For decades, seafood fanatics who lived in coastal areas could indulge in that guilty pleasure irreverently referred to as "trash fish" — think smoked mullet, sheepshead or lionfish — as a cheap alternative at seafood shacks to help wash down a Bud longneck and pass a good time. It was a blue-collar approach to dining, an alternative to the experiences at high-end restaurants where lobster, shrimp, tuna and salmon dominated the gilded menus.

That was then, before the world started to awaken to the horrors of over-fishing and the dire need to embrace the concept of sustainable seafood to prevent eating our favorites out of existence.

The concept gradually is blossoming into a trend thanks to efforts such as the Audubon Nature Institute’s Gulf United for Lasting Fisheries (or G.U.L.F.) program and its annual “Summer of Sustainability” dining series.

These dinners operate on two clashing and daunting numbers: 85 percent of the world’s fisheries have been pushed to their limits (according to the World Wildlife Federation), but 1 in 70 in Louisiana work in the seafood industry with an annual economic impact of $2.4 billion (according to the Louisiana Seafood Board).

The dinner, in its third season overall but the second as a series, features six-course meals prepared by some of New Orleans’ top chefs in a various Audubon properties — most recently in the “Dine with the Sharks” setting next to the shark tank inside the Aquarium of the Americas.

So instead of diving into such treasured (but endangered) seafood delights as bluefin tuna, halibut, sea bass or Atlantic salmon, diners open their palates to such alternatives as sheepshead, black drum and garfish.

If you think this is all “lipstick on a pig”-type dining, look no further than the evening’s opener, a delicious appetizer of cobia by Ryan Prewitt of James Beard Award-winning seafood restaurant Peche. Sweetening the deal was the preparation, in which the cobia was cured in lemon and salt and served with poached shrimp, grilled corn, basil and mint and served in a sauce made from roasted chilies, tomatoes, garlic and anchovies and accompanied by crispy whole wheat crepes.

The cobia, Prewitt notes, was fished out of the Gulf just an hour away by a spear fisherman — in adherence with Peche’s mission to source seafood with no intermediaries to keep the seafood fresh and not wasteful. But he also said diners are increasingly open to different kinds of fish in general. When he prepared sheepshead at a private dinner in Nashville, he ran up against a skeptical Louisiana native who initially thought he was being shortchanged with such a “lesser” offering — until he tasted it.

The potential is there, he said.

“For us to make (seafood) better managed and more productive, we have to get different kinds of fish into the food chain and we have to get them on plates and restaurants,” Prewitt said.

If anyone knows about cooking outside the box, it’s Susan Spicer, one of the first New Orleans chefs to blend and experiment with different flavors and approaches that didn’t have French names. Spicer also was among the first in New Orleans to avoid overfished species such as bluefin tuna and embraces this sustainability approach.

“The more educated people become and people know more about food and where it came from, it’s going to become more useful,” she said. “It’s important to know about what you’re buying, where it came from and what its story is. This is a fun way to remind people to think about this.”

The third and final “Summer of Sustainability” dinner will be held Aug. 10 at the Audubon Aquarium of the Americas. It’s “All About Shrimp” theme will feature dishes from Tenney Flynn (GW Fins), Brian Landry (Borgne), Dana Honn (Carmo), Allison Richard (High Hat Café), Chris Lynch (Commander’s Palace) and Tariq Hanna (Sucré).

In a related event, Seaworthy Restaurant, 630 Carondelet St., will host a Shrimp Boil-Off from 2 p.m. to 7 p.m July 29 to benefit the G.U.L.F. Institute. Chefs Ysaac Ramirez of Josephine Estelle, Ryan Haigler of Grand Isle and Seaworthy's own Chef Dan will "put their best to the test" with fresh shrimp from Pistol P’s Seafood. For $30 per person, guests may taste-test shrimp and fixings on the patio with beer in hand. Music will come courtesy of Lisa Ngyuen & DJ Suzy Q, and the winner will be crowned at sundown.