Text 3 It is a good time to be a fisherman.The global fish-price index of the UN's Food and Agricultural Organization（FAO）hit a record high in May.Changing consumer diets,particularly in China,explain much of the sustained upward movement.High oil prices,which increase the cost of fishing and transportation,also add to the price of putting fish on Lhe table.Not all fish are creaLed equal,however.There are two types of fish production:"capture"（or wild）and"aquaculture"（or farmed）.And they seem to be on different tracks.Fish such as tuna,the majority of which is cau~;ht wild,saw much bigger price increases than salmon,which is easier to farm.Overall,the FAO's price index for wild fish nearly doubled between 1990 and 2012,whereas the one for farmed fish rose by only a fifth.What explains this big difference?The amount of wild fish captured globally has barely changed in the past two decades.The ceiling,of about 90m tonnes a year,seems to have been reached at the end of the 1980s.Overfishing is one reason,as is the limited room for produclivity growth,particularly if consumers want high quality.Patrice Guillotreau of the University of Nantes tells the story of a fleet in France that decided to trawl,rather than line-catch,its tuna.It braughi more back to shore,but the fish were damaged.It could not be sold as high-value fillets and was only good for canning.The old ways of catching fish are still best if you want the highest profits,says Mr CuiUotreau.In contrast,the farmed-fish industry continues to make productivity improvements.Fish farms have found crafty ways to use lower quantities of fish meal as feed.In the early days of aquaculture,it could take up to ten pounds of wild fish to produce one pound of salmon.Now the number is down to five.That may still be an inefficient use of protein,but the ratio is set to improve further.Fish farms have also become more energy-efficient,meaning that they are less affected by higher energy pnces.And they have learned how to handle diseases beUer,reducing the quanlity of fish that ends up being unsellable.As a resuli of all these improvements,the global production of farmed fish,measured in tonnes,now exceeds the producUon of beef.Output is likely to continue growing:the FAO estimates thal by 2020 it will reach six times its I990 level.

Tuna and salmon are mentioned to show that______

• A.salmon is not as expensive as tuna
• B.tuna is more popular among consumers
• C.wild fish is more precious than farmed fish
• D.the prices of fish are in fact decided by FAO