Sea of activity at world's largest fish market

It's barely 6 a.m., but the world's largest fish market in Tokyo is already a sea of activity.

One in every five fish caught on the planet is brought to the Tsukiji Market for auction every year, about 1,800 tons and worth $20 million a day, reports "CBS This Morning" co-host Norah O'Donnell.

Compare that to the biggest fish market in the U.S., the Fulton Fish Market in New York City where 400 tons of seafood is sold daily.

Among the most coveted catches at Tsukiji include blue fin tuna, whose best specimens have fetched more than $1 million each and come from as far away as Norway, Spain and Massachusetts.

Beyond tuna, there's also shrimp, shellfish, wasabi and 400 different kinds of seafood, all sold and shipped out by mid-afternoon.

It's not exactly a warm welcome when they arrive, but there's plenty of interest in snapping up the best catch of the day.