We eat more fish than ever before. But what's the story behind the fish on your plate? Where did it come from? Which fish can we buy without worrying? What's the difference between wild, farmed and organic? What does overfishing mean - and should humans just stop eating fish altogether?

Paul Greenberg takes us on an eye-opening culinary journey from trawler to table, travelling to fair trade Eskimo fisheries, Norwegian mega salmon farms and rough South Pacific seas in search of wild tuna. Along the way he gives us the facts about fish, showing how the choices we make when we're faced with a seafood menu or supermarket shelf affect the whole world.

FISH RULES

WILD FISH

1. Don’t eat industrially harvested wild fish. Industrial-scale trawlers and longlines extract massive amounts of fish and also catch many fish unintentionally.

2. Do buy from smaller-scale fisheries that use hook-and-line or nets of modest size - they do less damage to the marine environment.

3. Don't eat a wild fish that travels too much. Highly migratory fish like the Altantic bluefin tuna cross dozens of national jurisdictions in the course of their lives. Regulating all the different nations that pursue such a far-ranging animal is difficult and over-fishing often occurs.

4. Don't eat a wild fish you don't know. 'New' fish that suddenly appear on menus the way orange roughy and Chilean sea bass did back in the 1980s are often newly discovered populations that lack adequate management to protect that fish's long-term viability. Fortunately there are many fish populations that are well-managed and they can be found in fishmarkets and restaurants with a little bit of effort.

5. Do use online resources to find well-managed fish. Useful sites include:

The Marine Conservation Society's Seafood Guide: http://www.goodfishguide.co.uk/

Fish2Fork's guide to responsible seafood eateries: http://www.fish2fork.com/

FARMED FISH

1. Don't eat fish a farmed fish that uses the wild environment for its home. Fish like salmon that are often farmed in the open marine environment in 'sea cages' can spread disease and attract sea lice to wild populations.

2. Do try farmed Arctic char, a similar fish to salmon that is grown entirely in containment and has a rich full flavour.

3. Don't eat a farmed fish that eats a lot of fish. Some fish like farmed salmon and ranched tuna are highly carnivorous and can require multiple pounds of wild fish to yield a single pound of edible flesh.

4. Do eat fish like tilapia and catfish which can be raised as vegetarians — their footprint on the marine environment is smaller.

5. Don't eat a farmed fish you don't know. Aquaculture is booming – growing by more than 10% a year in many parts of the world. But a lot of that fish is grown without adequate regulation for food safety and environmental protection.

6. Do use online resources to help you choose aquaculture products. A good starting place is:

The Aquaculture Stewardship Council: http://www.ascworldwide.org/

BEYOND FARMED AND WILD . . .

Choose the right fish but also fight the right fight: Choosing a fish that is well-managed or farmed responsibly is good, but what is even better is fighting for better regulation of fisheries and aquaculture.

Do fight to stop wasteful subsidies of the fishing industry.

Do fight to get salmon farms out of wild salmon migration routes.

Do fight for more marine protected areas.