Craig Robertson runs River Cruise CQ scenic tours and is finding the jellyfish are a problem when idling.
Craig Robertson runs River Cruise CQ scenic tours and is finding the jellyfish are a problem when idling. Steph Allen

EXPLAINED: Blooms of jellyfish in the Fitzroy River

FISHERMEN - and women - in the Fitzroy River will have noticed there have been a lot more jellyfish in the water in the past few months.

The jellyfish are seen in the main area of the river around the bridges and just look like little white blobs littered in the water.

Queensland Museum's Collection Manager of Sessile Marine Invertebrates, Dr Merrick Ekins, said it was quite common to see jellyfish around the waters at this time of year.

"A lot of time it happens around summer," Dr Elkins said.

Strong north easterly winds and waves can push them up into estuaries, along with strong swells and high tides.

Blooms can also occur from over-fishing.

 

BRING ON RAIN: Craig Robertson says the jellyfish numbers are the highest he has seen in 10 years.
BRING ON RAIN: Craig Robertson says the jellyfish numbers are the highest he has seen in 10 years. Steph Allen

In flood times and the first rains of the season, nutrients can be washed out.

Jellyfish also breed easily and small numbers can grow into big numbers "very quickly".

Craig Robertson, who runs River Cruises CQ scenic tours in the Fitzroy River, says he is having a lot of trouble with them.

They have been getting stuck in the intake of his motor because they are "just so thick at the moment".

 

Jellyfish bloom hanging around the boat.
Jellyfish bloom hanging around the boat. Craig Robertson

He can't idle his boat or sit still as they still get blocked up.

"I just have to make sure I am moving forward," he said.

While he only launched the cruises business earlier this year, Mr Robertson has been fishing in the river for the past 10 to 15 years.

He says the massive spike in the jellyfish bloom is "the worst he has ever seen".

Last weekend was also really bad, he said.

They have been thick this year and have been growing since the rains stopped in March or April, he said.

Part of the issue he said is that jellyfish don't survive in "brackish" water.

 

Jjellyfish blooms hanging around the boat.
Jjellyfish blooms hanging around the boat. Craig Robertson

Brackish water is water that has more salt than fresh water.

Jellyfish live in the salt water, and given there hasn't been much rain recently, there is no fresh water.

"As soon as one of the big storms come through it will wash them out," Mr Roberston said.

The jellyfish also feed on the prawn in the river and there is an abundance of them at the moment, he said.

The main area they are hanging around is what is called the "town reach" - the two to three kilometre reach where the CBD is, the bridges, and the railway line.

The Morning Bulletin understands the type of jellyfish spotted is "jelly blubber", the most common jellyfish found along the east coast of Australia.

Mr Robertson also confirmed they are the "non-stinging ones".

"They are no issues to anyone, they won't hurt anyone," he said.



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