Shellfish and the human species have a long affiliation. For the most part, it has been an unequal relationship with the shellfish providing sustenance, health benefits and ecological services and in return receiving human abuse through over-consumption, over-harvesting and destruction of their habitats. On the positive side, we humans have exalted shellfish in our art and culture and when necessary have implemented restoration efforts if only to maintain shellfish populations for our own well-being. Lucky for us, shellfish are forgiving, or at least very fecund, and given half a chance they rebound.
Recent evidence supports the consumption of shellfish by ancestral humans as early as 125,000 years ago on Africa’s Red Sea coast. Closer to home, about 4,500 years ago native Americans near Charleston, S.C. lived atop shell rings, complex structures constructed from shells. Archeological data tell us that in just a couple of years the Indians built one shell ring consisting of over 1.2 billion shells! Not surprisingly, by 3,000 years ago the Indians abandoned their shell ring habitats probably due to depleted shellfish stocks. Like over-harvesting, restoration efforts also have an early history. New investigations in British Columbia have identified extensive rock-fortified terraces constructed by native Americans that served as clam gardens as early as 4,000 to 5,000 years ago. In more recent history, the Romans plundered wild oyster beds in Britain followed by early efforts to culture them.
History repeats itself. Like the first people in America and the Romans, we still appreciate and consume shellfish as a tasty and nutritious food. Modern science confirms the traditional health benefits of eating shellfish. Mussels and oysters are among the best source of omega-3 fatty acids that have been touted as beneficial to cardiac health and the immune system, an aid to prevent macular degeneration, rheumatoid arthritis, asthma, kidney disease, lupus and cancer. New research supports historical aphrodisiac claims about oysters. Oysters are nature’s best source of zinc that increases testosterone in men and helps libido in women. Shellfish, along with liver, are particularly rich sources of vitamin B12 that may help prevent dementia early in the elderly.
Beyond the benefits derived from eating shellfish, ecologists stress the key role of shellfish in maintaining the integrity of marine environments. The dollar value of the “ecosystem services” provided by shellfish far exceeds their worth as a fishery product. Shellfish are nature’s vacuum cleaners. A single oyster can filter up to 15 gallons of seawater a day. In the process, it consumes microscopic algae and removes particulate matter and suspended sediments. This filtering improves water clarity and benefits the growth of eelgrass that in turn provides improved nursery habitat for finfish and a multitude of marine species. Further, nitrogen absorbed by the phytoplankton is incorporated into the proteins of growing shellfish and is removed from our water bodies when the shellfish are harvested. One calculation concludes that the nitrogen waste input from one person leaching into a watershed can be offset by about 3,750 rapidly growing oysters. In addition to this uptake of nitrogen in their tissues, even a greater amount of nitrogen is removed from the water by feeding shellfish and deposited in bottom sediments. Oyster reefs and aquaculture cages have been shown to provide environmental benefits similar to coral reefs. The nooks and crannies provide surface area, protection and habitat for many species increasing biodiversity and productivity that would be lacking on a barren bottom.
Today shellfish populations are in decline worldwide. The Nature Conservancy reports that in most bays it has surveyed oyster reefs have been reduced by over 90 per cent and many are at high risk of functional extinction. This decline is largely due to overfishing, pollution, destruction of habitat and diseases. As if this prognosis were not dire enough, there are new concerns that the increases in atmospheric carbon dioxide implicated in global warming threaten to increase the acidity of seawater and interfere with the ability of shellfish to make their shells.
Considering all that shellfish have done and still do to nurture the human race, isn’t it about time we reciprocated? Our shellfish populations are renewable and sustainable resources that when adequately protected and properly managed can rebound and continue to nurture the human species and help restore our battered environment. However, restoration is a two-way street.
On the local level, we at the Martha’s Vineyard Shellfish Group are doing our part to protect, restore and expand the Island’s shellfish populations. In our solar-assisted hatchery in 2008 we produced over 5.5 million seed quahaugs, over 10 million seed scallops, over 6 million eyed oyster larvae and more than 400,000 seed oysters. With the aid of Island shellfish constables, these seed shellfish were planted into Island ponds in an ongoing restoration effort. Please consider joining us in our efforts with your tax-deductible contribution to the Martha’s Vineyard Shellfish Group.
Rick Karney a shellfish biologist and longtime director of the Martha’s Vineyard Shellfish Group.