Experts reveal the truth behind why there may be more sharks in Sydney Harbour

An expert from the Department of Primary Industries has lifted the lid on why there may be more sharks lurking in the waters of Sydney Harbour.

An expert has revealed shark numbers are not increasing in Sydney waters, but warmer temperatures are bringing them closer to shore.

The spotlight on sharks has grown over the past week after Sydney diving instructor Simon Nellist was killed by a great white in Little Bay and fishermen have been hooking the animals in multiple locations across the harbour.

Two large sharks were also captured on SMART drumlines off the coast, with the Department of Primary Industries (DPI) confirming neither shark was the large animal suspected of killing Mr Nellist.

Both sharks were between 1.5 and two metres long and had been captured, tagged and then released 1km further offshore.

Two men found a bull shark in Sydney Harbour.

The men struggled to pull the shark back out into the water to release it. Picture: TikTok / @huss_fish

While fishers have reported greater numbers of the beasts in Sydney’s oceans, a DPI spokesman told NCA Newswire there is no scientific evidence which suggests numbers are increasing.

“DPI research has identified that sharks are present in NSW waters all year,” a spokesman said.

White Sharks are present over a wide range of sea surface temperatures.

However, he said Bull Sharks are more numerous in estuaries and coastal waters near Sydney in summer and autumn, when temperatures are warmer.

“Bull sharks are the most common species of potentially dangerous sharks found in Sydney Harbour,” the spokesman said.

“At various times of the year, other species of sharks can be found in the Harbour such as Dusky whaler, Wobbegong and Port Jackson.”

Sydney diving instructor Simon Nellist was killed by a Great White shark in Little Bay.

No scientific evidence suggests sharks are more likely to frequent Sydney waters after a storm, but heavy rainfall can put nutrients from the land into the ocean.

This brings a higher number of fish and other animals to feed, which in turn can attract sharks.

A study conducted by the Sydney Institute of Marine Science said the knowledge of large sharks in temperate, estuarine environments is limited.

The study traced 40 subadult and adult bull sharks in Sydney Harbour over the course of seven years and revealed the predators “exhibited clear seasonal patterns in their occurrence during the austral summer and autumn, with abundance peaking in January and February”.

“Water temperature was the key predictor for seasonal movements and return behaviour to this estuary, suggesting that increasing water temperatures as a result of climate change may lead to higher shark abundance and possibly longer periods of residency in Sydney Harbour,” the study said.

Addison Hodge, 15, was fishing with friends when he caught a 2.8m bull shark. Picture: Mosman Collective

Two young fishermen unexpectedly found themselves reeling in a huge bull shark in Sydney last week.

Footage posted to TikTok shows something powerful in the water take Hassan Alameri’s bait and a struggle ensues as he tries to reel the catch in.

His friend can be heard laughing in disbelief.

“Look at that!” he tells Mr Alameri.

A separate video then shows the pair wrestling with the bull shark, estimated to be about 2.5m in length, by the shore after they’ve managed to bring it in.

One of the men was even game enough to lift its jaw to check out rows of razor-sharp teeth.

It was a spectacular scene with a backdrop to the Sydney Harbour Bridge.