A small, unremarkable island off the coast of Fiji has turned out to be something scientists had never documented in this part of the Pacific. Researchers say it is an island formed entirely from shellfish left behind by communities that lived there more than 1,000 years ago.
The island lies near Culasawani, a lightly inhabited area on the northern coast of Vanua Levu, Fiji’s second-largest island. It covers roughly 3,000 square meters (32,000 square feet) and rises up to 60 centimeters (24 inches) above the high tide line. Between 70 and 90 percent of its composition is shellfish remains embedded in a sandy-clay matrix.
Patrick D. Nunn of the University of the Sunshine Coast in Queensland, Australia, led the study, published in the journal Geoarchaeology. His team concluded the site is a “midden island,” a landmass that grew from the accumulated shellfish discards of ancient settlers.
Radiocarbon dating of 10 shell samples placed their formation at around 760 CE, with dates ranging from approximately 420 to 1040 CE.
How an island formed entirely from shellfish in Fiji
The most likely explanation, according to Nunn’s team, is that early settlers built stilt-platform homes over the shallow coastal waters at the site. Over generations, discarded shells piled up on the seafloor beneath them.
A Fijian island formed entirely from shellfish waste left by ancient settlers has been identified by researchers, marking a unique archaeological discovery in the Pacific. pic.twitter.com/2CMNlLDxjb
— Tom Marvolo Riddle (@tom_riddle2025) April 3, 2026
As sea levels gradually fell, the accumulated debris rose above the waterline, and an island formed entirely from their shellfish waste slowly took shape. Researchers also considered the possibility that the site served only as a shellfish-processing spot, where people removed the meat and carried it elsewhere for consumption.
Every shellfish species recovered from the deposit was edible, including Anadara antiquata and Gafrarium tumidum, both common food sources in the region.
Pottery fragments were found throughout the site, pointing to repeated human activity. The absence of fish bones and stone tools led the researchers to lean toward the processing-site explanation rather than permanent habitation.
Edible species and pottery confirm ancient human presence
The team initially examined whether a tsunami had deposited the shells in a single event, since the layer showed no obvious internal stratification. They dismissed that possibility after finding the shell-dense sediment confined strictly to the island, with no thinning toward its edges, a pattern inconsistent with wave deposition.
Today, the island sits within a ring of mangrove forest. Researchers believe the mangroves took hold only after the settlement was abandoned, when falling sea levels and sediment from cleared inland areas built up around the river mouth.
Future work will survey the surrounding seafloor for similar deposits and gather local oral histories about any large waves that may have struck the coastline in the distant past.
