Lesson Plan – Tragedy of the Commons, Cod Fishery

The collapse of the cod fishery – MSY and tragedy of the commons


The collapse of the cod fisheries in the early 1990s finished what had started decades earlier – the continued overfishing of a species above its maximum sustainable yield (msy). The scientific data collected by the Canadian governments DFO (department of fisheries) in estimating cod stock, were said to have been off by as much as 100%. Newfoundland, the primary area in the world and in Canada where cod fishing took place, did not join Canada as a province until 1949. It was then, some day, that the real tragedy began; Newfoundland placed their most important resource in government hands to be managed and maintained by Canada. In 1992 John Crosbie announced the ban on cod fishing within 200 miles of Newfoundland. The ban was backed by the government, who has since payed dislocated workers and fisherman over 4 billion dollars in compensation. Outraged, and forced to adapt to a new way of life, or leave their home, Newfoundlanders have often wondered: just what went wrong? What could we have done to prevent this problem? One answer presented in an online video series (http://archives.cbc.ca/economy_business/natural_resources/topics/1595/) suggests that distributing our resources to be managed by private hands would create incentives to preserve them for the future. This tragedy of public resource ownership is commonly refereed to as: “The Tragedy of the Commons”. This lesson will explore exactly what this tragedy is and how we could learn from it in everyday life. It will also explore the concept of MSY and explain how miscalculations by Canadian scientists in MSY largely contributed to the collapse of the cod fishery.


  • Have students be able to explain and define what maximum sustainable yield is, and to understand how wildlife managers use it.
  • Students should be able to explain and define the “tragedy of the commons” and give an example of it in their own lives. Students should be able to see the pros and cons of private ownership vs. public ownership of resources.
  • Students should gain a brief overview of what happened in the cod fishery and know key points in the story, such as: where it took place (Newfoundland), who was involved (John Crosbie, scientists, etc) and be able to identify some key features of the cod species that makes them unique (large size, swim with open mouths, bottom feeders, etc).


  • Video of “Taking Stock” or access to a large projector and the internet to view the online videos.
  • Lots and lots of small candy to play my “Tragedy of the Commons game”
  • Chalk and blackboard or a marker and white board to explain MSY


  • Begin by briefly explaining the next few steps – tell the students we will watch a film about the fisheries and ask them to take notes on the film. Tell them there will be an easy quiz on the film at the end of it and if they were paying attention and taking notes, they should do fine. The basic things I want students to gain from the film are: a basic knowledge of cod and what exactly happened to the cod fishery. For the quiz you can include questions such as: list 3 things that are special about cod that make it a great food source. List 3 characters in the film and explain what happened in their life (ie. The fishermen who lost his job, etc). The film is called “Taking Stock” and was available in the library at University of Alaska Fairbanks. I am sure that a library in your town has a copy, or you may be able to reserve it through our inter-reserve library program and have it sent to you. If you cannot find the film, go to http://archives.cbc.ca/economy_business/natural_resources/topics/1595/There are clips from the film and other places there that have the same basic message and will be adequate for this lesson. I would recommend skipping the radio segments. I thought they didn’t have anything to add to the story of the cod. This is of course, except for the last radio segment of Mr. Crosbie talking about “The tragedy of the commons”. This is a must.
  • After having students view the video and taking the video quiz, ask the students the following question: Why do you think the cod fisheries were lost? What could we have done to prevent this incident? (if the students don’t bring it up themselves, ask them: what role did scientific evidence have in the decision to continue fishing? Was the evidence accurate? Who took the measurements and did anyone listen to the scientific community?) Ask the students what they think – is it right to close the fishery or is it better to keep it open and help the people of Newfoundland?
  • Get a piece of chalk and draw the MSY curve on the board. Write the definition of MSY which, in my own terms is: the largest yield (or catch) that can be taken from a species’ stock over an indefinite period. Talk about carrying capacity and define what it is: population size of the species that the environment can sustain indefinitely, given the food, habitat, water and other necessities available in the environment. Talk about factors that can affect carrying capacity, which are death and birth rates, as well as immigration or emigration of animals. Obviously 12 year old students are not going to understand the math involved, but they should be able to grasp a brief overview of what MSY is, how it uses carrying capacity to harvest at 50% of that, and they should know that wildlife managers use MSY in their daily work. The main point I want students to walk away with at this stage is: small miscalculations, even by a very small amount can lead to huge mistakes (such as the total collapse of a multi-billion dollar fish industry!) If you are confused at what exactly MSY is and how it had a role in the collapse of the cod fisheries, I would suggest reading the following:- good starting article here: http://www.pisces-rfr.org/UK/In_Brief/Entries/2008/3/1_Maximum_Sustainable_Yield.html

    - a great researcher and professor who’s thesis basically states that the entire reason fisheries collapsed in the 1990s was because of the governments decision to make MSY the standard for fisheries management in the 1950s: http://www-csgc.ucsd.edu/NEWSROOM/NEWSRELEASES/Carmel_Finley.html

    - a very good paper, but heavy reading about how fisheries management is approached and a bit about MSY as a population indicator: http://www.fao.org/DOCREP/005/Y3427E/y3427e07.htm

    ** It is my personal opinion, but according to the material I’ve read and the people I’ve talked to, MSY just isn’t a good indicator for harvest management. This is especially true in fisheries where we have trouble “seeing” our stock to begin with. This is an on-going argument in wildlife management and I’m sure will continue for decades to come**

  • Remind the students of what Mr. Crosbie said in the video or radio segment about creating “privately owned resources”. Introduce the topic of “The tragedy of the commons”, which is defined as: a situation in which multiple individuals, acting independently, and solely and rationally consulting their own self-interest, will ultimately deplete a shared limited resource even when it is clear that it is not in anyone’s long-term interest for this to happen.
  • In order to better understand this tragedy, students (and teacher perhaps, if you enjoy candy!) will play a little game I created. Have the students make a giant circle and stand on the outside of some masking tape on the floor. Before the game begins, scatter some candy, such a Hershey’s Kisses, on the floor. Tell the students that there will be two rounds of this game. In the first round, everyone should take some pieces of candy and they will get to keep them to eat later. In the second round, whatever is left will be tripled – the teacher should count the number of pieces left and add more in before the second round.Most likely, (if students are students) they will devourer all the candy in the first round when you say go. There should be nothing left for the second round. Then, have students play the game again, this time, divide the students into small teams, and section off areas of the circle into smaller ones. Each group will have their own area, from which no other group may take candy. Explain to them that the same rules apply, but they cannot touch the other team’s candy. Whatever the students keep in the first round will triple in the second. If things go well, students will be smart and save their candy, thus earning many more sweets later on ^_^
  • Clean up the area and while the students are munching on candy, tell them the candy represents natural resources, (such as animals, rain forest, etc) and ask them what happened. Why did the students want to save their candy when it was privately divided? Explain to them that this is public ownership of a resource vs. private ownership, and that this is “The Tragedy of the Commons”. Ask them how this can be applied to the fishery.
  • Also ask the students the following: Where else in their lives have they seen this tragedy? (the kitchen, or on the playground?) Ask them if they think common things like air, water and minerals are in the same situation? Why or why not?
  • Clean up your area and have the students do the following assignment: Write a half page paper on what the tragedy of the commons is, and what it means to them. Ask them to give a real life example in the paper, and explain how it applies to the cod fishery.


Please make sure students are safe through the whole process, especially the candy game. Younger students especially have a tendency to dash or dive into the circle in order to get the most sweets, and depending on the group you have, you may wish to do a different activity.

3 comments for “Lesson Plan – Tragedy of the Commons, Cod Fishery

  1. sktodd
    July 12, 2010 at 5:40 pm

    David, You are very thorough and imaginative in developing these. Excellent ideas for the videos, the candy game (!), and discussion topics.

    As an aside, one contributor to the cod collapse was that the scientists weren’t just basing the allowable catch on K/2, they were also trying to calculate the maximum harvest based on H< Growth-Mortality, which is a very different approach than K/2.

    However, they had very spotty scientific data on both growth and mortality, so what did they do? They used the existing harvest as an indicator of the health of the population! They assumed that if fishers were catching lots of fish, there must be a harvestable surplus (H must still be < net growth)! But the skippers were getting better at finding the fish and the trawlers were getting better at scooping them up, so THAT was the reason for the increase in harvest. Net growth was actually plummeting, but all the agency had to go on was the existing catch. Using the catch to estimate the next catch was lunacy. But they didn't have the means to find out what net growth was really doing.

    Defining MSY as K/2 rather than as net growth has many problems, but the biggest one is that we have no idea what K was when the fishery was untouched by modern man. If, as Robert Callum suggests, the cod were at 1/1000th of “natural” K when they set the quota at K/2, then they cut the population down when it was already dangerously low.

    Setting a harvest at MSY can work pretty well for trees because they stay put and you can measure them pretty accurately. But for fish that we really have no clue about the population statistics, it's obviously not working.

    We'll get into more of this in the fisheries section, but I agree with you that it's a shame we allow industrial fishing when we don't even have a clue what net growth is.

  2. hawynne
    July 19, 2010 at 7:11 pm

    I like chocolate soooo much more than bunnies! Great translation on the Tragedy of Commons bunny game we played!

  3. December 7, 2010 at 12:13 pm

    i have never had cod before…i do enjoy playing the game though

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