Mackerel and the Prisoner's Dilemma: When cooperation fails and resources are wasted
The mackerel stock in the Northeast Atlantic is collapsing. In 2023, the stock had decreased by 42% from 2022. Now, in October 2025, the International Council for the Exploration of the Sea (ICES) is proposing a 70% reduction in catches for 2026 – down to just 174,000 tonnes. Nevertheless, the actual catch for 2025 is estimated to be 755,000 tonnes, far above the scientific advice.
This is a classic example of The Prisoner Problem – a game-theoretic situation that explains why rational actors cannot cooperate, even when cooperation would be in all their best interests.
What is the prisoner's dilemma?
Imagine two criminals who are arrested and placed in separate rooms for questioning. The police need evidence, so they offer each of them a deal:
- If you turn on your partner and he stays silent, you go free and he gets 10 years.
- If you both accept, you will each get 1 year for a minor offence.
- If you both tell on each other, you'll each get 5 years.
The problem is that it is always better to cheat, no matter what the other person does. But when both follow this reasoning, they both get 5 years instead of the 1 year they would have got by cooperating.
The mackerel dispute
Iceland, Norway, the Faroe Islands, the United Kingdom, the European Union and Greenland are facing exactly this problem:
The collaborative conclusion: Everyone follows ICES's scientific advice and divides the catch fairly. The stock recovers and everyone benefits from sustainable fishing in the long term.
Reality: Each country sets its own quota based on the share it believes it is entitled to. When all countries act in this way, the total catch far exceeds sustainable levels.
Since 2010, unilateral quotas have averaged 40% over scientific advice. The consequence: the stock is now below the precautionary threshold and is heading for collapse.
Why doesn't cooperation work?
Lack of trust: If Iceland cuts its catches to help the stock, will Norway and the Faroe Islands then catch the same amount? Or will they just take Iceland's share?
Short-term incentives: The country that restricts hunting loses revenue NOW.
Long-term benefits: Restoring the population takes years and benefits everyone – including those who betray.
Position in negotiations: Iceland is issuing a quota amounting to 16.3 TP3T of the advice to strengthen its negotiating position, although it can be difficult to catch. Norway and the Faroe Islands have increased their quotas.
Where is this heading?
Without a binding agreement between all coastal states, this is heading for the complete destruction of a shared resource. The mackerel stock is also at risk, but a 41% smaller catch is recommended for it.
This is an example of the tragedy of the commons: rational actors destroy a shared resource because cooperation requires trust that no one can guarantee.
The only solution is a binding international agreement that can be enforced. Without it, the prisoner's dilemma will continue to force every nation to take more – until there is nothing left.