Darwin angler Greg Fry has reeled in a $10,000 barramundi, the first prize-winning fish snagged this season in the Northern Territory's million-dollar fish competition.

But the six red-tagged barra worth $1 million each remain free, along with more than 100 other fish carrying cash rewards.

"We were pretty stoked and had a small celebration on the boat. Everyone was high-fiving and so happy," Fry said after his success.

The lucrative catch was made at Manton Dam, south of Darwin, after a group of fishing buddies made a last-minute decision to try their luck.

"It was pretty quiet for the first hour or two, and then at around 2am on Sunday morning we hooked up and it was on from there," Fry said.

He plans to keep half the prize, with the other half to be shared among his mates.

"My wife's got a birthday coming up, so she might get a better present this year than in years gone past but other than that, it'll come in handy coming up to Christmas," he said. 

Season five of the fishing competition kicked off on October 1 with 121 tagged barramundi released into local waters.

One is worth $1 million if caught, with 100 worth $10,000 each and another 20 worth $5000.

The $5 million fish released in previous seasons are also still to be caught.

NT Primary Industries Minister Paul Kirby said the competition reinforced the Territory as a great place to fish.

"As well as being a favourite pastime for many Territorians, recreational fishing drives local jobs," he said.

"The government is serious about recognising recreational fishing for the benefits it brings our economy and lifestyle."

Over the past five years, 35 people have claimed more than $300,000 in prize money.