Though they sound like something you'd only eat adrift at sea without rations, crusty sea critters are being whipped into concoctions like barnacle ceviche (search) and sea urchin spaghetti as adventurous eaters take the plunge and chefs deal with declining fish populations.

Salma Abdelnour, senior editor of Food & Wine, said she's "definitely been seeing lots of sea urchin (search) everywhere, and barnacles (search) as well" on menus.

This bottom-feeder seafood trend, Abdelnour said, is happening partly because some types of seafood are no longer considered abundant enough to serve in restaurants. But it's primarily "a desire to get something exciting on the menu" that's fueling the crustacean craze, she said.

"The dining public is becoming more sophisticated and curious about food, and more adventurous about what they eat."

Scott Conant, chef at L'Impero (search) in New York, serves a soup of pureed asparagus, sea urchin and mussel broth, as well as a dish of sea urchins, spaghetti and glass eels, sprinkled with breadcrumbs and olive oil.

"A lot of people who come into the restaurant now are better traveled, they know more about food," Conant said. "I always like to think when there's a certain quality coming out of the kitchen, people are more apt to try something new."

Barnacles – marine crustaceans that in the adult stage form a hard shell and remain attached to submerged surfaces – are also being plucked from the deep.

"When I first saw barnacles they reminded me of E.T.'s toenails, but I was fascinated with how European countries have utilized them in cooking," said Chef Norman Van Aken, at Norman's in Coral Gables, Fla. (search), which features a paella nueva with traditional Spanish ingredients, including snails and barnacles, on its menu.

"They are kind of like a steamer clam in a mushroom cap shape," Van Aken said. "To eat them you pick up the cap and suck out the little thin stem that is the meat. They have a great exotic clam flavor."

As far as protecting the ocean's bounty, Van Aken is aware of the shortages, but said there are plenty of other ingredients to choose from.

"We continue to look for unique fish that are more sustainable, but you have to educate guests about what's new," he said. "We have to be mindful that there is not a limitless supply of everything."

Chefs have a dual responsibility, Conant agreed. "I want it to be interesting for the customer but I'm also trying to be sensitive to the environment," he said.

Conant also serves up a chilled Asian noodle and sea urchin salad, which uses the prickly hard-shelled creatures that are in the same family as starfish. And he said he monitors the Monterey Bay Aquarium Web site to review their seafood watch and find out what's best to use, what's cautionary and what should be avoided.

"I've never considered myself a do-gooder but there is a level of responsibility involved," he said. "Sometimes you get stuck as a cook, you need that creative influence."

Conant has seen the tides change for fish firsthand and the effects are reflected on his menu.

"I remember when I first started cooking, we would get enormous 10 feet long swordfish," he said. "In just 15 years, you don't find fish that size and that's kind of scary ... when it was considered endangered I didn't serve it."

And even bottom-feeders confront harvesting issues. The Tidal Pool, a soup of sea urchins and barnacles, was taken off the menu at New York City's Ilo because an oil spill in the seafood's habitat made obtaining it difficult, according to the restaurant's spokesperson.

But chefs and diners are willing to be creative in their creations and tastes, said Conant. "I can take salmon off the menu and never have to hear a person ask 'where's the salmon?'''

Van Aken added that people are enticed to try new things when they see the exotic new dishes on the menu.

"You won't see them at McDonald's," he said. "These are certainly foods you look at and think 'that's wild.'"