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Hungry turtles can clean up waterways

Cleaning up the Murray-Darling river system and eradicating carp could soon be the work of freshwater turtles following research from Western Sydney University, which showed the scavenging of hungry turtles can clean up waterways up to five times faster than natural decomposition.

Research found that reintroducing turtles to the river system could dramatically improve water quality, and Western Sydney University ecologist Ricky Spencer told ABC Online that turtles can be particularly useful in cleaning up waterways after fish-kill events.

"They love to eat and are always asking for food like fish and meat so they are really important in terms of cleaning up rivers of any dead fish," Spencer said.

Furthermore, the research found that reintroducing turtles could also help save costs associated with the National Carp Control Plan, which currently invests in the placement of carp herpes as a biological control agent.

"The initial release of the carp herpes virus may actually cost up to $2 billion to take the fish out of the water," Spencer said.

"We are now seeing that scavenging is performing a role that potentially would cost a lot of money to do if we wanted to clear the carp mechanically or go out with boats and nets."

Increasing turtle populations in the river system could help to regulate the river's nutrient levels, Spencer said.

"What would normally happen is that bacteria would break the carp down and release the nutrients into the water column, which can trigger things like blue-green algae and that's potentially what causes our rivers to turn green," Spencer said.

"Turtles regulate the carp, so instead they'll compete with that bacteria and nutrients and they'll store it and then release it in a more regulated fashion."

Although freshwater turtle species - the long-neck turtle, the broadshell turtle and the short-neck turtle - are native to the Murray-Darling river system, numbers have been declining due to predators and water-quality issues, University of Sydney PhD student Claudia Santori said.

"These species have declined considerably over the past few decades, so my interest was really to find out what the ecosystem is going to lose if these species go extinct," Santori said.

"After the fish kills, there were obviously some major impacts on water quality such as decreases in ammonia and other nutrients.”

Carp make up almost 90% of the river's biomass and have had a destructive effect on the river’s ecosystem and water quality.

Spencer said introducing more turtles to the river would require community involvement in order to make the project a success.

"Our '1 Million Turtles Program' is where communities can be actively involved in protecting turtle nests and creating turtle islands," he said.

"We're really trying to enable communities to do it because people love turtles and we want to harness that so we can actually start restoring our native turtle populations."