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It may be the best news about Chesapeake Bay oysters in more than a quarter of a century.

The Maryland Department of Natural Resources found a 92 percent survival rate in its fall oyster survey, the agency reported this week.

That’s the highest survival rate since 1985, and it means that two diseases that have decimated oysters in recent decades are on the wane.

Dermo and MSX, though harmless to humans, have killed countless oysters, which led to a frantic scramble to come up with strategies to save them.

Oyster sanctuaries were established, putting many acres of bay and river bottom off limits to watermen.

Meanwhile the state began leasing what were formerly public waters to individual watermen, inviting them to grow their own oysters for their exclusive use.

There has been resistance to all this from many watermen. What is the point of keeping oysters in a sanctuary where they can’t be touched if diseases are likely to kill them anyway? Why should watermen invest on stocking leased ground to grow oysters if they may well die before they reach marketable size?

So the survey showing that the great majority of oysters survived last year couldn’t come at a better time to validate the underpinning of Maryland’s new management strategies.

But let’s be clear. The good news comes courtesy of nature, not humans.

“Our continued commitment to renewing this iconic species has begun to pay off,” Gov. Martin O’Malley said in a statement. “Through balanced investments in aquaculture, sanctuaries, stewardship and enforcement, our native oyster is coming back.”

That is overstating the case. Those things didn’t keep young oysters alive last year. The course of these diseases is not completely understood, but DNR suggests that heavy rains last spring and late summer helped oysters by lowering salinity in the bay and its tributaries, knocking back the diseases. Both MSX and dermo were at the lowest levels on record.

What this news about the low mortality rate does do, however, is raise the possibility that the sanctuaries, the leasing program, the planting of baby oysters and crackdown on poaching could be spectacularly successful in the future.

A decade ago, these diseases killed off more than half of the oyster population — 59 percent — in a single year. If that were still the case, the efforts to replenish the species would hold far less promise than they do when the mortality rate is 8 percent.

The sanctuary program is intended to save oysters from extinction, so they can act as a natural filter to improve water quality. In time, the theory goes, the spat — bay oysters — from the sanctuaries will spread to public oyster bars still open to harvesting. If it works, the bay can have its oysters and we can eat them, too.

But the battle isn’t over. Will MSX and dermo roar back during a prolonged dry spell when salinity in the water rises? Or are the oysters that survived and are now reproducing more resistant to these diseases?

No one really knows what the next turn in the natural cycle will bring, but if the good news holds, Maryland is poised to take advantage of it to rebuild the oyster population in state waters.