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Simon P R Greenstreet - One of the best experts on this subject based on the ideXlab platform.
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modelling demersal Fishing Effort based on landings and days absence from port to generate indicators of activity
Ices Journal of Marine Science, 2009Co-Authors: Simon P R Greenstreet, Gayle J Holland, Thomas W K Fraser, V J AllenAbstract:Greenstreet, S. P. R., Holland, G. J., Fraser, T. W. K., and Allen, V. J. 2009. Modelling demersal Fishing Effort based on landings and days absence from port, to generate indicators of “activity”. - ICES Journal of Marine Science, 66: 886-901.For many components of marine ecosystems, the derivation of biologically significant, operational “pressure” indicators will rely on modelling Fishing mortality from indicators of anthropogenic “activity”. This essentially expands the well established Pressure-State-Response framework to one of Activity-Pressure-State-Response. Within the Common Fisheries Policy, the reporting of Fishing Effort data, the basic indicator of activity, is not mandatory. A modelling approach is therefore developed that utilizes the data that fishers are obliged to report (days absence from port, landings from each rectangle fished, and the gear used) to provide modelled estimates of Fishing Effort. The model is parameterized for the Scottish demersal Fishing fleet using data collected through the Scottish discards observer scheme, and Fishing Effort over the period 1997-2004 is modelled. Reported Effort data for the period 1960-1998 allowed validation of the model through direct comparison of modelled with reported data in 1997 and 1998. Combining the modelled and reported datasets revealed that Scottish Fishing activity levels, remarkably constant over four decades, had declined markedly since 2000. Temporal trends in UK quotas for the main targeted demersal species are considered to assess the effectiveness of catch limitation management as a means of regulating Fishing activity. Spatial patterns in Effort by the four main gear types used by the Scottish demersal fleet are described, and in general terms, these have changed little over the period 1960-2004. However, distinct spatial patterns emerged in the temporal trends in each ICES rectangle, associated with the recent overall decline in Scottish demersal Fishing activity. These patterns were not intuitive, and the implications of this for an ecosystem approach to management are discussed.
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Fishing effects in northeast atlantic shelf seas patterns in Fishing Effort diversity and community structure iii international trawling Effort in the north sea an analysis of spatial and temporal trends
Fisheries Research, 1999Co-Authors: John Alvsvag, Simon P R Greenstreet, A J R Cotter, Siegfried Ehrich, Astrid Jarreteichmann, N Mergardt, A D Rijnsdorp, O SmedstadAbstract:Abstract This paper describes trends in beam and otter trawling Effort in the North Sea from 1977 to 1995. Data are presented as total hours Fishing by English, German, Norwegian, Scottish and Welsh vessels for the period 1977–1995, and by Danish, Dutch, English, German, Norwegian, Scottish and Welsh vessels for the period 1990–1995. Analyses of temporal trends indicated that total international trawling Effort in the entire North Sea has increased slowly since 1977 and that it is currently (1995) 2.25 million h yr −1 of which 55% is due to beam trawling. Spatial analyses indicate that the proportion of beam trawling Effort increases from north to south. Plots of annual Fishing Effort by ICES statistical rectangle (211 boxes of 0.5° latitude×1° longitude) indicate that the majority of Fishing Effort in the North Sea are concentrated in a very few rectangles. Thus mean annual total Fishing Effort (1990–1995) was less than 2 000 h in 29% of rectangles and less than 10 000 h in 66% of rectangles. Total Effort exceeded 40 000 h in 4% of rectangles. The results indicate that assessments of the average area swept by trawls in the North Sea give a poor indication of the direct impacts of trawling on the biota. Some areas are intensively fished but many others are not. Our dataset is likely to underestimate trawling Effort in the southern North Sea (ICES Area IVc) because data for Belgian and French vessels were not available. However, the absence of French and Belgian data would not significantly alter total trawling Effort estimates from the central (IVb) and northern (IVa) North Sea.
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Fishing effects in northeast atlantic shelf seas patterns in Fishing Effort diversity and community structure ii trends in Fishing Effort in the north sea by uk registered vessels landing in scotland
Fisheries Research, 1999Co-Authors: Simon P R Greenstreet, Fiona B Spence, Aileen M Shanks, Julie A McmillanAbstract:Abstract North Sea Fishing Effort data (expressed as hours Fishing) for UK vessels landing in Scotland over the period 1960–1994 are analysed. Long-term temporal, spatial and seasonal trends in the use of particular gears are described. Pelagic Fishing Effort trends were clearly related to changes in the target species. Pelagic Effort, mainly pair-trawling targeted at sprats in the 1960s and early 1970s, declined markedly in the late 1970s. In the early 1980s pelagic Fishing Effort increased again, but was predominantly purse-seining targeted at herring. The spatial distribution of pelagic Effort shifted northwards, and changed from winter to summer. Demersal Fishing Effort varied little over three decades, but marked changes in the type of gear used were apparent. The use of seine nets decreased, particularly in the northwestern North Sea, and otter trawl Fishing increased. The spatial distribution of demersal Effort is now more widespread than in earlier years, but there has been little change in seasonal patterns.
Michel J Kaiser - One of the best experts on this subject based on the ideXlab platform.
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confidentiality over Fishing Effort data threatens science and management progress
Fish and Fisheries, 2013Co-Authors: Hilmar Hinz, Lee G Murray, Gwladys I Lambert, Jan G Hiddink, Michel J KaiserAbstract:Understanding the effects of Fishing fleets on both target and non-target species and managing these effects are essential to achieve Good Environmental Status (GES) for marine ecosystems. The use of high resolution Fishing Effort data in environmental studies has allowed significant scientific progress with respect to the environmental impacts of real Fishing fleets and provided a more realistic perspective on the wider ecological consequences of Fishing disturbance. A new EU council regulation and its interpretation, aimed at protecting the confidentiality rights of individual fishers, are currently hampering scientific access to this high-resolution Effort data and thus are endangering the provision of management advice based on best available knowledge. This study argues that the withholding of this information will seriously undermine the quality and accuracy of scientific output and ultimately damage fishers' livelihoods through poorly advised management. Furthermore, the council regulation runs contrary to the EU's initiative for greater transparency and its commitment to implement an ecosystem approach to fisheries management and the preservation of ecosystem services. The interpretation of the new EU council regulation by local administrations can thus only be viewed as a significant step back from these aims. Ultimately, while trying to protect fishers' rights it may work to their disadvantage and that of society.
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predicting the effects of area closures and Fishing Effort restrictions on the production biomass and species richness of benthic invertebrate communities
Ices Journal of Marine Science, 2006Co-Authors: Jan G Hiddink, Simon Jennings, Trevor Hutton, Michel J KaiserAbstract:To effectively implement an Ecosystem Approach to Fisheries (EAF), managers need to consider the effects of management actions on the fishery and the ecosystem. Methods for assessing the effects on target stocks are generally well developed, but methods for assessing the effects on other components and attributes of the ecosystem are not. Area closures and Effort controls are widely used fishery management tools that affect the distribution of Fishing Effort and may therefore have consequences for a range of species and habitats. An approach is developed to predict the effects of area closures and Effort control on the biomass, production, and species richness of benthic communities in the North Sea. The redistribution of beam trawling Effort as a result of management action was modelled with a random utility model, assuming that fishers selected Fishing grounds on the basis of their knowledge of past catch rates. The effects of trawling on benthic invertebrates were predicted using a size-based model that accounted for differences in habitat among Fishing grounds. Our simulations demonstrated that closures of different sizes and in different locations could have positive or negative effects on benthic communities. These predicted effects resulted from the trade-off between recovery in the closed areas and additional trawling effects in the open areas that arose from displaced Fishing activity. In the absence of Effort controls, closure of lightly fished areas had the strongest positive effect on benthic communities. Effort reduction also had a positive effect. Therefore, area closures in lightly fished areas, coupled with Effort reduction, are expected to minimize the effects of Fishing on benthic communities. As it was not possible to access full international data for the North Sea beam trawl fleet, the results of the analyses are illustrative rather than complete. Nevertheless, what is demonstrated is an effective approach for assessing the environmental consequences of fishery management action that can be used to inform management decision-making as part of an EAF.
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chronic Fishing disturbance has changed shelf sea benthic community structure
Journal of Animal Ecology, 2000Co-Authors: Michel J Kaiser, K Ramsay, C A Richardson, Fiona E Spence, A R BrandAbstract:Summary 1. Bottom Fishing using towed nets and dredges is one of the most widespread sources of physical disturbance to the continental shelf seas throughout the world. Previous studies suggest that degradation and ecosystem changes have occurred in intensively fished areas. Nevertheless, to date it has been difficult to attribute habitat and benthic community changes to Fishing Effort at a spatial scale that is truly representative of commercial Fishing activities. 2. In this study we present convincing evidence that chronic bottom-Fishing disturbance has caused significant and widespread changes in the structure of two distinct soft-sediment benthic assemblages and habitats. 3. Our study compared the benthic fauna found in areas that have been exposed to either high or low levels of bottom-Fishing disturbance over the past 10 years. We were able to validate the Fishing Effort data in some areas using scars in the shells of a long-lived bivalve mollusc (Glycymeris glycymeris) which result from Fishing disturbance. Shell scars occurred most frequently in bivalves collected from the area of highest Fishing Effort. 4. Multivariate analyses and the response of abundance/biomass curves indicated that chronic Fishing has caused a shift from communities dominated by relatively sessile, emergent, high biomass species to communities dominated by infaunal, smaller-bodied fauna. Removal of emergent fauna has thus degraded the topographic complexity of seabed habitats in areas of high Fishing Effort. The communities within these areas currently may be in an alternative stable state.
Julie A Mcmillan - One of the best experts on this subject based on the ideXlab platform.
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Fishing effects in northeast atlantic shelf seas patterns in Fishing Effort diversity and community structure ii trends in Fishing Effort in the north sea by uk registered vessels landing in scotland
Fisheries Research, 1999Co-Authors: Simon P R Greenstreet, Fiona B Spence, Aileen M Shanks, Julie A McmillanAbstract:Abstract North Sea Fishing Effort data (expressed as hours Fishing) for UK vessels landing in Scotland over the period 1960–1994 are analysed. Long-term temporal, spatial and seasonal trends in the use of particular gears are described. Pelagic Fishing Effort trends were clearly related to changes in the target species. Pelagic Effort, mainly pair-trawling targeted at sprats in the 1960s and early 1970s, declined markedly in the late 1970s. In the early 1980s pelagic Fishing Effort increased again, but was predominantly purse-seining targeted at herring. The spatial distribution of pelagic Effort shifted northwards, and changed from winter to summer. Demersal Fishing Effort varied little over three decades, but marked changes in the type of gear used were apparent. The use of seine nets decreased, particularly in the northwestern North Sea, and otter trawl Fishing increased. The spatial distribution of demersal Effort is now more widespread than in earlier years, but there has been little change in seasonal patterns.
O Smedstad - One of the best experts on this subject based on the ideXlab platform.
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Fishing effects in northeast atlantic shelf seas patterns in Fishing Effort diversity and community structure iii international trawling Effort in the north sea an analysis of spatial and temporal trends
Fisheries Research, 1999Co-Authors: John Alvsvag, Simon P R Greenstreet, A J R Cotter, Siegfried Ehrich, Astrid Jarreteichmann, N Mergardt, A D Rijnsdorp, O SmedstadAbstract:Abstract This paper describes trends in beam and otter trawling Effort in the North Sea from 1977 to 1995. Data are presented as total hours Fishing by English, German, Norwegian, Scottish and Welsh vessels for the period 1977–1995, and by Danish, Dutch, English, German, Norwegian, Scottish and Welsh vessels for the period 1990–1995. Analyses of temporal trends indicated that total international trawling Effort in the entire North Sea has increased slowly since 1977 and that it is currently (1995) 2.25 million h yr −1 of which 55% is due to beam trawling. Spatial analyses indicate that the proportion of beam trawling Effort increases from north to south. Plots of annual Fishing Effort by ICES statistical rectangle (211 boxes of 0.5° latitude×1° longitude) indicate that the majority of Fishing Effort in the North Sea are concentrated in a very few rectangles. Thus mean annual total Fishing Effort (1990–1995) was less than 2 000 h in 29% of rectangles and less than 10 000 h in 66% of rectangles. Total Effort exceeded 40 000 h in 4% of rectangles. The results indicate that assessments of the average area swept by trawls in the North Sea give a poor indication of the direct impacts of trawling on the biota. Some areas are intensively fished but many others are not. Our dataset is likely to underestimate trawling Effort in the southern North Sea (ICES Area IVc) because data for Belgian and French vessels were not available. However, the absence of French and Belgian data would not significantly alter total trawling Effort estimates from the central (IVb) and northern (IVa) North Sea.
A D Rijnsdorp - One of the best experts on this subject based on the ideXlab platform.
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a quantitative evaluation of the impact of beam trawling on benthic fauna in the southern north sea
Ices Journal of Marine Science, 2000Co-Authors: G J Piet, A D Rijnsdorp, Magda J N Bergman, J W Van Santbrink, J A Craeymeersch, J BuijsAbstract:Data on density of benthos species and on direct mortality caused by the passing of a beam trawl, together with Fishing Effort data for the Dutch beam-trawl fleet, were used to evaluate the annual population mortality caused by beam trawling in the Dutch sector of the North Sea. The effects of using environmental strata, instead of ICES rectangles for density distributions, and of using higher-resolution Fishing-Effort data on the population mortality estimates of 21 infauna and epifauna species were investigated. Variation in species abundance was markedly smaller based on sedimentdepth strata than based on ICES rectangles, and the resulting population mortality estimates differed significantly among species (ratio ranged from 0.3 to 1.6) depending on the overlap of the spatial distribution of a species and of beam-trawl Effort. Changing the resolution of Fishing Effort from ICES rectangles or sediment-depth strata to 1 minute latitude2 minute longitude square (11 nm) resulted in a systematic reduction of population mortality by a factor 0.7 due to the patchy Effort distribution. We argue that annual Fishing mortality should preferably be based on relevant environmental strata, and accuracy of the estimates increases markedly when the resolution of spatial Fishing Effort data sufficiently reflects the patchiness of the fleet’s activities. 2000 International Council for the Exploration of the Sea
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Fishing effects in northeast atlantic shelf seas patterns in Fishing Effort diversity and community structure iii international trawling Effort in the north sea an analysis of spatial and temporal trends
Fisheries Research, 1999Co-Authors: John Alvsvag, Simon P R Greenstreet, A J R Cotter, Siegfried Ehrich, Astrid Jarreteichmann, N Mergardt, A D Rijnsdorp, O SmedstadAbstract:Abstract This paper describes trends in beam and otter trawling Effort in the North Sea from 1977 to 1995. Data are presented as total hours Fishing by English, German, Norwegian, Scottish and Welsh vessels for the period 1977–1995, and by Danish, Dutch, English, German, Norwegian, Scottish and Welsh vessels for the period 1990–1995. Analyses of temporal trends indicated that total international trawling Effort in the entire North Sea has increased slowly since 1977 and that it is currently (1995) 2.25 million h yr −1 of which 55% is due to beam trawling. Spatial analyses indicate that the proportion of beam trawling Effort increases from north to south. Plots of annual Fishing Effort by ICES statistical rectangle (211 boxes of 0.5° latitude×1° longitude) indicate that the majority of Fishing Effort in the North Sea are concentrated in a very few rectangles. Thus mean annual total Fishing Effort (1990–1995) was less than 2 000 h in 29% of rectangles and less than 10 000 h in 66% of rectangles. Total Effort exceeded 40 000 h in 4% of rectangles. The results indicate that assessments of the average area swept by trawls in the North Sea give a poor indication of the direct impacts of trawling on the biota. Some areas are intensively fished but many others are not. Our dataset is likely to underestimate trawling Effort in the southern North Sea (ICES Area IVc) because data for Belgian and French vessels were not available. However, the absence of French and Belgian data would not significantly alter total trawling Effort estimates from the central (IVb) and northern (IVa) North Sea.