What Washes Up, What Swims Below
Three weeks of constant rain has left the surf on the East Coast various shades of brown. As the water washes down the river systems it collects refuse, natural and not, flushing it through the entrances and into the ocean. Easterly winds have then brought much of it ashore.
Beaches up and down the coast are strewn with flotsam, the nature of the debris reflecting local river use. On the Sunshine Coast, two pontoons for mooring private boats washed up on a beach, while further south in the Northern Rivers agricultural waste was more prevalent: oversized water tanks, wrapped hay bales, and the like.
Whatever its original purpose, surfers need to keep in mind that what they see on the beaches has come through the wave zone, and to look out for further matter - many rivers are still in flood.
Last week a cow, still alive, washed up at Duranbah after getting a ride down the Tweed River in floodwaters, and it wasn't the only live organism in the water.
All week, media has been warning about the dangers hidden within floodwater - infection-causing microbes - which, though diluted in the open ocean, are still of some concern. Closer to urban centres, sewage from pipes and overflowing septic tanks draining into the stormwater system becomes an issue.
As the surf has been good during this event, many surfers have chanced their luck. If you cut yourself while surfing near a river or an urban centre be sure to use antiseptic on it afterward. Irrespective of injury, using alcohol-based ear drops such as Aqua Ear is also a good idea after each session.
More menacing is what's swimming below. On Tuesday morning a surfer was bumped off their board at Maroubra. The surfer was uninjured, but their board sported fresh teeth marks. It's not known what type of shark it was.
A spokesperson for Randwick Council said the overcast conditions in Sydney - as well as murky water from torrential rain - meant surfers faced the heightened risk of a shark attack.
“We’re just stressing that now is not the time to be in the water,” she said.
Meanwhile, Madison Stewart - AKA Shark Girl - has issued a warning about the movement of bull sharks in the wake of the flooding:
"Big enough rainfall will change the normal distribution patterns of bull sharks within a river system and will move bulls out of a river system into a near shore beach area. They can’t cope with the drop in salinity in the water."
"River mouths also represent a food source for sharks with all run off flowing into the ocean from upriver, things like fertilizers and even sewage can cause fish to feed and congregate in the river mouth area."
"In murky water bull sharks thrive."
Comments
I'm calling nonsense on bullsharks not coping with a drop in salinity. There are numerous articles that discuss how the bullshark uses its kidney function to regulate salt in its body. They retain the salt and this allows them to survive (and thrive) in water levels with reducded salinity levels.
100%
Salinity may be below a critical lthreshhold evel though. They still require a little dont they? Id imagine in normal times theres a small amount of salinity up river. Currently thered be zero percent with all the rainfall thats fallen. Mskes sense to me.
BD, Bull Sharks can tolerate zero salinity. There are a couple spots on the east coast in the big rivers where they occur above the tidal limit and even above small rapids when they must have swum upstream during a flood.
I think in the Zambezi there are records of them occurring hundreds of kilometres upstream so they are not bothered swimming around the flooded river mouths in current conditions.
For real? I stand corrected. Thanks Distracted. I thought they required some small amount of salinity still. Incredible creatures. Apologies for my ignorance.
BD
https://www.qt.com.au/news/apn-shark-mauls/83637/
Yikes!
Poor horsey.
The only caveat on the Bull Shark living in freshwater is that is has a shorter lifespan based on some studies done, but not dramatically
Not an expert, but I think it might be the rapid change in salinity that causes them problems? Normally when they move through a river or estuary the change from salty to brackish to fresh might happen over hours or days. But when they come into contact with a big slug of floodwater the same change might take minutes or even just seconds.
I dont know about sharks but I surfed the NSW Central Coast on the weekend and it looked fairly clean aside from natural debris like sticks and seaweed, but while we were out there an ice chest (bigger than a normal family fridge) came right through the lineup. Got pitched on a big one and headed for the beach. Wouldn't have wanted to be inside of it.
Vic Hislop used to say the sharks (GWs) hang off the river mouths during floods to pick up easy meals from animals washed down the rivers. They would all be a bit revved up but hopefully well fed.
Multiple shark sightings in and around Manly now for the last two weeks since the water has gone bad. Usually there's one or two but nearly every day there have been sightings. Luckily no attacks but there have been also lots of sizey bait balls sitting closer inshore.
Be super vigilant and exit the water if a big bait ball starts boiling away or if you seen any weird water disturbances.
Bump a few days ago @ Lennox point...Bull Sharks are in their prime conditions atm..Take care
https://www.dorsalwatch.com/report/index.html?country=1
DPI Fisheries advise: tagged Bull Shark #1281 detected by Lennox Point receiver at 06:32:40 AM (AEDT) on 10-March-2022. Last detected at 07:37:17 PM (AEDT) on 09-March-2022 by Sharpes Beach receiver.
Any further rumours on the shark bump at Lennox. Heard nothing on the coconut wireless? Big shark? Small bull?
I'd say old mate at the Bra is a very lucky boy.
I noticed during heavy rain at Narrabeen lake that there was a layer of fresh water about 1 meter deep above the salty water below, so I would be thinking Sharks could probably remain in a flooded river system by just staying a bit deeper.
Rolysea had this same experience with a very experienced free-diver, spear fisherman years ago with the fresh water sitting layered above the salt. Clearly visible through our masks. I had never seen it before and felt unease due to the abnormally for my self. It felt very different visually and my instincts where immediately on alert. I discussed this with them when I returned to shore. It is the only time I have felt that they felt and showed unease too, They dive almost daily. Trust your gut. Conditions were over cast and dead glass. Visibility was clear with a greenish layer sitting perfectly above 1m 2m from surface maybe 8-10m of water. It was almost exactly what you see in a science experiment. Never forgot it.
Maybe it's not so much about the bull sharks capabilities but it's food source. Heavy rain certainly pushes a lot of the upstream sea life down stream, maybe due to there salinity needs?
I've definitely read studies of bull sharks being able to handle minimal to no salt content in water also.
Just saying - Ive been spearing in the dirty water at a pretty sharky spot and havent seen any
Those two pontoons mentioned in the story? There's apparently many more washing down the QLD rivers and their floatation - i.e polyester foam - is breaking apart and causing a calamity that'll take months, perhaps even years, to mend.
https://www.abc.net.au/news/2022-03-10/polystyrene-brisbane-floods-emergency-on-beaches-/100894566
Humanity can be so utterly short-sighted most of the time. This is terrible.
You want to see some of the shit trawlers drag up after big floods. Apart from the usual flood debris (sticks/logs,household items) you'd be suprised how many car bodies end up just offshore. I've seen a couple of trawlers bring back someones pride and joy on the deck of their boat .Plenty of wrecked boats end up on the bottom out there too. All of these still with fuel and oil.
Here in the States, they've found bulls 1,100 kms upstream in the Mississippi River. In Illinois. Don't think lack of salinity bothers them much.
And 4,000 ks up the Amazon.
Cull the bastards before 'shark encounters' on the NSW coastline goes through the roof.
As much as I fear the GW’s, they are more likely to be out in deep water, would be going after whales, seals, fish, and I tend to agree that they aren’t ‘looking’ for humans. But what does anyone know, they’re freaking sharks and they don’t go to psychology researchers to consider the question as to why they took a guy’s leg off.
Bull’s are more like eating machines, reckon they would give a fridge a go, they lurk in dirty water, can’t see what they’re shoving in their mouths as often as not, and don’t give a shit if they get it wrong (as if they have ever attended a psychologist’s couch - what the hell do I really know).
I’d rather be out in a clean ocean than at downtown George’s river, Picnic Point or even the Harbour. And yeah they seem to be fine with very small salt water content.
Yeah, old mate at Maroubra should buy a lotto ticket. I’ve been out of the water for two weeks, don’t like it but don’t regret the decision.
Think how many people ocean swim every day - tens of thousands - from Noosa, Mooloolaba, Gold Coast, Byron, all the way down to Sydney etc. Not sure of the numbers on the west coast as I've never ventured there, but the east coast I'm familiar with. Then think how many people get tagged / bumped by sharks. virtually zero. Sharks must be much smarter than we give them credit for.
Me and my mates grew up on the Mooloolah river. We swam in it almost daily every summer, paddled across it, drove boats in it etc, but I have yet to encounter a shark (more than a wobegong!) at all. I lived as a kid and still do, literally on the river, but have yet to encounter one of these beasts. My mother in law says my kids should be wary of bull sharks, but they paddle, swim etc in the river all the time and have never been scared off. I've free dived, spear fished, paddled to off shore islands to surf, but have yet to encounter a scary beast. I still hear stories of resident sharks (ironically in areas with good waves) but have yet to meet/ see these sharks.
I remember living on the Mooloolah river in a flood early 80s, the river came over our boundary (lucky I used to attach my legrope to a tree in our back yard), that was a pretty big flood!
Used to swim out to check the crab pots. never got bumped etc.
What am I missing?
Where are these creatures?
I think they are a scare tactic by those with little understanding of what's actually real!
Think about it - if sharks wanted to eat humans, there is a smorgasboard at every beach daily. But no one gets touched.
Pure bad luck if a person gets hit by a shark.
You can literally find multiple shark stories about every beach on the east coast including Mooloolabah by just Googling it.
Agree that chances of being attacked are low per swim/surf, but the stats over the last couple of years on the east coast are pretty bad.
In places with multiple recent fatalities in the area it must start to play on the mind knowing that your chances of being attacked have gone from virtually non-existent to just very low.
Troppo, personal experience doesn’t equate to science, but you go for it. How many bumps and sightings at GC, Manly, Maroubra, and a million other places. It’s a well known fact that floods drive fish and other animals down the river and out to sea, that’s been the way since long before humans have been around. Sharks have been around for 100s of millions of years. They know how it works.
No fisherman would go out swimming in dirty flood waters. They know.
This poor young Girl at Straddie
https://www.theage.com.au/national/death-in-the-shallows-20060114-ge1kld...
I fully agree that flood waters elevate shark risk on surf beaches. But I don't agree its about them being able to handle salinity changes- I think its more about feeding opportunity - brown water making it easy to launch an ambush attack on dopey flood effected fish. Last easter, for several days after the Clarence flooded - I watched literally hundreds of small bull sharks swimming up and down the wall on the Turners beach side of the break wall at Yamba. There was so many of them that you could see them through the chocolate water picking off the dopey flood effected fish. It could be that the fresh water was effecting the salt water fish and making them slow and dopey - or the freshwater fish that got pushed down to the mouth from oxygen depleted food waters. Or, it could be that the brown turbid waters giving them a hunting advantage on the beaches - those areas usually have clear water, which is difficult to execute a surprise ambush attack on passing fish. Whatever the cause - its pretty obvious that floods change shark behaviour and I will be steering clear of surf breaks near river mouths for a while.
Couple nibbles at Crowdy Bay. Could have been a lot worse.
https://www.portnews.com.au/story/7661444/surfer-attacked-by-bull-shark-...