Remains of an elaborate stone fish trap have been discovered on the seafloor off Southeast Alaska, and scientists say it proves Indigenous people occupied the region 1,000 years earlier than previously believed.
Known as a fish weir, the ancient trap dates back about 11,100 years, the Sealaska Heritage Institute reported in a news release.
That makes it likely “the oldest stone fish weir ever found in the world ... and it is the first one ever confirmed underwater in North America,” scientists said.
It was discovered over the summer as part of a project funded by NOAA Ocean Exploration to search seafloor caves for evidence of early human occupation, according to the release.
The trap sits about 170 feet below the surface of Shakan Bay, on the west side of Prince of Wales Island, officials told McClatchy News. It takes the shape of five to six “semi-circular structures” that are up to 6 feet wide. Time has worn the walls down to about 1 foot in height, the institute said.
“Likely the rocks were piled much higher 11,100 years ago. ... People would have maintained the weir seasonally by restacking rocks and adding more rocks and possibly wooden stakes,” the institute said.
Such traps were typically built close to shore, in spots that would have been covered at high tide. However, the change in sea floor levels has left the weir “over 2 km (1.2 miles) from the closest modern shoreline.”
“It further substantiates the great antiquity of Native people in Southeast Alaska,” said anthropologist Rosita Worl of the Sealaska Heritage Institute.
“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.”
Sonar evidence of a structure at the site was first recorded in 2010, but “funding constraints” prevented experts from confirming their theories until this year, the institute said.
A robotic underwater craft was used to investigate the structure, piloted by archaeologist Kelly Monteleone at the University of Calgary. She reports “the entire vessel was bouncing with excitement” when it was confirmed to be a weir in May.
“It wasn’t just me that was convinced (in 2010), but the burden of proof was on me,” Menteleone told McClatchy News.
“Other archaeologists and locals were extremely supportive based on the sonar. But, as my dissertation advisor taught me, I had to be sure before it became an archaeological site, i.e. before we were ‘sure’ it was actually there. So for the last 12 years, this location has been a ‘potential’ weir.”
Examples of ancient fish weirs have been found around the world, and often employed the use of pile stones, reeds and/or wooden posts, experts say.
They were often built as “low arced walls” across coastal gullies.
“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,” the institute says.
Other weirs have been found in Southeast Alaska, but the oldest dated to only around 5,740 years ago, the institute reports.
The age of the weir in Shakan Bay was established “based on sea level reconstruction,” officials said.
Worl believes it is the work of a people who had been in the region long enough to develop sophisticated skills.
“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,” she said in the release.
NOAA Ocean Exploration was a primary financial backer of the project, and it reports the team will return to Southeast Alaska next summer to continue exploring submerged caves and rock shelters using a SUNFISH autonomous underwater vehicle.