Cod Fishery Collapse

Cod and codfish are two names for the same fish. In the Baltic Sea it’s often called 'Dorsch' in German, while in the Atlantic it’s usually called 'Kabeljau' or simply cod. For centuries, this fish was one of the most important food sources in Northern Europe and North America. A collapse means that a fish stock doesn’t shrink slowly, but almost completely disappears within just a few years. Exactly that happened in 1992 off the Canadian island of Newfoundland: catch volumes had fallen to about one percent of their former level. The government banned fishing entirely, and an entire industry ended in a single day.

Why a fish stock doesn’t simply grow back

Many people imagine fish stocks like a savings account. You take out the interest each year and the principal remains intact. As long as you only catch as much as grows back, this works fine. The problem begins when, year after year, you take a bit more than is replenished.

At first, the stock shrinks almost imperceptibly. Modern ships with sonar and huge trawl nets still reliably find the remaining shoals of fish. Catch numbers therefore stay high for a long time and create a false impression of health. Only once the last shoals have been fished out does everything collapse at once.

After that, the stock often doesn’t recover on its own. In Newfoundland, an extensive fishing ban has been in place for over thirty years, and the cod still hasn’t come back. Other species such as crabs and shrimp have taken its place in the ecosystem. An ecosystem is the interplay of all living things in a habitat, and it can tip into a new state that remains stable.

How many small decisions add up to a collapse

Three factors work together. The first is technology: since the 1950s, factory ships have been able to catch, process, and freeze fish without ever entering port. The second is the size of the nets, which also scoop up juvenile fish before they’ve had a chance to reproduce. The third is politics, since catch quotas were regularly set higher than scientists had recommended.

On top of this comes a statistical problem. You can’t count fish in the ocean. Their numbers are estimated from catch volumes, and in Canada this estimate was systematically too optimistic. By the time the error was noticed, the stock was already largely gone.

Another amplifying factor is climate change. Warmer water contains less oxygen and shifts the areas where cod can spawn. In the eastern Baltic Sea, the fish today are noticeably smaller and thinner than they used to be. Overfishing and environmental change thus add up, rather than offsetting each other.

Cod in the news, in politics, and in the supermarket

In the Baltic Sea, this story is currently repeating itself on a smaller scale. Since 2019, a de facto fishing ban has applied to the eastern cod stock, and since 2022 also to the western stock. For many small coastal businesses in Mecklenburg-Vorpommern and Denmark, this means the end of their livelihood. Every autumn, the media report on the EU fisheries ministers' quota negotiations.

In the supermarket, you encounter this issue indirectly. Cod from the Barents Sea is considered comparatively well managed, and labels such as MSC are meant to indicate this. Fish sticks today are often made from Alaska pollock instead of cod, because cod has become scarcer and more expensive.

Beyond fishing itself, this case serves as a standard example in economics and politics. It shows how a shared resource gets ruined when every individual acts rationally and yet everyone ends up worse off. Economists call this pattern the tragedy of the commons. The same conceptual pattern shows up today in debates about water usage, fish stocks in the Pacific, or emissions.