A spokeswoman from marine rescue group ORRCA said the group was called to Mona Vale beach around 7am (AEDT) on Tuesday. ORRCA vice-president Shona Lorigan said the whale was dead when NSW National Parks and Wildlife Service officers arrived around 10am (AEDT).

The parks and wildlife service will now determine how to remove the whale.

The calf's mother had been swimming nearby, responding to the baby's distress calls.

Humane Society International spokeswoman Alexia Wellbelove said shark nets were "indiscriminate killers" of marine life and provided no real protection for humans. She said it was the first whale entanglement in NSW this year but urged more research into other possible shark deterrence methods.

"This is a tragedy that we don't want to see repeated," she said. "We're getting a growing number of entanglements each year." Lorigan said dolphins and turtles also became entangled in shark nets.