A BABY whale has died after being caught in a shark net off Mona Vale this morning.
The calf's mother and four other adult whales remain in the vicinity.
The baby humpback is understood to have become entangled in the net in the early hours of the morning and was spotted from the shore about 6am.
After authorities were contacted, staff from the National Parks and Wildlife and from ORRCA rushed to the scene to try to disentangle the calf.
ORRCA volunteer Shona Lorigan estimated that the calf was no older than three months, and about 6-7m long.
She estimated its mother's weight to be about 45t.
The calf was travelling with its mother on its southern migration to the Antarctic.
Local Andrew Hodgson told the Manly Daily that he saw the calf "thrashing around" the water at about 6am, with its mother circling around it.
"You could see the baby just bobbing around," he said.
Mona Vale Beach has been closed and the public is asked to stay away from the area.
FACEBOOK HAS ERUPTED IN DEBATE OVER THE USE OF SHARK NETS
The adult whales stayed close to the beach in a tight pack formation, swimming up and down the beach for most of the morning.
They then disappeared from sight but the calf's mother was expected to stay in the area for several hours.
The whale disentanglement team is remaining on the scene to ensure no other whales become entangled in the shark net.
The contractor who sets the shark nets is also on the scene.
The death of the whale calf will reignite the debate about shark meshing off Sydney's beaches, which was introduced in 1937 following a series of fatal shark attacks, including several on peninsula beaches.
Avalon-based Humane Society International spokesman Alexia Wellbelove said the death of the whale calf drove home an important message.
"For many years HSI has been seeking the removal of shark nets due to what we consider to be the unnecessary impacts these nets have on marine life, and this morning's entanglement of a whale is exactly what we hoped wouldn't happen," she said.
Ms Lorigan said an alternative to shark nets had to be found.
"I certainly hope what comes out of this is there is research into different forms of shark deterrence," she said.
"This was a beautiful baby whale.
"We need to find something else. We need to find another way."
A NPWS spokeswoman said arrangements are being made with Taronga Zoo for a necropsy to be performed to determine the precise cause of death.
