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Alex's Column 6/1/22

If you haven’t heard, there’s been a series of minor to major barramundi fish kills in the Mary River system.

Mostly it’s been around barrages at Shady Camp, but also at Corroboree Billabong.

It’s not uncommon for fish kills to take place after the first serious rainfall on the big river floodplains.

Late in the year before the heavy rains start, lagoons tend to stratify, meaning there are different levels of oxygen according to depth.

The most-oxygenated water is near the surface.

However, when big rain events happen, all sorts of debris, rotting vegetation and soil gets washed into the lagoons, and the layers are churned up, so to speak.

Sometimes it means that the oxygen-rich layer near the surface mixes with less-oxygenated water and the upshot is that there’s not enough oxygen overall to sustain aquatic life, and a fish kill is the end result.

Most of the fish kills were reported by Helifish pilots who at this time of year take their clients to various barrages to fish from.

According to Helifish pilot, Jeremy Smith, there were 100s and 100s of dead barra at a couple of locations, including some very big fish.

It’s sad to lose so many fish, and no doubt the manmade barrages contributed… they have in the past.

Notwithstanding the fish kills, all that rain was most welcome, and a great start to the wet season proper.

I spoke to old mate Andy Ralph who lives in Kakadu.

Andy said: “While the Christmas monsoon rain was a nice present for Kakadu’s creeks and rivers, we quickly need some follow-up rain to fill the floodplains and get everything pumping.

“East Alligator River at Cahill’s Crossing was well over 4m on Boxing Day, but has now settled down to 2m, while Magela Creek, Kakadu’s barometer for healthy wetlands and good a barra runoff, had dropped to less than a metre.

“While fishing the Alligator Rivers is understandably patchy, it’s that time of the year when the creeks and culverts come into their own, with South Alligator culvert and Magela Creek Crossing on Oenpelli Road in particular firing up.

“There’ve been reports of anglers bagging their legal limit on several occasions.

“But beware of crocodiles… big salties have been seen hanging around to also catch a barra, so stay Crocwise and never enter the water,” Andy rightly cautioned.

I also spoke with Jason Rogers who’s been wetting a line all over the place lately.

“Bynoe has been fishing really well, and not only for barra but also good goldies on lures,” Jason reported.

“My wife Melita and I snuck in some early runoff fishing and caught some nice barra at a couple of locations.

“The best fishing was at Corroboree just before the rains; we were catching 50-60 barra a day, including some nice ones,” Jason told me.

“But there was definitely a stench in the air, and I’m not surprised that there was a fish kill at Corroboree.”

Melita McKinnon fished with hubby Jason Rogers for some early runoff action.

This is one of several fish kills that occurred on the Mary River system.

Graham Tomson with two big barra that perished most likely after depleted oxygen levels following the recent heavy rains.


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