Eat more (for your health), but choose wisely (for the ocean's sake): A guide to five species, with recipes.

The next time you stare perplexed at your local seafood counter wondering what is good and sustainable, keep this in mind: I have the same problem.

Even after a decade of reporting on seafood, I find sustainable seafood choices are often tricky and usually influenced by regional, seasonal, and even political conditions that take some homework to fully understand. Black-and-white choices are rare. But increasingly, there are better shades of gray. Recently, I decided to talk over some of these gray areas with Barton Seaver, a Washington, D.C.—based chef who has been cooking through sustainability issues for his new book, For Cod and Country. Of course, we could have talked about a thousand species, but we decided to focus on archetypal American seafood items. Here is a distillation of what we concluded.

SHRIMP: No better example of seafood's troublesome gray area exists than shrimp. Catching wild shrimp often requires trawling gear that kills juvenile fish, sea turtles, and sea horses. Carelessly farmed shrimp can be tainted with antibiotics and destroy mangrove forests in sensitive tropical coastal zones. But good choices exist in each category. The Monterey Bay Aquarium and the Blue Ocean Institute have identified several American and Canadian wild shrimp fisheries as "best choices" either because of low-bycatch fishing gear—like the traps used to catch West Coast spot prawns—or because they are caught in a region where the ocean bottom is less susceptible to trawl impacts, as with the Northern Shrimp in Canada. "By buying wild-caught shrimp from fisheries that have employed these better methods, we're in fact subsidizing better management," Barton says. He also points out that several shrimp-farming companies have emerged that grow shrimp in closed-containment facilities and spare the mangroves. One standard for sustainable shrimp is set by the Marine Stewardship Council—look for the Council's blue-and-white check mark on packaging. To date the Council has certified one U.S. fishery—wild Oregon pink shrimp—and three varieties of Canadian shrimp.

On the farmed-shrimp front, Whole Foods and Wegman's are particularly good at identifying farms with best practices. As a default choice, stick with U.S. or Canadian shrimp.

STRIPED BASS, FARMED OR WILD: Surprisingly, finding a basic piece of white fish turns out to be one of the harder things to do nowadays. Cod, haddock, red snapper—all have had their problems. Striped bass, another classic white-fleshed fish, suffered an enormous population collapse in the 1980s as a result of overfishing and habitat pollution. But wild striped bass have come roaring back thanks to good management. By 1995, the National Marine Fisheries Service had declared the fish "fully rebuilt." Size limits, as well as low-impact hook-and-line and gill nets practices, have kept them that way. That said, recent unlawful poaching has caused sport fishermen to wage a campaign to have the fish recategorized as a sport fish—only animal. And wild "stripers" carry a PCB risk. If all that turns you off, then farmed striped bass are a good alternative. Grown in systems that limit the negative effects caused by runoff, farmed striped bass are a functionally sterile hybrid of striped bass and white bass, and can't easily interbreed with wild populations. In the kitchen, Barton favors a "hard sear" on the farmed version to bring out the fish's slightly muted flavors, whereas "low and slow" heat applied to the wild allows the flesh to baste in its own juices.

WILD AMERICAN LOBSTER: Whereas many fish and some wild shrimp are trawled in nets that pull in all kinds of things, lobsters are caught in traps or "pots" that don't disturb the seafloor and tend to only catch, well, lobsters. Mandated escape hatches mean that unwanted creatures can sneak out the back door, and a very carefully regulated management scheme has kept populations in decent shape. Should each of us then have license to scarf down an entire lobster every time we sit down to a seafood dinner? "If that lobster hadn't been caught by a human, it would have been somebody else's dinner," Barton points out. Because we must share lobsters with several species that also love to eat lobster, perhaps it's more appropriate to share a single lobster among several friends as the accompanying recipe suggests.

FARMED ARCTIC CHAR: Arctic char is a newcomer to aquaculture that's fairly closely related to salmon (they share the same taxonomic family, Salmonidae). Like salmon, char has a nice orange color and is high in omega-3s. But unlike farmed salmon, arctic char are not farmed in the open sea, do not cause the spread of sea lice to the wild, and do not escape and dilute the genetics of wild populations. "A lot of chefs call it salmon light," Barton notes. "It's got a mellower flavor than farmed salmon and not quite as much fat oozing out. I think it actually eats better."

FRESH OR FROZEN U.S.-CAUGHT PACIFIC ALBACORE TUNA: Two questions govern any wild fish's sustainability: (1) How many are there? and (2) How many should we catch?

With tuna it takes a lot of work to determine answers to these fundamental questions. Tuna are extremely migratory, sometimes traveling thousands of miles in their lifetimes. To know how many we can catch, we must gather fishing data from dozens of nations. Nevertheless, tuna is the most consumed finfish in America—with fish coming from all over the world. In looking through the different options, there seems to be consensus among ocean advocacy organizations that U.S.-caught Pacific Ocean albacore is a reasonable choice. Assessments indicate they are abundant. They are shorter-lived, quick to reproduce, and hence a little more resistant to fishing pressure than the larger bigeye and bluefin tunas. Ocean conservation organizations further stress selecting pole- or troll-caught albacore since the more industrial fishing methods like purse seining and long-lining can result in the bycatch of turtles, sharks, and billfish. But (and here's that darn seafood gray area again) as Gavin Gibbons at the National Fisheries Institute, a seafood industry advocacy organization, rightly points out, the purse seining and long-lining sectors have improved their bycatch numbers in recent years, and pole-catching tuna can lead to considerable bycatch of juvenile tuna. If you would like to sidestep the tuna question entirely, both Barton and I recommend trying U.S.-caught Spanish mackerel as a replacement.

It's true, by the way, that better-farmed and better-caught fish and shellfish cost a bit more. But in an era when we're starting to understand the ocean's limitations, no one should feel self-conscious about serving or accepting smaller portions. The more care we show enjoying the sea's resources, the more the sea will continue to reward us with its bounty.