Love is in the Water

Chesapeake Bay oysters were amorous last summer, and the seed they sent forth willy-nilly into the water has set into abundant spat.
    Natural Resources researches examining the intimate lives of 53 key oyster bars last fall found spat — or oyster babies — about five times higher than the 25-year median. Instead of 16, spat count per bushel was nearly 80, the overall highest since 1997.
    Oyster babies were most plentiful in saltier waters of the lower Bay. But they were also widely distributed in the Bay and its tributaries, even in the fresher waters where often no spat sets.
    Wide distribution is the best news of all, according to Mitchell Tarnowski, who captained the survey boat and crew from mid-October to December 18. Nobody knows what makes a good spat set, he explains. “But if that trend continues, we shold have more oysters in two to three years than we do now.
    “That’s a big if,” he allows. But this year’s survey gives cause for hope on two more fronts.
    The next piece of good news is the vitality of oysters.
    Survival is about 88 percent, the highest since 1985, when 90 percent of oysters survived. That’s the good old days, before a partnership of oyster diseases — dermo and MSX — put, in Tarnowski’s words “a stranglehold on the population.”
    Since ’85, oyster survival has been bad and worse, with a 26-year average of about 27 percent mortality punctuated by terrible highs like 2002’s, when nearly 60 percent of oysters died.
    There’s still more good news. Both those nasty diseases are showing reduced virulence. Dermo fell below its 21-year average to less than half the record-high levels of 2001. MSX is still above its 21-year average, yet MSX-related mortalities were not observed.
    In other words, the diseases are no longer killing off Chesapeake oysters, which may be developing immunity.
    “These moderate levels of natural oyster mortalities during recent years may reflect increases in disease resistances among oysters and their progeny that survived the severe disease pressures of the 1999-2002 drought,” said Chris Dungan, manager of oyster disease research. “Those same disease-selected oysters are the parents that spawned to produce the significant spat set of 2010.”
    If you’re feeling optimistic, you can take those high survival rates as another portent that we’re on the way to the more-oysters-healthier-Bay equation in which Maryland has so heavily invested.
    “For more than 15 years, the state and its partners have aimed to jump-start Mother Nature by investing in building the necessary infrastructure, deploying billions of oyster spat on shell and reclaiming thousands of acres of buried shell from derelict oyster reefs. Now, it seems she’s fighting with us,” says Natural Resources Secretary John Griffin. “These animals are proving just how resilient they can be given the right circumstances.”
    The best possible outcome is that this year sets a spiral of oyster production in motion, for more oysters means even cleaner water because every feeding oyster is a natural water filter.
    Oysters could propel us to a clean Bay — if we can help them keep that spiral moving.