NT News: Weevils ready to feast

Publish Date:
21st October 2017

Read entire story and view pictures on NT News website

by Alex Julius

WITH so much happening on the Top End angling scene, I just wonder if I can get it all in and give it justice this week.

Firstly, and most importantly to myself and many 1000s of anglers, last Friday there was a monumental release of ravenous Cyrtobagous salviniae weevils in our iconic Four Mile Hole in Kakadu National Park.

This has been an ongoing saga of considerable proportions.

Over the last four years, I’ve flagged a few times the dire situation at Four Mile Hole which had been literally blanketed by the noxious South American plant salvinia.

Following very poor wet seasons, last year it was so bad that Kakadu park management had no option other than to close the lagoon for the whole year.

To its credit, park management reopened Four Mile in May this year following a record wet season which had flushed an estimated 90 per cent of the salvinia out of the lagoon and down to tidal waters where it undoubtedly perished.

But it’s been steadily growing back and destined to blossom across the lagoon again if another good wet doesn’t eventuate.

Now there’s light at the end of the tunnel thanks to the Gundjeihmi Aboriginal Corporation in Jabiru and its proactive Djurrubu Rangers.

The corporation was looking for a program for its female rangers and Senior Field Ranger, Margaret Rawlinson, and hubby, Head Ranger Matt Rawlinson, encouraged the Djurrubu Rangers to commence a large-scale weevil-breeding program. “Somebody had to do it,” Matt told me.

“The whole program’s important because, if the salvinia takes over the waterways, there’ll be no fishing, and so many people love coming to Kakadu to fish.

“Without support and help, there will be no fishing – we need to get rid of the salvinia.

“We have eight 12,000L tanks each holding 3000-4000 weevils.

“They have a 28-day breeding cycle and we release once a month timed to capitalise on this cycle when the eggs are about to hatch,” Matt explained.

Between 1000 and 1500 weevils were released into Four Mile Hole, which is many, many times more than previous releases.

Interestingly, they were released with living clumps of salvinia that were raked into existing salvinia patches in the lagoon; although you could see the darker salvinia poured into the water was not nearly as healthy looking as the thriving plants already on the water.

Also present for the release was Kadadu Head Ranger for South Alligator, Kharn Spokes, and NT Weed Management’s scientists Louis Elliott and Chris Parker.

It was great to see a unified approach to attacking the salvinia.

Matt said the next release on a Kakadu-salvinia-infested waterway will be early January, and there are big plans ahead for Four Mile.

“As soon as we can get in, we’re going to absolutely hammer it with weevils so they’ve got all dry season to clean it up,” he told me.

Now how good is that?