Dwindling oyster reefs

StoryImage( ‘/Images/Story//Auto-img-118477883428268.jpg’, ‘Photo courtesy of www.nsf.gov‘, ‘More than 300 different species of animals may live on an oyster reef.‘);
StoryImage( ‘/Images/Story//Auto-img-118477888528492.jpg’, ‘Photo courtesy of www.sms.si.edu/K. Hill‘, ‘An oyster reef in the Indian River Lagoon, on the Atlantic Ocean side of Florida. The reef is composed of crassostrea virginica, also known as American oyster, Atlantic oyster, or the Virginia oyster, and is a species of oyster that is native to the Eastern Seaboard of North America. ‘);

Natural oyster reefs along the coasts of the United States are disappearing at an alarming rate, and nowhere is this more true than in the great Chesapeake Bay. Francis Louie Michel, a Swiss, visited Virginia in 1701 and recorded the following concerning oysters in his journal when he visited the colony: “The abundance of oyster is incredible. There are whole banks of them so that ships avoid them. A sloop, which was to land us at Kingscreek, struck an oyster bed, where we had to wait about two hours for the tide to turn. The Virginia oysters surpass those in England by far in size; indeed they are four times as large. I often had to cut them in two before I could put them in my mouth.”

But, now all of that has changed. In 1880, the oyster harvest in the U.S. was 154 million pounds of shucked meat, whereas in 2002, this figure had shrunk to 31 million pounds. In the Chesapeake Bay, the historical number of oyster reefs (also called oyster rocks. Beds, or bars by watermen was approximately 400,000 acres, and today there are barely 20,000 acres of reefs.

Oysters are filter feeders in that they pass water through their bodies, which extracts items of food such as algae, bacteria and other small organisms. This function is vital to the health of a body of water such as the Chesapeake Bay as fertilizer runoff and inadequately-treated sewage effluent, along with pollution from industry promotes the growth of algae to the point where the entire ecology of the body of water is impaired. Oysters and some other shell fish keep so-called algal blooms under control by literally using the tiny plants as food as water is filtered though their bodies. It has been estimated that 200 years ago, the oyster population of the Chesapeake Bay would pass the some 19 trillion gallons of water of the Bay through their bodies and filter it in one week. The time needed today to accomplish this is one year.

Many, except biologists interested in oysters, do not realize that an oyster reef is an ecological community in itself. Biologists have long known that many different types of animals are associated with the bivalves in their natural environment, and some of these organisms were, in fact, detrimental to the oyster itself. Most of these oyster scientists were stunned, however, when they read a report issued in 1962 by Dr. H.W. Wells, who had studied for years the animals that makes up the ecological community of an oyster reef. When he finally terminated his study, he was able to state that he had found 303 different species of animals that shared the reef or bar with their host oysters. Of course, all 303 species would not be found on the same reef at any given time or place, but a large number were found to be residents of the community most of the time. Considering this, one is apt to recall the limerick by Jonathan Swift when Dr. Wells’ findings are considered:

“So, naturalist observe a flea.

Hath smaller fleas that on him prey

And these have smaller still to bite em,

And so proceed ad infinitum.”

There are many reasons why the oyster reefs are disappearing from our coastal waters. The men who take their livelihood from the Chesapeake swear that is the invasion of the Bay by the two oyster diseases—the protozoan called MSX and the fungus called Dermo. While it is certainly true these microorganisms have devastated the oyster population, they are not the only cause of the oyster’s fate. In my opinion, which is shared by others, an important reason oyster populations have dropped so low is overfishing throughout the years. The disease may kill a high percentage of the oysters on a reef, but it will not get all of them. A few will have some inherent defense against the pathogens, and they will form the breeding stock for the next generation that will be more resistant to the diseases. This is the basic principle of natural selection, and given time, the oyster population will consist mainly of those resistant to the diseases.

But people want a quick fix to environmental problems. The planting of Japanese oysters that are supposed to be already resistant to the diseases is touted, as is the building of artificial reefs. Only time and natural laws will bring oyster reefs back to what they were formerly.

The last time I was in Baltimore, I feasted on oysters on the half shell, but they did not look like they came from the Chesapeake. The man in charge told me that his oysters had been shipped to Maryland from Galveston Bay, Texas, and that was about the only place he could get them. Alas, I read in the paper the other day that fishing for shell fish in Galveston was now prohibited because of pollution.

When confronted with the ecological disasters we encounter today, I constantly ask myself, “When will we ever learn?”

from the July 18-24, 2007, issue

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