The warning came after a similar episode last October, when a 50-year-old Central Coast man swimming at Samurai beach was attacked by a shark less than one week after a sperm whale carcass had washed up at the northern end of One Mile Beach.

A spokesperson for the NSW Department of Primary Industries said that an alert was posted online last Friday.

"The department alerts beachgoers via twitter and via the SharkSmart App to be sharksmart when whale carcasses are discovered washed up on a beach," the spokesperson said. "It's a cautionary measure meant for all beach users."

A National Parks and Wildlife Services spokesperson confirmed the whale was the second such beaching at popular One Mile within 12 months. "This is believed to be a juvenile humpback estimated to be close to 10m in length and weighing approximately 8 tonne.

"There was no obvious sign of injury or cause of death, however, as the east coast of Australia humpback population recovers it is not unusual to see juveniles strand generally due to failure to thrive or misadventure. These animals are entirely dependent on their mothers for their survival," the spokesperson said.

Port Stephens Council closed the beach last Thursday and Friday, before the carcass was removed and buried offsite.

One of Australia's leading whale experts, Catherine Kemper, a senior researcher at the South Australian Museum, said it was likely that the whale had died at sea and washed up on the beach. "I suspect the currents brought the carcass in, which is probably what happened with the sperm whale last year."

Ms Kemper said that there was no way of knowing the cause of death without a post-mortem, or visible external injuries that might suggest cause of death.

"Strandings of whales and dolphins have been happening for thousands of years. Some are related to human activities but most are natural deaths that result from many things, including disease, old age, or losing a mother.

"South Australia has an extensive program of collecting and studying dead whales and dolphins. I don't believe that NSW has such a program."

Come handy tips from sharksmart for those thinking of venturing back into the water include: don't swim too far from shore; don't swim with bleeding cuts or wounds; avoid swimming and surfing when it's dark or during twilight hours; avoid areas used by recreational or commercial fishers; avoid areas with fish feeding activity.