limits to stock assessments & dynamic ecosystems model projections for management
TRANSCRIPT
Limits to stock assessments & dynamic ecosystems;model projections for management
Twitter @DickeyCollas
Mark Dickey-Collas & Benjamin Planque
Panorama of stock assessmentsand MSE approaches includes:
Isolated single stock Multispecies
Environmental dynamic Data poor
Ensemble approaches+ +
Why use environmental dynamic?
Improve understanding of past changes byincluding environmental changes/shifts.
Improve predictions for management?
Look further forward than standardstock assessments.
Examples...
ProductivityNorth Sea herring
↘weight, ↗ maturityNorth East Atlantic mackerel
Hatun et al, 2009; Hatun et al 2009
Have the approaches been useful to understand the past?
Blue whiting
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
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
Why is prediction beyond short time horizon so difficult? La grande illusion
Was the pet included in the pet model?drawing Juliette Planque
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.”
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
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
Are models geared up to predict future states? Hazard warning
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.
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?
Operational Recommendations
• Keep monitoring and prepare for change• Remain responsive and adapt• Use MSE but don’t trust it
Science 2015
Conclusion
Robust fisheries management is about coping with an unexpected future, not preparing for a predicted future.
Thank you
Picture: Icelandic Wilderness