Limits to stock assessments & dynamic ecosystems model projections for management
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The document discusses the limitations of stock assessments and the challenges of predicting future marine ecosystem states using various modeling approaches. It emphasizes the importance of incorporating environmental dynamics to enhance understanding and management predictions, while recognizing that long-term predictions are often fraught with uncertainty due to factors like stochasticity and ecological surprises. Ultimately, it concludes that effective fisheries management should focus on adaptability and ongoing monitoring rather than reliance on precise future forecasts.
Limits to stock assessments & dynamic ecosystems model projections for management
- 1. Limits to stock assessments & dynamic ecosystems; model projections for management Twitter @DickeyCollas Mark Dickey-Collas & Benjamin Planque
- 2. Panorama of stock assessments and MSE approaches includes: Isolated single stock Multispecies Environmental dynamic Data poor Ensemble approaches+ +
- 3. Why use environmental dynamic? Improve understanding of past changes by including environmental changes/shifts. Improve predictions for management? Look further forward than standard stock assessments.
- 4. Examples... Productivity North Sea herring ↘weight, ↗ maturity North East Atlantic mackerel
- 5. Hatun et al, 2009; Hatun et al 2009 Have the approaches been useful to understand the past? Blue whiting
- 6. Have the approaches been useful to predict the future? Probably no. Predicted year in which the conditions become suitable for Atlantic cod. Wisz et al. 2015
- 7. Have the approaches been useful to predict the future? Probably no. Simulated biomass of adult cod in the Baltic Sea using 5 different food- web models. Niiranen et al. 2012
- 8. Why is prediction beyond short time horizon so difficult? La grande illusion Was the pet included in the pet model? drawing Juliette Planque
- 9. Why is prediction beyond short time horizon so difficult? La grande illusion “Models might be of limited use to project the future state of marine ecosystems decades into the future because several factors limit predictability; including ● stochasticity ● deterministic chaos ● enablement vs. entailment ● non-ergodicity ● ecological surprises ● irreducibility ● limits to upscaling.”
- 10. La grande illusion The known The unknown The unknownable Conservation of mass and energy Gravitation Fluid dynamics ecological empirical observations Fish recruitment How many species Trophic functional relationships Complex interactions and the curse of dimensionality Natural mortality Single pendulum
- 11. La grande illusion The known The unknown The unknownable Conservation of mass and energy Gravitation Fluid dynamics ecological empirical observations Fish recruitment How many species Trophic functional relationships Complex interactions and the curse of dimensionality Natural mortality Single pendulum Double pendulum
- 12. Are models geared up to predict future states? Hazard warning
- 13. Are models geared up to predict future states? Hazard warning Impossible to achieve realism, precision, and generality together. Model creation requires trade-off of one of these, often in conflict with the desires of end-users. Models are often employed without consideration of their limitations, such as projecting into unknown space without generalism, or fitting empirical models and inferring causality.
- 14. Do we need predictions beyond a few years for robust management? • Accept we only ever have partial understanding • We have ongoing monitoring and assessment • Business planning or fisheries management? • Adaptive management • Time line – a few years or longer?
- 15. Operational Recommendations • Keep monitoring and prepare for change • Remain responsive and adapt • Use MSE but don’t trust it Science 2015
- 16. Conclusion Robust fisheries management is about coping with an unexpected future, not preparing for a predicted future.
- 17. Thank you Picture: Icelandic Wilderness