Its delicious white flesh makes it one of Australia’s most prized fish species, but a barramundi caught by a teenager in the country’s tropical north came with an added bonus: a cash prize of a million Australian dollars (£520,000).

Landing the 2ft-long fish in a river in the Northern Territory promises to be life-changing for the family of Keegan Payne, 19

The teenager, who is one of eight children in an Aboriginal family that has struggled to make ends meet,  was out fishing on the Katherine River with friends and his little sister on Sunday when he snagged the “barra”, which had been tagged as part of a popular fishing competition.

The Million Dollar Fish contest was launched in 2015 with the aim of luring fishing enthusiasts to the creeks, rivers and estuaries of the Top End, as the Northern Territory is nicknamed, during the wet season, a time of thunderstorms, torrential rain and cloying humidity. The prize money is paid out by SportsBet, a sports gambling firm.

Fish evaded capture for nine years

Each year, barramundi are tagged and then released, with different tags commanding different amounts of prize money. Mr Payne landed the jackpot – a barramundi worth a million dollars that had evaded capture since the start of the competition.

Mr Payne, who describes himself as a “mad keen” fisherman, could hardly believe his luck. “This is crazy for us. We’re a big family, there’s eight of us, this is more money than we could ever ask for. This is just great,” he said.

“It means so much. This is a once-in-a-lifetime opportunity for me. I’m happy, really happy. It’s pretty hard going for us at the moment with money, but now with a million dollars, (we) don’t have to complain about it.”

He said that while he hoped to buy a four-wheel-drive vehicle and a boat and go on holiday to the US, his main priority was to help his parents pay off their mortgage.

He caught the big barramundi just in time – this year’s edition of the Million Dollar Fish competition ended at midnight local time on Tuesday.

The teenager’s big win was announced at a ceremony in Darwin, with a giant cheque delivered by helicopter by Eva Lawler, the chief minister of the Northern Territory.

Little sister spotted crucial red tag

The red tag sticking out of the fish was first spotted by his 11-year-old sister, Addyson, after they hauled the barramundi into their boat.

She recalled: “He didn’t see the tag, but I did and I said, ‘What’s that sticking out of it?’ And Keegan turned it around and he was like, ‘no way, no way.’ He was jumping around, screaming.”

Her brother added: “We were freaking out. We nearly crashed the boat, getting back to the boat ramp. Yeah, it was good.”

Also known as the giant perch or Asian seabass, barramundis are found in tropical waters.

They are known to put up a fight once hooked and can weigh up to 130lb. Wild barramundi is particularly prized by restaurants but the species is also farmed extensively.