A New Jersey boy has a colossal story to tell his fellow fourth graders when he returns to school this fall after he reeled in a "living dinosaur" from the Fraser River on Monday.

Nine-year-old Kegan Rothman and his father, Dan Rothman, were just hours into their week-long chartered fishing trip when Kegan hooked a monster white sturgeon near Chilliwack. He fought the fish down the river for nearly two hours.

Kegan Rothman

Kegan Rothman, 9, had to fight the white sturgeon for nearly two hours down the Fraser River before he was able to reel in the 272 kilogram monster. (Great River Fishing)

​"I was just saying to myself, 'When am I going to finish this? I'm tired,'" Kegan told CBC News on Wednesday.

The pursuit was made particularly challenging when the sturgeon somehow managed to wrap itself around a tree submerged in the water.

Kegan's father said that was a "blow" they just couldn't accept.

"We had already had the opportunity to see the fish. I was actually taking pictures of my son working the rod on the stern and the fish just came straight up, almost like a projectile from the water with its belly pronounced toward us," he said.

"To see the fish several times and then for it to get hung up and wrapped ... [we] were just saying to each other, 'No one's going to believe this. So what do we do?'"

The group eventually managed to dislodge the fish from the tree, allowing Kegan to reel it in, and manoeuvre it to shore for examination. The beast measured three metres long, more than a metre thick, and weighed an estimated 272 kilograms.

Kegan's father said, in the 30 years he's spent on the water, he's never seen a fish that big.

"These fish are hooked, but they're just never landed this size. It's very, very rare that they actually get the fish in. We're thankful and I'm thankful that Kegan was diligent and stuck with it."

'They are a living dinosaur'

That stick–to–itiveness is the reason Kegan and his father are on a fishing trip in the first place. 

Earlier this year, the pair made a deal that if Kegan achieved straight As in school, they would go sturgeon fishing.

"I asked him what he was interested in and he said he had been studying in science about the link between alligators and sturgeon to prehistoric ancestry, and I said, 'Would you like to catch a big fish? A sturgeon?'" said Dan Rothman.

Of course, Kegan said yes.

​"I got interested in dinosaurs because in science we were studying what happened to them. They're such amazing species and not very many people have an interest in them right now," said Kegan.

"I wanted to catch a sturgeon because they are a living dinosaur from the Jurassic period."

​Catch and release

This week's monster catch won't be hanging over the Rothmans' fireplace any time soon though. Most white sturgeon populations in B.C. are designated as endangered, and are protected under the federal Species At Risk Act.

They can, however, be fished from the Fraser River as long as they are released afterward.

That's perfectly okay with Kegan and his father. They snapped a few photographs and let the fish go.

"[Kegan] had remarked to me that he was happy about being able to return the fish. The fish will grow and the species will grow, and I'm grateful that he has that instilled in him and that he thinks that way," said Dan Rothman.

Watch the video to see Kegan letting the sturgeon go

The pair are set to continue their fishing adventure Thursday on the Pitt River.

"The bar's set kind of high now, right? I don't know if he's ruined for life now. I doubt it because he's ready to go again tomorrow," said Dan Rothman.

Kegan said he's hoping they'll catch a bigger one tomorrow — maybe even a 12-footer.

With files from the CBC's Luke Brocki