Muddy-sand was less sensitive, and though relatively most exposed, was less affected overall (RBS = 95%). Sand was most heavily trawled but least sensitive and least affected overall (RBS = 98%). Region-wide , >94% of habitat area had >80% RBS because most tra wling and impacts were confined to small areas. RBS was also applied to the region’s benthic invertebrate communities with similar results. 4. Conclu sions. Unlike qualitative or categorical trait-based risk assessments, the RBS method provides a quantitative estimate of status relative to an unimpacted baseline, with minimal requireme nts for input data. It could be applied to bottom-contact fish erie s world-wide, including situations where detailed data on characteristics of seabed habitats, or the abundance of seabed fauna are not available. The approach supports assessment against sustainability criteria and evaluation of alternative management strategies (e.g. closed areas, effort management, gear modifications).
Indirect effects of bottom fishing on the productivity of marine fish
Collie, Jeremy ; Hiddink, Jan Geert ; Kooten, Tobias van; Rijnsdorp, Adriaan D. ; Kaiser, Michel J. ; Jennings, Simon ; Hilborn, Ray - \ 2017
Fish and Fisheries 18 (2017)4. - ISSN 1467-2960 - p. 619 - 637.
Beam trawls - Benthic disturbance - Dredges - Fish yield - Otter trawl
One quarter of marine fish production is caught with bottom trawls and dredges on continental shelves around the world. Towed bottom-fishing gears typically kill 20-50 per cent of the benthic invertebrates in their path, depending on gear type, substrate and vulnerability of particular taxa. Particularly vulnerable are epifaunal species, which stabilize the sediment and provide habitat for benthic invertebrates. To identify the habitats, fisheries or target species most likely to be affected, we review evidence of the indirect effects of bottom fishing on fish production. Recent studies have found differences in the diets of certain species in relation to bottom fishing intensity, thereby linking demersal fish to their benthic habitats at spatial scales of ~10 km. Bottom fishing affects diet composition and prey quality rather than the amount of prey consumed; scavenging of discarded by-catch makes only a small contribution to yearly food intake. Flatfish may benefit from light trawling levels on sandy seabeds, while higher-intensity trawling on more vulnerable habitats has a negative effect. Models suggest that reduction in the carrying capacity of habitats by bottom fishing could lead to lower equilibrium yield and a lower level of fishing mortality to obtain maximum yield. Trawling effort is patchily distributed - small fractions of fishing grounds are heavily fished, while large fractions are lightly fished or unfished. This patchiness, coupled with the foraging behaviour of demersal fish, may mitigate the indirect effects of bottom fishing on fish productivity. Current research attempts to scale up these localized effects to the population level.
Modelling marine community responses to climate-driven species redistribution to guide monitoring and adaptive ecosystem-based management
Marzloff, Martin Pierre ; Melbourne-Thomas, Jessica ; Hamon, Katell G. ; Hoshino, Eriko ; Jennings, Sarah ; Putten, Ingrid E. Van; Pecl, Gretta T. - \ 2016
Global Change Biology 22 (2016)7. - ISSN 1354-1013 - p. 2462 - 2474.
As a consequence of global climate-driven changes, marine ecosystems are experiencing polewards redistributions of species – or range shifts – across taxa and throughout latitudes worldwide. Research on these range shifts largely focuses on understanding and predicting changes in the distribution of individual species. The ecological effects of marine range shifts on ecosystem structure and functioning, as well as human coastal communities, can be large, yet remain difficult to anticipate and manage. Here, we use qualitative modelling of system feedback to understand the cumulative impacts of multiple species shifts in south-eastern Australia, a global hotspot for ocean warming. We identify range-shifting species that can induce trophic cascades and affect ecosystem dynamics and productivity, and evaluate the potential effectiveness of alternative management interventions to mitigate these impacts. Our results suggest that the negative ecological impacts of multiple simultaneous range shifts generally add up. Thus, implementing whole-of-ecosystem management strategies and regular monitoring of range-shifting species of ecological concern are necessary to effectively intervene against undesirable consequences of marine range shifts at the regional scale. Our study illustrates how modelling system feedback with only limited qualitative information about ecosystem structure and range-shifting species can predict ecological consequences of multiple co-occurring range shifts, guide ecosystem-based adaptation to climate change and help prioritise future research and monitoring.
Prioritization of knowledge-needs to achieve best practices for bottom trawling in relation to seabed habitats
Kaiser, M. ; Hilborn, Ray ; Jennings, Simon ; Rijnsdorp, A.D. - \ 2016
Fish and Fisheries 17 (2016)3. - ISSN 1467-2960 - p. 637 - 663.
Best practices - trawl fisheries
Management and technical approaches that achieve a sustainable level of fish production while at the same time minimizing or limiting the wider ecological effects caused through fishing gear contact with the seabed might be considered to be ‘best practice’. To identify future knowledge-needs that would help to support a transition towards the adoption of best practices for trawling, a prioritization exercise was undertaken with a group of 39 practitioners from the seafood industry and management, and 13 research scientists who have an active research interest in bottom-trawl and dredge fisheries. A list of 108 knowledge-needs related to trawl and dredge fisheries was developed in conjunction with an ‘expert task force’. The long list was further refined through a three stage process of voting and scoring, including discussions of each knowledge-need. The top 25 knowledge-needs are presented, as scored separately by practitioners and scientists. There was considerable consistency in the priorities identified by these two groups. The top priority knowledge-need to improve current understanding on the distribution and extent of different habitat types also reinforced the concomitant need for the provision and access to data on the spatial and temporal distribution of all forms of towed bottom-fishing activities. Many of the other top 25 knowledge-needs concerned the
evaluation of different management approaches or implementation of different fishing practices, particularly those that explore trade-offs between effects of bottom trawling on biodiversity and ecosystem services and the benefits of fish production as food
Similar effects of bottom trawling and natural disturbance on composition and function of benthic communities across habitats
Denderen, Daniel van; Bolam, Stefan G. ; Hiddink, Jan Geert ; Jennings, Simon ; Kenny, Andrew ; Rijnsdorp, Adriaan D. ; Kooten, Tobias Van - \ 2015
Marine Ecology Progress Series 541 (2015). - ISSN 0171-8630 - p. 31 - 43.
Beam trawling - Bed shear stress - Benthic community - Biological trait approach - Bottom trawling - Disturbance - Ecosystem function - Otter trawling

Bottom trawl fishing has widespread impacts on benthic habitats and communities. The benthic response to trawling seems to be smaller or absent in areas exposed to high natural disturbance, leading to the hypothesis that natural and trawl disturbance affect benthic communities in a similar way. However, systematic tests of this hypothesis at large spatial scales and with data from sites spanning a large range of natural disturbance do not exist. Here, we examine the effects of trawl and natural (tidal-bed shear stress) disturbance on benthic communities over gradients of commercial bottom trawling effort in 8 areas in the North and Irish Seas. Using a traitbased approach, that classified species by life-history strategies or by characteristics that provide a proxy for their role in community function, we found support for the hypothesis that trawl and natural disturbance affect benthic communities in similar ways. Both sources of disturbance caused declines in long-living, hard-bodied (exoskeleton) and suspension-feeding organisms. Given these similar impacts, there was no detectable trawling effect on communities exposed to high natural disturbance. Conversely, in 3 out of 5 areas with low bed shear stress, responses to trawling were detected and resulted in community compositions comparable with those in areas subject to high natural disturbance, with communities being composed of either small-sized, deposit-feeding animals or mobile scavengers and predators. The findings highlight that knowledge of the interacting effects of trawl and natural disturbance will help to identify areas that are more or less resilient to trawling and support the development of management plans that account for the environmental effects of fishing.

Investigating the effects of mobile bottom fishing on benthic biota: a systematic review protocol
Hughes, K.M. ; Kaiser, M.J. ; Jennings, S. ; Rijnsdorp, A.D. - \ 2014
Environmental Evidence 3 (2014). - ISSN 2047-2382 - 20 p.
Background Mobile bottom fishing, such as trawling and dredging, is the most widespread direct human impact on marine benthic systems. Knowledge of the impacts of different gear types on different habitats, the species most sensitive to impacts and the potential for habitats to recover are often needed to inform implementation of an ecosystem approach to fisheries and strategies for biodiversity conservation. This knowledge helps to identify management options that maximise fisheries yield whilst minimising negative impacts on benthic systems. Methods The methods are designed to identify and collate evidence from experimental studies (e.g. before/after, control/impact) and comparative studies (spanning a gradient of fishing intensity) to identify changes in state (numbers, biomass, diversity etc.) of benthic biota (flora and fauna), resulting from a variety of mobile bottom fishing scenarios. The primary research question that the outputs will be used to address is: "to what extent does a given intensity of bottom fishing affect the abundance and/or diversity of benthic biota?" Due to the variety of gear and habitat types studied, the primary question will be closely linked with secondary questions. These include: "how does the effect of bottom fishing on various benthic biota metrics (species, faunal type, trait, taxon etc.) vary with (1) gear type and (2) habitat, and (3) gear type-habitat interactions?" and (4) "how might properties of the community and environment affect the resilience (and recovery potential) of a community to bottom fishing?"
Nouvelles strategies alimentaires pour un vieillissement optimisé des seniors européens – Projet européen FP7 NU-AGE
Meunier, N. ; Caumon, E. ; Lyon, N. ; Caille, A. ; Berendsen, A.M. ; Groot, C.P.G.M. de; Feskens, E.J.M. ; Santoro, A. ; Franceschi, C. ; Pietruszka, B. ; Brzozowska, A.M. ; Jennings, A. ; Fairweather-Tait, S. ; Cano, N. - \ 2014
Evaluating targets and trade-offs among fisheries and conservation objectives using a multispecies size spectrum model
Blanchard, J.L. ; Andersen, K.H. ; Scott, F. ; Hintzen, N.T. ; Piet, G.J. ; Jennings, S. - \ 2014
Journal of Applied Ecology 51 (2014)3. - ISSN 0021-8901 - p. 612 - 622.
large fish indicator - north-sea - ecosystem models - marine ecosystems - trophic cascades - celtic sea - community - management - abundance - climate
Marine environmental management policies seek to ensure that fishing impacts on fished populations and other components of the ecosystem are sustainable, to simultaneously meet objectives for fisheries and conservation. For example, in Europe, targets for (i) biodiversity, (ii) food web structure as indicated by the proportion of large fish and (iii) fishing mortality rates for exploited species that lead to maximum sustainable yield, F-MSY,F- are being proposed to support implementation of the Marine Strategy Framework Directive. Efforts to reconcile any trade-offs among objectives need to be informed by knowledge on the consequences of alternate management actions. We develop, calibrate and apply a multispecies size spectrum model of the North Sea fish community to assess the response of populations and the community to fishing. The model predicts species' size distributions, abundance, productivity and interactions and therefore provides a single framework for evaluating trade-offs between population status, community and food web structure, biodiversity and fisheries yield. We show that the model can replicate realistic fish population and community structure and past responses to fishing. We assess whether meeting management targets for exploited North Sea populations (fishing species at F-MSY) will be sufficient to meet proposed targets for biodiversity and food web indicators under two management scenarios (status quo and F-MSY). The recovery in biodiversity indicators is 60% greater when fishing populations at F-MSY than if status quo (2010) fishing rates are maintained. The probability of achieving a food web target was 60% under both scenarios in spite of major community restructuring revealed by other indicators of community size structure. Synthesis and applications. Our model can be applied to evaluate indicator targets and trade-offs among fisheries and conservation objectives. There is a significant probability that reductions in fishing mortality below F-MSY would be needed in Europe if managers make a binding commitment to a proposed large fish indicator target, with concomitant reductions in fisheries yield.
Implications of using alternative methods of vessel monitoring system (VMS) data analysis to describe fishing activities and impacts
Lambert, G.I. ; Jennings, S. ; Hiddink, J.G. ; Hintzen, N.T. ; Hinz, H. ; Kaiser, M.J. ; Murray, L.G. - \ 2012
ICES Journal of Marine Science 69 (2012)4. - ISSN 1054-3139 - p. 682 - 693.
trawl disturbance - benthic communities - different habitats - scale - sea - regression - abundance - patterns - biomass - size
Understanding the spatial distribution and intensity of fishing activity is a prerequisite for estimating fishing impacts on seabed biota and habitats. Vessel monitoring system data provide information on fishing activity at large spatial scales. However, successive position records can be too infrequent to describe the complex movements fishing vessels make. High-frequency position data were collected to evaluate how polling frequency and the method of analysis influenced the estimates of fishing impact on the seabed and associated epifaunal communities. Comparisons of known positions with predictions from track interpolation revealed that the performance of interpolation depended on fleet behaviour. Descriptions and indicators of fishing intensity were influenced significantly by the analytical methods (track reconstruction, density of position records) and grid-cell resolution used for the analysis. These factors can lead to an underestimation of fishing impact on epifaunal communities. It is necessary to correct for such errors to quantify the effects of fishing on various ecosystem components and hence to inform ecosystem-based management. Polling at intervals of 30 min would provide a desirable compromise between achieving precise estimates of fishing impacts on the seabed and minimizing the cost of data collection and handling.
Comparing government agendas: executive speeches in the Netherlands, United Kingdom, and Denmark
Mortensen, P.B. ; Green-Pedersen, C. ; Breeman, G.E. ; Chaqués Bonafont, L. ; Jennings, W. ; John, P. ; Palau, A. ; Timmermans, A. - \ 2011
Comparative Political Studies 44 (2011)8. - ISSN 0010-4140 - p. 973 - 1000.
political attention - queens speech - policy - parties - competition - programs - states - matter - model - us
At the beginning of each parliamentary session, almost all European governments give a speech in which they present the government’s policy priorities and legislative agenda for the year ahead. Despite the body of literature on governments in European parliamentary democracies, systematic research on these executive policy agendas is surprisingly limited. In this article the authors study the executive policy agendas—measured through the policy content of annual government speeches—over the past 50 years in three Western European countries: the United Kingdom, the Netherlands, and Denmark. Contrary to the expectations derived from the well-established “politics matters” approach, the analyses show that elections and change in partisan color have little effect on the executive issue agendas, except to a limited extent for the United Kingdom. In contrast, the authors demonstrate empirically how the policy agenda of governments responds to changes in public problems, and this affects how political parties define these problems as political issues. In other words, policy responsibility that follows from having government power seems much more important for governments’ issue agendas than the partisan and institutional characteristics of governments
Effects of the core functions of government on the diversity of executive agendas
Jennings, W. ; Bevan, S. ; Timmermans, A. ; Breeman, G.E. ; Brouard, S. ; Chaqués-Bonafont, L. ; Green-Pedersen, C. ; John, P. ; Mortensen, P.B. ; Palau Roque, A. - \ 2011
Comparative Political Studies 44 (2011)8. - ISSN 0010-4140 - p. 1001 - 1030.
political attention - mathematical-theory - public-opinion - policy - communication - punctuations - speech
The distribution of attention across issues is of fundamental importance to the political agenda and outputs of government. This article presents an issue-based theory of the diversity of governing agendas where the core functions of government—defense, international affairs, the economy, government operations, and the rule of law—are prioritized ahead of all other issues. It undertakes comparative analysis of issue diversity of the executive agenda of several European countries and the United States over the postwar period. The results offer strong evidence of the limiting effect of core issues—the economy, government operations, defense, and international affairs—on agenda diversity. This suggests not only that some issues receive more attention than others but also that some issues are attended to only at times when the agenda is more diverse. When core functions of government are high on the agenda, executives pursue a less diverse agenda—focusing the majority of their attention on fewer issues. Some issues are more equal than others in executive agenda setting
Honey, I cooled the cods: Modelling the effect of temperature on the structure of Boreal/Arctic fish ecosystems
Pope, J.G. ; Falk-Pedersen, J. ; Jennings, S. ; Rice, J.C. ; Gislason, H. ; Daan, N. - \ 2009
Deep-Sea Research. Part II, tropical studies in oceanography 56 (2009)21-22. - ISSN 0967-0645 - p. 2097 - 2107.
north-sea cod - gadus-morhua - species-diversity - transient dynamics - predator-prey - marine fish - food webs - coexistence - size - biodiversity
Historically colder regions of the North Atlantic had fisheries dominated by only a few fish species; principally cod and capelin. Possible population dynamic mechanisms that lead to such dominance are investigated by considering how a charmingly simple published multispecies model of the North Sea would react if the system operated at a lower temperature. The existing model equations were modified to describe temperature effects on growth, fecundity and recruitment and the model was rerun based on typical temperatures for the North Sea and a colder system. The results suggest that total fish biomass in the colder system increases but the community is more vulnerable to a given rate of fishing mortality. In the colder system, within species density dependence is reduced but relative predation rates are higher. Consequently, intermediate-sized species are vulnerable to relatively high levels of predation throughout their life history and tend to be excluded, leading to a system dominated by small and large species. The model helps to explain how temperature may govern coexistence and competitive exclusion in fish communities and accounts for the observed dominance of small and large species in Boreal/Arctic ecosystems.
Comparer les productions législatives: enjeux et méthodes
Brouard, S. ; Wilkerson, J. ; Baumgartner, F.R. ; Timmermans, A. ; Bevan, S. ; Breeman, G.E. ; Breunig, C. ; Chaqués, L. ; Green-Pedersen, C. ; Jennings, W. ; John, P. - \ 2009
Revue internationale de politique comparée 16 (2009)3. - ISSN 1370-0731 - p. 381 - 404.
Sur quels enjeux politiques les parlements légifèrent-ils ? Cette interrogation d’apparence anodine n’a que rarement fait l’objet d’une attention soutenue, particulièrement dans une perspective comparée. Pourtant la production des lois constitue l’un des éléments structurants d’une communauté politique et de la compétition démocratique. Dans cet article, notre objectif est à la fois d’étudier la « politique de l’attention » au sein de l’agenda législatif et d’en discuter les défis méthodologiques. De cette perspective, nous proposons l’étude de trois méthodes de comparaison des productions législatives. Enfin nous tirons quelques leçons de ces résultats et esquissons un agenda de recherche. What are the policy issues on which parliaments produce legislation ? This apparently insignificant question has only rarely been studied closely, particularly from a comparative perspective. However, the production of laws is one of the formative elements of a political community and of democratic competition. In this article, our aim is to study the “attention policy” within the legislative agenda and discuss the methodological challenges. From this perspective, we propose to study three methods of comparing legislative production. Finally, we shall draw lessons from these results and prepare a research agenda
Comparer les agendas gouvernementaux: les ‘discours du Trône’ aux Pays-Bas, au Royaume-Uni, au Danemark et en Espagne
Breeman, G.E. ; Chaqués, L. ; Green-Pedersen, C. ; Jennings, W. ; Mortensen, P.B. ; Palau Roque, A. ; Timmermans, A. - \ 2009
Revue internationale de politique comparée 16 (2009)3. - ISSN 1370-0731 - p. 405 - 421.
This article studies the effect of changes of government on the development of government agendas from the “Speeches from the Throne” in the United Kingdom, Spain, the Netherlands and Denmark. In addition to the theory of the mandate, the explanations in terms of political heritage and the intrusion of issues are also tested. Despite their undeniable differences, the four countries studied have very similar dynamics in their executive agendas, which are not greatly affected by changes in government. In addition, over the long term, the economic issue, which has been dominant for a long time, is declining almost simultaneously in the four countries, to the benefit of the intrusion of new issues.
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