Major tuna fish companies have quietly downsized cans from six ounces to five over the last year, and consumers are paying more for less of the lunchtime staple enjoyed in more than 70 million American households. Chicken of the Sea, Starkist, Bumble Bee, Progresso, and Genova began putting 16 percent less tuna in slightly smaller cans over a year ago, but because of inventory, the larger cans were available in many major metropolitan area supermarkets until recently, according to several producers.

Canned fish joins a list of dozens of products downsized with no price reduction over the last decade, including cereals, coffee, toilet paper, and even mayonnaise.

“This shrinkage has been going on for years and it’s outrageous,” said a mother of two. “I remember when you could make three kids sandwiches from a can of tuna, but that was a while ago.”

During the last 18 months, Snickers King Sized Bars went from 3.7 ounces to 3.29 ounces, Lay’s Classic Family Size Potato Chips shrunk from 16 ounces to 14 ounces, a package of Bounty Paper Towels thinned out from 138 two-ply sheets to 128 two-ply sheets, and pints of Haagen-Dazs ice cream are no longer pints, but 14 ounces.

“This shrinkage has been going on for years and it’s outrageous,” said Jane Fleetwood, a mother of two who lives in New York City. “I remember when you could make three kids sandwiches from a can of tuna, but that was a while ago.”

Following the tuna can timeline, more than 10 years ago, it came in seven-ounce cans, then were diminished to 6 ½ ounces, then 6 1/8, and now a flat five.

Americans bought 1.5 billion cans of tuna last year, according to AC Nielsen data.

Fish company spokeswomen said the most recent downsizing was due to rising prices for tuna, first canned in 1903, and competition, although it is unclear which company cut the can first in the most recent episode.

Pam Becker, a spokeswoman for Progresso, said, “In order to better align to the current category package sizes, we did move to a five-ounce can for Progresso, making it easier for consumers to compare our brand with other national brands of the same size.”

Amanda Rozier, a spokeswoman for Chicken of the Sea said, “Chicken of the Sea followed its competition and industry in the reduction of package sizes.”

The tuna companies declined to discuss price, which for consumers varies from store to store.

But Robert Ivers, vice president of Fairway Market, which annually sells more than 400,000 cans of tuna at its five stores in the New York City metropolitan area, said the canners all raised their prices over the last 18 months.

“They dropped the size and they raised the prices, and some of that increase we had to pass along, but not all, because we’ve decided to make smaller margins of profit,” he said.

“A year ago we were selling Bumble Bee solid white for $1.25 a can; now it’s $1.66. Genova used to be $1.66 for a five-ounce can; now it’s $1.99,” said Ivers.

Meanwhile, serving sizes on most producers’ cans are listed at two ounces, baffling some consumers, who find it hard to conceive of a two-ounce tuna sandwich.

“It’s a double whammy for customers,” said Ivers. “I have a 9-year-old daughter and a 5-year-old son, so now what do I do? I put in extra mayonnaise.”

And, he noted, canned salmon is not exempt from the trend.

“Same thing happening there,” he sighed.

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