A diver was killed by a 13-foot shark Saturday off a beach in southwestern Australia, in the region’s fourth shark-related fatality since September, according to authorities.

The news that 33-year-old businessman Peter Kurmann had died while diving with his brother Gian Kurmann came one day after fishery managers adopted new protections for sharks in the western and central Pacific Ocean.

The two brothers were diving off Stratham Beach, about 140 miles south of Perth. State police spokeswoman Sgt. Naomi Smith said Peter Kurmann appeared to be killed instantly, while his brother was not hurt, according to the Associated Press.

After 32-year-old American George Thomas Wainwright was killed on Oct. 22 while diving near Rottnest Island, 11 miles west of Perth, West Australian authorities issued an order to capture and kill the great white shark involved in the incident, but failed to capture the animal.

On Saturday, the Fisheries Department launched a probe to try to pinpoint the shark species involved in the incident, and dispatched a government boat to the area where the strike occurred in an effort to capture a shark spotted there by aerial surveillance.

Fishing nations of the Western and Central Pacific Fisheries Commission — including the United States and Australia — agreed Friday in Guam to protect the oceanic whitetip shark in the region.

Oceanic whitetips were once common in tropical waters, but their numbers have dropped precipitously in recent years. The commission conducted an analysis that estimated that barring fishing vessels from retaining, transporting and landing the species could cut their mortality in fishing operations by up to 75 percent.

The International Union for Conservation of Nature lists oceanic whitetip sharks as globally vulnerable to extinction; Sonja Fordham, president of the advocacy group Shark Advocates International, said Friday the species is “seriously overfished.”

Matt Rand, who directs the Pew Environment Group’s global shark conservation program, hailed the new protections for oceanic whitetips but lamented Kurmann’s loss.

“Of course it’s tragic every time there’s an accident with a shark. It is very rare,” Rand said in an interview.

“Unfortunately sharks are being wiped out of the world’s oceans very rapidly,” Rand added, saying the new measures “affords an opportunity for the species to recover and play a key role in the marine ecosystem, keeping the marine ecosystem in balance.”

At the same time, fishery managers rejected a proposal by Australia to ban the intentional setting of nets on whale sharks — which is done in an effort to catch tuna congregating near them. Japan objected to the measure.

“An estimated 75 whale sharks were killed as a result of interactions with the region’s purse seine fishery in 2009 and 2010,” said Rebecca Regnery, deputy director of wildlife for Humane Society International. “We are perplexed and dismayed by continuing delays in adopting such basic and sensible safeguards for these globally threatened and economically important species.”