TIME BOMB: The drought and bushfires have set up the Richmond and Wilsons rivers for a potential major fish kill.
TIME BOMB: The drought and bushfires have set up the Richmond and Wilsons rivers for a potential major fish kill.

Flooding spells disaster for thousands of local fish

AND SO it begins.

Have a crack at the lower estuaries this weekend if it's safe to do so, because in a week's time, local fishing will have radically changed.

A warning of moderate flooding for the Wilsons and minor flooding for the Richmond rivers will lead to a rapid reduction in the size of the estuary and a drastic change in conditions for many thousands of fish.

Let's hope they can get away before the bad runoff gets them.

Fish in the lower estuaries have the best chance of survival and there'll be some good catches over the next few days if your trusty raincoat has survived two years of lack of use.

Sunday's full moon will bring higher than usual tides, thanks to a developing trough crossing into the Coral/Tasman sea, and a blocking high near Tasmania.

Gathering runoff from the lower Richmond/Wilsons catchment and whatever flood peak is generated will also affect tides and tidal run.

The Richmond from about Wardell downstream will have plenty of life for now and the flathead, bream, whiting and school jew that have been frequenting the area can still be targeted.

The Ballina rock walls should fish well and there'll be plenty of hopefuls joining the usual diehards on the breakwalls chasing big mulloway.

As the water murks up and the big predators get to work on the sheltering mullet, this is a great time to try a lure. But throw it in the wrong place and you'll cop a serve from an angry bait fisho.

Don't forget the long gaff and the grippiest footwear you can find.

Runoff threats

THE local Ballina runoff will mainly comprise "macadamia mud" from the red soils of the Alstonville Plateau, through the Tuckean and Emigrant catchments.

Longtime Ballina locals will remember that until about a decade ago, North Creek used to be the first to clear after a flood. What happened? Who was responsible? Can it be fixed?

If you observe fish kills, call the NSW hotline on 1800 043 536.

Over the big drought, saltwater species have been regularly encountered as far upstream as Lismore on the Wilsons and just downstream of Casino on the Richmond.

Flathead, school mulloway, bream, luderick, trevally, garfish, mullet and many more have spread out as food stocks proliferated in abnormally clear and brackish water.

Conditions led to recreational and commercial catches unseen for 20 years, including marketable hauls of large school prawns.

Now it's a matter of hoping the majority of the fish can escape downstream before encountering one of three major dangers.

They can choke to death within minutes if they are unable to escape this toxic, anoxic runoff.

The initial anoxic runoff threat is likely to be from bushfire ash - a minor threat from the Nightcap fires in the upper Wilsons catchment and a massive threat from the Myall Creek Rd fire, which devastated almost the entire Bungawalbyn catchment.

What comes out of Bungawalbyn could well seal the fate of fish upstream and downstream.

If that first pulse of bushfire runoff isn't too bad, it's what happens next in the backed-up agriculture drains between Coraki and Wardell that is critical.

This water is stripped of oxygen by unique local soil chemistry, aided by respiring bacteria that help rot flooded terrestrial vegetation, especially if we get hot, sunny weather after the rains.

When the floodgates open, out comes the blackwater and everything in its way is dead or dying within the day.

This is the scenario that led to massive fish kills in 2001 and 2008, on a scale unprecedented in Australia and requiring the river to be closed for months.

It's only after the flood peak has gone through and water levels begin to return to normal that the slow-burning death of acid runoff does its job, as pH numbers sink to levels that can eat through oyster shells and burn the protective slime layer on a fish to allow red spot ulcers to thrive.


Vic brainwave

THE Victorian Fisheries Authority has set up a tag-recapture competition to encourage rec fishers to return to fire-ravaged parts of East Gippsland and north-east Victoria to boost the sagging tourism industry.

The VFA has already begun tagging up to 1000 fish in the rivers and lakes of East Gippsland and north-east Victoria for the competition, which will run for a year.

The first 10 people to catch a fish with a golden tag and report it will win $10,000 in prizes.

All tagged fish caught and reported thereafter will be worth $2000 each for the duration of the promotion.

Tagged species include black bream, dusky flathead and King George whiting in East Gippsland, and in the north-east, Murray cod, brown trout and rainbow trout.

The competition will bring people back to towns like Mallacoota, Cann River, Bemm River, Orbost, Marlo, Lakes Entrance, Lake Tyers, Omeo, Dartmouth, Mitta Mitta, Corryong, Tallangatta and Bright.

A starting date will be set in consultation with Visit Victoria.

The VFA is probably the most proactive manager of rec fisheries in the country, with a strong presence on social media and a staff eager to react to public feedback.

The authority is also strongly campaigning to hit a target mark of one million rec fishers in Victoria.

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