There is a global crisis concerning this exotic delicacy, and oysters  may eventually disappear altogether. Oysters are a favorite food in every part of the world and every culture, except in vegetarians’ kitchens. This shellfish, rich in zinc, is necessary for the production of testosterone in higher animals, including humans.

Not just oysters are at risk, but also other shellfish and the ocean’s entire food chain. All Marine life, as well as the upper part of the food chain, including humans, depends on this small, savory bivalve for nutrition.

Oysters are filter feeders and pull seawater over gills that contain minute hairs called cilia. These cilia push plankton, algae, and other nutrient particles into the oyster’s mouth along with seawater and pollutants. These little bi-valves are responsible for doing a big job and can filter up to five liters of seawater an hour, including the pollutants and their food. They eat what they need and excrete the rest in waste pellets that sink to the bottom of the water and decompose harmlessly into the atmosphere as nitrogen.

Oysters’ gills extract oxygen as well as food. Their heart is a three-chambered pump that circulates colorless blood, rich in oxygen, to all parts of the body. Two kidneys filter the pollutants and waste products out of the blood and package them into the waste pellets.

Oysters are able to change their sex during their lives, (protandric) starting out as males. At one year of age, they are able to release sperm. At two or three years of age, they convert to females, and begin releasing eggs. Speculation is that they may change back and forth several times during their lifetimes, according to the amount of nutrients at their disposal. A single female can produce up to 100 million eggs annually, however, most do not live to be adult oysters.

Tiny, free swimming Oyster larvae are part of the ocean’s ‘plankton soup’. When they attach themselves to rocks, shells, or other solid objects, they are known as spats  and live out the rest of their lives in that one place. The spats mature at about one year, and continue growing for a couple more years, until they reach eating size. The spats gravitate to adult oyster beds to attach themselves. The adults are farmed from these oyster beds and early larval oysters are replanted into the bed.

A couple of inches in size is the ideal for human consumption. ‘Eating oysters’ are different from the ‘pearl oysters’, the latter of which secrete concentric circles of nacre to cover up a small irritant, such as a grain of sand, which over the years, is destined to become a pearl.

The oyster die-off  begins in the larval stage, before they become spats and attach themselves to a permanent position. In 1998, some fisheries noticed that their larvae were dying off, and blamed the El Nino weather pattern. The problem increased at an alarming rate over the next few years, and by 2005, had spread to other fisheries and the wild population. Fishery scientists soon found a higher than normal concentration of a bacterium known as vibrio tubiashii in the seawater where the infected oysters lived. This bacterium thrives in unusually warm water with low oxygen, known as the dead zone, and produces a toxin that is deadly to shellfish. It is thought that this problem is a product of global warming and a higher than normal acid level in the seawater. Also of possible importance, are the shellfish diseases, dermo, and the MSX parasite, plasmodium.

Researchers think that these problems may all contribute to the die-off of the oysters and are working to alleviate them. However, the problem remains, albeit at a lesser rate than before. Perhaps there is an answer somewhere that will solve the problem, and oyster lovers will be spared an oysterless future.