Welcome to Fishy Business! Your challenge today is to work as a group to run one of four fishing firms working the same stretch of sea, the Saltmere fishing ground. Season by season you decide how many fishing boats to send out to catch fish.
The winner is the firm that makes the most profit across all the seasons: the value of the fish you land, minus what it costs to run your boats. Sending out more boats can mean a bigger catch, but each boat costs money whether it catches much or not, and the fish only keep coming if the sea is not pushed too hard. You all share the same area.
This is a discussion activity; the firms, the harbourmaster and the Saltmere ground are invented for teaching. Figures are approximate and used only as a neutral, illustrative model of how a shared fish stock behaves.
The real-world parallel referenced later (the collapse of the Atlantic cod fishery on the Grand Banks off Newfoundland, and the 1992 fishing ban that followed) is a well documented historical case. Sources: Britannica, the Encyclopedia of Newfoundland and Labrador Heritage, and Wikipedia. Example data, as of June 2026.
Each group runs one firm: Blackwake Trawlers, Hookjaw Marine, Net Ripper Fisheries and Rogue Tide Trawling. They make that firm's catch decisions for the whole game.
Five seasons with no shared rules, then a class discussion, then five more under whatever rule the room agrees.
Each firm picks its number for the season in private. No firm sees another's choice until all four are shown together: either entered in secret and revealed on screen, or held up by every group at once.
Sealed bids: type each firm's number into its box, read off a slip the group hands you, or have each group's rep come up and type their own. It shows as dots, so no other group can read it, then you reveal all four together. Or a show of hands: groups hold up their boats on a count of three and you tap each tile to record them. Switch at any time.
Each firm competes for the most profit across the five seasons, shown on the leaderboard. Profit is the value of the fish landed (priced per tonne) minus the cost of running the boats. A boat lands a full haul when the stock is healthy and almost nothing when the sea is fished out, but it costs the same to send out either way. So the score, the state of the sea, and how carefully each firm fishes all move together.
This is not a lesson where the screen tells students the answer. It is a lesson where students do what happens, then work out why. By the end, open questions for the room to settle for themselves:
Split the class into four groups of roughly equal size. Give each group a firm: Blackwake Trawlers, Hookjaw Marine, Net Ripper Fisheries, Rogue Tide Trawling. Tell them they are a fishing business working the Saltmere ground alongside three competitors. Their job, each season, is to decide how many boats to send out.
Each season the ground can support about 16 boats in total before the catch outpaces what the fish can replace. The four firms do not have to agree on anything. Each decides for itself, chasing its own profit.
For each of the first five seasons:
The room will notice the stock going backwards. That is the point. Let them notice it, do not say it for them.
This is the moment the whole activity is built around. After Season 5, the screen shows the state of the stock and asks: what rule should the industry try?
Open the floor. Let the room propose a rule. The common starting point is a catch limit of 4 boats per firm: the ground's capacity of 16 shared across four firms. Other ideas worth raising: a charge for fishing over the limit, paying more for boats that use kinder methods, or a simple industry agreement to hold back. The mechanic here uses a per-firm catch limit, which you set with the picker.
Then the second spell begins. Same ground, same firms, one new rule. Watch what changes.
The report shows both spells side by side: total catch, state of the stock, and how each firm did. It is a built-in springboard for the closing conversation: which spell left the industry better off, what did the rule actually do, and where else does this pattern appear?
After five seasons of that, the four firms sit down together. Open the floor to your class: what rule should the industry try?
The common starting point is an agreed catch limit: each firm allowed at most a fixed number of boats per season, the same kind of limit real fishing industries use. Take a suggestion from the room, set it below, then return to the water.
Each firm may send out at most this many boats per season:
The ground can support about 16 boats across the four firms. A limit of 16 boats is the total fishing the rule will allow.
How each group's firm fared across the two spells.
The Saltmere ground is a shared resource. No single firm owns it, and the fish are there for whoever takes them first. That mix creates a hard problem for any business.
Each season, every firm could see that sending out more boats would mean a bigger catch and more profit, now. But the cost, fewer fish left for the seasons to come, did not fall on that firm alone. It was shared across the whole ground, every firm, and every future season, including the firms that held back. The gain was private. The cost was spread. And once the sea was fished out, the boats still cost money to run while the nets came up empty, so the firms that kept pushing turned a profit into a loss.
So each firm, acting sensibly for its own profit, had a reason to take a little more. Add four firms doing the same, and the stock cannot keep up. This is the tension at the heart of sustainability: short-term profit pulling against the long-term health of the very resource the business depends on.
A catch limit does not change the sea or the firms. It changes the choice each firm faces. By capping every firm's catch, it stops the shared cost from ever growing faster than the fish can replace themselves. Businesses and regulators reach for the same idea in many forms:
Each fleet is given a catch limit, so the total taken stays within what the stock can replace.
Parts of the sea are closed to fishing, giving stocks room to recover.
Firms and customers pay more for fish caught in ways that protect the stock, rewarding the long view.
Competing firms agree shared rules, so no single firm loses out by being the only one to hold back.
A real example: the Grand Banks off Newfoundland was once one of the richest fishing grounds on Earth. It was fished faster than the cod could recover, and in 1992 the fishery was closed. A ban meant to last two years lasted more than thirty, and tens of thousands of people lost their work. A vivid reminder of what is at stake when a shared resource is pushed past what it can give.
Strip away the boats and this is a decision every business with a resource faces. Marina's way of weighing it: