Since oyster bars that are made up of live oysters support more prey than oyster bars made up of dead shell, any threats to oyster bars will negatively impact associated gamefish.  Unfortunately, numerous threats to oysters exist.  Too much sediment can bury oysters, and many estuaries are inundated with sediment-laden water draining farmland, housing developments, and urban areas.  Too many nutrients can cause plankton blooms that, when the plankton dies, create hypoxia (low oxygen) or anoxia (no oxygen) that last for periods long enough to kill oysters.  Runoff heavy in nutrients comes from farms and suburban lawns, from urban sewage outfalls, and from livestock.  The herbicides and pesticides that often accompany this runoff can also stress oysters.  Boat wakes from channels that border oyster bars can prevent juvenile oysters from colonizing reefs, thus dooming a reef to eventual death.  Too much physical disturbance from tonging, dredging, and frequent boat groundings can damage or even destroy reefs as well.

Since oysters and their predators and diseases are strongly influenced by salinity, changing the flow of freshwater into estuaries can have dire consequences.  If, for example, release of water from dams causes long periods of high freshwater flows, salinities may drop enough to kill oysters in the upper portions of an estuary.  If, on the other hand, so much freshwater is diverted from rivers by cities or agriculture, salinities in most of the estuary may become high enough to allow predators and disease to become established farther into the estuary than they would under natural conditions.  In both scenarios (which are already realities in some areas), the health of oysters and oyster bars decline.

Oyster bars influence water current patterns, so changing their location, size, or orientation (by dredging, for example) can have unpredictable impacts on the flow of water and sediments, causing unpredictable problems that effect gamefish and prey. For example, currents may become stronger and carve deep holes in the bottom or wipe out areas of seagrass that had previously been protected by the removed bar.  Or currents may be completely blocked, creating a stagnant area behind an altered bar that holds few prey and gamefish. 

As we are learning in so many of our estuaries, oysters are an essential component of a healthy coastal ecosystem.  They are also important habitats for gamefish and their prey.  In some areas, they are THE most important gamefish habitat.  Effective stewardship means making sure these habitats remain viable parts of our coastal ecosystems.  And remember, once an oyster bar is gone it’s probably gone for good because oyster larvae need the hard substrate provided by adult oysters to survive. 

All material copyright Aaron Adams 2007, 2008, and beyond, unless noted.