Tyson Foods this fall took a 5 percent stake in Beyond Meat, the company proudly bringing customers fake meat that bleeds.

With Impossible Foods' new "burgers," made for high-end restaurants, and a long list of more established companies, like Morningstar Farms, Gardein, Amy's Kitchen, and Dr. Praeger's, it's never been so easy to forgo animal-based protein.

Another piece of the nearly $5 billion plant-based food economy: vegan seafood.

Fake tuna. Fake crab cakes. Fake scallops. With nary a net, customers of Fresh & Co., a New York City salad chain, can get Tomato Sushi in their quinoa bowls. New York's May Wah Vegetarian Market sells vegan salmon, scallops, and tuna, along with your classic vegan spare ribs and stewed mutton. At Whole Foods, shoppers can pick up Gardein Crabless Cakes or Breaded Vegan Fish Fillets from Sophie's Kitchen.

Vegans seem psyched. "Growth has been phenomenal," at 20 percent or more a year, said Eugene Wang, managing partner at Sophie's Kitchen. Wang started developing his seafood alternatives because his daughter is allergic to shrimp. That also led him to ditch soy and wheat in search of allergen-free ingredients. Now he uses mainly yellow pea for the protein, and Konjac, also known as Japanese or elephant yam, for the shellfish texture.

Curious omnivores may want to start with breaded and fried.

Big Food is taking notice. Even before Tyson's October investment in vegan meat, Pinnacle Foods acquired Gardein Protein International, Inc., which also sells plant-based chicken and beef products, for $154 million in 2014. Wang said he has been approached by several Fortune 500 companies. For now they are "just asking questions," he said, but he is looking for investors to help him meet the demand he's already seeing.

A number of legal skirmishes in the space in recent years attest to the close attention being paid to the upstarts. In 2014, Unilever, maker of Hellmann's, sued the vegan company Hampton Creek for its Just Mayo product, alleging fraud for giving consumers the impression it was made with eggs. It ended up dropping the suit-and coming out with its own vegan mayonnaise.

Now, inevitably, it has come to this: a legal skirmish over a product called Chickpea of the Sea.

Tofuna Fysh, a small, 18-month-old Portland, Oregon, company marketing faux tuna fish, "fysh" sauce, and "fysh" oil, recently received a cease-and-desist letter over his trademark application for the name and a jingle on the company website. Founder Zach Grossman recognizes he's probably going to have to give up the trademark, but he'd dearly like to hold on to the jingle.

"I think that would be a fair compromise here," said David H. Bernstein, a partner at Debevoise & Plimpton with a specialty in trademark law, who isn't involved in the case.

"We have had a productive dialogue," a Chicken of the Sea representative said. "We hope to amicably resolve the issue in a timely manner."

The Plant Based Food Association, a new trade group for protein alternatives, provides labeling guidance to its members, as well as marketing help, said executive director Michele Simon. Vegan seafood companies are "up and coming" but still represent a small fraction of the group's membership, she said, adding that consumers seem to be less aware of the environmental and human welfare issues surrounding the fishing industry.

"Land animals tend to get more sympathy," she observed.