Environmental Systems
Modelling Prompt: Fishery
After completing this worksheet, you should have realized that tigers, chitals, boats and fishes are all the same at the end of the day.
Software you need for this modelling prompt:
A fishery
The following has been observed (example taken from Bossel 2004, p.202): There is a lake with some fishery. Without fishery, the fish population will depend on the lake's carrying capacity. The catch of the fisher(wo)men depends on the number of (identical) boats available and the actual fish population. Having some boats is an expensive undertaking regarding the initial costs and running coasts. The latter make old boats uneconomic so they are withdrawn (cost neutral). For the fisher(wo)men at the specific lake, a good life is the one with a maximum net-income.
Modelling
Please model the fishery system using a stock and flow diagram. In contrast to the tiger and chital example where the initial stocks have been set to 0.1 each, your model should be able to handle initial values larger than 1.
Simulation
- initial fish stock (or similar): 5,000 t
- initial boat number (or similar): 100
- values for all other variables are up to your choice.
Interpretation of simulation results
- To which of those is the fishery most similar? Why is that the case?
- Which generic structures can be found between the fisher model and the one for tigers and chitals?
- Does the system behavior change if you use other values for your variables?