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Evaluation and management implications of uncertainty in a multispecies size-structured model of population and community responses to fishing.

Thorpe RB, Le Quesne WJ, Luxford F, Collie JS, Jennings S - Methods Ecol Evol (2014)

Bottom Line: This unfiltered ensemble was reduced to 188 plausible models, the filtered ensemble (FE), by screening outputs against fish abundance data and ecological principles such as requiring species' persistence.Effects of parameter uncertainty on estimates of single-species management reference points for fishing mortality (F MSY, fishing mortality rate providing MSY, the maximum sustainable yield) and biomass (B MSY, biomass at MSY) were evaluated by calculating probability distributions of estimated reference points with the FE.There was a 50% probability that multispecies F MSY could be estimated to within ±25% of its actual value, and a 50% probability that B MSY could be estimated to within ±40% of its actual value.Signal-to-noise ratio was assessed for four community indicators when mortality rates were reduced from current rates to F MSY.Further, the power of an ongoing international monitoring survey to detect predicted responses of size spectrum slope was higher than for other size-based metrics.Synthesis and applications: Application of the ensemble model approach allows explicit representation of parameter uncertainty and supports advice and management by (i) providing uncertainty intervals for management reference points, (ii) estimating working values of reference points that achieve a defined reduction in risk of not breaching the true reference point, (iii) estimating the responsiveness of population, community, food web and biodiversity indicators to changes in F, (iv) assessing the performance of indicators and monitoring programmes and (v) identifying priorities for data collection and changes to model structure to reduce uncertainty.

View Article: PubMed Central - PubMed

Affiliation: Centre for Environment, Fisheries and Aquaculture Science (CEFAS), Lowestoft Laboratory Lowestoft, NR33 0HT, UK.

ABSTRACT

Implementation of an ecosystem approach to fisheries requires advice on trade-offs among fished species and between fisheries yields and biodiversity or food web properties. However, the lack of explicit representation, analysis and consideration of uncertainty in most multispecies models has limited their application in analyses that could support management advice.We assessed the consequences of parameter uncertainty by developing 78 125 multispecies size-structured fish community models, with all combinations of parameters drawn from ranges that spanned parameter values estimated from data and literature. This unfiltered ensemble was reduced to 188 plausible models, the filtered ensemble (FE), by screening outputs against fish abundance data and ecological principles such as requiring species' persistence.Effects of parameter uncertainty on estimates of single-species management reference points for fishing mortality (F MSY, fishing mortality rate providing MSY, the maximum sustainable yield) and biomass (B MSY, biomass at MSY) were evaluated by calculating probability distributions of estimated reference points with the FE. There was a 50% probability that multispecies F MSY could be estimated to within ±25% of its actual value, and a 50% probability that B MSY could be estimated to within ±40% of its actual value.Signal-to-noise ratio was assessed for four community indicators when mortality rates were reduced from current rates to F MSY. The slope of the community size spectrum showed the greatest signal-to-noise ratio, indicating that it would be the most responsive indicator to the change in fishing mortality F. Further, the power of an ongoing international monitoring survey to detect predicted responses of size spectrum slope was higher than for other size-based metrics.Synthesis and applications: Application of the ensemble model approach allows explicit representation of parameter uncertainty and supports advice and management by (i) providing uncertainty intervals for management reference points, (ii) estimating working values of reference points that achieve a defined reduction in risk of not breaching the true reference point, (iii) estimating the responsiveness of population, community, food web and biodiversity indicators to changes in F, (iv) assessing the performance of indicators and monitoring programmes and (v) identifying priorities for data collection and changes to model structure to reduce uncertainty.

No MeSH data available.


Frequency distribution of community metrics predicted with models in the filtered ensemble (FE) and expressed as the ratio of values of each metric at FHIST and FMSY (black histogram). The vertical grey line is the mean ratio of values of each metric at FHIST and FMSY. Vertical shaded bands indicate 50% (dark) and 90% (light) uncertainty intervals for the prediction at FHIST, with intervals presented as a proportion of the mean metric value. Metrics are (a) mean length, (b) proportion of large fish, (c) size spectrum slope and (d) mean maximum weight.
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fig04: Frequency distribution of community metrics predicted with models in the filtered ensemble (FE) and expressed as the ratio of values of each metric at FHIST and FMSY (black histogram). The vertical grey line is the mean ratio of values of each metric at FHIST and FMSY. Vertical shaded bands indicate 50% (dark) and 90% (light) uncertainty intervals for the prediction at FHIST, with intervals presented as a proportion of the mean metric value. Metrics are (a) mean length, (b) proportion of large fish, (c) size spectrum slope and (d) mean maximum weight.

Mentions: If a community metric is to provide feedback on effects of management action, then it should show a response to these effects and this should be detectable in monitoring data. This requires that the change in metric value following a defined management action should be greater than uncertainty in prediction, and the predicted change in the metric value should be detectable given interannual variation in data. To compare theoretically expected change in community metrics with uncertainty in prediction, the ratio of the metric at FHIST:FMSY, for each FE variant, was compared with the 50% and 90% uncertainty intervals for the prediction at FHIST, where the 50% and 90% uncertainty intervals were expressed as a proportion of the mean metric value (Fig. 4). The mean change in the values of the metrics fell outside the 50% uncertainty interval for MMW, LFI and SSS, but not for ML. For MMW, LFI and SSS, the predicted change in indicator values for the entire FE lay outside the 50% uncertainty interval, and for SSS, predicted change also lay outside the 90% interval. Thus, SSS is expected to be the most responsive community indicator.


Evaluation and management implications of uncertainty in a multispecies size-structured model of population and community responses to fishing.

Thorpe RB, Le Quesne WJ, Luxford F, Collie JS, Jennings S - Methods Ecol Evol (2014)

Frequency distribution of community metrics predicted with models in the filtered ensemble (FE) and expressed as the ratio of values of each metric at FHIST and FMSY (black histogram). The vertical grey line is the mean ratio of values of each metric at FHIST and FMSY. Vertical shaded bands indicate 50% (dark) and 90% (light) uncertainty intervals for the prediction at FHIST, with intervals presented as a proportion of the mean metric value. Metrics are (a) mean length, (b) proportion of large fish, (c) size spectrum slope and (d) mean maximum weight.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4390044&req=5

fig04: Frequency distribution of community metrics predicted with models in the filtered ensemble (FE) and expressed as the ratio of values of each metric at FHIST and FMSY (black histogram). The vertical grey line is the mean ratio of values of each metric at FHIST and FMSY. Vertical shaded bands indicate 50% (dark) and 90% (light) uncertainty intervals for the prediction at FHIST, with intervals presented as a proportion of the mean metric value. Metrics are (a) mean length, (b) proportion of large fish, (c) size spectrum slope and (d) mean maximum weight.
Mentions: If a community metric is to provide feedback on effects of management action, then it should show a response to these effects and this should be detectable in monitoring data. This requires that the change in metric value following a defined management action should be greater than uncertainty in prediction, and the predicted change in the metric value should be detectable given interannual variation in data. To compare theoretically expected change in community metrics with uncertainty in prediction, the ratio of the metric at FHIST:FMSY, for each FE variant, was compared with the 50% and 90% uncertainty intervals for the prediction at FHIST, where the 50% and 90% uncertainty intervals were expressed as a proportion of the mean metric value (Fig. 4). The mean change in the values of the metrics fell outside the 50% uncertainty interval for MMW, LFI and SSS, but not for ML. For MMW, LFI and SSS, the predicted change in indicator values for the entire FE lay outside the 50% uncertainty interval, and for SSS, predicted change also lay outside the 90% interval. Thus, SSS is expected to be the most responsive community indicator.

Bottom Line: This unfiltered ensemble was reduced to 188 plausible models, the filtered ensemble (FE), by screening outputs against fish abundance data and ecological principles such as requiring species' persistence.Effects of parameter uncertainty on estimates of single-species management reference points for fishing mortality (F MSY, fishing mortality rate providing MSY, the maximum sustainable yield) and biomass (B MSY, biomass at MSY) were evaluated by calculating probability distributions of estimated reference points with the FE.There was a 50% probability that multispecies F MSY could be estimated to within ±25% of its actual value, and a 50% probability that B MSY could be estimated to within ±40% of its actual value.Signal-to-noise ratio was assessed for four community indicators when mortality rates were reduced from current rates to F MSY.Further, the power of an ongoing international monitoring survey to detect predicted responses of size spectrum slope was higher than for other size-based metrics.Synthesis and applications: Application of the ensemble model approach allows explicit representation of parameter uncertainty and supports advice and management by (i) providing uncertainty intervals for management reference points, (ii) estimating working values of reference points that achieve a defined reduction in risk of not breaching the true reference point, (iii) estimating the responsiveness of population, community, food web and biodiversity indicators to changes in F, (iv) assessing the performance of indicators and monitoring programmes and (v) identifying priorities for data collection and changes to model structure to reduce uncertainty.

View Article: PubMed Central - PubMed

Affiliation: Centre for Environment, Fisheries and Aquaculture Science (CEFAS), Lowestoft Laboratory Lowestoft, NR33 0HT, UK.

ABSTRACT

Implementation of an ecosystem approach to fisheries requires advice on trade-offs among fished species and between fisheries yields and biodiversity or food web properties. However, the lack of explicit representation, analysis and consideration of uncertainty in most multispecies models has limited their application in analyses that could support management advice.We assessed the consequences of parameter uncertainty by developing 78 125 multispecies size-structured fish community models, with all combinations of parameters drawn from ranges that spanned parameter values estimated from data and literature. This unfiltered ensemble was reduced to 188 plausible models, the filtered ensemble (FE), by screening outputs against fish abundance data and ecological principles such as requiring species' persistence.Effects of parameter uncertainty on estimates of single-species management reference points for fishing mortality (F MSY, fishing mortality rate providing MSY, the maximum sustainable yield) and biomass (B MSY, biomass at MSY) were evaluated by calculating probability distributions of estimated reference points with the FE. There was a 50% probability that multispecies F MSY could be estimated to within ±25% of its actual value, and a 50% probability that B MSY could be estimated to within ±40% of its actual value.Signal-to-noise ratio was assessed for four community indicators when mortality rates were reduced from current rates to F MSY. The slope of the community size spectrum showed the greatest signal-to-noise ratio, indicating that it would be the most responsive indicator to the change in fishing mortality F. Further, the power of an ongoing international monitoring survey to detect predicted responses of size spectrum slope was higher than for other size-based metrics.Synthesis and applications: Application of the ensemble model approach allows explicit representation of parameter uncertainty and supports advice and management by (i) providing uncertainty intervals for management reference points, (ii) estimating working values of reference points that achieve a defined reduction in risk of not breaching the true reference point, (iii) estimating the responsiveness of population, community, food web and biodiversity indicators to changes in F, (iv) assessing the performance of indicators and monitoring programmes and (v) identifying priorities for data collection and changes to model structure to reduce uncertainty.

No MeSH data available.