Required Software

To open these system models, you will need to download a software called Vensim.

To run the model press the first green play button called Simulate in the top, middle of the toolbar. To adjust the parameters such as dolphin death rate, press the second green play button called SyntheSim. When you run the model using SyntheSim, slider bars will appear under the variables you can change. Feel free to change the variable and watch the graph change. Warning, when you run the SyntheSim it might be laggy so be patient.

Model 1: Just Dolphins

In this model the only quantity is dolphins. There is a birth rate for dolphins that increases the dolphin population. There is a dolphin death rate and number of fisherman boats that decrease the dolphin population. Our model scale is from 0-360 days (approximately a year).

If the birth rate of the dolphins increases then the dolphin population will grow exponentially. If the dolphin death rate or number of fisherman boats increases then the dolphin population will decrease exponentially. If the dolphin birth rate is equal to the dolphin death rate times the number of fisherman boats then the dolphin population will remain constant

Conclusion

This model proves that the population of fisherman (fish boats) and dolphin populations are inversely related to each other.

Model 2: Dolphins, Fish, and Fisherman Boats

In this model the quantities are dolphins, fish, and fisherman boats. Each quantity has a birth rate and a death rate that increases or decreases the population. Since both dolphins and fisherman boats eat/catch fish, the more dolphins or fisherman, the higher the fish death rate. This also means that if there are more fish, than more dolphins and fisherman boats will be born. Also, since Fisherman Boats kill Dolphins in their nets, the more the fisherman boats, the higher the dolphin death rate. Our model scale is from 0-360 days (approximately a year).

The graph of the fisherman population and fish population will always have the same shape. If we increase the fish birth rate, the number of fish will increase and the maximum number of dolphins in the 1 year period will also increase. If decrease the number of fisherman boats by decreasing the fisherman death rate, the dolphin population will increase and at some times be more than the number of fish. If we increase the dolphin death rate due to fisherman boats the dolphin population will decrease during the one year period

Conclusion

We learned that by decreasing the fisherman population by as little as 5%, the dolphin population can increase by 20% in a one year period. Our model also proves that the number of fish and fisherman boats are directly proportional. We also observed that as fish population increases so does the dolphin population but if the fish population increases so does the fisherman boat population which kills dolphins. We found that the dolphin population peaks a few days after the fish population does. This is because this is when the fish population is the highest while the fisherman population is the lowest.