Clam Aquaculture and Clam Farming

Clam Aquaculture and Clam Farming

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The fossil record shows clams were one of the first foods eaten by modern humans, homo sapiens. Preliterate coastal people knew that clams were (a) easy to cook, (b) the hard-shelled were OK to eat raw and (c) delicious. Most people today buy their clams fresh from a market. Generally these clams are still dug by hand, or with specialized rakes. But as the world’s appetite for seafood outstrips population growth, in recent decades scientists and entrepreneurs have looked into “farming” both fish and shellfish. 

This trend is not without risks. Where fish are concerned, problems with fecal contamination, disease spread through close-crowded stocks and leaks from farms into the ocean have caused problems. But clam farming in the U.S. is thriving. First developed in the 1960s, cultured clams are considered less of a threat to the environment than farmed fish. Still the industry is not without its problems: an August 2007 study in the journal Shellfisheries Research revealed a threefold higher percentage of infection by a thraustochyrprid, Quahog Parasite X, in cultured stock than in adjacent wild hardshell clams.

The Northern hardshell clam, Mercenaria mercenaria, and softshell clam, Mya arenaria, are most often farmed. The former is better known as littlenecks (the smallest size), cherrystones (about the size of a half-dollar) or quahogs (largest), an Indian word pronounced “CO-hog.” Mya arenaria is better known as the steamer clam.

The Cape Cod Cultured Clam Corporation was one of the first US firms dedicated to clam farming, beginning in the 1970s. Small steamers ready to spawn were kept in tanks. Their spelt (reproductive emissions) was carefully collected for introduction to nutrient-filled tanks, to grow the clams to a field-plantable size. The company was successful for a time but succumbed to liquidity problems. Another market player, the Aquacultural Research Corporation of Chapin Beach, Cape Cod is still active, and supplies clams wholesale to the Seattle Fish Company.

Aquaculture has been growing rapidly worldwide for decades. In 2009, farmed shellfish and fish surpassed wild stocks as the major source of seafood. The National Oceanographic and Atmospheric Administration (NOAA) estimates that 84 percent of the seafood consumed in the US is now imported, and half of that is produced by aquaculture. The problem with US clams has been their own success: whereas oysters “as big as dinner plates” were noted by Henry Hudson in what is now New York City, in the early 17th century, civilization has reduced the production of shellfish beds through overharvesting and by pollution. Even major improvements to US water quality wrought by the Clean Water Act have been only somewhat successful in returning native shellfish to former abundance, as in Chesapeake Bay.

Clam fans will have to become more knowledgeable about not only the types of clams they prefer but their source. The most promising news about clam and other shellfish farming is its minimal impact on adjacent ecosystems. Unlike fish farms, accidental release of shellfish farm byproducts has not been associated with significant environmental damage, nor has there been manifest danger so far from inbred farmed species contaminating the larger gene pool. The increased prevalence of disease in cultured clams is common to all farmed animals. Science will eventually discover ways to isolate and treat these diseases, so that farmed clams are as healthy as clams from the oceans.

A farmed clam is still a clam: delicious! And we have the famed Wellfleet Oyster as a model. Most oyster fans today don’t know modern Wellfleets most often come from “grants,” sunken, stocked cages submerged in areas of Cape Cod Bay, and auctioned to individual farmers for fixed terms. Yet the Wellfleet Oyster remains the most famous in the world, instantly distinguishable from any competitor.

The future for farmed clams in the United States and worldwide looks bright. Sinking clams and oysters in cages has also been found effective in cleansing bays and harbors of nitrogen and phosphate-driven plankton “blooms,” while the shellfish have remained safe to eat.

Most people cannot distinguish taste the difference between farmed and non-farmed clams. They are different in appearance. The rings on a farmed clam shell are darker about two-thirds of the way in from the edge.

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