Scientists Discover Ancient Fish Trap in Southeast Alaska
A remotely operated underwater vehicle provided by Sunfish, Inc. explores a stone fish trap in Shakan Bay, on the west side of Prince of Wales Island.
A semicircle of stones beneath Shakan Bay, on the west side of Prince of Wales Island, could be the oldest fish weir ever found.
“Bouncing with Excitement”
Scientists estimate the structure was assembled at least 11,100 years ago, based on sea level reconstruction.
“The extrapolated 11,100-year date is actually quite late,” says co-principal investigator Kelly Monteleone, an archaeologist at the University of Calgary. “I anticipate we will find evidence in Southeast Alaska that dates it to at least 16,000 years ago.”
The structure was first found in 2010 by use of side-scan sonar technology, which detects and images objects on the seafloor. Scientists suspected the vague image to be that of a stone weir, but mostly due to funding constraints, the team was not able to confirm their hypothesis.
The scientists, in partnership with Sealaska Heritage Institute (SHI), returned to the site earlier this year with the help of Sunfish, Inc., a robotics company specializing in undersea exploration and inspection.
“The entire vessel was bouncing with excitement when we realized it was indeed a weir,” says Monteleone, who was piloting the underwater craft. “Personally, I felt relief after a decade of saying this was a weir. Finally confirming the location was satisfying and exhilarating.”
Stone weirs, or tidal fish traps, were typically low arched walls made of boulders and sited across gullies. The weirs were built so that during high tide, the fish would swim over the stone walls, and as the tide ebbed, the fish would be trapped behind them, allowing fishers to catch them with nets, spears, and other means.
“Those stacked rocks. That is exactly what I was told it would look like,” says Sealaska shareholder Roby Medina, captain of the Klawock-based vessel Showtime, which was used to conduct this year’s underwater surveys.
Fish weirs—which also were made of other materials, such as reeds or wooden posts—were commonly used around the world in ancient times, and other stone weirs have been documented in Southeast Alaska. However, this is by far the oldest one ever found, and it is the first one ever confirmed underwater in North America.
A remote underwater vehicle explores a semicircle of stones, which appear to have been stacked when Shakan Bay, on the west side of Prince of Wales Island, had a lower sea level.
Prior to the discovery, the oldest known weirs dated from 7,500 to 8,000 years ago. In Southeast Alaska, the oldest dated weir is 5,740 to 5,490 calendar years old, Monteleone says.
Previous scientific studies confirmed that Indigenous people lived in Southeast Alaska at least 10,000 years ago, so the age of the weir pushes the date of human habitation in the region even earlier.
“It further substantiates the great antiquity of Native people in Southeast Alaska,” says SHI President Rosita Worl, an anthropologist by training. “It also demonstrates that Native people had acquired knowledge about salmon behavior and migrations, then developed the technology to harvest a significant number of salmon.”
Worl and the research team agree that people were likely in Southeast Alaska a few thousand years prior to the construction of the Shakan Bay weir.
“It would have taken time for our people to learn enough about the environment and fish behavior to develop the technology to make the weir and to fish it successfully,” Worl says.
The team includes Monteleone’s co-principal investigator, Kristof Richmond of Sunfish Inc.; Vera Pospelova, who specializes in dinoflagellate cyst analysis at the University of Minnesota; Nancy Bigelow of UAF, who specializes in microfossil and pollen analysis; lead diver Jill Heinerth; Vickie Siegel, the field operations manager for Sunfish; and additional Sunfish team members.
“I am excited that we are able to use science and technology to substantiate our beliefs and oral traditions that say we have lived in Southeast Alaska since time immemorial and to incorporate our knowledge into these narratives,” Worl says.
The research team is continuing to explore underwater caves in Southeast Alaska for evidence of early human occupation.