USGS - science for a changing world

Northern Prairie Wildlife Research Center

  Home About NPWRC Our Science Staff Employment Contacts Common Questions About the Site

The Clamor Over Clams

Uses For Clams

You probably remember seeing clams while fishing, or perhaps you found them to be good skipping stones in your younger days. Most people don't equate the "skipping stone" clams with the deepfried ones at local restaurants, but they are closely related.

Are North Dakota clams edible? The answer is a qualified yes. However, eating them may not be without some health risk.

The clams' low position on the food chain and manner of feeding allow for ingestion of unhealthy by-products of human activities, which may be in our lakes, rivers, and streams. When a clam filters out the micro-organisms from sediments, it may also be absorbing toxics such as heavy metals, pesticides, industrial pollutants, and naturally occurring toxics such as arsenic.

If North Dakota clams aren't in demand for their edible qualities, why were they such an interesting subject at coffee shops and in government offices around the state? Are there other uses for clams we may not realize? As a matter of fact there are.

Up until the 1960s, almost everybody in this country used clams on a daily basis. They probably didn't know it, but many buttons were once made of pieces of clam shells. Clam beds in the big rivers of the southern and eastern United States were commercially harvested for their shells, which were used to make pearl buttons. Southern states, in particular, have a long tradition of mussel harvesting and many people made their living picking, selling, and buying shells for the button industry.

With the advent of plastics and other synthetic materials, the demand for mussel shells dropped dramatically. However, in recent years interest in commercially harvesting mussels has boomed. A new use for mussel shells has emerged and the pressure to harvest large quantities of shells has become intense.

The cultured pearl industry has discovered a quick way to make pearls by taking a piece of high quality mussel shell and inserting it into a living oyster. Naturally occurring pearls are deformities inside the shell of a clam or oyster. When a piece of foreign matter, such as a grain of sand, gets lodged between the organism's shell and inner tissues, the oyster covers it with a secretion or nacre called mother-of-pearl. Over the course of several years more layers are laid around the intruding piece of material, forming a hard, white-colored object, known as a pearl. Sometimes these pearls are spherical, others are differently shaped.

Pearls are valuable because they are rare and demand is high. Cultured pearls are desirable because they can be created relatively fast by taking large pieces of mussel shells that are the same color as mother-of-pearl and adding only a layer or two of nacre. This will save up to several years of time, thus more pearls can be produced quicker and cheaper. By using perfectly round pieces of shell, you can get consistently round pearls for a less expensive price so more people can afford to buy them.

Oriental cultures value powdered pearls as a medicinal treatment. Pearls are also used by biological supply houses and for some costume jewelry production.

Previous Section -- Life History
Table of Contents
Next Section -- Clam Industry Demand

Accessibility FOIA Privacy Policies and Notices

Take Pride in America logo logo U.S. Department of the Interior | U.S. Geological Survey
Page Contact Information: Webmaster
Page Last Modified: Saturday, 02-Feb-2013 05:27:02 EST
Sioux Falls, SD [sdww54]