On Another Front:
Juvenile Oyster Disease
As if MSX and Dermo were not enough, an apparently unrelated die-off of young oysters begin hitting New England in the late 1980s. Known simply as "juvenile oyster disease," this latest threat adds another culprit to the list of oyster killers.
The disease appears to hit hatchery-reared oysters more than those in the wild, according to Steve Jordan, director of the Cooperative Oxford Laboratory. "It's possible that the die-offs are caused by stress," he says, from overcrowding in an aquaculture facility, for example - but he doesn't think that's it.
"Research has now shown that the disease is transmissible," he says. "We also know that higher salinities cause expression of the disease." According to Jordan, "Everything bears the earmark of an opportunistic infection."
"There has been some research that suggests the involvement of Vibrio species," says Jordan, "but so far that work is still inconclusive."
Other work, undertaken by researchers like Eugene Small at the University of Maryland College Park, suggests that this juvenile oyster disease may be caused by a protozoan parasite, probably a ciliate of the family Ciliaphora . The College Park research team is currently examining oysters to determine the presence of suspect microorganisms.
"We recommend that oyster growers work with survivors from stocks that have already been exposed," says Jordan. These survivors have the best chance of having developed resistance to the disease, he says.
The Frank M. Flower and Sons oyster company on Long Island, hard hit by the disease, is cooperating closely with the University of Maryland, the Oxford Lab and others. The approach of using resistant strains seems to be working for the Flower oyster growers, with production once again returning to high levels. This
is promising, since at one point the disease was cutting oyster production in some parts of the region by as much as 50 to 90 percent.