The Fishing Game Model:
The model for the fisheries based on the basic model in the Fishbanks game. Two curves control increases in fish population, and the individual ship catches. The curves are integrated over the year and during the fishing season to provide the results of each year's fishing.
Regeneration of fish: This curve shows that birthrate is proportional to the numbe of existing fish. But, as the number approaches the maximum population, the birthrate drops due to lack of habitat and food. This is a very simple model and includes all birthrate effects, such as that of predation. Also, it assumes that all fish are equal and that all fish can reproduce, and the overall population will reproduce at the rate shown by the curve.
Ship effectiveness: Each ship catches a maximum of 25 fish/ship. This may vary because of weather factors. As the fish population declines, the density of fish is lower and it is harder to catch fish, so the catch declines. In the real world, many factors affect the catch. Technology has made it possible for fishermen to find and catch fish, even when the population is low.
Scenarios: The "No Limits" fishing season is 90 days. When the fishing season is shortened in the "Limit Fishing Season" scenario, the ship effectiveness is reduced under the assumption that the catch rate is proportional to the length of the season. The "Marine Reserves" scenario models a separate reserve area for each fishing region. No fish are caught in the reserve. Fish migrate slowly from the reserve to the fishing area, depending on the difference in density of fish in the reserve and the fishing area. "Catch Shares" simply stops the catch when each boat has caught the limit. The ship effectiveness curve still applies, so if a company sends too few ships to sea, the catch may not reach the "Catch Share" limit. If the company sends too many ships to fish, the income per ship will be reduced, so the player needs to determine the optimu number of ships using the modeling tool.