Several popular Sydney beaches remained closed on Friday after fears there would be a shark attack following the death of a humpback that washed ashore.

The five-meter whale was first seen last Friday as it floated offshore at Avalon beach. It then washed ashore on Wednesday at Long Reef, deceased with many shark bites along the body.

Instagrammer Thomas Mesaglio was the one who first sighted the washed-up whale on Wednesday. He took pictures of the carcass as it lay in the Long Reef Aquatic Reserve, noting it had a lot of bites.

The tides shifted soon, and they took the dead whale back out to sea, depositing it on North Narrabeen, which is a popular beach destination.

The Northern Beaches Council then removed the body on Thursday morning and took it to the waste dump located at Lucas Heights to the south.

The operation was managed by council staff, trained in whale recovery and disposal. It has been liaising with the Department of Primary Industries and Surf Lifesaving NSW to track movements of the dead whale since the time it was first seen offshore at Avalon.

The council has since issued a closure notice of the beaches from Narrabeen down to the Fisherman’s beach due to suspected increased shark activity.

The presence of a carcass in the water increases shark concentration several folds as they are drawn to the scent of blood and meat in the water. Incidentally, this also makes them more aggressive, leading to a dangerous situation for surfers and beachgoers.

The council has placed warning signs along the Collaroy Basin as well, warning the beachgoers to stay out of the waters.

The 'Organization for Rescue and Research of Cetaceans' in Australia also issued the same warning to make locals keep out of the water.

A spokesperson for ORRCA, Jools Farrel, said she would not necessarily call the event a feeding frenzy, but it is nature after all.

She added it was natural when whales, dolphins and seals die while at sea, but the sharks are well known as scavengers as they clean up the carcasses which are left behind.

She also stated that beachgoers and surfers need to use their common sense and stay out of the water, particularly at dawn and dusk, when the sharks come out to hunt.

The dead whale has also been classified as a biohazard to the area. So closing the beaches serves two purposes to protect the local population.

Humpback whale Pixabay