The Tragedy of the Commons part 1: Unregulated Fishing

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Big Idea

Students learn about the environmental problems outlined in "the Tragedy of the Commons" by simulating economic competition between fishing companies in an unregulated ocean.


This lesson sequence provides a simulation to illustrate the thesis of Garrett Hardin’s seminal work, the Tragedy of the Commons.  The article itself is a fascinating read and I highly recommend it, though it is probably a bit beyond the reach of all but the most academically high achieving high school students.  Rather than assign the article as a reading assignment, I mention the article and summarize what is generally agreed to be the main idea:

Without regulation, individuals acting in their own rational self interest will eventually deplete common resources because: 1) the benefits gained from exploiting common resources go to the individual that does so, while 2) the costs of such exploitation are shared equally by all individuals using the common resources.

Rather than begin our exploration of the nature of environmental science with such a deep dive into abstract, theoretical considerations, I find it better to approach the same content in a game-like simulation where exploiting the common resources confers obvious benefits (e.g., more candy!).  In this simulation, each individual in a group of four becomes the owner of a fishing company trying to catch the most fish (candy) out of an ocean fishery (plastic plate).  


This lesson sequence requires substantial preparation on the part of the teacher to have all the necessary materials and worksheets ready for the first day of the activity.  I recommend giving yourself at least a day or two buffer just in case you have trouble locating any materials.

The materials you’ll need:

  1. Plastic Plates (I prefer blue) to be “The Ocean”
  2. Bendy straws (sufficient for at least 2 per student)
  3. Small plastic cups (sufficient for one per student to hold their "catch")
  4. Four large bags of candies to represent four species of fish (It would be possible to use the different colors of a multicolored candy (such as M&Ms, Skittles, jelly beans, etc.) as different species, but that would require some extra prep time to sort them by color.  If you were to do this, I would suggest Skittles as the economic choice as their small size means there are more pieces per bag.  I used:
    • Peanut M&Ms
    • Skittles
    • red licorice bites
    • black licorice bites


Connection to Standard:

This lesson asks students to participate in a simulation to model the environmental effects of a an unregulated economy.  To perform the simulation, students must follow a complex, multistep procedure.  Following each day of the simulation, students must use the data they collected and their anecdotal experiences as evidence to support claims and make predictions.  


Warm Up

10 minutes

I begin by letting students know that we’re going to be conducting a simulation to model the relationship between economics and the environment… and that’s pretty much it.  I purposely keep them in the dark on this first day as the point is for them to see how an unregulated, “winner take all” approach to natural resources winds up making loser out of everyone.  

I simply tell them that they are each the owner of a fishing company trying to make the most money possible by catching the most fish.  I let them know that after they total up their earnings in each round, they get to eat their "catch".  As I’m sure you can imagine, this delights them greatly.  

I ask for a volunteer to distribute one blue plastic plate to each lab group and let the class know that this plate represents the fishery in their group’s region of the ocean.  I then ask another volunteer to distribute 2 straws per student and I explain that these are their fishing tools* and that they are expressly FORBIDDEN from using their hands while “fishing”.  I try and drive home this point with an announcement that this is obviously not a real fishing situation, it is a model, and that the model doesn’t work if people cheat.  If necessary, I let them know that cheating will result in a failing grade for the project.


*It’s up to each individual student how to use the straws to catch the candy.  Some may use them as chopsticks, some may use air pressure of the straw to pick up pieces, others will connect two straws to have a longer “fishing pole”.

I then distribute the “fish” to each group’s region of the ocean, placing 6 pieces of each candy on each group’s plate.


50 minutes

Before we begin the simulation I let the students know that they will have to act strategically because the candy “fish” are not of equal value.  I then show the following values,





Red Licorice




Black Licorice



I let them know that they will have to make at least $10 per round to stay in business, and that they will fish for ten seconds only.  


Game on!

Once they are ready, we begin the first round by shouting, "GO!", and after 10 quick seconds I yell, “Stop! Stop! Stop! round is over!”.  

After this first round, I distribute the Accounting Form worksheet to each student and explain to them that they need to count up how many of each fish they caught to figure out how much money they earned that round.  


While they are doing this accounting, I walk around to each group and restock their region’s fishery according to the following rules:

  • For every two surviving fish of a particular species, one fish of that species is added.  (e.g., if there are 4 M&Ms remaining, I add 2 more to the ocean.  If there are 7 skittles, I only count the “couples” and add 3)
  • If there are is only one fish of a particular type remaining, it is the “last of its kind” and no more will be added to that region.


As I walk around restocking the fisheries of the different groups (without explaining this rule), some groups that did particularly well at "fishing" are upset that they aren’t receiving many new pieces of candy.

One interesting result may be that the lower value fish (e.g., black licorice) have greater survivors than the higher value fish (e.g., M&Ms).  I intentionally select black licorice as the lowest economic value as it’s also the least coveted by students to eat.  Depending on your students’ particular tastes, you may want to select a different “nasty” candy for them to avoid.  This models the trend in real-world fisheries where highly sought after species numbers are declining while less appetizing species remain.  

Managing "the Books"

After I have restocked each fishery, I distribute one copy of the International Fishing Commission Report worksheet to each group.  Since everyone begins with 6 of each species, I tell them to put 6 in each category for round 1, and then to enter their current populations as the starting population of round 2.  They should also total each column (e.g., the first round would have 6 of each species for a total population of 24).    

It’s very important to check that all groups are doing this because, unlike their accounting form, there is no written record of the starting populations for each fish species.  

As far as the revenue chart, one member of the group should write in the revenue for the round for each member as well as total revenue for the entire region.  They should keep track of this every round, but at least these values are also recorded on the accounting forms if any group fails to complete this chart.

After all the accounting and population counts have been completed, students get ready for another round and we repeat this process three more times.  


Extinction Sale (Everything Must Go)

Before the final round, I announce that it is the final round and if they want to win the prize, they need to be competitive.  After this final round though, I still do a final restocking and have the students write down another round’s “starting population”.  However, instead of calling it "Round 5", I have them label it “Your children’s future” to spice it up a bit.

Wrap Up

5 minutes

It is quite likely on this first day that some groups will have completely depleted their fishery before four rounds of the simulation.  Once a group’s fishery is depleted, they are effectively “out of the game” and they do not participate in subsequent rounds.  Students may act a bit surly or sullen about this, but I reply, “You should have managed your fishery better” or “you should have had a long term plan”.  As a slight consolation, I give these groups’ members the Day 1 Questions worksheet early and, if they are willing, enlist their help in managing the candy resources between rounds.  

Once all rounds have been finished, I distribute the Day 1 questions worksheet to all students and ask them to complete it as homework for the next day.  I then ask who had the highest final balance after four rounds.  In the event that there is a student that the student with the highest final balance came from a group that depleted their fishery.  I add insult to injury and say, “No, I’m sorry… you’re dead.  Your money couldn’t buy any fish because they were all GONE.”  

Whomever has the highest final balance AND managed to keep their fishery in business until the end of the final round gets a prize of an actual large candy bar.  If no one meets these criteria, I hold up the candy bar and let them know that they could have won this, if only they hadn’t been so greedy and left a little bit for the future.  Needless to say, some students leave class this day a little upset with me.  But that’s ok… there’ll be a chance for redemption the next day.