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About Markets

As fish move along the supply chain, from fishers to middlemen to exporters to consumers, the yellowfin tuna in our model are traded three times. At each trading point or market, prices are negotiated and fluctuate with supply and demand as the fish product changes hands.

We have arbitrarily named each market after the buyers: the middleman market, the exporter market, and the consumer market.

Each market has a current price, and tracks the volume of fish traded. Suppliers bring the fish to sell, and buyers bring a demand for fish. If demand outstrips supply, they negotiate a higher price. If there is a surplus of supply, prices drop and part of the product may get spoiled.

Move the initial conditions between under-fishing and over-fishing to see how markets react to changes in supply and demand.


When neither over- not under-fishing, catch is relatively stable,

When under-fishing, catch increases as fish stocks rebound,

When over-fishing, catch drops over time,

as are prices

more supply bring prices down

lack of supply drives prices up

and total consumer demand.

and consumer demand rises due to falling prices.

and consumer demand shrinks due to rising prices.