Foreign trawlers - mostly Chinese - are plundering the seas off West Africa. Their fishing methods are pushing stocks to the brink.
The trade is worth $1bn a year but countries like Sierra Leone retain very little of what's earned.
The foreign trawlers buy licences to fish from Sierra Leone's government, but their actions are putting local fishermen out of work.
Fish is a vital source of protein for Sierra Leoneans, but the fish are getting smaller and more expensive. Some cost a dollar – in a country where most people live on a dollar a day.
Part of the problem is poor regulation. Sierra Leone has one marine patrol vessel and thousands of square miles of ocean to monitor.
The BBC went out to sea with a government team in search of foreign trawlers.
When we set out, foreign boats were tipped off. Satellite tracking shows them running away, heading far out to sea.
A Chinese fleet is suspected of illegal activity. Trawling in pairs, the fleet catches 60-100 tonnes a day. This method is illegal in Sierra Leone but the ships haven't been prosecuted.
Foreign trawlers do provide employment but conditions onboard are grim. Locals earn $100 a month and are often at sea for nine months of the year.
Sierra Leone is one of the poorest countries in the world. Its fish continue to be sent around the world to markets such as China and the EU.