A 7-foot-long, 240-pound sturgeon has been caught in Michigan. Scientists believe she's more than 100 years old.

• A sturgeon measuring 7 feet long and 240 pounds was found and released in Michigan.
• The scientists who made the find said they believed the fish was female and over 100 years old.
• "Imagine everything that fish has lived through and seen," one biologist said.

Biologists found a nearly 7-foot-long, 240-pound sturgeon in Michigan's Detroit River that they believe could be over 100 years old.

Three scientists with the US Fish and Wildlife Conservation Office in Alpena, Michigan, were on the river in April trying to measure its sturgeon population.

One of the biologists, Jason Fischer, told The Washington Post that the team usually caught 40- to 60-pound fish but could tell that one it started pulling in was bigger.

The fish turned out to be 6 feet, 10 inches long.

In a post announcing the find, the Alpena Fish and Wildlife Conservation Office called the fish a "real life river monster."

It added that it believed the fish was female and that the size suggested "that she has been roaming our waters over 100 years."

The conservation office added that the fish was one of the largest lake sturgeon ever recorded in the US and was "quickly released back into the river after being processed."

"Imagine everything that fish has lived through and seen," said the biologist Paige Wigren, who was part of the team that found the sturgeon, according to the Associated Press.