Monday April 5, 2010
Systems dynamics programs allow scientists to be able to program simulations without actually having to know a programming language.
For this challenge, you'll want to install your choice of system dynamics program. One such program is Vensim, which is free for educational use.


The news spotlight has been on tuna lately, and one species in particular: bluefin tuna. These fish are considered such a delicacy in Japan that a single fish can sell for thousands of dollars at auction. However, overfishing during the past century has been leading to the decline of these giant animals.

Use a system dynamics modeling program, such as Vensim, to model the decline of these animals, as well as to predict the future behavior of the population. Here are a few facts about the fish. The more you include, the more accurate your model will be:

  • Bluefin tuna take four years to mature. Before that, they are considered juveniles.

  • The natural death rate for juvenile bluefins is .36 naturally and .3 from fishing. That is, 36% of juveniles each year will die from natural causes, and 30% of the juveniles each year will die from fishing.

  • In adults, the natural death rate is .1 and the fishing death rate .35.

  • Adult bluefin can live to be 20 years old.

  • Assume an initial adult population of 3,000 individuals. Find an initial juvenile population that will allow stability without fishing.

  • Use your model to estimate how long the bluefin tuna will continue to exist if current fishing rates continue. Find a fishing rate that will allow recovery to a stable population, and estimate how long this rate will need to be in effect before stability is established.

    Additional Resources:

    Various statistics on the fish, including helpful reproductive and death statistics:

    Florida Museum of Natural History

    World Wildlife Fund Statistics
    Show solution
    Challenge Resources:
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