Hooked up
Whether you’re trolling for a big barra on the Daly, flicking a plastic into the lilies on a Kakadu billabong, or c chasing macs on the blue water, we’ve got you covered
AS a young bloke, I enjoyed dragging a prawn net through the shallows of Darwin Harbour and Shoal Bay. It was hard work, but the reward was a bucket of small prawns, barely big enough to eat. The other reward was the joy of discovering what was lurking in the murky shallows, revealed as the net was pulled into the last few inches of water.
We caught small tripletail, flathead, stingrays, a zillion glassfish, stingers, whiting, longtoms, gar, blue crabs, mullet, sardines, and even a stonefish or two.
Dragging on the Ludmilla mudlfat near Nightcliff one morning, we hauled in a load of baby barra, all carefully released. The barra were lucky that day, as it was cool. I was impressed by how superheated the water over the harbour’s mudflats could become.
In warmer areas, everything in the net died as it was dragged into the hot water.
Fortunately, for free-swimming fish, localised hot water is usually not a problem. If the flats get hot, they can go elsewhere. But for fish fry such as barramundi, temporarily trapped in high tide pools, excessive heat is not so easy to escape.
It is the marine life that can’t move that doesn’t do so well in extreme conditions. And that’s what we have seen this year. Researchers revealed the worst recorded mass bleaching event in the Great Barrier Reef’s history, caused by warm water.
This week, they announced a follow-up on this bleaching event.
About 80 to 100 per cent of coral reefs surrounding Lizard Island off Far North Queensland were now dead from bleaching, they said.
James Cook University spokesman Professor Andrew Baird said researchers visited 50 reefs between Townsville and Lizard Island this month.
He told the ABC the results were confronting.
“What we’re seeing now is lots and lots of dead corals ... there’s not much coral at all, north of Port Douglas,” he said.
Worse, he said there was only a slim chance the northern third of the Great Barrier Reef could rejuvenate, and it would depend on the health of the southern reef sections.
“There’s still a lot of reef which could supply the propagules for the reef up north to recover, but it’s likely to take a very long time because the scale of the event around Lizard Island and further north was so large,” he said.
“It will also depend on it not bleaching again, particularly in those areas that are still in good condition.”
He said most of the reefs surveyed off the coast of Townsville and further south were only lightly bleached and were in reasonably good condition.
“That’s a positive, but with the current trajectories of carbon dioxide and ocean temperatures, there’s nothing to say that those areas might not bleach as soon as next year,” he said.
The researchers said the final death toll from the bleaching in the north would not be known until all surveys were completed in midNovember.
The two previous major GBR bleaching events were in 2002 and 1998.
The latest bleaching event happened about the same time that thousands of hectares of mangroves died in the Gulf of Carpentaria.
One might think shallow tropical waters will
be ground zero for global warming, being vulnerable to superheating.
But things are changing in the southern latitudes.
There has been a mass kelp die-off along the Tasmanian coast, and Atlantic salmon farmers have been told to have mass mortality plans in place for their Port Macquarie farms.
The Tasmanian abalone season has been a disaster, with divers saying the fishery has likely collapsed.
While overfishing has been blamed for lost abalone stocks, scientists are saying hot water has been smashing Tasmania.
For more than 100 days over the last summer, the water temperature rose by as much as 4C above average.
CSIRO researcher Alistair Hobday said the recent El Nino dwarfed other warm water events.
Warm water events also occurred off Tasmania in 2009, 2010 and 2013.
So there can be little surprise in the ongoing decline of kelp, crayfish and abalone.
Some scientists have suggested the global run of record hot years might take a break in 2017 as the world moves to a slight La Nina pattern.
Given this scenario, if 2017 defies that prediction and breaks heat records again, it must be time for governments to start taking warming far more seriously.
Our fisheries are the canaries in the coal mine.
Barramundi fish kills happened under normal build-up conditions.
Under a warming scenario, these kills will only get worse.
There will also probably be new, unforeseen consequences.
If you thought global warming wasn’t going to affect you, it might be time to rethink.
Your sport could soon be on the line.