“When something is so abundant in your environment, and it tastes so darn good that it becomes a part of your everyday diet, and all of a sudden it’s gone or priced really high — people are in shock,” said Steve Pettus, a managing partner of the restaurant group Dickie Brennan & Company.

Bourbon House, one of Mr. Pettus’s restaurants, recently added a note to its menu about the shortages, along with market pricing for oysters, a rarity in a region where inexpensive oysters are a profitable draw for many restaurants.

“In peak season, we go through 30,000 pounds of half-shell oysters in a week,” said Rob Heffner, a vice president of Gulf Coast Restaurant Group, the Mississippi company that operates 11 Half Shell Oyster House locations and another oyster-focused restaurant, the Southern Pearl, on the Gulf Coast.

A dozen raw oysters still go for around $16 at the Half Shells, Mr. Heffner said, even though they cost his company 32 percent more than last year — and over three times as much as they did a decade ago , when the company was founded.