SSS 2009-03-27（在线收听）

This is Scientific American's 60-Second Science. I'm Karen Hopkin. This will just take a minute.

If you’ve ever popped open a jar of the pickled fish, you know that herring like to stick together. Actually, it’s something they do naturally, even before they’re crammed into a container. In the ocean, millions of herring often band together in shoals that can stretch for miles. Now scientists say that herring shoals can form in seconds, as long as you have the right number of fish.

The scientists used a souped-up kind of acoustic sensing that allowed them to image an area 100 kilometers in diameter about once a minute. Because sound waves get bounced off the bodies of the fishes, the researchers could count how many herring were around, and see exactly when they coalesced into a shoal.

They found that herring start to shoal around sunset, gathering together when the fading light makes it safer for them to rise from the seabed. Then, once the fish reach the critical density, they rapidly come together into one big happy mass o’ fish, results published in the March 27th issue of the journal Science.

Shoaling allows the fish to engage in bouts of synchronized spawning, and helps to protect them from predators. Because there’s safety in numbers. Especially when you’re all packed together like sardines.

Thanks for the minute for Scientific American's 60-Second Science. I'm Karen Hopkin.