Carnegie says "there's been a lot of attention given to these up-river, low salinity refugia. They've been viewed as the key source reefs that are exporting larvae into the higher salinity waters." Disease-ravaged reefs in higher salinities have been valued primarily for their fishery, which has sought to harvest doomed oysters before they succumbed.
Carnegie and Burreson's research, however, paints a different picture. They've found clear evidence that oysters in the Bay's saltier waters are developing resistance to both MSXthe focus of their paperand Dermo, despite the increasing prevalence in the Bay of the parasites responsible for the two diseases. This is only possible through reproduction by resistant oysters in high-disease areas, thus their call for a focusing of restoration efforts onto these disease-resistant areas and populations.
Carnegie says "We basically need to confront the diseases head-on where they are most active, rather than avoiding them by working in low salinities. It's in the high-disease areas that resistance is developing most rapidly, so restoration efforts should be focused there."
Recent restoration initiatives in Virginia have included the designation of numerous sanctuary reefs in higher salinities and a rotational harvest scheme in the lower Rappahannock River, but these have been controversial. "Harvesters have viewed such efforts with skepticism," says Carnegie, "because the protected oysters would likely be lost to diseases. Yet our results suggest that strategies like these that increase the number of resistant oysters are precisely the right approach."
In fact, Carnegie and Burreson point out that restoration efforts focused on low-salinity refugia may actually be counter productive. Carnegie says "our study makes very clear what happens when oyster larvae from the low-salinity refugia settle in high salinity watersthey are removed quickly by the parasites because the
|Contact: David Malmquist|
Virginia Institute of Marine Science