ecosim beth fulton 2012. time dynamic ecopath = initial conditions define duration environmental...
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Ecosim
Beth Fulton2012
Time dynamicEcopath = initial conditionsDefine − Duration− Environmental drivers− Contaminants option− Fleet dynamics option
ECOPATH, ECOSIM and ECOSPACE
Ecosim
Basic equation
iiiiij j
ijjiii BeFMIQQg
dtdB
ECOPATH, ECOSIM and ECOSPACE
Ecosim
Flow-control: (top-down to bottom-up)− Sensitive parameter − check with sensitivity analysis, time series fitting, two-
model comparison, Bunfished/B0 , Fmax/M)
Feeding time adjustment rate Predator effect on feeding time− 1.0 = stop feeding if predation risk high − 0.0 = ignore predation risk high
Other mortality (top predators sensitive to this) Catchability Environmental tolerances
Ecosim – Group info
ECOPATH, ECOSIM and ECOSPACE
Ecosim – Group info
Ontogenetic changes (growth vs reproduction, egg production)
Feeding related changes (diets, feeding time, handling time)
Trophic effects (predator/prey dynamics)
ECOPATH, ECOSIM and ECOSPACE
Ecosim Covers…
Forcing functions (seasonal, long-term, environmental, productivity…)
ECOPATH, ECOSIM and ECOSPACE
Ecosim – Forcing functions
Drawn or imported Apply to different groups / interactions on ‘Apply FF’ Primary productivity over time (apply to primary
producers or their interactions)
ECOPATH, ECOSIM and ECOSPACE
Ecosim Covers…
Mediation effects
ECOPATH, ECOSIM and ECOSPACE
Ecosim - Mediation
How you put in non-trophic interactions− done in very similar way to forcing (apply using
‘Apply FF’ sheet but select mediation option)
Ecosim - Mediation
Vulnerability = rate become vulnerable to predators
ECOPATH, ECOSIM and ECOSPACE
Ecosim – vulnerabilties
Parameterise which wins out hunger or fear
Depending on parameterisation can create many alternative functional responses (LV, Holling types, ratio dependent etc)
ECOPATH, ECOSIM and ECOSPACE
Ecosim – vulnerabilties
Unavailable prey B-VUnavailable prey B-V
Available prey VAvailable prey V
B = Total prey biomass;V = Vulnerable prey biomass;v = Behavioral exchange rate;P = Total predator biomass;a = Predator rate of search.
B = Total prey biomass;V = Vulnerable prey biomass;v = Behavioral exchange rate;P = Total predator biomass;a = Predator rate of search.
v(B-V)v(B-V)
vVvV
Fast equilibration
between B-V and V
implies V=vB/(2v+aP)
Fast equilibration
between B-V and V
implies V=vB/(2v+aP)
PredatorP
PredatorP
aVPaVP
Ecosim – vulnerabilties
Vulnerable prey
Fishing effort over time
Biomass/original biomass
Ecosim – forecasts fishing effects
Output ► Run Ecosim− is everything flat (or changing according to the
Biomass Accumulation)?− if ‘wild’ look at balance, small plankton, discard effects
ECOPATH, ECOSIM and ECOSPACE
Ecosim – check Ecopath
ECOPATH, ECOSIM and ECOSPACE
Input ► Fishing rate− pick fleet− sketch a disturbance (fishing rate change)
Ecosim – check Ecopath
Go to Output and rerun− if everything OK the trajectories come back to initial
value (eventually)− are all groups reacting at the speed you expect them
to?
Ecosim – check Ecopath
Relative or absolute biomasses Mortality rates, F, Z, catches Effort data Forcing factors (primary productivity) Incorporates goodness of fit measure (weighted SS) Anomaly fitting (productivity, recruitment) Fit to data Similar to single species assessment
Ecosim – using past time series
Compare time series
Group info parameters Vulnerabilities− high v = Lotka-Volterra like with small perturbations
= top-down − low v = bottom-up− explore settings to edge of stability− fit to data
Ecosim – sensitivity analysis
Remove fishery− check system evolution− should maintain all species− recheck vulnerabilities (higher less stable)− fit to data
Ecosim – sensitivity analysis
Fisheries policy search (economic, social, biological objectives)
Ecosim Extras
Management Strategy Cycle (reproducing management cycle)
Ecosim Extras - MSE
Enter options, regulations etc
Ecosim Extras - MSE
Multiple runs to see probability of outcomes
Ecosim Extras - MSE
Ecosim Example
Catch and effects at different levels of depletion
Ecosim Example
Compared to other models
Example
Thank you