What is the Big Deal about Oysters?

Ok, so why does everyone make such a big deal about oysters and the Chesapeake Bay? Fine, so they are good to eat. But why do the environmentalists make such a fuss over them? How does their health affect us?

Currently, oysters are less than 1% percent of the population in the Bay when the first Europeans came here. For several hundred years after their arrival, there wasn’t much of a problem. But, in the 1800s and then the 1900s when things became more mechanized and people started dredging oysters from boats, the oysters started being decimated.

At one point in their lives oysters are free swimming but they very soon settle down and start forming shell which protects them and also fastens them to a surface so they can no longer move unlike a scallop. So if they get sediment on top of them, they are out of luck and die. As farming increased (and land development in general) and the amount of sediment runoff increased that stressed or killed oysters.

The Caribbean had coral reefs. Up until sometime in the 1800s, the Chesapeake had oyster reefs. At low tide you would even see the tops of them at times. They were very rich environments. Not only were the oysters there but they supported numerous small crustaceans, invertebrates and fish. Larger fish then were attracted as well.

But this environment was destroyed by over harvesting. The dredges, a kind of trawl dragged behind boats, would scrape along the reef and pick up oysters and disturb others. At one point, the reefs were so numerous that they were almost like extensions of the land and the rivers flowed along them. You needed to be careful that you didn’t run aground. Over time though they were knocked down and degraded by the dredging. This also destroyed the habitat for the all the other creatures mentioned, causing a decrease in them as well.

There was another impact. Oysters are filter feeders and it has been estimated that originally they would filter all the water in the Chesapeake Bay in a week. Now it is probably years. This means that the water is not as clear. That affects the sub aquatic vegetation, (seaweed) and causes die offs, especially in combination with the increased sedimentation. The seaweed patches are another important area where small creatures can hide and be less likely to be eaten.

More recently, two viruses have attacked the oysters. Probably in part because of their decrease numbers and increased sedimentation and pollution they were stressed and more susceptible to disease.

We have heard people talk about how clear the water in the Chesapeake was up until the early 1950s. Because the oysters filtered the water it apparently was like the water in the Caribbean. You could frequently look right to the bottom.

There was a great example of the effects of the filtering not too long ago. There is a small mussel that lives in the Bay and is normally not very plentiful. However, for some reason in 2004 the conditions were perfect for it and millions of them grew on every possible surface in the Magothy River. They were on pilings, boat hulls, you name it, they were there. That year the water was amazingly clear. The next year things went back to normal and they died off and the water got much more turbid / cloudy.

So, rather than complaining about restrictions in oyster harvest, we should be applauding. If some areas are restricted it is likely the overall harvest will go up. It will also have a major impact on the abundance of other animals including commercially important fish and crabs.

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