Chapter 9 Changing policies within the simulation

9.1 Dynamic changes

Policies can be modified while the simulation is running. The idea of POSEIDON is that the agents ought to be able to adapt to whatever you throw at them without having to stop and recode them. Hopefully this section will give you some confidence that this is indeed the case.

9.2 Switch to quotas 2 years in the simulation

Start POSEIDON and the abstract scenario without making any modifications to the parameters. After pressing play, the tab called Policies will become available in the top of the controller. We can use it for, among other things, change the regulations of the fishery.
Run the model for 2 years, then:

  1. Click on the Policies tab
  2. Choose Mono-IQ for the Global Regulations parameter
    • This regulation means that fishers will be given individual non-tradeable quota (mono refers to these quotas being only valid for the first species).
  3. Change Individual Quota to 500 or 600
    • This is the maximum yearly amount of fish catchable by each boat
  4. Press the button Change regulations for all agents

You will see the fishery starting to pulse as quotas ends and replenish as well as a progressive retreat of the fishing front as biomass grows back in previously depleted areas.
You can also look at data such as Species 0 Landings, both yearly and daily, to see the aggregate effects of this policy change.

9.3 Closed Season

Let’s switch from a quota system back to a maximum number of days at sea system:

  1. Click on the Policies tab
  2. Choose Fishing Season for the Global Regulations parameter
  3. Change Season Length to 200
    • This implies that only 200 days out are allowed for each boat each year
  4. Press the button Change regulations for all agents

The fishery will still pulse, but this time at regular time intervals. Again, you can look at the data to get a better idea of what this means in aggregate.

9.4 Draw MPAs on the fly

Let’s remove effort constraints but add some MPAs in the area.

  1. Click on the Policies tab
  2. Choose Fishing Season for the Global Regulations parameter but set season length to 400
    • Any number above 365 really means that there is no season
  3. Press the button Change regulations for all agents
  4. Press the button Draw new MPAs
  5. Now if you click and hold on the map you can draw MPAs
    • This will look like grey boxes in the model
  6. You can do this repeatedly until you click again on the Draw new MPAs button

The fishery will not pulse but the agents will scrupulously avoid protected areas.