Posted by: maximos62 | February 22, 2013

Bull sharks, heavy metals and kayaking

Setting out with seven novice kayakers and one who’d already done a little paddling there were spills right from the start, despite the wide beamed craft. With minor corrections made to the basics, like climbing in and out of kayaks, we were soon paddling about in Blackwattle Bay.

Next it was time to demonstrated basic paddling techniques and then suggest a few strategies to avoid capsizing. We watched a lot of this on YouTube, the week before.

There are many videos like this one available on YouTube.

Another useful YouTube video explained how to climb back into a kayak after capsizing.

Paddling on towards the ANZAC Bridge, the M4 Distributor Freeway, the most common question was, “How deep is the water here?”

The truth is I wasn’t sure. I know that Anzac bridge has a maximum clearance of 28.5 metres above high water and I know Sydney Harbour is deep in places but it’s a drowned river valley, Ria coastline, and in a practical sense I realise that parts of the harbour are quite shallow Bays like Blackwattle Bay, I reasoned, have been so heavily modified and polluted with industrial sediments, I wasn’t sure, but I thought the maximum depths were probably 6 to 10 metres. Later I confirmed, with a visit to the “>OzCoasts website, that the . . . seabed morphology of Sydney Harbour is complex and irregular with a series of deep ‘holes’ up to 45 m deep, and shoals where the water depth can be less than 3 m.

syd_figure1

So all I could say was, Well these bays are quite shallow, with a lot of sediment that’s built up in the bottom.

The next question was the inevitable, What about the sharks? Are there any?

Yes, there are. There are Bull Sharks. In fact there’s a lot of research that’s been done on Bull sharks because they’re one species that are known to attack humans. What the research shows is that they’re seldom seen and only likely to be a problem if you were swimming in murky turbid water. Even so they do attack people from time to time.

In 2009 Navy Clearance Diver, Paul de Gelder was attacked by a Bull Shark near Garden Island, losing a forearm and leg in the incident.

As a regular kayaker I often think about sharks yet, considering the extent of swimming and boating in Sydney Harbour, Port Jackson, it is comparatively rare for people to see Bull Sharks. I’ve never seen one. The manager at the marina where I store my kayak, formerly a professional diver who frequently worked in the harbour, has never seen one. Strangely though, my nephew who arrived from the UK last year recently watched from the balcony of a friends apartment as a Bull Shark swam around near Gladesville Bridge.

The ABC has a useful fact sheet on sharks.

The Sydney Aquarium has an excellent exhibit on the research conducted on the Bull Sharks of Sydney Harbour.

NSW Department of Primary Industries researchers Dr Amy Smoothey and Dr Vic Peddemors from the Cronulla Fisheries Research Centre studied the bull sharks in Sydney Harbour. Based on her research to date Dr Smoothey believes that a certain amount of mystery surrounds the behaviour of bull sharks, in Australian waters, and that without an extensive amount of research, misconceptions are left unchallenged.

There’s the misconception that every time you put your big toe in the Sydney Harbour, you are going to get it bitten by a shark, Dr Smoothey said.

But that is not the case, sharks and humans can, and will continue to, co-exist in Sydney Harbour.

For example, on Australia Day in 2011, our results showed that seven tagged sharks were in Sydney Harbour at the same time as thousands of people – yet there were no incidents, not even a sighting.

This suggests that bull sharks may not be the voracious predator that we once thought, she said.

http://www.dpi.nsw.gov.au/archive/news-releases/fishing-and-aquaculture/2012/curl-up-with-a-shark-scientist

There is actually a worksheet for the National Geographic program that can be downloaded here.

Clearing ANZAC bridge, with a light breeze off the Tasman, I wasn’t thinking much about how deep the water was, nor was I concerned about sharks. I was thinking about the bottom of the harbor, wondering just what layers of industrial detritus lay hidden beneath the waters. This to my mind was the greatest hazard in the inner harbour.

When I moved to Blackwattle Bay, Glebe, in 1967, there was still industry. Much later I research the area and encountered some expected results. The sad story is quite clear in Gavin Birch’s A short geological and environmental history of the Sydney estuary, Australia.

He tells us that by 1828, metal foundries, coppersmiths and paint manufacturers were established adjacent to Blackwattle Bay due to readily available water supply.

He goes on to observe that by 1880 the sediments of Darling Harbour, Blackwattle Bay and Rozelle Bay had become moderately contaminated with heavy metals.

Finally by 1922 the sediments in Darling Harbour, Blackwattle Bay and Rozelle Bay had become highly contaminated with heavy metals .

Birch cites the results from a sediment core sample taken from Blackwattle Bay that yielded a maximum of about 2000 μg/g of heavy metals.

Since it had been raining that morning, in fact persistently through January, storm water pollution was the most visible sign and the biggest issue in the harbour at the moment.

riveryachts

Paddling up the Parramatta River several days earlier, shots like this one gave the lie to the flotsam bearing waters that lapped at my kayak. Yet, apart from these very wet periods the water quality in Sydney Harbour has improved greatly since I was a boy. As a whole Sydney Harbour is no longer a working port and this has helped greatly.

Passing under the old Glebe Island Bridge we were soon off the site of the old Colonial Sugar Refinery. Here we did a small drill turning into the slight wash of some passing motorboats. It’s a good place to do this as there’s a 4 knot speed limit in Blackwattle Bay so the wash is minimal. It was an enjoyable drill. The students had a real sense of being in control of their kayaks, turning to face the small waves.

Such a successful drill behind us we paddled on to the old Glebe Island container terminal where HMAS Manoora and HMAS Kanimbla. It’s the same spot where Ex HMAS Adelaide was moored before her unfortunate scuttling off the coast of Avoca.

Suddenly there was a call from behind me. One of the students had capsized, his kayak now half full of water. Tying it to mine I organised for him to hold onto the rear of the strongest paddlers craft while two students paddled close behind him and the rest paddled ahead to a small wharf on the other side of the bay, just below the complex of apartments that have replaced the CSR sugar refinery.

There wasn’t the slightest sense of panic, rather there was a strong practical sense of teamwork. Soon we’d righted the kayak, drained the water and had its occupant back in command of his craft.

Paddling back with the north easter behind us, I heard one of the students say,

“This is the best sport I’ve ever done.”


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