This week’s Menindee fish kill is third major kill in the upper Darling River  in five weeks. It reportedly involves hundreds of thousands of fish, coming on top of an estimated “up to a million” three weeks ago. On January 15, the ABC reported that contractors would start  the next week on the task of cleaning up the fish carcasses and that they had a window of five days to remove them before most would have sunk to the bottom to rot.

With the wait that occurred to appoint the contractors, it is plain that huge numbers would have sunk into the mud where the bacteria that causes putrefaction would have massively added to the oxygen depleted water problem initially caused by algal blooms. Ecosystem disaster language is being used without exaggeration.

A Central Darling Shire Council spokesman said that there were “very few contractors with the resources to deal with a problem of this scale.”  But the task they would face with a million floating dead fish is of galactic proportions.

Removing a million fish in five days before they sink means 200,000 a day. If contractors worked eight hours a day at the task, that would require 25,000 per hour or 417 a minute. If the average fish weighed 2kg, that would mean 50 tonnes per hour would need to be hauled in from drag nets, then removed into dump trucks and transported to landfill.

The figure of a “million” dead fish has been repeated in nearly every news report of the biggest kill. It remains a guesstimate because no one knows with any accuracy how many fish are actually in our rivers. It could be less, but with many thousands of fish having already sunk, it may well have been even more.

Drag netting a river as narrow as the Darling, with its river bank vegetation, tree roots and dead wood often blocking your way is a totally different proposition to unimpeded ocean net fishing where massive numbers can be scooped up quickly. The disruptions and entanglements this would cause would mean untold thousands of fish will need to be painstakingly removed with scoops and gaff hooks where nets can’t be used.

 

Source: Sydney Morning Herald

If this Armageddon scale clean-up was in fact proceeding on schedule, embattled politicians would have surely lost no time in having the flotilla of boats, the armies of workers, the convoys of dump trucks laden with carcasses and the squadrons of bulldozers burying the bodies shown on every news bulletin, just like we saw with the unforgettable pictures of the 1996 gun buyback.  So where are they? “Porcine aviation” is a likely apposite comparison.

These unplanned incidents should give us alarming pause at the still-active plans to release carp herpes virus into Australian rivers in the hope that this will eradicate these maligned river rabbits. Championed by Barnaby Joyce, the National Carp Control Plan has not yet been abandoned, despite its leader resigning last year  The same blithe assurances we have just seen with the Menindee mass kills have also been given about clean-up teams whisking away the millions of dead carp.

Yet in all that has been said about the herpes release plan, no detail has been provided about clean-up, beyond vague talk about paying local Dad’s Army groups to remove and dispose of dead fish. The task here would be more than daunting. The Lachlan river is 1,440 kilometres long, the Murrumbidgee 1,600 and the Murray-Darling, 2,507km.  Huge stretches of these are sparsely populated.

The unplanned clean-up “death rehearsal” in real world conditions we are now seeing shows that herpes cure for the carp problem may well be far worse that the concerns it now poses. To cap off the folly, last November, aquatic zoologists from the University of Sydney concluded that the carp virus plan would not work anyway, saying there was little evidence to suggest that repeated carp virus outbreaks would recur at a magnitude to counter the reproductive potential of surviving, resistant carp.

Disclosure: I am patron of the Australian Koi Association. See previous writing on this issue here:

Chapman S. Plan to kill carp with herpes could prove as foolish as the cane toad. Sydney Morning Herald 2018; May 4.

Chapman S. Carpageddon is coming, but we’re not prepared. Sydney Morning Herald 2017 Apr 11

Chapman S. Stinking dead fish portend major problem with carp herpes release. The Conversation 2017; Jan 18.

Chapman S. Should we release the deadly carp virus into our rivers and water supplies? The Conversation April 18, 2016