Beth Fulton
2012

Ecosim
 Time dynamic
 Ecopath = initial conditions
 Define
− Duration
− Environmental drivers
− Contaminants option
− Fleet dynamics option
ECOPATH, ECOSIM and ECOSPACE

Ecosim
 Basic equation dB i dt
 g i
 j
Q ji
  j
Q ij
 I i


M i
 F i
 e i

B i
ECOPATH, ECOSIM and ECOSPACE

Ecosim – Group info
 Flow-control: (top-down to bottom-up)
− Sensitive parameter
− check with sensitivity analysis, time series fitting, twomodel comparison, Bunfished/B
 Feeding time adjustment rate
0
, F max
/M)
 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 Covers…
 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 – Forcing functions
 Forcing functions (seasonal, long-term, environmental, productivity…)
ECOPATH, ECOSIM and ECOSPACE

Ecosim Covers…
 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 - Mediation
 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 – vulnerabilties
 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
 Vulnerable prey
Unavailable prey
B-V
B = Total prey biomass;
V = Vulnerable prey biomass; v = Behavioral exchange rate;
P = Total predator biomass; a = Predator rate of search.
v(B-V) vV
Predator
P aVP
Available prey
V
Fast equilibration between B-V and V implies V=vB/(2v+aP)

Ecosim – forecasts fishing effects

Ecosim – check Ecopath
 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
 Input ► Fishing rate
− pick fleet
− sketch a disturbance (fishing rate change)
ECOPATH, ECOSIM and
ECOSPACE

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 – using past time series
 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

 Compare time series

Ecosim – sensitivity analysis
 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 Extras
 Fisheries policy search (economic, social, biological objectives)

Ecosim Extras - MSE
 Management Strategy Cycle (reproducing management cycle)

Ecosim Extras - MSE
 Enter options, regulations etc

Ecosim Extras - MSE
 Multiple runs to see probability of outcomes

Ecosim Example

Ecosim Example
 Catch and effects at different levels of depletion

Example
 Compared to other models

Thank you