What is it about?
This is a study of the uncertainty in modelling fish community dynamics caused by our lack of understanding key biological processes. We study a 21-stock fish community in the North Sea and evaluate impacts on key fisheries reference points (FMSY, BMSY). We find with high confidence that :- a) predictions of F are less uncertain than those of B. b) BMSY is less than 0.5 x virgin biomass (B0). c) the slope of the community size spectrum is the best indicator of fishing impacts of the 4 considered.
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Why is it important?
The international legal framework requires that fisheries are managed to the principle of maximum sustainable yield (MSY) from an ecosystem perspective. ICES mandates the use of multispecies (taking account of stocks eating/interfering with other stocks) and mixed fisheries (different stocks being caught together by particular fleets) models in providing advice. However, in practice multispecies models are not used much in the advice process due to concerns that they are too complex to understand, and the uncertainties associated with them are too high. Here we investigate the model parameter uncertainty associated with a multispecies model in a rigorous manner. By being honest about the uncertainties, we show where the model can produce a signal useful to decision-makers, and hence increase confidence in its use.
Perspectives
In my view, this paper provides the basis of a new way of assessing fisheries management outcomes, where those outcomes are expressed in a 2-dimensional framework of risk and reward. In so doing, we get to the heart of the age-old management dilemma; how do we balance today's exploitation against preservation for use tomorrow? We have subsequently used this framework to look at fleet management and the application of ICES-style "pretty good yield" ranges, as seen in: a) Assessing fishery and ecological consequences of alternate management options for multispecies fisheries R.B. Thorpe, P.J. Dolder, S. Reeves, P. Robinson, and S. Jennings ICES Journal of Marine Science, 2016, 73(6), 1503-1512 DOI 10.1093/icesjms/fsw028 b) Risks and benefits of catching pretty good yield in multispecies mixed fisheries R.B. Thorpe, P.J. Dolder, and S. Jennings ICES Journal of Marine Science, 2017 DOI 10.1093/icesjms/fsx062 See https://www.researchgate.net/profile/Robert_Thorpe/
Robert Thorpe
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This page is a summary of: Evaluation and management implications of uncertainty in a multispecies size‐structured model of population and community responses to fishing, Methods in Ecology and Evolution, December 2014, Wiley,
DOI: 10.1111/2041-210x.12292.
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