Mixed-fishery or ecosystem conundrum? Multispecies considerations inform thinking on long-term management of North Sea demersal stocks

2009 ◽  
Vol 66 (7) ◽  
pp. 1107-1129 ◽  
Author(s):  
Steven Mackinson ◽  
Barrie Deas ◽  
Doug Beveridge ◽  
John Casey
Keyword(s):  
North Sea ◽  
Single Species ◽  
Ecosystem Model ◽  
Ecosystem Approach ◽  
Maximum Sustainable Yield ◽  
The North ◽  
Trade Offs ◽  
Management Plans ◽  
Term Management

Signatories of the 2002 World Summit on Sustainable Development declaration committed to maintain or restore fish stocks to levels that can produce the maximum sustainable yield (MSY), a goal that has been challenged on a number of grounds. The European Commission has stated an objective to manage fisheries (independently) to achieve MSY by 2015, which has catalysed the Regional Advisory Councils’ (RACs) thinking on MSY and how it relates to their goal of developing long-term management plans. This study uses an ecosystem model of the North Sea to investigate questions relating to MSY in the context of mixed demersal fisheries for cod, haddock, and whiting. Results suggest that it is not possible to simultaneously achieve yields corresponding to MSYs predicted from single-species assessments and that the contradictory response of whiting is central to the trade-offs in yield and value for mixed demersal fisheries. Incompatibility between mixed-fishery and ecosystem-scale considerations exemplifies the difficult conceptual and practical challenges faced when moving toward an ecosystem approach.

scholarly journals Achieving maximum sustainable yield in mixed fisheries: a management approach for the North Sea demersal fisheries

2016 ◽  
Vol 74 (2) ◽  
pp. 566-575 ◽  
Author(s):  
Clara Ulrich ◽  
Youen Vermard ◽  
Paul J. Dolder ◽  
Thomas Brunel ◽  
Ernesto Jardim ◽  
...  
Keyword(s):  
North Sea ◽  
Regional Scale ◽  
Single Species ◽  
Maximum Sustainable Yield ◽  
Management Approach ◽  
Sustainable Yield ◽  
Total Allowable Catch ◽  
The North ◽  
Trade Offs ◽  
The North Sea

Achieving single species maximum sustainable yield (MSY) in complex and dynamic fisheries targeting multiple species (mixed fisheries) is challenging because achieving the objective for one species may mean missing the objective for another. The North Sea mixed fisheries are a representative example of an issue that is generic across most demersal fisheries worldwide, with the diversity of species and fisheries inducing numerous biological and technical interactions. Building on a rich knowledge base for the understanding and quantification of these interactions, new approaches have emerged. Recent paths towards operationalizing MSY at the regional scale have suggested the expansion of the concept into a desirable area of “pretty good yield”, implemented through a range around FMSY that would allow for more flexibility in management targets. This article investigates the potential of FMSY ranges to combine long-term single-stock targets with flexible, short-term, mixed-fisheries management requirements applied to the main North Sea demersal stocks. It is shown that sustained fishing at the upper bound of the range may lead to unacceptable risks when technical interactions occur. An objective method is suggested that provides an optimal set of fishing mortality within the range, minimizing the risk of total allowable catch mismatches among stocks captured within mixed fisheries, and addressing explicitly the trade-offs between the most and least productive stocks.

Combined analyses reveal environmentally driven changes in the North Sea ecosystem and raise questions regarding what makes an ecosystem model’s performance credible?

2014 ◽  
Vol 71 (1) ◽  
pp. 31-46 ◽  
Author(s):  
Steven Mackinson
Keyword(s):  
Primary Production ◽  
North Sea ◽  
Ecosystem Model ◽  
Ecosystem Approach ◽  
Trophic Levels ◽  
Fish Stock ◽  
Supporting Evidence ◽  
Sea Temperature ◽  
The North ◽  
The North Sea

When an ecosystem model of the North Sea is calibrated to data from multiple trophic levels, the model estimated the primary production required to support the food web correlates temporally with observed changes in sea temperature and nutrient levels, supporting evidence from empirical analyses. However, a different result is given from an alternative calibration using fish stock data only. The inference taken from the emergent primary production – temperature relationship and empirical data are that, on balance, there is stronger overall evidence to support the calibration constrained at multiple trophic levels. Two important implications of the findings are (i) that the relative importance of fishing and environmental effects is likely to be interpreted differently depending on the calibration approach and (ii) the contrasting model calibrations would give different responses to fishing policies. It raises questions regarding how to judge the performance (and credibility) of an ecosystem model and the critical importance of conducting empirical and modelling analyses in parallel. Adopting a combined approach to ecosystem modelling is an important step in the pursuit of operational and defensible tools to support the ecosystem approach to management.

scholarly journals Low-frequency variability in North Sea and Baltic Sea identified through simulations with the 3-D coupled physical–biogeochemical model ECOSMO

2017 ◽  
Vol 8 (3) ◽  
pp. 801-815 ◽  
Author(s):  
Ute Daewel ◽  
Corinna Schrum
Keyword(s):  
Baltic Sea ◽  
North Sea ◽  
Decadal Variability ◽  
Model Simulation ◽  
Ecosystem Model ◽  
Biogeochemical Model ◽  
Ecosystem Productivity ◽  
The North ◽  
The North Sea

Abstract. Here we present results from a long-term model simulation of the 3-D coupled ecosystem model ECOSMO II for a North Sea and Baltic Sea set-up. The model allows both multi-decadal hindcast simulation of the marine system and specific process studies under controlled environmental conditions. Model results have been analysed with respect to long-term multi-decadal variability in both physical and biological parameters with the help of empirical orthogonal function (EOF) analysis. The analysis of a 61-year (1948–2008) hindcast reveals a quasi-decadal variation in salinity, temperature and current fields in the North Sea in addition to singular events of major changes during restricted time frames. These changes in hydrodynamic variables were found to be associated with changes in ecosystem productivity that are temporally aligned with the timing of reported regime shifts in the areas. Our results clearly indicate that for analysing ecosystem productivity, spatially explicit methods are indispensable. Especially in the North Sea, a correlation analysis between atmospheric forcing and primary production (PP) reveals significant correlations between PP and the North Atlantic Oscillation (NAO) and wind forcing for the central part of the region, while the Atlantic Multi-decadal Oscillation (AMO) and air temperature are correlated to long-term changes in PP in the southern North Sea frontal areas. Since correlations cannot serve to identify causal relationship, we performed scenario model runs perturbing the temporal variability in forcing condition to emphasize specifically the role of solar radiation, wind and eutrophication. The results revealed that, although all parameters are relevant for the magnitude of PP in the North Sea and Baltic Sea, the dominant impact on long-term variability and major shifts in ecosystem productivity was introduced by modulations of the wind fields.

scholarly journals Low frequency variability in North Sea and Baltic Sea identified through simulations with the 3-d coupled physical-biogeochemical model ECOSMO

2017 ◽  
Author(s):  
Ute Daewel ◽  
Corinna Schrum
Keyword(s):  
Baltic Sea ◽  
North Sea ◽  
Decadal Variability ◽  
Model Simulation ◽  
Ecosystem Model ◽  
Biogeochemical Model ◽  
Ecosystem Productivity ◽  
The North ◽  
The North Sea

Abstract. Here we present results from a long-term model simulation of the 3d coupled ecosystem model ECOSMO II for a North and Baltic Sea setup. The model allows both multi-decadal hindcast simulation of the marine system and specific process studies under controlled environmental conditions. Model results have been analysed with respect to long-term multi decadal variability in both physical and biological parameters with the help of empirical orthogonal function (EOF) analysis. The analysis of a 61-year (1948–2008) long hind cast reveals a quasi-decadal variation on salinity, temperature and current fields in the North Sea in addition to singular events of major changes during restricted time frames. These changes in hydrodynamic variables where found to be associated to changes in ecosystem productivity that are temporally aligned with the timing of reported regime shifts in the areas. Our results clearly indicate that for analysing ecosystem productivity spatially explicit methods are indispensable. Especially in the North Sea a correlation analysis between atmospheric forcing and primary production (PP) reveals significant correlations for NAO and wind forcing for the central part of the region, while AMO and air temperature are correlated to long-term changes in the southern North Sea frontal areas. Since correlations cannot serve to identify causal relationship we performed scenario model runs with perturbing the temporal variability in forcing condition emphasizing specifically the role of solar radiation, wind and eutrophication. The results revealed that, although all parameters are relevant for the magnitude of PP in the North Sea and Baltic Sea, the dominant impact on long-term variability and major shifts in ecosystem productivity was introduced by modulations of the wind fields.

scholarly journals Risks and benefits of catching pretty good yield in multispecies mixed fisheries

2017 ◽  
Vol 74 (8) ◽  
pp. 2097-2106 ◽  
Author(s):  
Robert B. Thorpe ◽  
Simon Jennings ◽  
Paul J. Dolder
Keyword(s):  
Good Yield ◽  
Maximum Sustainable Yield ◽  
Fishing Mortality ◽  
Interacting Species ◽  
Risks And Benefits ◽  
The North ◽  
Trade Offs ◽  
The North Sea ◽  
Stock Collapse

Abstract Multispecies mixed fisheries catch ecologically interacting species with the same gears at the same time. We used an ensemble of size-based multispecies models to investigate the effects of different rates of fishing mortality (F) and fleet configurations on yield, biomass, risk of collapse and community structure. Maximum sustainable yield (MSY) and FMSY for 21 modelled species’ populations in the North Sea were defined at the Nash equilibrium, where any independent change in F for any species would not increase that species’ MSY. Fishing mortality ranges leading to “Pretty Good Yield” (F-PGY), by species, were defined as ranges yielding ≥0.95 × MSY. Weight and value of yield from the entire fishery increased marginally when all species were fished at the upper end of F-PGY ranges rather than at FMSY, but risk of species’ collapse and missing community targets also increased substantially. All risks fell markedly when fishing at the lower end of F-PGY ranges, but with small impacts on total fishery yield or value. While fishing anywhere within F-PGY ranges gives managers flexibility to manage trade-offs in multispecies mixed fisheries, our results suggest high long-term yields and disproportionately lower risks of stock collapse are achieved when F ≤ FMSY for all component stocks.

scholarly journals Indicators of the health of the North Sea fish community: identifying reference levels for an ecosystem approach to management

2006 ◽  
Vol 63 (4) ◽  
pp. 573-593 ◽  
Author(s):  
Simon P.R. Greenstreet ◽  
Stuart I. Rogers
Keyword(s):  
North Sea ◽  
Time Series Data ◽  
Size Structure ◽  
Single Species ◽  
Ecosystem Approach ◽  
Reference Points ◽  
Series Data ◽  
Anthropogenic Activity ◽  
Data Sets ◽  
The North

Abstract The shift in emphasis away from the single-species focus of traditional fisheries management towards an ecosystem approach to management requires application of indicators of ecosystem state. Further, an ecosystem approach to management requires the identification of ecological reference points against which management objectives might be set. In applying indicators, identifying reference points, and setting objectives, an obvious requirement is that the indicators respond primarily to the anthropogenic activity being managed and are sufficiently sensitive that impacts of the activity and the responses to management action are clearly demonstrable. Here we apply a suite of 12 indicators to Scottish August groundfish survey data collected in the northern North Sea over the period 1925–1997. These include indicators of size structure, life-history character composition, species diversity, and trophic structure within the community. Our choice of analytical design has two purposes; first to show that fishing has unequivocally affected these various aspects of the structure of the groundfish community, and second to illustrate an approach by which long time-series data sets might be used to identify possible management reference points. The results are discussed in the context of selecting ecological indicators in support of an ecosystem approach to management and determining appropriate reference points for objective-setting.

scholarly journals Lessons learned from stock collapse and recovery of North Sea herring: a review

2010 ◽  
Vol 67 (9) ◽  
pp. 1875-1886 ◽  
Author(s):  
Mark Dickey-Collas ◽  
Richard D. M. Nash ◽  
Thomas Brunel ◽  
Cindy J. G. van Damme ◽  
C. Tara Marshall ◽  
...  
Keyword(s):  
North Sea ◽  
Time Management ◽  
Single Species ◽  
Time Frame ◽  
Maximum Sustainable Yield ◽  
Lessons Learned ◽  
Reference Points ◽  
Ecosystem Change ◽  
The North ◽  
Stock Collapse

Abstract Dickey-Collas, M., Nash, R. D. M., Brunel, T., van Damme, C. J. G., Marshall, C. T., Payne, M. R., Corten, A., Geffen, A. J., Peck, M. A., Hatfield, E. M. C., Hintzen, N. T., Enberg, K., Kell, L. T., and Simmonds, E. J. 2010. Lessons learned from stock collapse and recovery of North Sea herring: a review. – ICES Journal of Marine Science, 67: 1875–1886. The collapse and recovery of North Sea herring in the latter half of the 20th century had both ecological and economic consequences. We review the effect of the collapse and investigate whether the increased understanding about the biology, ecology, and stock dynamics gained in the past three decades can aid management to prevent further collapses and improve projections of recovery. Recruitment adds the most uncertainty to estimates of future yield and the potential to reach biomass reference points within a specified time-frame. Stock–recruitment relationships must be viewed as being fluid and dependent on ecosystem change. Likewise, predation mortality changes over time. Management aimed at maximum sustainable yield (MSY) fishing mortality targets implies interannual variation in TACs, and variability in supply is therefore unavoidable. Harvest control rules, when adhered to, aid management greatly. We advocate that well-founded science can substantially contribute to management through improved confidence and increased transparency. At present, we cannot predict the effects of collapse or recovery of a single stock on the ecosystem as a whole. Moreover, as managers try to reconcile commitments to single-species MSY targets with the ecosystem-based approach, they must consider the appropriate management objectives for the North Sea ecosystem as a whole.

scholarly journals Long-term series in ichthyoplankton: sole and sprat at French coast of the North Sea from 1975 to 1994

1998 ◽  
Vol 21 (1) ◽  
pp. 113-121 ◽  
Author(s):  
Daniel Woehrling ◽  
Geneviève Le Fèvre-Lehoërff
Keyword(s):  
North Sea ◽  
The North ◽  
The North Sea

scholarly journals A floristic description of the Afromontane fynbos communities on Platberg, Eastern Free State, South Africa

Koedoe ◽  
2008 ◽  
Vol 50 (1) ◽  
Author(s):  
Robert F. Brand ◽  
Pieter J. Du Preez ◽  
Leslie R. Brown
Keyword(s):  
Natural Resources ◽  
Plant Communities ◽  
Conservation Management ◽  
Alien Invasive Species ◽  
Ecological Processes ◽  
The North ◽  
Shrub Community ◽  
Management Plans ◽  
Twinspan Classification

Within the Platberg area and the wider Drakensberg region, the shrinking natural resources and the threat posed to biodiversity are of concern to conservation management and require an understanding of long-term ecological processes. The vegetation of Platberg was investigated as part of an ecological survey to establish Afromontane floristic links to the Drakensberg as well as for the management of natural resources. From a TWINSPAN classification, refined by the Braun-Blanquet method, four main plant communities were identified, which were subdivided into fynbos, wetland, a woody/shrub community and grassland. A classification and description of the fynbos are presented in this article.The analysis showed the fynbos divided into two communities comprising four sub-communities and seven variants. The fynbos community had an average of 28.34 species per relevé, ranging from 14 to 54 species per sample plot. Twenty-four endemic or near-endemic Drakensberg Alpine Centre (DAC) species and 22 exotic (alien-invasive) species were recorded. Numerous floristic links with the DAC, Cape flora fynbos and grassland bioregions to the north and west were also found. The description of the fynbos plant communities can serve as a basis for the formulation of management plans for the area.

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