THOUSANDS of sharks have been spotted taking a snooze on the ocean floor – and to the amazement of scientists they’re all female.
The “girls-only shark slumber party” has left experts stumped as they can’t explain why there are in this exact spot and without any males.
Scientists don’t know why it’s an only-female gathering in this spot[/caption]
Thousands were seen taking a snooze[/caption]
Moment was caught by underwater robot[/caption]
They were previously seen here six years ago during the first survey of Beagle Marine Park, in Bass Strait off the coast of Victoria, Australia.
Port Jackson sharks are often found in rocky environments or at the bottom of the sea across southern Australia.
They can grow to about 1.65 metres in length and are nocturnal, so they tend to sleep during the day then hunt at night on squids, octopuses and crustaceans.
Port Jacksons are considered quite friendly as sharks go and divers regularly interact with them.
Now the “spectacular” but mysterious sleepy gathering of Port Jackson sharks has been found again using an underwater robot onboard a South Australian Research and Development Institute (SARDI) research vessel.
Dr Jacquomo Monk, from the University of Tasmania Institute for Marine and Antarctic Studies (IMAS) said the sharks were “tightly packed like a carpet spread across the seafloor”.
“We had been hoping to see the sharks again on this survey,” the voyage leader explained.
“Coming upon them twice in a 3000-square-kilometre park is like finding a needle in a haystack.
“It was very exciting when we managed to traverse over a rise in the reef to get a glimpse of the sharks snoozing 65-metres below the vessel in almost the same location as they were six years ago.”
Port Jackson sharks are known to mate in late winter – they have a distinctive spiral egg casing that they lay onto reefs for protection.
It’s common for male and female Port Jackson sharks to live separately but scientists can’t explain why it “appears to be only for females”.
But it may be that they go there to breed or “fatten up” before moving on to areas where they typically lay their eggs.
“This poses more questions than answers for us, but we know that the males and females of this species often live apart, except when mating,” Dr Monk continued.
“We don’t know exactly why the females are here.
“Perhaps they are feasting on the local delicacy – doughboy scallops – before the long trip north to lay their eggs.
“Seeing them again does tell us that the area is important to them.”
University of Tasmania Institute for Marine and Antarctic Studies team investigates[/caption]
Port Jackson sharks: Key facts
Port Jacksons are considered pretty friendly as sharks go with no reported fatal attacks on humans.
They are a type of bullhead shark from the Heterodontidae family, found across Southern Australia.
Port Jackson sharks are known for their distinctive large, blunt head with prominent forehead ridges, as well as dark brown harness-like markings on a lighter grey-brown body.
The species is often found in rocky environments or near the bottom of the ocean.
Female Port Jackson Sharks tend to mature between 11 and 14 years old, while males mature sooner, at around 8 to 10 years.
