Archaeologists have unearthed what they believe are the oldest known fish traps that date back to at least 9,000 years.

The remains of seven basket traps were discovered in the Baltic Sea off Sweden by a team of marine archaeologists from Stockholm's Sodertorn University.

The ancient finger-thick hazel rods are thought to be the remains of stationary basket traps, the researchers said.

"This is the world's oldest find when it comes to fishing," Johan Ronnby, a professor in marine archaeology, was quoted as saying by British media.

Arne Sjostrom, a fellow archaeologist who worked on the Sodertorn project, said the sticks seemed to have been used as a "sort of fence to lead the fish into a creel or they were part of the actual creel".

The traps were found in a submerged ancient river valley off Sweden's southern coast at a depth of 5-12metre.

According to Sjostrom, many examples of similar traps had been found in other parts of the world. Only one of the baskets has been carbon-dated and is estimated to be around 9,000 years old, he added.

In addition to the fishing equipment, the archaeologists also found leftover food and other waste likely thrown in the river by early residents, '' reported.

However, no settlements have yet been found, Ronnby was quoted as telling the Sveriges Radio (SR).

The discovery was made as part of a research project by the MARIS maritime archaeology institute at Sodertorn dubbed the "Landscapes Lost".

Launched in 2011, the project aims to survey and examine the postglacial river mouth of Verke river's well as the archipelago off of Blekinge in southern Sweden.

Researchers hope their work will shed light on how people lived and what the now-underwater landscape looked like 9,000 years ago.