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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 distributions for the predicted power of the North Sea International Bottom Trawl Survey (IBTS) to detect modelled changes in the values of community metrics for all demersal fishes (Lifetype D1, Table 1) when fishing mortality is reduced from FHIST to FMSY over 5-year (grey) and 15-year (black) periods. Metrics are (a) mean length, (b) proportion of large fish, (c) size spectrum slope and (d) mean maximum weight. Vertical lines denote mean power for all model variants in the filtered ensemble (FE).
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fig05: Frequency distributions for the predicted power of the North Sea International Bottom Trawl Survey (IBTS) to detect modelled changes in the values of community metrics for all demersal fishes (Lifetype D1, Table 1) when fishing mortality is reduced from FHIST to FMSY over 5-year (grey) and 15-year (black) periods. Metrics are (a) mean length, (b) proportion of large fish, (c) size spectrum slope and (d) mean maximum weight. Vertical lines denote mean power for all model variants in the filtered ensemble (FE).

Mentions: Power of the North Sea IBTS to detect changes in community metrics was assessed by comparing the magnitude of change in mean metric values when model F transitioned from FHIST to FMSY with the magnitude of interannual variation in metric values from IBTS data. For community metrics applied to all demersal species (Table 1, see Lifetype D1), there was a 0·6 to 0·8 mean power of detecting a change in ML, MMW or LFI that occurred over 5 years and a mean power of >0·9 of detecting a change in SSS (Fig. 5). After 15 years simulated monitoring, mean power was still <0·8 for ML, ≈0·9 for MMW, ≈0·95 for the LFI and 1·0 for SSS. For all community metrics except SSS, there was significant variation in power among FE variants after 15 years. For example, for LFI, power ranged from 0·7 to 1·0. Power to predict changes in community metrics for all demersal species was generally a little lower than for strictly demersal species (Table 1, see Lifetype D2), but SSS still provided greatest power after 5 and 15 years (Fig. S8).


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 distributions for the predicted power of the North Sea International Bottom Trawl Survey (IBTS) to detect modelled changes in the values of community metrics for all demersal fishes (Lifetype D1, Table 1) when fishing mortality is reduced from FHIST to FMSY over 5-year (grey) and 15-year (black) periods. Metrics are (a) mean length, (b) proportion of large fish, (c) size spectrum slope and (d) mean maximum weight. Vertical lines denote mean power for all model variants in the filtered ensemble (FE).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig05: Frequency distributions for the predicted power of the North Sea International Bottom Trawl Survey (IBTS) to detect modelled changes in the values of community metrics for all demersal fishes (Lifetype D1, Table 1) when fishing mortality is reduced from FHIST to FMSY over 5-year (grey) and 15-year (black) periods. Metrics are (a) mean length, (b) proportion of large fish, (c) size spectrum slope and (d) mean maximum weight. Vertical lines denote mean power for all model variants in the filtered ensemble (FE).
Mentions: Power of the North Sea IBTS to detect changes in community metrics was assessed by comparing the magnitude of change in mean metric values when model F transitioned from FHIST to FMSY with the magnitude of interannual variation in metric values from IBTS data. For community metrics applied to all demersal species (Table 1, see Lifetype D1), there was a 0·6 to 0·8 mean power of detecting a change in ML, MMW or LFI that occurred over 5 years and a mean power of >0·9 of detecting a change in SSS (Fig. 5). After 15 years simulated monitoring, mean power was still <0·8 for ML, ≈0·9 for MMW, ≈0·95 for the LFI and 1·0 for SSS. For all community metrics except SSS, there was significant variation in power among FE variants after 15 years. For example, for LFI, power ranged from 0·7 to 1·0. Power to predict changes in community metrics for all demersal species was generally a little lower than for strictly demersal species (Table 1, see Lifetype D2), but SSS still provided greatest power after 5 and 15 years (Fig. S8).

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.