Jiro Ono, 89, widely considered the world's greatest sushi chef, has some dire news for aficionados of raw fish: The delicacy's best days may be behind us.

"The future is so bad," the owner of the three Michelin star-rated restaurant Sukiyabashi Jiro, who was the subject of the 2011 documentary "Jiro Dreams of Sushi," told CQ in December. "Even now I can't get the ingredients that I really want. I have a negative view of the future. It is getting harder to find fish of a decent quality."

The reason is overfishing, particularly of the endangered bluefin tuna, a sushi staple.