Once extinct Murray crayfish on track to ‘thrive again’ in SA’s River Murray

In short:

A second group of Murray crayfish has been released into the river in South Australia, including two females carrying around 2,000 eggs each.

Almost 300 crays in total have been released as part of an ongoing project to re-establish the protected species locally.

What’s next?:

The crayfish movements will be monitored ahead of future releases using tracking devices.

The Murray crayfish is on track to become a thriving species once again in South Australia, one year on from its successful re-introduction to the river system.

200 crayfish were released in a secret Riverland location last year as part of an ongoing Nature Glenelg Trust and Murraylands and Riverland Landscape Board project.

Now, another 80 have joined them to continue growing the species’ population after a 40-year period of extinction in the state. 

The species is protected in SA and threatened in Victoria, NSW and the ACT.

Aquatic ecologist Dr Nick Whiterod said the chances of the crayfish naturally moving back into the SA river system were slim.

“The nearest population is probably 300-400km upstream and they’re a big slow-moving animal,” he said.

“So, they’re not coming back here without the assistance that is reintroducing them.”

He said it had taken about 10 years of work to make sure the project was “a sound thing to do”.

“We’re very confident that the spot they’re going in is suitable for them and they can survive there,” he said.

Releasing the next generation

Nature Glenelg Trust senior aquatic ecologist, Dr Sylvia Zukowski, said it was “pretty exciting” to help release two “berried” females into the river system for the first time in 40 years.

The two females were each carrying thousands of eggs.

“They’ll build little burrows in [muddy banks] or find a burrow and go hide out while they’re in berry,” she said.

“When their eggs hatch, the little babies will stay on the mum for another couple of months.

“After that she’ll come out the river, shake them all off, get rid of them, and she’ll run back in and the little babies can deal with themselves.”

In an Australian-first initiative, many of the released Murray crayfish have been fitted with radio tracking devices.

Data collected from 30 crays tracked from the first release has provided insight into their behaviour and movement.

It showed all 30 had a 100 per cent survival rate.

“We’ve been able to detect their movement occurring so we know they’re surviving,” Dr Whiterod said.

“If we can release them over multiple years and get as many individuals as possible back into the wild, it gives them the best chance of establishing a population here and being self-sustaining.”

Cultural significance

The Murray crayfish is a totem for the local First Nations people.

Ngarrindjeri men Brenton Rigney and Roy Giles said re-establishing the species was a culturally significant project.

“It’s good to know that people are organising this,” Mr Rigney said.

“They can release crayfish back into the rivers down this neck of the woods and for everybody to enjoy it, for our kids’ future, you know, that’s pretty nice.”

Roy Giles said it was incredible to see them again after growing up along the River Murray.

He said he remembered eating them with his family as a child.

“I think my children will spin out to see them, when they grow up a bit,” he said.

“I’d like to thank the people who have done this … it’s been really good to help them out [with the second release].”