This is Scientific American.

60 Second Science.

I'm Emily Schwang.

Half of all fish people eat worldwide now come from fish farms,

so farms need to do more to keep up with demand.

And if we look for the future at today's per capita

fish intake around the world,

we would need to double aquaculture production.

Ron Hardy is the University of Idaho's director of aquaculture research.

He presented his research at the recent International Symposium on Fish Nutrition

and Feeding in Sun Valley Idaho, which he also chaired.

In the wild, Rainbow Trout eat insects and other smaller fish.

But Hardy says there aren't enough little fish to feed larger fish in the wild and still meet market demand as human

population increases. So he's used selective breeding to create strains of farmed fish that get by on food that's less expensive than little fish.

Feed made from soybeans, corn, and wheat.

Some of the farmed fish really thrive.

Sixteen years ago, Hardy had to wait a year for a one pound

trout. These days his efforts yield trout up to four times as large in the same

amount of time. So it'd be kind of like if you're going to breed, I don't know, bucks.

So we've got everything from Wrought Wilders to little Scottys or whatever.

But the farmed fish aren't completely vegetarian.

So beans don't have skeletons.

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