About 35 feet beneath my old house, Catchall, which sits on a cliff overlooking a lovely Bay creek, lies a bed of ancient oyster shells. Not our modern Eastern Oyster, Crassostrea virginica, but the shells of Isognomon, an extinct species that lived in the middle Miocene Era about 10 million to 14 million years ago. There was no Chesapeake Bay then; these shellfish lived in a coastal indentation called the Salisbury Embayment.

Generation upon generation of Isognomon shells slowly accumulated into a thick stratum which today erodes from the embankment into our creek as wind and storms slowly chew away at the base of our cliff. Someday, far in the future, sea level rise and erosion will claim old Catchall as well.

Twelve or more thousand years ago, when sea level was much lower than it is today, ancient tidal estuaries like the Chesapeake lay far off the North American East Coast. There, the oyster species we have today grew unmolested and unharvested. On the windowsill, I have a shell from one of those estuaries, dredged from what is now the sea floor scores of miles at sea. It is more than an inch-and-a-half thick, and I can count the major growth divisions marking its age at more than a quarter century. I hold it often, contemplating what those long lost estuaries must have been like.

Sea level rose about 100 feet before it began to intrude into coastal valleys that eventually shaped the “new” Chesapeake Bay toward the end of the last glaciation. Migrating along with the growing estuary was the Eastern Oyster, which found this habitat perfect and led the early Native Americans to call the waterbody, Chesapioc, or “Great Shellfish Bay.”

Over the next 6,000–10,000 years, the shell of slowly expiring and sequentially accumulating generations of oysters built up and sustained communities composed not only of oysters but a myriad of clinging, crawling, burrowing and creeping organisms that made up the oyster reef community.

These deposits grew, like today’s coral reefs in tropical waters, as a living veneer covered with millions of organisms, growing on top of a massive, non-living core of older shell. Such reefs, or “oyster rocks” did well off points of land in the Bay’s winding salty rivers, or along channels where swirling tides fed them abundantly with a constant, if dilute, soup of living plankton.

There is a paradox here because an oyster living solitarily on the bare bottom might well glean more of that dilute soup than its crowded neighbors. But the overall advantage to the community of living together always won out and reefs or rocks prospered in the Bay. As a continuing population, not as individuals, they lived for thousands of years virtually unmolested by large-scale predators or human harvesting. Some oysters lived for decades and grew to be a foot in length.

Researchers have calculated that an oyster of that size might produce a billion gametes in a single spawning event. Today’s “market oyster” of a pitiful 3 inches or so, might only produce 10,000 at a spawn. The fecundity increases geometrically with the size of the parent. So explain this to me — we selectively harvest the biggest and the best, then kill and eat them. Where would livestock be if farmers consistently did that?

The Chesapeake is not unique in forming oyster reefs of great size. In 1967, geomorphologist Gene Rusnak diagrammed a cross section through San Antonio Bay on the Texas Gulf Coast which showed the incremental burial of many ancient oyster reefs — the result of slow inundation and filling in as sea level rise occurred.

The reefs tried to compensate as living shells grew upon the remains of predecessors as estuarine sediments accumulated around them. Some reefs persist today, growing upward ahead of the sediment at an estimated 1 meter per century — a process that has continued for thousands of generations and built deposits up to 35 feet deep. Other reefs did not and are entombed as much as 45–60 feet below the bottom of San Antonio Bay.

An analogous process has probably been going on, but is largely unmapped in the Chesapeake, although deep, ancient and commercially attractive deposits are known in both the Lower and Upper Bay.

Many oyster reefs of substantial antiquity formed major features on the Bay bottom at the time of European contact. While most such reefs are unclearly known, there are “reef-core” deposits perched amidst the sediments of the James River which have accumFlated since the ancient Wisconsonian (post glacial) channel was cut.

The adaptive significance of these massive concentrations of shellfish were many. The reefs grew in mass and created turbulence in the passing water that both exposed all of the reef’s shellfish to plankton for feeding and broadcast gametes (sperm and eggs), which would have had a better chance of bumping into and fertilizing a counterpart.

The resulting supply of young oyster larvae (veligers) and juveniles (spat) being deposited on the reef and swept by the tide to nearby locations was prodigious. Jim Wesson, of Virginia’s Marine Resources Commission, has estimated that in the reef environment, the enhancement of the larvae might be 26,000 times more than for oysters scattered on flat bottom.

Robart Tindall, sailing master aboard the first ships settling the Jamestown Colony, realized the value of the Chesapeake’s grand rivers and harbors. He spent some of his time in 1607 sailing around the lower Bay, chiefly the mouths of the James and York rivers, mapping shoals and hazards to navigation, many of which were emergent oyster reefs.

A later version of his chart, perhaps with augmentation from the logbooks of other mariners, was published in an atlas of the Dutch West India Company as “Caert Vande Riuer POWHATAN” about 1638. It shows what are probably 15 oyster reefs, distributed well upriver toward, but not reaching, Jamestown Island. One group of these clearly represents what came to be known as Long Shoal Bar in Burwells Bay. This represented more than a mile-long phalanx of virtually solid oysters. Despite later relentless dredge-harvesting, this reef was said to emerge at mean low water as late as 1897.

The upward growth of oyster reefs meant that at some point, the highest shellfish were exposed at low tide. In winter, they were subjected to the scouring of ice borne on the tide and the eventually lethal freezing of tissue. In the summer, such exposure dried the reef tops and subjected them to broiling temperatures sufficient to kill many oysters. Young oysters were also subject to the adept shucking bills of the American Oystercatcher, Haematopus palliatus. The net result of all this was a relatively flat top to the reef.

Professor Emeritus William Jennings Hargis, of the Virginia Institute of Marine Science, tells of extant letters written by the crew of Monitor-class Union warships stationed in the James River. They report rowing to the oyster rocks and walking about to gather oysters by hand three times a day without any harvesting gear.

This is probably how Native Americans harvested most of their oysters at wading depth, although John White’s 1585 drawings show what might be a kind of oyster rake in the hands of a Native American fisherman. Using “tongs” to grab oysters from deeper water seems to have been a European colonial invention, and using dredges in the Chesapeake came much later.

C.H. Stevenson, in his history of oystering in the Bay, notes that once New England and other East Coast beds had been harvested — virtually to extinction — oystermen began visiting the Chesapeake in about 1808 to rape its vast abundance of natural shellfish beds.

Area governments quickly recognized that this indiscriminate harvest-and-run incursion would soon do great damage. By 1820, the first laws on harvesting emerged. Local watermen, though, wanted to harvest just as much as the outsiders, and over the years, a number of strategies were tried to maximize this taking from the commons, each one partially but ineffectually checkmated by additional laws, regulations and licensing.

Stevenson and others note that oysters were not just harvested, but reef cores were literally “mined” at first by hand tongers receiving 2–4 cents a bushel for living or dead shells, which were burned to produce calcium-based lime. This was used to make mortar for construction, and oyster shell lime mortar permeates the 17th and 18th century rubble at Jamestown. It was also used as an amenity on agricultural soil, spread at the rate of 75–100 bushels an acre with good effect on crop yields.

The mining of shell “empties” was prohibited in Worcester County, MD, by 1852, but that did not stop an aftermarket for the immense piles of shell, shucked of its meats, accumulating all around the Bay.

All the while, the commercial harvest of the shellfish was increasing, especially after the introduction of widespread railroads, which allowed the transport of live or shucked oysters great distances. A bushel of oysters brought watermen an average 70 cents during 1863–5, years of military activity on the Chesapeake.

Crisfield, a sleepy backwater on Maryland’s lower Eastern Shore, became an “oyster capital” when the railhead reached its waterfront. By the 1870s, 600 vessels landed oysters at the town and 20–30 railroad cars carried oysters from its houses daily.

Baltimore was also an important point of transshipment. Railroad cars packed with oysters left the city each week, bound for points as far distant as the U.S. West Coast, where new gold rush money was creating a market for luxury seafood items. When the supply faltered in bad years, like 1892, the per-bushel price skyrocketed to $1.50, a record for that time. For comparison, Eastern Shore watermen are receiving $18-20 a bushel in 2001. Should you want to shuck a bushel yourself, they retail at $40.

In 1878, Fransis Winslow was commissioned to survey the oyster resource of Maryland, which had always harvested more than Virginia, because of its large areas with favorable salinity that optimized oyster growth. He warned that the overharvest — and particularly the taking of young oysters of less than 3 inches — was asking for trouble. As Clyde MacKenzie of the National Marine Fisheries Service says: “In the 1880s, record landings were being made and too much money was being earned to think of conservation.”

In 1894, Stevenson reports, the 11 Maryland counties bordering the Bay harvested 219,000 bushels of oysters and it was the dominant feature of the regional economy. Eleven thousand people were directly employed in oyster work and multiples of that were in associated and dependent trades. This was a precarious situation and with good reason there was “grave fear as to its long continuance.”

He noted that Maryland harvested 11 million bushels in 1892, and Virginia almost 6 million in 1891. For comparison, the United States harvested a total of 29.7 million bushels in 1891, and an additional 5.4 million bushels were harvested by the rest of the world that year. Stevenson figured that in the 19th century, up until his writing in 1894, 395 million bushels had been taken from the Bay.

Working the “rocks” was especially damaging because, as Stevenson pointed out, much of the clean, living, shell veneer was where juvenile oyster spat “struck” and grew. When the surficial adult oysters were dredged away, they brought with them, and to their doom, 1–50 baby oysters at the same time. Also on my windowsill, sit two such shells, encrusted with dozens of young oysters killed when the single adult was shucked.

The carnage was immense, both for the animals and the shell resource they depended upon for their community structure. Joe DeAlteris, while working at VIMS, analyzed navigation charts from the mid-19th through much of the 20th centuries, and calculated that about 5 feet of oysters had been removed from lower Bay “rocks” by dredging. By the late 19th century, the well-known skipjacks, which were only developed about 1880, comprised a fleet of a thousand dredging boats. We look upon today’s remnants of this fleet with nostalgia, but it was a tough business and its skippers worked very hard, destroying the Bay’s once abundant oysters.

The frenzy of harvest was inconsiderate to the fate of the resource, directed only toward the maximum harvest from the commons. Immigrant labor was viciously exploited by oystermen and during some of this period, foreign workers outnumbered the local people employed.

As the resource was harvested down, violence broke out between Maryland and Virginia and rampant disregard for harvest regulations led to the establishment of an “Oyster Navy” complete with armed ships. First there were schooners and men armed with rifles, later, steamers with heavier guns were brought to bear.

Today, shell from shucked oysters is considered a valuable ecological resource and most of it is rigorously returned to the environment in the hope that young oysters will grow upon it as substrate.

It’s almost inconceivable to read a report issued in 1898 by the Maryland Geological Survey on status of the state’s highways. Along the sandy Eastern Shore, the only material locally available for hardening road surfaces was oyster shell. Arthur Newhall Johnson, the writer, indicated that 250 miles of oyster shell road traversed the Shore, the longest a single stretch reaching from Queen Anne to Crisfield.

This inventory probably didn’t include private lanes or drives. These municipal roads, in horse and wagon times, were only 18 feet wide, but Johnson figured that they consumed 58,000 bushels of shell per mile. This castoff shell at the time cost only 2 cents a bushel, plus a penny to haul it, but the 250 miles represented almost 14,500,000 bushels.

The maintenance consumed 2,000-3,000 bushels per mile, or somewhere around 62,500 additional bushels per year.

Beneath hooves and wagon wheels, the shell quickly crushed into annoying dust and rutted easily if water was allowed to accumulate. Johnson argued strongly that gravel should be barged in from elsewhere in the Chesapeake and used instead. His argument was economical — the roads would last 10 times longer without repair — not ecological, but he was thinking in the right direction.

In hindsight, we have 20/20 vision but all the way down this long slope of decline for the oyster — and shell — resource, expert observers warned again and again that such abuse could not be sustained. Where it led is clear today. The road back, should there be one, is quite another story.