Eleven years ago, chef James Corwell had a revelation in Japan. He was teaching cooking to the U.S. Navy stationed there, and one morning, he woke up before dawn to make a pilgrimage to Tokyo’s Tsukiji fish market, the largest in the world. Under the roof of an open-air warehouse, he walked the aisles and perused row after row of hulking frozen tuna, steam rising from their carcasses. Corwell, one of the only certified master chefs in the United States, was astounded.

“It’s an impressive amount of fish, a stupendous amount of fish,” he says. “I got hit with this really visible situation and thought, how can the oceans possibly keep up?” Indeed, commercial fishermen have fished Pacific bluefin to just four percent of unfished levels, according to a 2012 assessment by the International Scientific Committee for Tuna and Tuna-like Species in the North Pacific Ocean. Now, all three species are vulnerable or endangered.

Corwell began formulating a plan to create a tuna alternative. A decade later, he founded Tomato Sushi. He chose the bright fruit for its high levels of glutamic acids, which also create the savory taste in meat, he says. In the future, he plans to use eggplant as another fish replacement and carrots as a salmon substitute, too.

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To mimic the texture and mouthfeel of Ahi tuna, Corwell cuts tomatoes into slivers, puts them into plastic bags, vacuum-seals them, and cooks the fruit in boiling water, a process called sous-vide. It’s a gentler method than baking, pan-frying, or cooking them any other way, he says, and it keeps the tomato a little fleshy, like fish. He also uses natural seasonings to create the fishy aroma and flavor (and is experimenting with various ingredients, such as algae, to enhance the effect). The result is rosy strips of moist and tender tomato that, when placed over a roll or sticky rice, look and taste like the real thing, he says. He currently sells bulk orders to restaurants through his website.

If you aren’t within reach of one of those establishments, there are other imitation seafood options for consumers who are vegetarian, allergic, environmentally conscious, or simply intrigued. Over the past several years, more and more food stores—including Whole Foods, Safeway, and Wegmans—have been stocking freezers and shelves with boxes of imitation prawns, tuna, smoked salmon, and other seafood alternatives.

The trend reflects a growing interest among consumers in meat substitutes. According to the market intelligence firm Mintel, “conventional channel, natural supermarket, and specialty supermarket sales of meat alternatives reached $553 million in 2012, representing eight percent growth from 2010.” And a Mintel survey found that more than 35 percent of consumers used meat substitutes in 2013. (Only seven percent of those surveyed identified as vegetarian.)

Sophie’s Kitchen is one manufacturer whose fish-free products adorn grocery store shelves. Company founder Eugene Wang’s preferred ingredient is konjac, a root vegetable also known as Japanese yam, which has been used in Asia for more than five centuries. Wang chose the starchy vegetable because it grows quickly, is pretty bland, and, when mixed with other ingredients, helps achieve the consistency of shrimp. He pairs it with kelp “to give a hint of ocean flavor.”

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But taste and mouthfeel are just part of the equation—achieving a shrimp-like resemblance is also important to Wang. After shredding the vegetable and adding a few ingredients like pea protein or potato starch, he puts the mixture into molds that imitate the crustacean’s body. He then uses turmeric to tinge the mold with orange stripes and adds other spices that lend a “cooked seafood” look.

Once consumers see and feel the similarity to real shrimp, says Wang, “your brain tells you that this is just like the real deal.” Sophie’s Kitchen also makes other products, including faux crab cakes, salmon-less smoked salmon, and canned “VeganToona.”

Even though plant-based substitutes like konjac, pea protein, and tomato aren’t going to pack as much protein or fatty acids like omega-3s or omega-6s into every bite, they offer an advantage over seafood in another way: They don’t carry the high levels of mercury and pollutants such as PCBs that are often found in fish we harvest from the ocean.

Given the alternatives, maybe it’s worth leaving more fish in the sea.

*This article was updated on July 24, 2015, to reflect the following correction: An earlier version stated that Chef James Corwell uses molecularly altered yeast extract to create the aromas and fish flavor in tomato sushi. While his team did experiment with this ingredient, they ultimately chose not to include it in their final product. We have updated that sentence to indicate that Corwell’s team uses natural seasonings to provide fish-like flavor and aroma.

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