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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    Estimating the spatial position of marine mammals based on digital camera recordings
    Hoekendijk, J.P.A. ; Vries, J. de; Bolt, K. van der; Greinert, J. ; Brasseur, S.M.J.M. ; Camphuysen, C.J. ; Aarts, G.M. - \ 2015
    Ecology and Evolution 5 (2015)3. - ISSN 2045-7758 - p. 578 - 589.
    porpoises phocoena-phocoena - harbor porpoises - habitat selection - wadden sea - north-sea - marsdiep - inlet - cetaceans - currents - density
    Estimating the spatial position of organisms is essential to quantify interactions between the organism and the characteristics of its surroundings, for example, predator-prey interactions, habitat selection, and social associations. Because marine mammals spend most of their time under water and may appear at the surface only briefly, determining their exact geographic location can be challenging. Here, we developed a photogrammetric method to accurately estimate the spatial position of marine mammals or birds at the sea surface. Digital recordings containing landscape features with known geographic coordinates can be used to estimate the distance and bearing of each sighting relative to the observation point. The method can correct for frame rotation, estimates pixel size based on the reference points, and can be applied to scenarios with and without a visible horizon. A set of R functions was written to process the images and obtain accurate geographic coordinates for each sighting. The method is applied to estimate the spatiotemporal fine-scale distribution of harbour porpoises in a tidal inlet. Video recordings of harbour porpoises were made from land, using a standard digital single-lens reflex (DSLR) camera, positioned at a height of 9.59m above mean sea level. Porpoises were detected up to a distance of 3136m (mean 596m), with a mean location error of 12m. The method presented here allows for multiple detections of different individuals within a single video frame and for tracking movements of individuals based on repeated sightings. In comparison with traditional methods, this method only requires a digital camera to provide accurate location estimates. It especially has great potential in regions with ample data on local (a)biotic conditions, to help resolve functional mechanisms underlying habitat selection and other behaviors in marine mammals in coastal areas.
    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.
    Offshore wind park monitoring programmes, lessons learned and recommendations for the future
    Lindeboom, H.J. ; Degraer, S. ; Dannheim, J. ; Gill, A.B. ; Wilhelmsson, D. - \ 2015
    Hydrobiologia 756 (2015)1. - ISSN 0018-8158 - p. 169 - 180.
    renewable energy development - north-sea - communities - impacts - benthos - farms - power - biodiversity - assemblages - management
    Over a decade of monitoring offshore wind park environmental impact triggered a reflection on the overall objectives and how to best continue with the monitoring programmes. Essentially, basic monitoring has to be rationalised at the level of the likelihood of impact detection, the meaningfulness of impact size and representativeness of the findings. Targeted monitoring is crucial and should continue to be applied to disentangle processes behind observed impacts, for instance the overarching artificial reef effect caused by wind parks. The major challenge, however, remains to achieve a reliable assessment of the cumulative impacts. A continuous international consultation and collaboration with marine scientists, managers, government officials and industry will be needed to ensure an optimisation of the future monitoring programmes.
    Microplastic in a macro filter feeder: humpback whale Megaptera novaeangliae
    Besseling, E. ; Foekema, E.M. ; Franeker, J.A. van; Leopold, M.F. ; Bravo Rebolledo, E. ; Kühn, S. ; Mielke, L. ; Heberle-Bors, E. ; Ijzer, J. ; Kamminga, P. ; Koelmans, A.A. - \ 2015
    Marine Pollution Bulletin 95 (2015)1. - ISSN 0025-326X - p. 248 - 252.
    marine-environment - plastic ingestion - balaenoptera-physalus - mediterranean sea - north-sea - debris - identification - pollutants - particles - additives
    Marine filter feeders are exposed to microplastic because of their selection of small particles as food source. Baleen whales feed by filtering small particles from large water volumes. Macroplastic was found in baleen whales before. This study is the first to show the presence of microplastic in intestines of a baleen whale (Megaptera novaeangliae). Contents of its gastrointestinal tract were sieved, dissolved in 10% potassium hydroxide and washed. From the remaining dried material, potential synthetic polymer particles were selected based on density and appearance, and analysed by Fourier transform infrared (FTIR) spectroscopy. Several polymer types (polyethylene, polypropylene, polyvinylchloride, polyethylene terephthalate, nylon) were found, in varying particle shapes: sheets, fragments and threads with a size of 1 mm to 17 cm. This diversity in polymer types and particle shapes, can be interpreted as a representation of the varying characteristics of marine plastic and the unselective way of ingestion by M. novaeangliae.
    Short-term impact of deep sand extraction and ecosystem-based landscaping on macrozoobenthos and sediment characteristics
    Jong, M.F. de; Baptist, Martin ; Lindeboom, H.J. ; Hoekstra, P. - \ 2015
    Marine Pollution Bulletin 97 (2015)1-2. - ISSN 0025-326X - p. 294 - 308.
    potential environmental-impact - marine aggregate extraction - eastern english-channel - north-sea - belgian part - large-scale - community structure - gravel extraction - coastal waters - united-kingdom
    We studied short-term changes in macrozoobenthos in a 20 m deep borrow pit. A boxcorer was used to sample macrobenthic infauna and a bottom sledge was used to sample macrobenthic epifauna. Sediment characteristics were determined from the boxcore samples, bed shear stress and near-bed salinity were estimated with a hydrodynamic model. Two years after the cessation of sand extraction, macrozoobenthic biomass increased fivefold in the deepest areas. Species composition changed significantly and white furrow shell (Abra alba) became abundant. Several sediment characteristics also changed significantly in the deepest parts. Macrozoobenthic species composition and biomass significantly correlated with time after cessation of sand extraction, sediment and hydrographical characteristics. Ecosystem-based landscaped sand bars were found to be effective in influencing sediment characteristics and macrozoobenthic assemblage. Significant changes in epifauna occurred in deepest parts in 2012 which coincided with the highest sedimentation rate. We recommend continuing monitoring to investigate medium and long-term impacts.
    New lipid envelop-containing dsDNA virus isolates infecting Micromonas pusilla reveal a separate phylogenetic group.
    Martinez Martinez, J. ; Boere, A. ; Gilg, I. ; Lent, J.W.M. van; Witte, H.J. ; Bleijswijk, J.D.L. van; Brussaard, C.P.D. - \ 2015
    Aquatic Microbial Ecology 74 (2015)1. - ISSN 0948-3055 - p. 17 - 28.
    emiliania-huxleyi - dna viruses - phaeocystis-globosa - coastal waters - algal viruses - north-sea - abundance - prasinophyceae - diversity - dynamics
    Viral infection of phytoplankton has major implications for biochemical and energy cycles, community dynamics, and microbial evolution in the marine environment. The non-bloom forming picoplankter Micromonas pusilla, a significant component of the plankton community worldwide, is known to be susceptible to infection by both dsDNA and dsRNA viruses. Logically, comprehensive knowledge of the ecology of M. pusilla requires a better understanding of the diversity and infection mechanisms of their viruses. Here, we investigated 19 new M. pusilla-specific viruses (MpVs) isolated from different locations and years. We performed partial characterization of those MpVs including structural characteristics, genome size, phylogenetic analysis based on partial DNA polymerase gene sequences, host range, and stability at different temperatures and upon exposure to chloroform. Combined, these characteristics allowed classification of the MpVs into 2 groups. Exposure to chloroform led to loss of infectivity by all MpVs in one group, which suggests the presence of an outer lipid envelope. In addition, all except one of the members in that group formed a monophylogenetic clade that was distinct from all other MpV isolates. The distinctive characteristics of the 2 MpV groups suggest different infection strategies, which may have important implications for the ecology of both host and virus populations in the environment. Knowledge gained from our study adds value to the MpV isolates as a scientific resource as it will aid in developing and testing in the laboratory new hypotheses about the ecological and biogeochemical implications of M. pusilla viral infection in the environment.
    Marine ecosystem services: linking indicators to their classification
    Hattam, C. ; Atkins, J.P. ; Beaumont, N.J. ; Boerger, T. ; Boehnke-Henrichs, A. ; Burdon, D. ; Groot, R.S. de; Hoefnagel, E. ; Nunes, P.A.L.D. ; Piwowarczyk, J. ; Sastre, S. ; Austen, M.C. - \ 2015
    Ecological Indicators 49 (2015). - ISSN 1470-160X - p. 61 - 75.
    macrofauna communities - north-sea - management - valuation - framework - areas - need
    There is a multitude of ecosystem service classifications available within the literature, each with its own advantages and drawbacks. Elements of them have been used to tailor a generic ecosystem service classification for the marine environment and then for a case study site within the North Sea: the Dogger Bank. Indicators for each of the ecosystem services, deemed relevant to the case study site, were identified. Each indicator was then assessed against a set of agreed criteria to ensure its relevance and applicability to environmental management. This paper identifies the need to distinguish between indicators of ecosystem services that are entirely ecological in nature (and largely reveal the potential of an ecosystem to provide ecosystem services), indicators for the ecological processes contributing to the delivery of these services, and indicators of benefits that reveal the realized human use or enjoyment of an ecosystem service. It highlights some of the difficulties faced in selecting meaningful indicators, such as problems of specificity, spatial disconnect and the considerable uncertainty about marine species, habitats and the processes, functions and services they contribute to.
    Testing for sufficient signal resetting during sediment transport using a polymineral multiple-signal luminescence approach.
    Reimann, T. ; Notenboom, P.D. ; Schipper, M.A. De; Wallinga, J. - \ 2015
    Quaternary Geochronology 25 (2015). - ISSN 1871-1014 - p. 26 - 36.
    optically stimulated luminescence - anomalous fading correction - regenerative-dose protocol - ir irsl protocol - single-grains - fluvial deposits - holocene sediments - k-feldspars - north-sea - quartz
    Abstract We present a multiple luminescence signal measurement procedure that simultaneously measures six different luminescence signals from a single polymineral aliquot (i.e. multiple-signal, short MS-SAR approach). The six signals show different bleaching rates in bleaching experiments, ranging from rapid bleaching for the quartz dominated blue stimulated luminescence signal (measured at 125 °C, BSL-125), to the slow-bleaching polymineral thermoluminescence signal. The bleaching rate of the infrared stimulated luminescence (IRSL) measured at room temperature (IR-25) and elevated temperature post-IR IRSL (pIRIR-90, pIRIR-155, pIRIR-225) signals decrease with increasing measurement temperature. Owing to these different bleaching rates, the MS-SAR approach allows inference of the degree of bleaching, and thereby information on the transport history of sediments. We test this approach by applying the MS-SAR to four coastal samples from a well-monitored sand-nourishment site at the Dutch coast. Our results show that the proposed MS-SAR approach can be utilised to construct bleaching plateaus which provide an independent and time-effective measure of the degree of poor bleaching in a sediment sample based on the measurement of only a few large aliquots. We propose that the MS-SAR protocol can be used to profile the age, luminescence properties and degree of bleaching of minimal prepared polymineral. This pre-profiling will allow the selection of suitable samples for full luminescence dating analysis in a target-orientated and time-effective manner.
    Assessing uncertainty associated with the monitoring and evaluation of spatially managed areas
    Stelzenmueller, V. ; Fernandez, T.V. ; Cronin, K. ; Rockmann, C. ; Jak, R.G. ; Hoof, L.J.W. van - \ 2015
    Marine Policy 51 (2015). - ISSN 0308-597X - p. 151 - 162.
    environmental assessment - north-sea - framework - science - implementation - indicators - quality - nusap
    Marine spatial planning (MSP) is advocated to support an ecosystem approach to marine management, as it allows consideration of multiple management objectives including marine conservation. The monitoring and evaluation of both implemented marine plans and the planning process itself is susceptible to various uncertainties. Here, uncertainties related to a stepwise monitoring and evaluation framework for spatially managed areas were characterised and quantified with the help of two modified and developed tools. In particular, Walker-type and pedigree matrices were utilised to assess both the sources and respective relative levels of uncertainty present in the assessment of nine European case studies that conducted a stepwise monitoring and evaluation process applying a common framework. Across the southern and northern European case studies major sources of uncertainty were found in relation to the knowledge base, management scenarios with related objectives and data availability. Although case studies made flexible use of the framework to account for the particularities of the local realms, the revealed pattern of associated uncertainty was highly consistent across the case studies. The scored pedigree matrices showed that the criteria ‘stakeholder engagement’ and ‘cross validation’ had greatest influence on the overall robustness of the case study assessments. The observed distribution of median pedigree scores was within acceptable ranges with respect to simulated possible score distributions. In addition, a sensitivity analysis revealed that the scoring of the pedigree criteria by five or more experts would result in less variable interquartile ranges of respective median scores. In conclusion, the developed complementary tools showed great flexibility in characterising and assessing uncertainty despite context-dependent differences among case studies such as geographical area, quality of available data, level of spatial management implementation or management objectives. Moreover, the obtained findings allow prioritising efforts and future research to support an iterative monitoring and evaluation of marine spatial plans.
    Managing a complex population strucutre exploring the importance of information from fisheries-independent sources
    Hintzen, N.T. ; Roel, B.A. ; Benden, D.P.L.D. ; Clarke, M. ; Egan, A. ; Nash, R.D.M. ; Rohlf, N. ; Hatfield, E.M.C. - \ 2015
    ICES Journal of Marine Science 72 (2015)2. - ISSN 1054-3139 - p. 528 - 542.
    herring clupea-harengus - state-space model - north-sea - stock assessment - spawning components - management advice - british-isles - celtic sea - dynamics - atlantic
    Natural resource managers aim to manage fish stocks at sustainable levels. Often, management of these stocks is based on the results of analytical stock assessments. Accurate catch data, which can be attributed to a specific population unit and reflects the population structure, are needed for these approaches. Often though, the quality of the catch data is compromised when dealing with a complex population structure where fish of different population units mix in a fishery. The herring population units west of the British Isles are prone to mixing. Here, the inability to perfectly allocate the fish caught to the population unit they originate from, due to classification problems, poses problems for management. These mixing proportions are often unknown; therefore, we use simulation modelling combined with management strategy evaluation to evaluate the role fisheries-independent surveys can play in an assessment to provide unbiased results, irrespective of population unit mixing and classification success. We show that failure to account for mixing is one of the major drivers of biased estimates of population abundance, affecting biomass reference points and MSY targets. When mixing of population units occurs, the role a survey can play to provide unbiased assessment results is limited. Either different assessment models should be employed or stock status should be considered from the survey data alone. In addition, correctly classifying the origin of fish is especially important for those population units that are markedly smaller in size than other units in the population complex. Without high classification success rates, smaller population units are extremely vulnerable to overexploitation.
    Benthos distribution modelling and its relevance for marine ecoysystem management
    Reiss, H. ; Birchenough, S.N.R. ; Borja, A. ; Buhl-Mortensen, L. ; Craeymeersch, J.A.M. - \ 2015
    ICES Journal of Marine Science 72 (2015)2. - ISSN 1054-3139 - p. 297 - 315.
    species distribution models - predicting suitable habitat - niche factor-analysis - sea-floor integrity - pseudo-absence data - western baltic sea - climate-change - north-sea - logistic-regression - spatial prediction
    Marine benthic ecosystems are difficult to monitor and assess, which is in contrast to modern ecosystem-based management requiring detailed information at all important ecological and anthropogenic impact levels. Ecosystem management needs to ensure a sustainable exploitation of marine resources as well as the protection of sensitive habitats, taking account of potential multiple-use con¿icts and impacts over large spatial scales. The urgent need for large-scale spatial data on benthic species and communities resulted in an increasing application of distribution modelling (DM). The use of DM techniques enables to employ full spatial coverage data of environmental variables to predict benthic spatial distribution patterns. Especially, statistical DMs have opened new possibilities for ecosystem management applications, since they are straightforward and the outputs are easy to interpret and communicate. Mechanistic modelling techniques, targeting the fundamental niche of species, and Bayesian belief networks are the most promising to further improve DM performance in the marine realm. There are many actual and potential management applications of DMs in the marine benthic environment, these are (i) early warning systems for species invasion and pest control, (ii) to assess distribution probabilities of species to be protected, (iii) uses in monitoring design and spatial management frameworks (e.g. MPA designations), and (iv) establishing long-term ecosystem management measures (accounting for future climate-driven changes in the ecosystem). It is important to acknowledge also the limitations associated with DM applications in a marine management context as well as considering new areas for future DM developments. The knowledge of explanatory variables, for example, setting the basis for DM, will continue to be further developed: this includes both the abiotic (natural and anthropogenic) and the more pressing biotic (e.g. species interactions) aspects of the ecosystem. While the response variables on the other hand are often focused on species presence and some work undertaken on species abundances, it is equally important to consider, e.g. biological traits or benthic ecosystem functions in DM applications. Tools such as DMs are suitable to forecast the possible effects of climate change on benthic species distribution patterns and hence could help to steer present-day ecosystem management.
    Identification and typing of Brucella spp. in stranded harbour porpoises (Phocoena phocoena) on the Dutch coast.
    Maio, E. ; Begeman, L. ; Bisselink, Y.J.W.M. ; Tulden, P.W. van; Wiersma, L. ; Hiemstra, S. ; Ruuls, R. ; Gröne, A. ; Roest, H.I.J. ; Willemsen, P.T.J. ; Giessen, J. van der - \ 2014
    Veterinary Microbiology 173 (2014)1-2. - ISSN 0378-1135 - p. 118 - 124.
    marine mammal brucella - north-sea - adjacent waters - infection - pinnipedialis - ceti - cetaceans - lungworms - emphasis - exposure
    The presence of Brucella (B.) spp. in harbour porpoises stranded between 2008 and 2011 along the Dutch coast was studied. A selection of 265 tissue samples from 112 animals was analysed using conventional and molecular methods. In total, 4.5% (5/112) of the animals corresponding with 2.3% (6/265) Brucella positive tissue samples were Brucella positive by culture and these were all confirmed by real-time polymerase chain reaction (real-time PCR) based on the insertion element 711 (IS711). In addition, two more Brucella-positive tissue samples from two animals collected in 2011 were identified using real-time PCR resulting in an overall Brucella prevalence of 6.3% (7/112 animals). Brucella spp. were obtained from lungs (n=3), pulmonary lymph node (n=3) and lungworms (n=2). Multi Locus Variable Number of Tandem Repeats (VNTR) Analysis (MLVA) typing based on the MLVA-16 showed that the Brucella isolates were B. ceti. Additional in silico Multi Locus Sequence typing (MLST) after whole genome sequencing of the 6 Brucella isolates confirmed B. ceti ST 23. According to the Brucella 2010 MLVA database, the isolated Brucella strains encountered were of five genotypes, in two distinct subclusters divided in two different time periods of harbour porpoises collection. This study is the first population based analyses for Brucella spp. infections in cetaceans stranded along the Dutch coast.
    (Per)chlorate reduction at high temperature: Physiological study of Archaeoglobus fulgidus and potential implications for novel souring mitigation strategies
    Liebensteiner, M. ; Stams, A.J.M. ; Lomans, B.P. - \ 2014
    International Biodeterioration and Biodegradation 96 (2014). - ISSN 0964-8305 - p. 216 - 222.
    sulfide-oxidizing bacteria - sulfate-reducing bacteria - oil-field - nitrate reduction - north-sea - sp-nov. - perchlorate - water - thiosulfate - archaea
    The recent finding that Archaeoglobus fulgidus is able to couple (per)chlorate reduction to growth expanded this trait to the hyperthermophilic range of life. This sulfate-reducing archaeon is considered to be one of the major contributors to souring in hot oil reservoirs. Therefore, it is important to study its physiology in depth, particularly in view of novel souring mitigation strategies. A. fulgidus does not possess the classical (per)chlorate reduction pathway, as it lacks the key enzyme chlorite dismutase. Rather, the microorganism seems to couple (per)chlorate reduction to sulfur metabolism. Growth experiments show the strict necessity of sulfur compounds to sustain perchlorate reduction. Furthermore, the chemical formation of elemental sulfur was observed during perchlorate reduction, a compound that is biologically reduced again. Additional experiments showed that tetrathionate, but not elemental sulfur and polysulfide, serves as an electron acceptor for growth by A. fulgidus. Taken together these results provide further evidence for the importance of chemical and biological redox reactions involving sulfur compounds during (per)chlorate reduction. In non-reduced media also, nitrate could be reduced by A. fulgidus, though not coupled to growth. This observation and the fact that A. fulgidus had prolonged adaptation phases on sulfate after long-lasting growth on perchlorate are of interest in the development of new souring mitigation strategies using nitrate and/or (per)chlorate.
    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.
    Technological Development and Fisheries Management
    Eigaard, O.R. ; Marchal, P. ; Gislason, H. ; Rijnsdorp, A.D. - \ 2014
    Reviews in Fisheries Science & Aquaculture 22 (2014)2. - ISSN 2330-8249 - p. 156 - 174.
    individual transferable quotas - time-varying catchability - fishing power increases - trawl fishery - unit-effort - technical efficiency - demersal fisheries - mixed fisheries - fleet dynamics - north-sea
    Many marine fish stocks are overexploited and considerable overcapacity exists in fishing fleets worldwide. One of the reasons for the imbalance between resource availability and fishing capacity is technological development, which continuously increases the efficiency of the vessels—a mechanism referred to as “technological creep.” We review how the introduction of new and more efficient electronic equipment, gear design, engines, deck equipment, and catch-handling procedures influences the capture efficiency (catchability) of commercial fishing vessels. On average, we estimate that catchability increases by 3.2% per year due to technological developments, an increase often ignored in fisheries management. The documentation and quantification of technological creep improves the basis for successfully integrating the effects of technological development (and catchability changes) in fisheries management regulations and policies. Ways of counteracting the undesired effects of technological creep are discussed as are the potential management benefits from improved fishing technology. Specific suggestions are given on the selection, application, and tuning of fisheries management tools that can be used to improve the balance between harvesting capacity and resource availability.
    Assessing the state of pelagic fish communities within an ecosystem approach and the European Marine Strategy Framework Directive
    Shephard, S. ; Rindorf, A. ; Dickey-Collas, M. ; Hintzen, N.T. ; Farnsworth, K. ; Reid, D.G. - \ 2014
    ICES Journal of Marine Science 71 (2014)7. - ISSN 1054-3139 - p. 1572 - 1585.
    cod gadus-morhua - north-sea - celtic sea - southern benguela - condition indexes - energy reserves - horse mackerel - forage fish - indicators - management
    Pelagic fish are key elements in marine foodwebs and thus comprise an important part of overall ecosystem health. We develop a suite of ecological indicators that track pelagic fish community state and evaluate state of specific objectives against Good Environmental Status (GES) criteria. Indicator time-series are calculated for the EU Marine Strategy Framework Directive “Celtic Seas” (CS) and “Greater North Sea” subregions. Precautionary reference points are proposed for each indicator and a simple decision process is then used to aggregate indicators into a GES assessment for each subregion. The pelagic fish communities of both subregions currently appear to be close to GES, but each remains vulnerable. In the CS subregion, fishing mortality is close to the precautionary reference point, although the unknown dynamics of sandeel, sprat, and sardine in the subregion may reduce the robustness of this evaluation. In the North Sea, sandeel stocks have been in poor state until very recently. Pelagic fish community biomass is slightly below the precautionary reference point in both subregions.
    Predation control of zooplankton dynamics: a review of observations and models
    Daewel, U. ; Hjoello, S.S. ; Huret, M. ; Ji, R. ; Maar, M. ; Niiranen, S. ; Travers-Trolet, M. ; Peck, M.A. ; Wolfshaar, K.E. van de - \ 2014
    ICES Journal of Marine Science 71 (2014)2. - ISSN 1054-3139 - p. 254 - 271.
    central baltic sea - sprat sprattus-sprattus - southern benguela system - individual-based models - large marine ecosystem - mussel mytilus-edulis - planktonic food-web - long-term dynamics - early-life stages - north-sea
    We performed a literature review to examine to what degree the zooplankton dynamics in different regional marine ecosystems across the Atlantic Ocean is driven by predation mortality and how the latter is addressed in available modelling approaches. In general, we found that predation on zooplankton plays an important role in all the six considered ecosystems, but the impacts are differently strong and occur at different spatial and temporal scales. In ecosystems with extreme environmental conditions (e.g. low temperature, ice cover, large seasonal amplitudes) and low species diversity, the overall impact of top-down processes on zooplankton dynamics is stronger than for ecosystems having moderate environmental conditions and high species diversity. In those ecosystems, predation mortality was found to structure the zooplankton mainly on local spatial and seasonal time scales. Modelling methods used to parameterize zooplankton mortality range from simplified approaches with fixed mortality rates to complex coupled multispecies models. The applicability of a specific method depends on both the observed state of the ecosystem and the spatial and temporal scales considered. Modelling constraints such as parameter uncertainties and computational costs need to be balanced with the ecosystem-specific demand for a consistent, spatial-temporal dynamic implementation of predation mortality on the zooplankton compartment.
    Effects of pile-driving on harbour porpoises (Phocoena phocoena) at the first offshore wind farm in Germany
    Daehne, M. ; Gilles, A. ; Lucke, K. ; Peschko, V. ; Adler, S. ; Kruegel, K. ; Sundermeyer, J. ; Siebert, U. - \ 2013
    Environmental Research Letters 8 (2013)2. - ISSN 1748-9326
    air bubble curtain - north-sea - underwater noise - aerial surveys - baltic sea - detection thresholds - marine mammals - t-pods - waters - abundance
    The first offshore wind farm 'alpha ventus' in the German North Sea was constructed north east of Borkum Reef Ground approximately 45 km north off the German coast in 2008 and 2009 using percussive piling for the foundations of 12 wind turbines. Visual monitoring of harbour porpoises was conducted prior to as well as during construction and operation by means of 15 aerial line transect distance sampling surveys, from 2008 to 2010. Static acoustic monitoring (SAM) with echolocation click loggers at 12 positions was performed additionally from 2008 to 2011. SAM devices were deployed between 1 and 50 km from the centre of the wind farm. During aerial surveys, 18¿600 km of transect lines were covered in two survey areas (10¿934 and 11¿824 km2) and 1392 harbour porpoise sightings were recorded. Lowest densities were documented during the construction period in 2009. The spatial distribution pattern recorded on two aerial surveys three weeks before and exactly during pile-driving points towards a strong avoidance response within 20 km distance of the noise source. Generalized additive modelling of SAM data showed a negative impact of pile-driving on relative porpoise detection rates at eight positions at distances less than 10.8 km. Increased detection rates were found at two positions at 25 and 50 km distance suggesting that porpoises were displaced towards these positions. A pile-driving related behavioural reaction could thus be detected using SAM at a much larger distance than a pure avoidance radius would suggest. The first waiting time (interval between porpoise detections of at least 10 min), after piling started, increased with longer piling durations. A gradient in avoidance, a gradual fading of the avoidance reaction with increasing distance from the piling site, is hence most probably a product of an incomplete displacement during shorter piling events.
    Parasites in the Wadden Sea food web
    Thieltges, D.W. ; Engelsma, M.Y. ; Wendling, C.C. ; Wegner, M. - \ 2013
    Journal of Sea Research 82 (2013). - ISSN 1385-1101 - p. 122 - 133.
    cockle cerastoderma-edule - oyster crassostrea-gigas - mediated indirect interactions - periwinkle littorina-littorea - trematode renicola-roscovita - amphipod corophium-volutator - mussel mytilus-edulis - east frisian coast - sylt-romo bight - north-sea
    While the free-living fauna of the Wadden Sea has received much interest, little is known on the distribution and effects of parasites in the Wadden Sea food web. However, recent studies on this special type of trophic interaction indicate a high diversity of parasites in the Wadden Sea and suggest a multitude of effects on the hosts. This also includes effects on specific predator–prey relationships and the general structure of the food web. Focussing on molluscs, a major group in the Wadden Sea in terms of biomass and abundance and an important link between primary producers and predators, we review existing studies and exemplify the ecological role of parasites in the Wadden Sea food web. First, we give a brief inventory of parasites occurring in the Wadden Sea, ranging from microparasites (e.g. protozoa, bacteria) to macroparasites (e.g. helminths, parasitic copepods) and discuss the effects of spatial scale on heterogeneities in infection levels. We then demonstrate how parasites can affect host population dynamics by acting as a strong mortality factor, causing mollusc mass mortalities. In addition, we will exemplify how parasites can mediate the interaction strength of predator–prey relationships and affect the topological structure of the Wadden Sea food web as a whole. Finally, we highlight some ongoing changes regarding parasitism in the Wadden Sea in the course of global change (e.g. species introduction, climate change) and identify important future research questions to entangle the role of parasites in the Wadden Sea food web.
    Harbour porpoises Phocoena phocoena in the Eastern Scheldt: A resident Stock or trapped by a storm surge barrier?
    Jansen, O.E. ; Aarts, G.M. ; Reijnders, P.J.H. - \ 2013
    PLoS ONE 8 (2013)3. - ISSN 1932-6203
    sea-level rise - stable-isotope analysis - food-web - feeding ecology - carbon isotopes - marine mammals - north-sea - nitrogen - diet - delta-c-13
    Coastal protection measures are planned and executed worldwide to combat the effects of global warming and climate change, in particular the acceleration of sea level rise, higher storm surge flooding and extensive coastal inundation. The extent to which these defensive measures may impact coastal and estuarine ecosystems is still poorly understood. Since the building of a storm surge barrier, movement of harbour porpoises Phocoena phocoena in and out of the Eastern Scheldt tidal bay (SW-Netherlands) may be limited. To measure residency, porpoises stranded along the Dutch North Sea coast between 2006 and 2008 were sampled for muscle (n = 102) and bone tissue (n = 118), of which 9 muscle (8.8%) and 12 bone samples (10.2%) were collected from animals stranded within the Eastern Scheldt. Stable carbon (d13C) was analysed to get insight into the habitat use and residency of porpoises in the Eastern Scheldt. Our data showed significantly higher d13C values in the muscle of porpoises stranded within the Eastern Scheldt (µ = -17.7‰, SD = 0.4‰) compared to animals stranded along the Dutch coast (µ = -18.3‰, SD = 0.5‰). This suggests that most porpoises stranded in the Eastern Scheldt foraged there for a longer period. The distinct d13C signature of animals from the Eastern Scheldt was not observed in bone tissue, suggesting a relatively recent shift in habitat use rather than life-long residency of porpoises within the Eastern Scheldt. The high number of strandings within the Eastern Scheldt suggests a higher mortality rate compared to the Dutch coastal zone. Our study indicates that along with other changes in the physical environment, the storm surge barrier may play an important role in determining the residency of porpoises in the Eastern Scheldt, and that the area might act as an ecological trap for porpoises entering it.
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