Monday, November 18, 2013

Last week we touched on the reasons a Florida archaeologist might be interested in shellfish ecology, and all of the potential information and/or data that can be derived from the study of these invertebrates. Today, we're going to look at some of the "usual suspects" found both on Northeast Florida beaches and inside prehistoric shell middens.

Knobbed Whelk (Busycon carica

This large gastropod (single-valved and spiral-shaped shell) ranges from Massachusetts to the Cape Canaveral region, and is found throughout NE Florida in estuaries and bays in 1 m of water, and even in some open-coast habitats up to 50 m. Knobbed whelks are carnivores, feeding on bivalves such as oysters and clams.

Knobbed whelks were not only used as a subsistence resource by Timucuan Indians, but also as a utilitarian tool. The entire shell could easily be hafted to a wooden pole, creating a shell axe or hammer. Axes were necessary to fell trees for village structures, hallow trees for canoes, and any other cutting needs.

Common or Eastern Oyster (Crassostrea virginica)

The venerable oyster has certainly solidified its place on the dinner tables of both Native and modern populations alike. Perhaps no other shellfish is as recognizable. Oysters are quite hardy, living in a range of salinities, from estuaries, bays, and brackish sounds, to full seawater habitats. They are filter feeders, attaching themselves to hard structures on the seafloor. Oyster beds create their own mini-ecosystem or reef, supporting numerous other aquatic organisms.

Oysters are the most common shell in Florida middens, serving a multitude of purposes. These critters were food for Natives, served as construction materials for mounds and walkways (many offshore islands along Florida's coasts are made almost ENTIRELY of oyster midden), and even as expedient tools such as scrapers. Carl Halbirt, city archaeologist of St. Augustine, has excavated numerous prehistoric middens with these sorts of tools.

Quahog Clam 
(Mercenaria mercenaria [Northern] and Mercenaria campechiensis [Southern])

The "hard clam" is found up and down the U.S. Atlantic seaboard, and all along the Gulf coast down to the Yucatan peninsula in Mexico. Thus, the quahog can survive in a variety of climes, at differing levels of salinity. It gets its name for a reason, the shell is extremely hard and durable (It's number one predator, the lighting whelk, damages its own shell when trying to break open a quahog!). Also, they're extremely long lived, with specimens recorded to be 500+ years old! For this reason, they are an extremely useful tool for archaeologists to study past estuary and ocean environments. 

Although they're most common in the northeast United States, this shellfish is found nearly everywhere on Florida's coasts, especially in the northeast Florida region. The Timucuan Indians would have relied heavily on the quahog clam, for a variety of daily needs. The hard outer shell was could be fastened to a stick, for use as a shovel and/or hoe for horticultural needs. Also, it was cut into pieces for jewelry, and small expedient tools, just like the oyster. Of course, the hard clam was a valuable and reliable food source as well. 

Coquina Clam (Donax variabilis)

As seen in this photograph, coquina comes in a variety of colors, and is found up and down the Atlantic coast of the U.S., as well as the Gulf coast all the way into Texas. Coquina is particularly abundant in northeast Florida, where coquina stone concretions form naturally. Like other bivalves, they're filter feeders, consuming plankton and detritus.

Coquina was an extremely valuable resource, both prehistorically as food for Florida Natives, but also as building material for historic settlers in Northeast Florida. Coquina was used to construct sugar mills, iconic structures like the Castillo de San Marcos and Fort Matanzas, and hundreds of fences, walls, and smaller buildings. Interestingly, today, coquina is a proxy of how healthy a particular beach habitat is.

Atlantic Giant Cockle (Dinocardium robustum) and Shark's Eye (Polinices duplicatas)

The Atlantic giant cockle--also called the great heart cockle--is the largest cockle species found in northeast Florida and thus was an important shellfish subsistence resource for Timucua Natives and other prehistoric groups. It's easily identified by its bright orange and white check-stamped colors and its parallel ridges.

The Shark's eye (or "moon snail") is also common to northeast Florida beaches and prehistoric shell middens, though the prehistoric ones are often much bigger (could they have been overfished in the past?).

Stay tuned for more on northeast Florida shellfish archaeology and environmental posts!

Text and Images, Ryan Harke, FPAN Staff. Credit to for the knobbed whelk photograph, for the coquina, shark's eye, and giant cockle photos.

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