Presentation by Mark Dickey-Collas and Benjamin Planque at the 7th World Fisheries Congress, Busan, Korea, 23-27 May 2016

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