Leading Australian surfer Ethan Ewing has received a death threat after Brazilian fans erupted at judging at the World Surf League’s Surf Ranch Pro.

The Californian wave pool event, which finished Sunday, was won by local surfer Griffin Colapinto, who beat Brazilian veteran Italo Ferreira in the men’s final.

New rankings leader Colapinto scored 17.77 to Ferreira’s 17.13, however much of the fury was stirred earlier when Ewing ousted another Brazilian Gabriel Medina in the quarter-finals.

Ewing and Medina, who has made the Surf Ranch final in each of the four times an event has been held there and won it twice, both scored 16.67 with the Australian advancing to the final four on a countback having posted the highest wave of the day with a 9.07.

Post competition Medina sent an open letter to the WSL complaining about the fairness of the judging, adding to rising criticism that the organisation had a set against the “Brazilian Storm” that has dominated men’s surfing in recent years.

“Dear WSL, Please understand the importance of this discussion ... the surfing community, especially the Brazilian one, has been appalled by the lack of clarity and inconsistency in the definition of grades for many years now, but lately it has been even more shocking,” three-time world champion Medina posted on Instagram.

“It’s clear that the judges’ assessment is now rewarding very simple surfing, incomplete transitions, and PROGRESSION and VARIETY is being completely taken out of the equation. This is very frustrating and threatens the growth of the sport.

“Fans and sponsors will not accept that this continues and, for the foreseeable future, will end up pulling away as they expect an equal and fair trial for the sport.”

Medina said that his coaches have spoken to the WSL to discuss the “lack of appreciation for tricks” but the feedback was “quite defensive, with bad examples to illustrate their points”.

“The WSL urgently needs to clarify its criteria and apply fair judgement to preserve the evolution of the sport,” he wrote.

Medina’s letter stirred Brazilian fans, who vented on the WSL’s social media, targeting world No.4 Ewing.

“One day, you will compete here in Brazil and us will remember you. Get ready,” one wrote.

“I’m saying again, here in Brazil, we will kill you. Saquarema will be your funeral.”

Queenslander Ewing posted the direct message responding, “How good are surfing fans!”

The tour moves to Saquarema in Rio for an event late next month.

While not as pointed, Filipe Toledo and Italo Ferreira posted in support of their countryman, also questioning the judging fairness and transparency.

Despite their complaints Brazilian men have won the world title in six of the past eight years, with Hawaiian John John Florence breaking up the run.

They have also won three events this year, with Toledo winning at Sunset Beach, Joao Chianca winning in Portugal and Medina taking the Margaret River title, with Chianca and Toledo sitting two and three in the rankings.

The WSL rejected the criticism and said Medina’s comments were “unacceptable”.

“Surfing is an ever-evolving, subjective sport and we appreciate a robust debate around the progression of our sport and the criteria used to judge our competitions,” a WSL spokesperson told Reuters.

“However, it is unacceptable for any athlete to question the integrity of our judges who ... are elite professionals.”