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Unique chance to witness annual shark spawn

Environment

Scientists, divers and marine ecologists are preparing for a mass aggregation of harmless Port Jackson sharks in shallow waters off the coast of a major Australian city.

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Hundreds of the small sharks have begun gathering around reefs in southern Adelaide for breeding and are expected to stay for about a month.

Last year’s aggregation near the Adelaide beaches of Noarlunga and Aldinga was the biggest in the area in living memory with hundreds of the sharks seen clumped together at a time.

In response, conservation groups are staging SharkFest! for the first time this year to give people the chance to dive with the sharks and learn more about their place in the marine environment.

The November 10 -11 event includes guided dives, which have already sold out, as well as education sessions and pamphlets targeted at fishermen.

Not for profit groups Experiencing Marine Sanctuaries and Reef Watch are organising SharkFest! with support from Department for Environment and Water and Natural Resources Adelaide and Mount Lofty Ranges.

Port Jackson sharks, Heterodontus portusjacksoni, are the largest of the Heterodontid sharks and take their name from Port Jackson, more commonly known as Sydney Harbour, where they were first sighted in the 18th century. Females can grow up to 1.65m while males only reach a metre in length.

Experiencing Marine Sanctuaries co-founder and project manager Carl Charter said while annual aggregations of the small sharks had been previously known, they were gathering in larger numbers along the Adelaide coastline in recent years.

He said Port Jackson sharks were harmless and provided the ideal metropolitan setting to educate divers and fishers about the environmental value of sharks and rays.

“We’re trying to organise some surveys so we can start collecting data on where they aggregate and how many because we do get random reports from people all over the place that they are seeing large groups of Port Jackson sharks,” Charter said.

“For them to aggregate in such huge numbers along the Adelaide coast last spring hasn’t happened before – not that anyone can remember anyway.

“Someone counted about 100 in a minute in an area the size of a small house block.

“I’ve heard of people going out on stand up paddle boards on very calm days and being able to see them quite clearly in shallow water.”

Port Jackson sharks are known as “the puppies of the sea” because of their inquisitive, playful personalities and dog-like faces. Photo: Carl Charter

The sharks congregate around reefs and rocky shelves where they mate and the females lays pairs of spiral-shaped eggs every 10 to 14 days, for a total of 16 eggs. The sharks, which can live up to 35 years, then hang around for a few weeks before heading out to deeper waters.

The eggs take about 10-11 months to hatch with new pups ranging in size from 18-32cm. Reports suggest there are also large numbers of baby Port Jackson sharks around Adelaide at the moment.

Charter said a number of freshly hatched Port Jackson sharks had been recently caught from local jetties with some fishermen killing them because they were seen as a pest.

He said fishermen would also be spoken to during the SharkFest! weekend about the value of small sharks and rays to the marine environment and how to return them to the water safely.

“We’re trying to educate people that the sharks are a very important part of the marine ecosystem and we should be encouraging them to come in and do their thing,” he said.

“We’ll get people out there in the water to experience the sharks with their own eyes.”

Divers are preparing for the huge aggregation of Port Jackson sharks in South Australia. Picture: Carl Charter.

Charter said Port Jackson sharks were known as “the puppies of the sea” because of their inquisitive, playful personalities and dog-like faces.

He said their harmless nature made them a perfect introduction for people worried about sharks.

“There’s no actual chance of anyone being injured buy a Port Jackson shark unless they picked one up and put their hand in its mouth then they might get a crushed finger.

“We’ll be taking people snorkelling in two or three metres of water and seeing them below us and under ledges,” he said.

“There’s a lot of hype out there about sharks and how dangerous they are and how they attack people but when it comes to the small species of sharks and rays they are harmless and we should be educating people on how to protect them and conserve the species.

“It’s a great experience for people in such shallow water in the Adelaide metro area – there’s probably not anything as spectacular as an aggregation of small sharks.”

Citizen scientist and diver Sue Newson has been conducting Port Jackson Shark surveys near her southern New South Wales home of Jervis Bay for almost 20 years.

Newson will travel to Adelaide next month to see the aggregation and will give a talk about the species as part of Sharkfest!.

She said the right sort of education was crucial when it came to shaping public perceptions of small shark species such as the Port Jackson.

“Unfortunately anything that has the word shark in it is seen as potentially nasty but with Port Jacksons you can lay beside one and they will probably just sit there and stare at you – they’re so cute,” Newson said.

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