Sushi’s widespread popularity in America has turned an exotic and extravagant food into an everyday lunch special and takeout menu item. But there’s a dark side to the last 20 years of accumulating lovers of rice-rolled chunks of fish, and that’s overfishing. It’s why sushi restaurants are capitalizing on America’s vegan craze and trading in Bluefin tuna for tomato.

“I can’t imagine at all that sushi in the future will be made of the same materials we use today,” Japanese sushi chef and restaurant owner Jiro Ono told the Foreign Correspondents Club of Japan. “I told my young men three years ago sushi materials will totally change in five years,” he said. “And now, such a trend is becoming a reality little by little.”

Raw high-end tuna has been a staple of Japanese cuisine for centuries, dating back more than 1,000 years ago when Golden carp was fished, fileted, and fermented by fishermen in freshwater lakes. They served the fish with rice, and its popularity among locals grew with the rising merchant class and prosperity of the city of Japan. It wasn’t until the 1820s when fish was served so fresh there was no need to preserve or ferment it, speeding up the entire sushi-making process. Soon after, sushi bars sprouted up throughout Japan and advancements in refrigeration allowed sushi to travel long distances and eventually expanded into a global market.

Sushi Roll Swap Out

Fish of all sorts were being caught and sold at high frequencies and quantities. Los Angeles was the first American city to sell sushi in 1966 and quickly began catering to celebrities throughout Hollywood. The love for the Japanese cuisine spread and with it came a series of evolutions and ingredient introductions, such as cream cheese, spicy mayonnaise, and of course deep-fried rolls. Western influence laced its way through the seaweed rice rolls, giving birth to the “California Roll,” which is made with cucumber instead of fish, for Americans who were wary of uncooked cuisines.

That’s not the only reason for swapping fish for alternatives. The southern Bluefin tuna is near extinction, and it has everything to do with overfishing. Less than nine percent of the original stock will be able to reproduce successfully because we’ve fished all the rest each spawning season, according to the Fisheries and Resources Monitoring System. Tuna is by far one of the most popular sushi menu items, created with avocado, spicy tempura, cucumber and other creations.

Tuna’s threat level, though, was relatively low before humans started consuming them at large quantities. They're an apex fish, and with no predation they're able to grow more than 8 feet long and weigh up to 600 pounds, accumulating higher mercury levels along the way. It takes tuna 12 years to reach sexual maturity, but they’re usually caught when they’re 3 years old, weighing about 30 pounds, and unable to reproduce.

Oceans can’t keep up with our love for sushi, and restaurant owners are taking a hit from the high prices of the extinct fish (albeit sushi isn’t the only reason for overfishing). It’s why the vegan tomato, sweet potato, cucumber, avocado, and asparagus rolls have entered the sushi menu in full force with hopes of diverting a portion of the fish market demand.