A vast government effort to bring oysters back to the Chesapeake Bay has turned out so dismally that it has the ring of a math-class riddle. How do you spend $58 million to get more of something and wind up with less of it?

Since 1994, state and federal authorities have poured these millions into rejuvenating the famous bivalves and the centuries-old industry that relies on them.

They have succeeded at neither.

Estimates show there are fewer oysters in the bay and fewer oystermen trying to catch them. If those estimates are accurate, the effort would be a failure of environmental policy that stands out for its scale, even on a bay where policymakers frequently promise big and deliver small.

Scientists and activists say the missteps of the save-the-oyster campaign will have consequences far beyond the half-shell bar. The whole Chesapeake will struggle, they say, missing a species that was as vital to its ecosystem as coral reefs are to theirs.

“You’ve got fewer oysters and fewer oystermen and fewer oyster-related businesses,” when the goal was to help all three, said Robert Glenn of the Coastal Conservation Association of Maryland. “Clearly, your money was not well spent.”

Officials who have led these programs defend their work, in part, by pointing to the factors arrayed against them. The bay’s dirt chokes oysters. Diseases harmless to human diners kill them by the millions.

In spite of these factors, officials say, they have put millions of oysters in the bay that wouldn’t have been there otherwise.

“I wouldn’t use the word ‘failure.’ We obviously have not achieved the restoration response that we had hoped for,” said Thomas O’Connell, director of the Maryland state fisheries service. “Every year we have learned to do it better. But there is no oyster restoration (instruction) book out there.”

For decades, governments have tried in vain to change this picture. Since 1994, federal and state officials together have spent about $19 million in Virginia and $39.7 million in Maryland on oyster projects.

But at last count, oyster numbers appeared to have declined since 1994. One EPA estimate found they had fallen about 20 percent.