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Native congolli fish thriving in Lower Lakes and Coorong after brush with extinction

By Jessica Schremmer, Thursday June 25, 2020 - 12:35 EST
ABC licensed image
Native congolli fish need to spend parts of their lifecycle in fresh and salt water. - ABC licensed

Congolli fish faced extinction during the Millennium Drought, but a new survey has found the native species to be thriving in the Lower Murray.



South Australian Research and Development Institute (SARDI) research scientist Chris Bice said the fish population was once again dominant in the Lower Lakes, Coorong and the Murray River.

"They have bounced back fantastically well," he said.

"We now see around 60,000 or more congolli fish in our annual standardised monitoring, and up to 200,000 in some seasons."

Congolli are small-bodied native Australian diadromous fish that need to spend different parts of their four to five-year lifecycle in freshwater and saltwater.

Adult female congolli fish live in freshwater, but migrate downstream to spawn in the ocean.

Mr Bice said the juvenile population then migrated into the Coorong and upstream into the Lower Lakes during spring and summer.



But during the Millennium Drought, water flows and the connection between the Lower Lakes, Coorong estuary and the sea dried up, preventing the fish from migrating.

"There was no water, and no water could be discharged to the Coorong," Mr Bice said.

"The barrages were completely shut, the females that were attempting to migrate downstream to their spawning grounds simply couldn't do so.

"These adult females were stuck in freshwater not being able to spawn and many of these fish were around four to five years of age at the time.

"So, it really was quite concerning for the persistence of the species in the area."



Fish help restore ecosystem health

Commonwealth Environmental Water Holder Jody Swirepik said her team focussed on restoring environmental water flows and recovering species like the congolli fish after the Millennium Drought.

"We have water that has been secured under the Murray-Darling Basin Plan and part of the aim of that water is to try and make sure that flows do actually flow until the end of the system," Ms Swirepik said.

"So, the challenges have been really keeping that constant connection between the Lower Lakes and the Coorong.



"What we found in the last five years, it has almost all come of environmental water that has maintained that connection, so that is a great affirmation that we have been on the right track."

Mr Bice said congolli fish were also an important food source in the aquatic food webs in the Coorong and its recovery was significant for the entire ecosystem.

"They are both predators themselves and prey for other animals," he said.

Congolli are key prey for for the mulloway, an important recreational and commercial fish of the Coorong, and also for waterbirds such as pelicans.


- ABC

© ABC 2020

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