SAN DIEGO — The canned-tuna industry is swimming upstream, hurt by health warnings of mercury contamination and a perception that its product is just plain boring.

Now the major players are renewing efforts to hook customers.

Canned-tuna producers are promoting the fish as a low-fat protein, laden in omega-3 fatty acids that are believed to benefit the heart. They're trotting out new advertising. And they're moving beyond the can, offering products in foil pouches, including steaks and flavored fillets.

"Tuna doesn't always equal sandwich," said John Signorino, chief executive of San Diego-based Chicken of the Sea International. "This can be a dinner food."

The effort is starting to rejuvenate business at Chicken of the Sea and its rivals, Del Monte Foods Co. of San Francisco and Bumble Bee Foods of San Diego.

Signorino's goal is to push consumers to more lucrative products such as Chicken of the Sea's 'ahi steak in a garlic and herb marinade. He also wants to develop other offerings in line with America's increasingly sophisticated palate.

Tuna steaks, which retail for $2.89 to $3.89 for a 5.25-ounce serving, are anywhere from three to five times as profitable as a 99-cent can of tuna, the company said.

In addition, Chicken of the Sea is diversifying into other seafood. The company is the U.S.'s largest purchaser of salmon, making up 8 percent of sales, Signorino said.

Though the company thinks there is still a "good future" for tuna, Signorino said, salmon looks to be a growth business. It has all the healthful benefits of tuna, he said, but "none of the baggage."

New products like the steaks and updated packaging helped Chicken of the Sea, a unit of Thailand's Thai Union Frozen Products, one of the world's top canned-tuna producers, swing from a loss to a small profit last year, Signorino said.

Chicken of the Sea, whose financial results aren't made public, has an estimated 20 percent of the U.S. consumer market. Its revenue is believed to be about $400 million a year, including sales of seafood and salmon products as well as sales to wholesale clubs and the food-service trade.

Likewise, Bumble Bee owner Connors Bros. Income Fund of Toronto said in a recent report to shareholders that "the expansion of flavored and ready-to-eat tuna items continues to add volume and profit to the business."

Del Monte Foods, the U.S.'s largest tuna company with an estimated third of the market, said last month that sales in its consumer division rose 3.5 percent to $573.4 million, helped in part by its new StarKist Tuna Fillets.

The growth is welcome news to an industry that saw sales of "shelf stable" tuna — in cans or pouches — drop almost 6 percent to $1.01 billion last year from 2001, according to market researchers at ACNielsen. The data don't include sales at Wal-Mart Stores Inc. or kits with tuna and other food such as crackers.

During the same period, the volume of tuna sold sank 18 percent to 383 million pounds as prices climbed because of rising costs of both the fish and the metal of cans, ACNielsen said.

In a study of American eating trends, market researcher NPD Group found that 19 percent of those surveyed in 2005 reported eating canned tuna at least once in the previous two weeks. That's down from 25 percent in 2001.

Tuna executives attribute much of the decline to the mercury issue.

Studies have found that high concentrations of mercury in pregnant women, nursing mothers and young children are harmful to brain development. Large predator fish, such as swordfish, shark and tuna, tend to contain more mercury than smaller species. Canned light tuna typically contains less of the heavy metal than does canned albacore or white tuna.

Two years ago, the Food and Drug Administration and the Environmental Protection Agency warned pregnant women, nursing mothers and young children to limit consumption of fish species that have elevated mercury levels, including tuna.

Consumer Reports magazine this year went further, advising that pregnant women "avoid canned tuna entirely." The magazine reached its conclusions after reviewing federal data that showed canned light tuna can sometimes contain as much or more mercury as canned albacore.

FDA testing updated in January found that the average level of mercury in light canned tuna was 0.12 parts per million, well below the 1-part-per-million federal limit for commercial fish. Albacore tuna averaged 0.34 parts per million, about a third of the FDA maximum.

However, the FDA tests also found that some samples of light tuna were close to the federal limit, and that some albacore exceeded the limit.

Industry representatives called the Consumer Reports warning irresponsible. "Consumer Reports is not the right organization to be giving health advice to the U.S. consumer on food and nutrition," said Anne Forristall Luke, president of the U.S. Tuna Foundation.