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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Development of the EcoQO for the North Sea fish community
Greenstreet, S.P.R. ; Rogers, S.I. ; Rice, J.C. ; Piet, G.J. ; Guirey, E. - \ 2011
ICES Journal of Marine Science 68 (2011)1. - ISSN 1054-3139 - p. 1 - 11.
size-based indicators - ecosystem approach - transfer efficiencies - reference points - food webs - body-mass - model - management - fisheries - spectra
Development of the Ecological Quality Objective (EcoQO) for the North Sea demersal fish community is described. Size-based metrics were identified as the most effective indicators of the state of the community, but such metrics are also sensitive to environmental influence. Redefining the large fish indicator (LFI) produced a metric more sensitive to fishing-induced change and therefore more useful to managers. Fish stocks were thought to be exploited at a sustainable rate in the early 1980s, so in a process echoing the precautionary approach to fish stock management, this was considered the reference period for the LFI, suggesting a value of 0.3 as the appropriate EcoQO. The LFI declined from around 0.3 in 1983 to 0.05 in 2001, followed by a recovery to 0.22 in 2008. However, analyses of the longer-term groundfish survey data suggest that, even were fishing pressure to be reduced to early 20th century levels, the LFI would be unlikely to rise much above a value of 0.3. The response of the LFI to variation in fishing pressure suggested a more complex relationship than anticipated, underscoring the need for operational theoretical size-resolved multispecies fish community models to support management towards broader ecosystem objectives.
Length-weight relationships of 216 North Sea benthic invertebrates and fish
Robinson, L. ; Greenstreet, S.P.R. ; Reiss, H. ; Callaway, R. ; Craeymeersch, J.A.M. ; Boois, I.J. de - \ 2010
Journal of the Marine Biological Association of The United Kingdom 90 (2010)1. - ISSN 0025-3154 - p. 95 - 104.
size-based model - community structure - food webs - hermit-crabs - body-size - abundance - diversity - prey - indicators - biomass
Size-based analyses of marine animals are increasingly used to improve understanding of community structure and function. However, the resources required to record individual body weights for benthic animals, where the number of individuals can reach several thousand in a square metre, are often prohibitive. Here we present morphometric (length weight) relationships for 216 benthic species from the North Sea to permit weight estimation from length measurements. These relationships were calculated using data collected over two years from 283 stations. For ten abundant and widely dispersed species we tested for significant spatial and temporal differences in morphometric relationships. Some were found, but the magnitude of differences was small in relation to the size-ranges of animals that are usually present and we recommend that the regression relationships given here, based on pooled data, are appropriate for most types of population and community analyses. Our hope is that the availability of these morphometric relationships will encourage the more frequent application of size-based analyses to ben hue survey data, and so enhance understanding of the ecology of the benthic/demersal component of marine ecosystems and food webs.
Unsuitability of TAC management within an ecosystem approach to fisheries: An ecological perspective
Reiss, H. ; Greenstreet, S.P.R. ; Robinson, L. ; Ehrich, S. ; Jorgensen, L.L. ; Piet, G.J. ; Wolff, W.J. - \ 2010
Journal of Sea Research 63 (2010)2. - ISSN 1385-1101 - p. 85 - 92.
marine protected areas - sea fish community - north-sea - mixed fisheries - sustainable use - catch rates - indicators - resources - fleet - simulation
Fisheries management in European waters is gradually moving from a single-species perspective towards a more holistic ecosystem approach to management (EAM), acknowledging the need to take all ecosystem components into account. Prerequisite within an EAM is the need for management processes that directly influence the ecological effects of fishing, such as the mortality of target and non-target species. Up until recently, placing limits on the quantities of fish that can be landed, through the imposition of annual total allowable catches (TACs) for the target species, has been the principal management mechanism employed. However, pressure on non-target components of marine ecosystems is more closely linked to prevailing levels of fishing activity, so only if TACs are closely related to subsequent fishing effort will TAC management serve to control the broader ecosystem impacts of fishing. We show that in the mixed fisheries that characterise the North Sea, the linkage between variation in TAC and the resulting fishing effort is in fact generally weak. Reliance solely on TACs to regulate fishing activity is therefore unlikely to mitigate the impacts of fishing on non-target species. Consequently, we conclude that the relationship between TACs and effort is insufficient for TACs to be used as the principal management tool within an EAM. The implications, and some alternatives, for fisheries management are discussed
Effects of fishing disturbance on benthic communities and secondary production within an intensively fished area
Reiss, H. ; Greenstreet, S.P.R. ; Sieben, K. ; Ehrich, S. ; Piet, G.J. ; Quirijns, F. ; Robinson, L. ; Wolff, W.J. ; Kroncke, I. - \ 2009
Marine Ecology Progress Series 394 (2009). - ISSN 0171-8630 - p. 201 - 213.
southern north-sea - plaice pleuronectes-platessa - bottom trawling disturbance - atlantic shelf seas - different habitats - invertebrate communities - infaunal communities - spatial-distribution - trophic structure - grand-banks
Demersal fishing alters seabed habitats and affects the structure and functioning of benthic invertebrate communities. At a critical level of disturbance, such communities may approach an equilibrium disturbed state in which a further increase in disturbance has little additional impact. Such arguments have been used to suggest that an ecosystem approach to fisheries management (EAFM) should protect lightly fished areas and deflect fishing activity into areas that are already intensively fished. In this study, the effects of variation in fishing disturbance on the secondary production, species diversity, abundance, biomass, and community structure of benthic infauna were examined in a region of the German Bight (North Sea) that has been intensively trawled for decades. Variation in fishing disturbance across the study area was determined using automated position registration and vessel monitoring through satellite. Even in such a heavily fished area, linear regression analyses revealed that biomass, species richness, and production decreased significantly with increasing fishing intensity. Although redundancy analyses (RDA) showed that sediment characteristics were influential in determining the structure of the infauna community, partial RDA revealed that fishing continued to have an impact on community structure in terms of biomass. These results suggest that, in implementing an EAFM, managers will need to consider the possibility that, even in areas with high chronic fishing disturbance, further increases in fishing activity may still cause additional damage to benthic invertebrate communities.
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
Modelling the direct impact of bottom trawling on the North Sea fish community to derive estimates of fishing mortality for non-target fish species
Piet, G.J. ; Hal, R. van; Greenstreet, S.P.R. - \ 2009
ICES Journal of Marine Science 66 (2009)9. - ISSN 1054-3139 - p. 1985 - 1998.
atlantic shelf seas - capture efficiency - long-term - ecosystem approach - theoretical-model - sampling trawl - indicators - length - catchability - fisheries
This study introduces a spatially explicit model that combines abundance data for all the main fish species in the demersal North Sea fish community with international effort data and estimates of gear-, species-, and size-dependent catch efficiency to determine the mortality of non-target fish species caused by bottom trawl fisheries and its spatial variation. Where necessary information was lacking, assumptions were made, and a sensitivity analysis performed to examine the impact of these issues on model results. Model outcomes were validated using international landings and discard data for five target species: cod, haddock, whiting, sole, and plaice. This showed that depending on its configuration, the model could reproduce recorded landings and discards of these species reasonably well. This suggests that the model could be used to simulate rates of fishing mortality for non-target fish species, for which few data are currently available. Sensitivity analyses revealed that model outcomes were most strongly influenced by the estimates of gear catch efficiency and the extent to which the distributions of fishing effort and each species overlapped. Better data for these processes would enhance the contribution that this type of model could make in supporting an ecosystem approach to fisheries management
Using MPAs to address regional-scale ecological objectives in the North Sea: modelling the effects of fishing effort displacement
Greenstreet, S.P.R. ; Fraser, H.M. ; Piet, G.J. - \ 2009
ICES Journal of Marine Science 66 (2009)1. - ISSN 1054-3139 - p. 90 - 100.
marine protected areas - fisheries management - ecosystem approach - reserve design - community structure - species-diversity - factory trawlers - adjacent fishery - predatory fish - scotian shelf
The use of Marine Protected Areas (MPAs) to address regional-scale objectives as part of an ecosystem approach to management in the North Sea is examined. Ensuring that displacement of fishing activity does not negate the ecological benefits gained from MPAs is a major concern. Two scenarios are considered: using MPAs to safeguard important areas for groundfish species diversity and using them to reduce fishing impacts on benthic invertebrates. Appropriate MPAs were identified using benthic invertebrate and fish abundance data. Fishing effort redistribution was modelled using international landings and fishing effort data. Closing 7.7% of the North Sea to protect groundfish species diversity increased the fishing impact on benthic invertebrates. Closing 7.3% of the North Sea specifically to protect benthic invertebrates reduced fishing mortality by just 1.7¿3.8%, but when combined with appropriate reductions in total allowable catch (TAC), 16.2¿17.4% reductions in fishing mortality were achieved. MPAs on their own are unlikely to achieve significant regional-scale ecosystem benefits, because local gains are largely negated by fishing effort displacement into the remainder of the North Sea. However, in combination with appropriate TAC reductions, the effectiveness of MPAs may be enhanced.
Assessing the sampling effort required to estimate a species diversity in the groundfish assemblages of the North Sea
Greenstreet, S.P.R. ; Piet, G.J. - \ 2008
Marine Ecology Progress Series 364 (2008). - ISSN 0171-8630 - p. 181 - 197.
atlantic shelf seas - long-term trends - fish community - ecosystem approach - regional processes - area relationship - spatial-patterns - survey trawls - size-spectra - richness
Conserving and restoring biodiversity are key objectives for an ecosystem approach to management in the North Sea, but ecological quality objectives for the groundfish community instead concentrate on restoring size structure. Species richness and diversity estimates are strongly influenced by sampling effort. Failure to account for this has led to the belief that species richness and diversity indices are not adequate indicators of ‘state’ for the groundfish community. However, adherence to a standard procedure that is robust within respect to sampling effort influence should allow these metrics to perform a state indicator role. The Arrhenius power and Gleason semi-log species–area relationships are examined to determine whether they can provide modelled estimates of species richness at the ICES (International Council for the Exploration of the Sea) rectangle scale. Of these, the Gleason semi-log appears most reliable, particularly when a randomised aggregation process is followed. Aggregation of at least 20 trawl samples is required to provide empirically derived index values that are representative of the communities sampled, and therefore sensitive to drivers of change in these communities. However, given current groundfish survey sampling levels, combining 20 half-hour trawl samples to provide single estimates of species richness and diversity will require considerable aggregation over time and/or space. This can lead to estimates of a or local richness/ diversity becoming inflated through the inclusion of elements of ß or regional richness/diversity. For the North Sea groundfish assemblage, this occurs when the distance between the focal position and the location of the most distant sample exceeds 49 km
Mapping spatial variation in demersal fish species diversity and composition in the North Sea: accounting for species- and size-related catchability in survey trawls
Fraser, H.M. ; Greenstreet, S.P.R. ; Fryer, R.J. ; Piet, G.J. - \ 2008
ICES Journal of Marine Science 65 (2008)4. - ISSN 1054-3139 - p. 531 - 538.
atlantic shelf seas - marine protected areas - community structure - long-term - richness - patterns - reserves - trends - productivity - evenness
The paper maps spatial patterns of groundfish species diversity. It considers how the catchability of different fish species in two different types of bottom trawls, the IBTS GOV and the 8-m beam trawl, influences the estimates of species diversity. Maps of groundfish species diversity derived from these two survey trawls are compared to determine the extent to which the maps of spatial variation in groundfish species diversity are influenced by gear type. Catchability-at-length coefficients were applied to the IBTS data to raise the observed catches to estimates of "actual" numbers of fish present in the path of the trawl, which are then used to produce maps of "actual" species diversity across the North Sea. Finally, these raised maps of "actual" groundfish species diversity are shown to be more explainable based on physical environmental parameters such as depth. We suggest that species diversity maps that take account of catchability provide more reliable information on which to base management decisions than "gear-biased" views. The implications for management are discussed, with particular emphasis on using closed areas to conserve marine biodiversity
Taking account of catchability in groundfish survey trawls: implications for estimating demersal fish biomass
Fraser, H.M. ; Greenstreet, S.P.R. ; Piet, G.J. - \ 2007
ICES Journal of Marine Science 64 (2007)9. - ISSN 1054-3139 - p. 1800 - 1819.
cod gadus-morhua - north-sea fish - swimming endurance - diel variation - size spectra - fisheries management - community structure - capture efficiency - seasonal-variation - prey abundance
Groundfish surveys are a key component of current scientific data monitoring and data-collection activities undertaken in support of fisheries management. Recent requirements to develop and implement an ecosystem approach to management are placing increasing and varied demands on such datasets. Successfully incorporating ecosystem and environmental objectives within fisheries management will, for example, require greater understanding of foodweb trophodynamics, which in turn requires detailed information on the abundance and distribution of fish predators and prey species on spatial scales hitherto rarely considered. However, no trawl gear catches all the fish in its path, so density estimates provided by such trawl samples do not reflect true densities of fish. Catchability in a trawl gear is affected by many factors and varies both between species and between different sized conspecifics, and therefore has the capacity to confound our understanding of predator¿prey interactions and of the relative abundance of different species and size classes of fish at any point in time or space. To overcome such problems, estimates of the catchability of each size class of each species sampled in a given survey are required for trawl sample densities to be raised to the actual densities of fish present at each location sampled. Here, we present a method for estimating catchability coefficients for 1-cm size classes of fish species sampled by the Grande Overture Vertical trawl during the third quarter ICES International Bottom Trawl Survey. The catchability coefficients obtained are applied to survey data collected between 1998 and 2004 to examine annual variation in actual abundance of the demersal fish assemblage in the North Sea.
Species composition, diversity, biomass and production of the benthic invertebrate community of the North Sea
Greenstreet, S.P.R. ; Robinson, L. ; Reiss, H. ; Craeymeersch, J.A.M. ; Callaway, R. ; Goffin, A. ; Jorgensen, L. ; Robertson, M. ; Kroncke, I. ; Boois, I.J. de - \ 2007
Aberdeen : Fisheries Research Services Marine Laboratory (Fisheries research services collaborative report no. 10/07) - 65
zeedieren - mariene ecologie - soortendiversiteit - biomassa - ongewervelde dieren - noordzee - marine animals - marine ecology - species diversity - biomass - invertebrates - north sea
Review of theoretical community ecology: implications for marine communities
Greenstreet, S.P.R. ; Robinson, L. ; Reiss, H. ; Kroncke, I. ; Callaway, R. ; Snelgrove, P. ; Costello, M. ; Bergmann, M. ; Hiddink, J. ; Fraser, H. ; Craeymeersch, J.A.M. - \ 2007
Aberdeen : Fisheries Research Services Marine Laboratory (Fish. Res. Serv. Collaborative Report 08/07) - 127
mariene ecologie - zeedieren - marien milieu - ecologie - mariene biologie - marine ecology - marine animals - marine environment - ecology - marine biology
Species composition, diversity, biomass and production of the demersal fish community of the North Sea
Greenstreet, S.P.R. ; Fraser, H. ; Piet, G.J. ; Robinson, L. ; Callaway, R. ; Reiss, H. ; Ehrich, S. ; Kroncke, I. ; Craeymeersch, J.A.M. - \ 2007
Aberdeen : Fisheries Research Services Marine Laboratory (Fisheries research services collaborative report no. 07/07) - 94
vissen - soortendiversiteit - zeedieren - noordzee - diergemeenschappen - demersale vissen - demersale visserij - fishes - species diversity - marine animals - north sea - animal communities - demersal fishes - demersal fisheries
Relationships between tacs, fish landings and fishing effort in the North Sea
Greenstreet, S.P.R. ; Robinson, L. ; Callaway, R. ; Reiss, H. ; Ehrich, S. ; Piet, G.J. ; Craeymeersch, J.A.M. - \ 2007
Aberdeen : Fisheries Research Services Marine Laboratory (Fisheries research services collaborative report no. 06/07) - 152
vis vangen - visserij - quota's - visserijbeheer - mariene ecologie - noordzee - visvangsten - fishing - fisheries - quotas - fishery management - marine ecology - north sea - fish catches
The ecological disturbance caused by fishing in the North Sea
Greenstreet, S.P.R. ; Robinson, L. ; Piet, G.J. ; Craeymeersch, J.A.M. ; Callaway, R. - \ 2007
Aberdeen : Fisheries Research Services Marine Laboratory (Fisheries research services collaborative report no. 04/07) - 169
vis vangen - visserij - ecologische verstoring - mortaliteit - mariene ecologie - noordzee - fishing - fisheries - ecological disturbance - mortality - marine ecology - north sea
Current knowledge of the ecological disturbance caused by fishing to marine fish and benthic invertebrate communities is reviewed. This review considers the various components of mortality caused by fishing (eg landings, discards, trawl escapees, etc) and examines the information currently available, or required, to determine the importance of each component in assessing the mortality of fish and benthos caused by fishing
Methodology for the combined sampling of marine groundfish and benthic invertebrate communities
Callaway, R. ; Robinson, L. ; Greenstreet, S.P.R. ; Reiss, H. ; Fraser, H. ; Kroncke, I. ; Craeymeersch, J.A.M. ; Boois, I.J. de - \ 2007
Aberdeen : Fisheries Research Services Marine Laboratory (Fish. Res. Serv. Collaborative Report 11/07) - 23
zeedieren - vissen - ongewervelde dieren - methodologie - bemonsteren - visserij - diergemeenschappen - marine animals - fishes - invertebrates - methodology - sampling - fisheries - animal communities
Managing fisheries to conserve North Sea groundfish and benthic invertebrate species diversity
Greenstreet, S.P.R. ; Robinson, L. ; Callaway, R. ; Reiss, H. ; Ehrich, S. ; Piet, G.J. ; Kroncke, I. ; Craeymeersch, J.A.M. - \ 2007
Aberdeen : Fisheries Research Services Marine Laboratory (Fisheries research services collaborative report no. 05/07) - 136
visserij - vissen - soortendiversiteit - zeevissen - zeedieren - natuurbescherming - noordzee - fisheries - fishes - species diversity - marine fishes - marine animals - nature conservation - north sea
Concerns over man’s impact on the environment and ecosystems of the world have resulted in a shift in emphasis in the management of marine natural resources. Consequently, an ecosystem approach to management (EAM) is in the process of being developed and implemented for the North Sea
Potential pressure indicators for fishing, and their data requirements
Piet, G.J. ; Quirijns, F.J. ; Robinson, L. ; Greenstreet, S.P.R. - \ 2007
ICES Journal of Marine Science 64 (2007)1. - ISSN 1054-3139 - p. 110 - 121.
ecosystem-based management - marine capture fisheries - southern north-sea - competitive interactions - community indicators - temporal trends - impact - mortality - metrics - shelf
Indicators of fishing pressure are necessary to support an ecosystem approach to fisheries management (EAFM). We present a framework that distinguishes four levels of pressure indicators that move from being a simple description of anthropogenic activity to more precisely describing the actual pressure on the ecosystem and its components, but which require increasingly more information to be quantified. We use the example of the Dutch beam trawl fleet in the North Sea to compare these pressure indicators, as the level of information used is increased. The first level is that of fleet capacity (e.g. number of vessels), the second is fishing effort, usually expressed as the number of hours fishing or days at sea, the third incorporates fishing parameters such as the proportion of time actually spent fishing, fishing speed, or gear characteristics, e.g. the size of the beam trawl in order to determine the frequency with which an area is fished, and at the fourth level, the most informative measure of fishing pressure, annual fishing mortality, is available for a few commercial species from stock assessments. For other species, it can be calculated from the lower level pressure indicators through the incorporation of the chance of individuals of a species coming into contact with the fishing gear and the encounter mortality, which is the portion of mortality caused by the passing of the gear. Comparison of trends and absolute values shows that the pressure indicators at different levels differ considerably in their description of both present and historical fishing impact in the North Sea. Therefore, for an EAFM, we advise using the highest level pressure indicator that can be obtained with the data available.
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