Why Chipotle doesn't serve seafood

Seafood is becoming a hot commodity in Mexican-themed dining.

"The better-for-you trend is really strong right now and people are looking for healthier options," Ralph Rubio, founder of up-and-coming Mexican fast-casual restaurant Rubio's, told Nation's Restaurant News.

But don't expect to see seafood on Chipotle's menu.

"Seafood is difficult in our case because we don't have freezers and it doesn't hold very long unless it's frozen," Chipotle representative Chris Arnold told Business Insider.

He also said the brand is wary of adding new menu items.

"Maintaining a really focused menu lets us do the things we do really well," Arnold said. "That's always been a key part of our model."

Chipotle has stuck to the same menu since it opened, adding only a few items like the Sofritas vegetarian protein.

The company prides itself on serving "food with integrity." This means antibiotic-free, naturally raised meats and local produce.

Rubio's is known for its fish tacos and seafood burritos, while Taco Bell has sold shrimp tacos in the past.

Chipotle's high standards have led to a shortage of carnitas.

Hundreds of restaurants have stopped serving pork after the company found that suppliers weren't meeting its standards.