The black drum Mitchell was arrayed at a jaunty angle, its bright, light-tasting sauce was a reduction of bouillabaisse broth and it rested over a cool, crunchy tangle of mirliton slaw. It was nothing revolutionary, but it did feel contemporary and since it was served at Arnaud’s Restaurant, the dish was definitely a signal.

It’s one of a half-dozen revamped or altogether new dishes that joined Arnaud’s menu this fall. Plenty of restaurants devise that many specials every day. But very few restaurants, even in New Orleans, have a history and significance like this one. Taken together, the menu changes amount to the most visible sign to date of the next-generation family owners at Arnaud’s putting their mark on the old-line French Creole restaurant.

Katy Casbarian, 37, and her brother Archie Casbarian, 39, have been running Arnaud’s together since the death of their father, Archie A. Casbarian, in 2009. They have been treading lightly and describe themselves as caretakers for the legacy of a restaurant that dates to 1918, and one they know has a place in the traditions of many other families.

But part of that legacy has been a gradual evolution. Since buying the restaurant in 1978, the Casbarian family has renovated, expanded and gently maneuvered the restaurant to respond to the market. Jazz combos are a fixture in the front dining room, for instance, and in 1994, the family added their adjacent oyster bar and casual cafe, Remoulade, an underappreciated oasis for quick, quality Creole flavors on Bourbon Street.

After nearly six years at the helm, the Casbarian siblings decided it was time for some lighter touches on Arnaud’s menu and set longtime chef Tommy DiGiovanni to the task.

Roasted quail Elzey, once piped with a murky foie gras mousse, is now filled with a moist, very mild seafood boudin, arranged around a crunchy rice cake made from the same boudin and splashed with a tart raspberry gastrique. The requests for a vegan entree that have grown through the years are now answered with mirliton stuffed with eggplant tapenade and squash, finished with roasted red pepper coulis.

For another new dish, a crust of thin-sliced, crisp-edged potato is fused to Gulf fish, with a buttery, anise-scented sauce. At dessert, there’s now frozen praline soufflé and a chocolate bombe, a dark, dense dome filled with ganache over a cookie crust.

More new dishes are in the works, though the Casbarians assert that some dishes will never change. That includes shrimp Arnaud, the very sharp house remoulade; trout meunière; and oysters Arnaud and Bienville, two of the five baked oyster dishes prepared here, to name a few of the classics.

These menu changes don’t feel sweeping, and that feels apt. They’re adding options around the edges to what remains a trove of definitive French Creole tradition, where meals start with airy soufflé potatoes and end with bananas Foster prepared table side and where grilled pompano David with dashes of lemon and garlic may still be the simple, utterly satisfying highlight of any meal.

Charles Abbyad, maître d’ here for a generation, still runs the dining room like a steamship captain, suave with guests, brusquely efficient when keeping the wheels of service turning. That must be quite a job. On busy nights, Arnaud’s can feel like an old hotel, with parties in motion around a warren of 18 dining rooms. Between them, the restaurant even maintains its own small museum, a captivating if somewhat spooky gallery of glittering gowns and vintage Carnival ephemera collected by previous Arnaud’s owner Germaine Cazenave Wells.

The restaurant’s French 75 bar has become a top destination for craft cocktail mavens, thanks to head bartender Chris Hannah. But there’s a second bar here, the Richelieu Bar. A tucked-away chamber, nestled and windowless, it’s a comparatively quiet spot to get a postprandial and watch the traffic of dolled up regulars, camera-toting visitors and tuxedoed waiters shuttling dessert carts between dining rooms.

Change has come to all of the city’s old line restaurants in the years since Hurricane Katrina, often with drama. Arnaud’s is changing too, though it seems steady, channeled by the fundamentals of history, personality and ritual. There’s not really a change of direction here, just a change of a few courses.

Follow Ian McNulty on Twitter @IanMcNultyNOLA.