In 1979, organisers of Port Lincoln's annual Tunarama festival wanted to honour the fish that gave their seaside community on South Australia's west coast a reason to exist.

A 10kg plastic tuna is used in the initial heats of the tuna toss. ( ABC West Coast SA: Samantha Jonscher )

Forty years later, the tribute they created lives on.

"Port Lincoln is tuna," Sharon Humenick, current Tunarama president, said.

"They noticed at the time that one of the criteria to actually get a job on the tuna boats was to be able to chuck tuna a certain distance."

This was a key skill.

At the time, tuna fishers would throw their catch from the boat's deck onto the waiting truck above when they arrived back from sea.

"They decided that the tuna toss would be a great way to celebrate the industry," Ms Humenick said.

"They went and practised on the beach with various sizes before settling on nine or 10 kilograms — 20 pounds in those days — as the optimum weight for the tuna toss."

Initially the event was just for fishers, but the following year the general public was invited to enter and the tuna toss became a Guinness Book of World Records event.

Today contestants still compete to throw a frozen nine or 10kg Southern Bluefin Tuna, with a rope handle threaded through its gills, as far as they can.

But since 2008, competitors have had to throw a weighted, plastic tuna in the initial heats on the first day of the two-day competition.

Four fish are donated by the industry each year for the event.

The donated fish are 'mort' — undersized tuna that have died of natural causes.

No fish are killed for the tuna toss: the industry donates fish of a certain weight that have died of natural causes. ( ABC West Coast SA: Samantha Jonscher )

Hammer throwers take notice

2019 tuna toss winners Althea Mackie and Timothy Heyes. ( ABC West Coast SA: Samantha Jonscher )

It was not long before the tuna toss and its hefty cash prize caught the eyes of hammer throwers.

Today, winners of each category take home $1,000 and second place wins $500.

"I suppose people say they are at disadvantage with hammer throwers but we want it to be open to everyone," Ms Humenick said.

The first man to hold the record was John Penny, a Port Lincoln local training for the Olympic hammer throw.

The current record is held by Australian Olympic hammer thrower, Sean Carlin, who threw 37.23 metres in 1998.

He also holds the Australian hammer throw record.

The 2019 men's tuna toss winner, Timothy Heyes, said the sport's technique seemed to suit the tuna toss, but that the two were quite different.

"It's heavier and shorter than what I'm used to," he said.

"The weighting is also really different. A hammer has all the weight on the bottom, but the tuna has its weight distributed.

"I'm definitely going to come back and go for the record."

Due to changes in the way the industry fishes, finding the right size of mort tuna is becoming harder. ( ABC West Coast SA: Samantha Jonscher )

The women's record of 22.15m was set in 2002 by hammer thrower Brook Kruger.

This year the women's trophy was awarded to hammer thrower Althea Mackie for her 12.35m throw.

She started hammer throwing at 40 and nine years later, after her second year winning the tuna toss, said, "I hope to win this when I'm 50".

Practice makes perfect

Michael Proude tossed a tuna on his wedding day. ( Supplied: Michael Proude )

Hammer throwers are not the only ones who take the competition seriously.

The Proude family of Port Lincoln has made the tuna toss a family tradition.

Michael Proude and his son Levi Proude start practising a week out from the toss, using a homemade 7kg sandbag that is mended and restuffed each year.

"The movement of throwing a sandbag or a fish … is not an everyday movement, so you have to make sure you don't injure yourself," said Levi Proude.

"But we practise to get our technique right.

"Strength matters but technique is key."

Michael Proude is a six-time tuna toss winner who even made a point of competing in the toss on his wedding day.

"We got married in '92 and when the heats came, I went down in my tux and shoes and actually tossed the fish," he said.

"I made the finals and ended up coming second that year."

The father and son have a friendly competition: Levi came second to his dad by three centimetres in 2016.

"Dad's always done it, so I like to continue the tradition," Levi Proude said.

This year, Michael Proude was not able to compete because he was injured, but his son placed second.

"When you see someone with a hammer throw technique in the heats, you know you don't have a chance," Levi Proude said.

"I'm pretty chuffed to have come second to a pro and to have beaten the average thrower."

Levi Proude begins practising for the tuna toss a week out from the competition using a homemade sandbag. ( ABC West Coast SA: Samantha Jonscher )

Future uncertain

Rubber fish may have to be used all the time in future competitions. ( ABC West Coast SA: Samantha Jonscher )

Due to changes in how and when fishers catch tuna, it is becoming more difficult for the industry to find mort fish of the correct size for the toss.

"It's getting very hard," Ms Humenick said.

"We might have to look at using the rubber fish all the time. I don't know what's going to happen.

"It's just natural progression with the tuna industry, and that is what it is.

"The competitors really prefer to throw the real tuna."