In evaluating potential risks and benefits of introducing nonnative oysters into the Bay, the National Academy of Sciences committee said it found relatively little scientific support for many common assumptions about oysters in the Bay.
These five “myths” need to be treated with more scientific scrutiny if progress is to be made resolving the oyster problem, the committee said. They may not be the only “myths” about oysters in the Bay, the committee said, but they do reveal major gaps in knowledge that add to the uncertainty about whether a nonnative oyster should be introduced.
Declines in the oyster fishery and water quality of the Chesapeake Bay can be quickly reversed.
The committee said there is no “quick fix” either to the Bay’s water quality problems or the dismal state of the native oyster, both of which have been in decline for decades. With the oyster in particular, a series of actions—the establishment of sanctuaries, hatchery enhancement of the stock, construction of reef habitats and the placement of spat on shells—have all failed to yield quick results. “Progress on reversing the long-term decline in oyster populations and water quality will be achieved only when unrealistic expectations for a quick fix are replaced with a long-term commitment to systematic approaches for addressing the Bay’s complex, multidimensional problems,” the committee said.
Oyster restoration, whether native or non-native, will dramatically improve water quality in the Chesapeake Bay
Although oysters have a tremendous ability to filter water, it is a “fault of logic” to assume that today’s water quality problems result from a decline in oysters and can therefore be corrected by efforts to restore the population. Nutrient pollution, increased sediment, shifts in climate and more toxic chemical pollution have all added to the Bay’s stress over the past century, and could delay—or even prevent—any water quality improvements stemming from the restoration of the oyster population. Further, although the oyster has declined, other invasive bivalves have taken oven much of the filtering job carried out by oysters. Water quality improvements would likely be confined mainly to shallow water areas while large amounts of algae would still reach the middle and deeper portions of the Bay, where they degrade water quality and contribute to problems with low-oxygen concentrations. Addressing problems in those areas would require “much more comprehensive efforts” than oyster restoration.
Restoration of native oyster population has been tried and will not work.
Despite “considerable resources” in restoration efforts, there have been no large-scale reversals in the native oyster decline. But that does not mean future efforts will fail, especially as more efforts are placed on using the disease-resistant oyster strains being developed for restoration. Recent restoration efforts were also set back by drought conditions, which allowed diseases to thrive in the Bay. “A series of more typical, colder and wetter winters could give restoration efforts a substantial boost relative to progress in the recent past,” the committee said.
Aquaculture of triploid Crassostrea ariakensis will solve the economic problems of a devastated fishery and restore the ecological services once provided by the native oyster.
The committee said aquaculture with triploid oysters “is likely to be limited by relatively high costs of material and labor.” Such oysters are likely to be too expensive to supply the packing houses in the region, which have to import oysters from elsewhere to meet their needs. Aquaculture oysters may be more suited for the half-shell market, which pays premium prices but has a smaller demand. “Thus, contained aquaculture of triploid oysters would likely involve only a fraction of the Bay’s oyster industry and the scale would be too small to make a noticeable difference in the water quality of the Chesapeake Bay.”
Crassostrea ariakensis will rapidly populate the Bay, increasing oyster landings and improving water quality.
The notion that the Suminoe oyster will rapidly invade the Bay is heralded both by those who see it as a salvation for the oyster fisher, and those who fear ecological disaster. But the available information does not suggest a foreign oyster population would have a rapid rate of growth in the Bay. A wild population of C. ariakensis on the West Coast of the United States, where it was accidentally introduced in the 1970s, has not spread, But the committee cautions that may not necessarily be a predictor for the East Coast. Populations would also be limited by lack of habitat because of sedimentation, which has reduced the area available for settlement by larvae produced by the native species.