“One billion people eat seafood every day, and it can be sustainable if we manage the oceans well,” Andy Sharpless, the CEO of Oceana, said last night at a book launch party at Azur in Washington, D.C. While guests noshed on sustainably produced lobster beignets, sardine sushi, and raw oysters (pictures), they heard about The Perfect Protein, the new book written by Sharpless and Suzannah Evans.

As guests swilled squid ink-infused tequila cocktails (pictures), Chef Frederik de Pue spoke a few minutes about the sustainability-inspired fare at Azur, a new seafood restaurant in downtown Washington. “It’s our responsibility as chefs to educate people,” de Pue said.

“Go into a supermarket, and you see the same seafood every day,” said de Pue. “We serve things you don’t find every day.”

Yesterday, that meant those sardines, which had a smoky taste, presented on a cracker with a drizzle of sauce.

It’s perhaps no coincidence that a sardine embosses the cover of The Perfect Protein. “The sardine is as good as tuna from a food point of view,” said Sharpless. (It may be a little bit of an acquired taste, as my companion didn’t care for it.)

Sharpless explained that eating lower on the marine food chain, such as small fish like sardines and herring, may be better for the environment. It could give larger predatory fish like tuna a chance to recover, since many of those long desirable species have seen declines as much as 90% around the world.

Small fish, often thought of as “bait fish” historically, also tend to be lower in mercury and other toxins, because they don’t live very long. They also reproduce prodigiously.

“We don’t want to eat all the small fish, of course, but I think we can harvest more of them and still leave plenty for other ocean creatures to eat,” said Sharpless.

To Sharpless, that’s a doable goal, and it will require a combination of policy changes, enforcement, and consumer support. Main actions needed, according to Sharpless, including putting a stop to overfishing through science-based catch limits, protecting fish nursery areas through reserves, and stopping bycatch of unwanted fish.

“We can protect biodiversity and feed the world,” he said.

Sharpless added, “If you love tigers or gorillas, you should also care about the ocean, because if we don’t feed people from the sea, they’ll take all the land to try to feed themselves.” That doesn’t make sense in his view, because Sharpless explained that the ocean is an efficient producer of protein, as well as a habitat for rich biodiversity.

Speaking of the land, for the first time in modern history, global production of farmed fish (aka aquaculture) has overtaken the production of beef, according to an article from environmental think tank Earth Policy Institute.

In 2012, the world produced 63 million tons of beef and 66 million tons of farmed fish. This year, consumption of farmed fish may also pass consumption of wild-caught fish.

Via email today, Sharpless said, “A lot of people think that farming fish is the answer to global food security, that by choosing farmed fish over wild we are reducing pressure on the world’s oceans and giving them a break. We have to be careful with this assumption though, because when assessing the benefit of farmed fish it really comes down to what that fish ate. ”

Sharpless explained that many popular food species like salmon are carnivorous, often devouring other fish.  So when farmed, they eat upwards of five pounds of small fish to produce just one pound of salmon, a net loss of protein.

“We’re actually taxing the oceans every time we eat farmed salmon instead of relieving it,” said Sharpless. “Aquaculture should add edible protein to the world, not reduce it.”

But, in a wrinkle on this theme, “farming shellfish is a responsible practice,” he said. That’s because oysters, mussels, and clams are all filter feeders that don’t compete for food people can eat.

“They produce healthy, edible protein at a net gain and help clean the oceans in the process. They’re an ally in ocean conservation and people should really eat as much of these as they can stomach,” said Sharpless.

Still, he added, “As appealing as farming our way to abundance may sound, we should be focusing on ensuring that the oceans can produce more and more wild fish on their own… It’s a truly renewable wild resource if we manage it properly.”

Chris Mann, an expert on aquaculture and a director of Environment with The Pew Charitable Trusts, said choosing the right type of farm-raised fish can be a bit complicated. “It’s a quite complex analysis, it’s a little like that paper versus plastic bags debate,” he said.

“Given the trends, it was inevitable that farmed seafood would overtake beef,” Mann continued. “So the challenge is not whether we should do aquaculture, but rather, what forms should we use?”

In general, Mann said he agreed with Sharpless’s assessment that farmed shellfish tend to offer the least environmental impact, followed by farmed fish that aren’t fed animal protein. If they must be fed fish or animal protein, that should be sustainably harvested, he added.

Mann said the “greenest” diet would be a vegetarian one, but said, “If we’re going to eat meat we’d be better off eating fish and shellfish than most terrestrial animals.” He explained that cold-blooded animals process food more efficiently.

Carl Safina, author, conservationist, and Ocean Views contributor, said he isn’t surprised that farmed fish have overtaken beef, because the process is more efficient. “It’s probably more like Step One in a long-term downsizing,” said Safina.

He explained that people will soon start eating more farmed carp and tilapia, because they are lower on the food chain, and therefore more efficient–a driving force in an increasingly overpopulated world.

“We’re down mainly to two mammals (cows and pigs) and two birds (chickens and turkeys), and seafood is probably headed in that same direction as the spectacular variety of our overfished ocean yields to a few easily farmed, efficiently fed fish,” said Safina. “A crowded world has less room for choices; that’s the bull lurking in this china shop.”

At the close of last night’s book launch, Sharpless urged guests to go home and cook some more sustainable seafood (check out National Geographic’s Seafood Decision Guide to help you make a selection).  Guests were also encouraged to read The Perfect Protein, a book celebrity and ocean advocate Ted Danson has called “the Omnivore’s Dilemma for the Oceans.”

For those who return to Azur to sample the full menu, they can look forward to hand-harvested scallops; branzino with farro verde, gribiche sauce, and bacon; and lightly poached pollock.

Brian Clark Howard covers the environment for National Geographic. He previously served as an editor for TheDailyGreen.com and E/The Environmental Magazine, and has written for Popular Science, TheAtlantic.com, FastCompany.com, PopularMechanics.com, Yahoo!, MSN, and elsewhere. He is the co-author of six books, including Geothermal HVAC, Green Lighting, Build Your Own Small Wind Power System, and Rock Your Ugly Christmas Sweater.