Although governing authorities are important in setting up ITQs, so is policing of the system by the fishermen themselves.

ECONOMIST: Fishing and conservation

After a decade of using ITQs in the halibut fishery, the average fishing season now lasts for eight months.

ECONOMIST: Fishing and conservation

The Alaskan halibut and king crab fisheries illustrate how ITQs can change behaviour.

ECONOMIST: Fishing and conservation

The use of ITQs changes this by dividing the quota up and giving shares to fishermen as a long-term right.

ECONOMIST: Fishing and conservation

Jeremy Prince, a fisheries scientist at Murdoch University in Australia, has been involved in ITQs since they were pioneered in the early 1980s by Australia, New Zealand and Iceland.

ECONOMIST: Fishing and conservation

So, if Dr Costello and his colleagues are right and the profit motive can drive the sustainability of fisheries, why do the world's 10, 000-plus fisheries contain only 121 ITQs?

ECONOMIST: Fishing and conservation

But evidence that ITQs work is a powerful new hook to capture the political will and public attention needed to spread an idea that could avert an ecological disaster.

ECONOMIST: Fishing and conservation