Native Americans in Ancient Florida Developed Pre-electricity Fish Storage

Archaeologists deduce purpose of huge walled fish ponds on an artificial island built by the powerful Calusa kingdom over 1,000 years ago

Ruth Schuster
Ruth Schuster
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Reconstruction of a Calusa terraces made of shells, on display at the Florida Museum of Natural History
Reconstruction of a Calusa terraces made of shells, on display at the Florida Museum of Natural HistoryCredit: Moni3
Ruth Schuster
Ruth Schuster

Fish farming of a sort goes back to the beginnings of human civilization and much like the advent of agriculture itself, seems to have developed independently in different places around the world. Now evidence of early aquaculture of a sort has been discovered in ancient Florida.

Carp seem to have been cultivated more than 8,000 years ago in the Yangtze Delta, China. Gilthead sea bream, aka denise, were the subject of proto-aquaculture about 3,500 years ago off the Sinai coast in what is today Egypt. At about the same time, tilapia were cultivated for consumption, also in Bronze Age Egypt.

Now a team of scientists has reported in the American journal Proceedings of the National Academy of Sciences on evidence suggesting large-scale fish capture and storage at Mound Key, Florida by a Native American group known as the Calusa. The fish were kept in artificial pools built about 600 years ago on an artificial island that itself had been created as much as 1,500 years ago from a midden of food refuse. Namely, oyster and other shells.

A mastodon meets his maker

The peopling of the Americas began as the Ice Age waned and the glaciers retreated, enabling humans to cross the Bering land bridge from today’s Russia to Alaska, possibly starting as much “early”as 23,000 years ago. There were apparently multiple migrations and routes, but researchers posit that all Native American groups today, that have been studied to date, arose from ancestral populations that migrated across the Bering bridge more than 15,000 years ago. Once in the Americas, these early occupiers apparently spread rapidly.

The earliest evidence of human occupation in Florida itself goes back 14,550 years, when somebody ate a mastodon. The evidence at the now-submerged site of Page-Ladson include the predated pachyderm’s butchered bones as well as stone tools. Mastodons and other mega-fauna went extinct in that area at roughly 12,000 years ago, give or take. During the intervening millennia, the Native people of Florida developed diverse ways of life, many of which focused on hunting for fish and shellfish in the state’s coastal waters.

Mound KeyCredit: Viktorwills

The Calusa people ruled over southern Florida about 600 years ago and are likely descended from individuals who reached the area over 14,500 years ago (and possibly other, later migrations).

The disappearance of giant mammals does not necessarily mean that early Native Americans were desperately seeking a new protein source, Prof. Victor Thompson, coauthor of the new study published in PNAS and director of the University of Georgia archaeological laboratory, explains to Haaretz.

Actually, Thompson suggests, most indigenous groups probably had a diverse diet. If they had a staple source of meat it was probably deer, supplemented with small animals such as rodents and local plants. “It would be a lot easier to hunt deer than a giant mastodon, which would be very dangerous if poked with a stick,” Thompson points out.

Globally, the evidence indicates that coastal-dwelling hominins and humans alike happily ate fish and gastropods as least as far back as 125,000 years ago. This use of aquatic foods accelerated after the Ice Age, and going by the Calusa middens, otherwise known as refuse piles, found throughout southwestern Florida, they collected these resources on a grand scale – even creating an artificial island out of these midden materials.

Prehistoric hydroengineering

Meanwhile, researchers report that some sort of hydro-engineering also goes back to almost the dawn of modern civilization. It took different forms depending on what the specific existential problems were. In the arid Middle East, for instance, water-storage technology began to develop thousands of years ago and reached some stunning achievements, such as sustaining the fabled gardens of Babylon, Persia and Petra.

In waterlogged Florida, previous excavation at Mound Key had found the mysterious man-made pools surrounded by walls also made of shells and sediment, called “water courts”. Now Prof. Thompson and a team of scientists from the University of Florida, the Florida Museum of Natural History, Florida Gulf Coast University, the University of West Georgia, and the College of Idaho have shed light on the Calusa people’s enigmatic hydro-engineering efforts. The water courts of Mound Key – which today towers at its tallest point over 10 meters above present sea level – served as fish ponds, and may even have been key to the rise of the powerful Calusa kingdom from the smaller polities that preceded it.

Let’s start with the anthropogenic island itself, the archaeological site of Mound Key. It’s about 51 hectares (almost 130 acres) in area, probably about 1,500-plus years old and contains, by volumetric calculation, at least 500,000 cubic meters of oyster shells and other gastropod detritus.

To put things into proportion, Thompson helpfully explains that the Great Pyramid of Giza is around 2.5 million cubic meters in volume. “The ancient Egyptians didn’t eat the stones before they built it, which is a key difference,” he says.

About 1,000 years ago, the islanders built the “Grand Canal” that bisected their island, and built artificial tributaries off that; there could plausibly have been rope bridges across the canals. And around 300 years after the Grand Canal’s construction they built two great fish ponds enclosed in walls with one opening – a gate – to the Grand Canal. The scientists think these gates were made of organic materials that have long since deteriorated. And this artificial island became the capital of the great Calusa kingdom by the 16th century C.E., possibly thanks in part to its fish economics.

The smoking fish

Another theory had been that the ponds were used to husband conch. After further assessment, the team lead by Thompson thinks not – mainly because “juvenile marine gastropods prefer shallow, seagrass-rich environments that would have been difficult to duplicate in watercourts.”

Also, the researchers found fish scales in the sediments inside the water courts that correspond to the period of their use, but no such scales in sediment cores taken from the bay beyond Mound Key.

Scales found in artificial pools at Mound Key, Florida Credit: Zachary S. Randall / Florida Mus

This proto-fishing farming could help explain how the Calusa achieved their cultural complexity and dominance of southern Florida, the team posits: These water courts were large-scale storage facilities for live fish that apparently exceeded their personal requirements.

As for sustaining a wider population than the residents of Mound Key, the researchers note that on the edges of one water court, they found evidence of drying and smoking racks, which were likely used for fish. They conclude that fish not needed for immediate consumption would have been kept in the water courts – “live storage” facilities. When convenient they could be caught, dried, and smoked for future consumption.

Indeed, storing food in the hot and humid climate of Florida was a problem in the pre-electricity age.

Possibly fish were ushered into the pools through the Grand Canal when the seas were high, and then got gated inside. Thompson believes, however, that the Calusa were catching fish in the open sea – which, around their island, was shallow enough for a person to walk on the seabed. The Calusa constructed massive canoes (“they were a maritime kingdom,” he adds) to do just that. They would then bring the wild fish to the pools and keep them there until they needed them, or had the leisure to smoke them for later consumption. The fish in the pools couldn’t escape because the berms were never submerged, even in high tide.

Analysis of the faunal remains revealed an enigmatically large proportion of mullet bones during the fish pond period and interpretation remains pending investigation. “One thing we’re still working on is exactly how large-scale climate change impacted these areas,” Thompson explains.

Over the time Mound Key was occupied, there were at least two major climatic changes: the Medieval Warm Period (aka the Medieval Climatic Anomaly), from around 850 to 1200 C.E., followed by the Little Ice Age, which lasted until 1850 C.E. Evidence suggests that sea levels fluctuated during these times, which would have effected salinity and the existence of different species in the Florida bays. But clearly, Thompson says: “The Calusa adapted to climatic shifts in salinity that were due to global temperature changes and this affected which fish were available.”

Diorama of the inside of the hut of a Calusa chief, Florida Museum of Natural HistoryCredit: Wtc69789

Like shooting fish in a lagoon

Proto-aquaculture in ancient China and Egypt wasn’t that different in substance, it seems. Scientists from the University of Haifa explained in Nature in 2018 that isotope analysis of sea bream teeth found at 12 ancient coastal and inland archaeological sites in what is today Israel show that all originated in the shallow, hyper-saline Bardawill lagoon on the northern Sinai coast, which connects to the Mediterranean Sea when the winter seas are high.

The Israeli team’s point of origin was the discovery of fish bones in inland towns throughout ancient Israel.

“In the Bronze age, about 3,500 years, there was a retail system taking fish all over Israel,” Prof. Guy Bar-Oz of University of Haifa tells Haaretz. “The fish all had the isotopic fingerprint of Bardawil.” Remains of fish that could be traced to Bardawil were found from Eilat to Hazor, from Megiddo to Jerusalem.

Key to the theory: The sea breams as being from Bardawil were all the same size, about 30 centimeters or the size of a plate – which is interesting, Bar-Oz explains, because in fish, size is a function of age: “So their mortality pattern looks like very specific harvesting. That’s why we called it proto-aquaculture.”

It doesn’t seem that the ancient denizens of the Bardiwil beaches were farming the fish per se, meaning breeding and feeding them. The researchers believe that the lagoon would fill with water and fish when the Mediterranean was high and become effectively isolated from the sea in summer. Evaporation from this quite-closed lagoon explains why it became hyper-saline, Bar-Oz explains. And the people would “harvest” the fish stuck in the lagoon.

Bits from a Calusa fishing netCredit: Moni3

Can we know if the aquaculturalists of yore fed the fish as we feed farmed fish? Maybe.

Asked how on earth we could detect fish-feeding thousands of years after the event, Bar-Oz explains that corn (in the Americas) and millet (China) have distinctive isotopic signatures. When domestication of millet in China began about 10,000 years ago, suddenly all the animals around gave off millet signals.

“If a mouse eats millet and a cat eats the mouse, both will have the millet signal,” Bar-Oz says. So, if the ancient Floridians fed their fish with corn, which also has a unique isotopoic signal, it would be indicative that actual aquaculture took place.

So the Calusa built an island from seashells, created advanced hydro-engineering structures on it, stored or farmed fish in great artificial pools and in the 16th century, controlled southern Florida. Now they are gone – at least from there.

Their descendents are likely still walking around Havana, though. When the Spanish, under Pedro Menéndez de Avilés arrived in the southeastern part of latter-day Florida in 1566, the Calusa controlled the territory from south of Tampa bay to the Florida Keys, Prof. Thompson explains.

Menéndez met with Calusan King Caalus (called “Carlos” by the Spanish), whose sister married the Spaniard admiral in a good-will gesture. Caalus, according to records, tried to persuade his new friend to attack an enemy but Menéndez declined. The king then decided to assassinate Menéndez for his cheek, but was assassinated himself. The Spanish set up Caalus’ former captain on the throne but wound up killing him too. This caused the Calusa to burn and then abandon Mound Key to rid them of the Spanish. Indeed the Spanish beat a retreat and the Calusa rebuilt, Thompson relates.

Come 1697 some Franciscan missionaries arrived. They were sent packing in three months, but in subsequent years British-backed slavers armed with guns began raiding Calusa territories. By the mid-1700s there was a mass exodus from the area, on Spanish ships of all things, to Cuba, and it is there that descendants of this people likely live to this very day.

Lake Bardawil in the northern SinaiCredit: NASA
Sea bream, a popular fish for thousands of yearsCredit: Roberto Pillon /

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