GUANGLU ISLAND, China — Sea cucumbers are like chickens, Cong Xuanzhi explained. He did not mean the taste.

He was describing how sea cucumbers, the unlovely cousins of starfish and sea urchins, end up on the tables of the Chinese today.

“Some are raised in pens,” Mr. Cong said, wearing blue overalls and white rubber boots, and standing outside a long cinder-block building that contained 54 pools filled with sea cucumbers, redolent of the sea. “And some are free range.”

That’s a figure of speech, strictly speaking, since the creatures barely move in their lives. Mr. Cong’s comment, though, highlights yet another consequence of China’s enormous economic transformation, which has lifted millions of people out of poverty and also stoked a voracious appetite for delicacies like the sea cucumber.