An angler reeled in a record-breaking 9-foot 'prehistoric' catfish. He let it go because he didn't want to 'stress' the amazing creature.

• An angler caught a 9-foot-long "monster" catfish in an Italian river after a 40-minute battle.
• The enormous wels catfish is likely "world record" breaking in length.

A huge wels catfish reeled in by an angler in an Italian river is believed to be the largest ever caught in a river.

It is likely a "world record" breaking in length, coming in at 9.3 feet long, but the fisherman chose not to also weigh the "monster" to see if it was the heaviest catfish ever for fear of harming it.

The gigantic fish was caught by life-long Alessandro Biancardi late last month in the Po River in northern Italy.

"When we measured the fish on the mat. Under the incredulous eyes of many anglers, the meter stopped at 285 centimeters. It was the new world record catfish," Biancardi wrote on his fishing team's Madcat's blog.

Madcat creates and sells fishing equipment in Europe and supports anglers who catch large fish.

Describing the battle to land the amazing creature, Biancardi wrote on Madcat's website, "I calmly managed to fight what I felt to be a prehistoric fish."

"In silence, I approached the first spot, and after a few casts, a powerful bite arose. The fish stood still some seconds before starting a very complicated fight."

After "40 endless minutes," Biancardi realized when the fish finally surfaced, he had "hooked a monster," he wrote, saying it almost caused him to panic that he was "alone facing the biggest catfish I had ever seen in 23 years ."

However, Biancardi said he never imagined it would likely be the longest catfish ever caught.

Ten people witnessed the official measuring of the fish on a mat, Madcat said, and documentation was sent to qualify for the International Game Fish Association catch-and-release length record.

This fish will beat the International Game Fish Association's current wels catfish length record by 1.57 inches if confirmed by the association.

The current all-tackle record for a wels catfish for weight is 297 pounds and nine ounces caught in the River Po in 2010, USA Today reported. The heaviest catfish ever recorded was a Mekong giant catfish that weighed 646 pounds in Thailand.

Even so, the fishermen let the beast go without weighing it, saying he "feared to stress" the rare specimen.

"I decided to safely release it, hoping it could give another angler the same joy he gave to me," he said.