The deep, dark waters of the Atchafalaya River are known for big fish.

For generations, local commercial fishermen have been netting catfish, carp, gar and gasper goo. But recently, a few fishermen have caught something they'd never seen before in the fresh water river.

"I called Wildlife and Fisheries, the agent down here, they told us to bring it in, they wanted to see 'em," said fisherman Clyde Dufour.

Dufour fishes an area of the Atchafalaya near Simmesport, at the old river control structure. It's is where the Mississippi River feeds into the Atchafalaya, 140 miles upriver from the Gulf of Mexico.

"I said uh, I don't know what we got here. A log in the webbing or a big catfish or something," said Dufour.

It was 4 a.m. and still dark when Dufour and his partner felt the extra weight in their net.

"I jumped back and said, what the heck is this. I didn't know what it was," he recalled.

But Dufour's question was answered when the fish plopped into their 20 foot boat.

"When it opened the mouth it got, I don't know how many different set of teeth in it. They got a bunch of teeth in there," Dufour said.

It turned out to be an 80 pound bull shark.

"After we got it in the boat, we fought with it, it was going to bite us," Dufour said.

As the two fishermen tugged on their net, they pulled in four more sharks.

It was the bull shark they told us, and that's the meanest one they got."

"They're probably the most dangerous species of shark without a doubt because they're very aggressive."

John Hewitt is in charge of all the animals in the Aquarium of the Americas where he keeps about 20 sharks, but none of them bull sharks.

"I've seen them attack other sharks and fish and it's impressive," Hewitt says.

Bull sharks able to live in fresh water up to 140 miles from the Gulf of Mexico.

"A bull shark has the capability of being either salt water or fresh water. Their kidneys are capable of dealing with both," Hewitt said.

Harry Blanchet is the Marine Fisheries Chief for the state of Louisiana.

“It’s a species that’s found throughout much of the major part of the Mississippi River all the way up to places like Illinois, Indiana,” Blanchet explained. "Sharks are out there but you chances of encountering one are really pretty small."

Sharks are being caught elsewhere in the Atchafalaya Basin. Henderson fisherman Wilven Hayes caught two bull sharks in his hoop nets this past Summer.

"The first one surprised me, but the second one, really, I didn't know what the heck was going on any more. You got families that go on the weekend in the Summer time and you got young kids swimming and water skiing," Hayes said.

There are also some popular swimming holes near Clyde Dufour's fishing spot at Old River. He's now caught 28 sharks in the area. The biggest was 160 pounds. But bull sharks can get much larger.

"They can get well over 400 pounds (and) nine feet in length. That's a formidable animal," Hewitt said.

"Now we respect the river now, we don't go back swimming in the mud hole," Dufour says.

The bull sharks are an unusual and even dangerous catch. But they are also a natural part of the Atchafalaya River swamp.

Fisheries experts say they know of no reason why more sharks are being caught now in the Atchafalaya Basin. They say bull sharks, because the fish can adapt to fresh water, can spend their entire lives feeding and living in rivers.LINK