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ABC News
14-05-2025
- Science
- ABC News
Mary River cod turns the tables on one of its biggest threats by eating them
A critically-endangered fish could be turning the tables on one of its biggest threats by eating them. In the Mary River, stretching 291 kilometres from the Sunshine Coast to the Great Sandy Strait, the invasive pest species tilapia have been an ongoing problem. They compete for food and habitat, as well as eating the eggs and juveniles of the river's endangered species such as the "bum-breathing" Mary River turtle, Australian lungfish, the white-throated snapping turtle, and the Mary River cod. During a routine survey last month by Burnett Mary Regional Group (BMRG) conservationists tilapia remains were found in the mouths of two Mary River cod. Its chief executive Tom Espinoza said they were not surprised by the finding, even documenting a cod eating a tilapia, but were excited to finally have evidence of the predation. "There was always the hope and suspicion that they [cod] were eating everything," Mr Espinoza said. "One of the cod that had the tilapia in its mouth would have been about 80cm long, and the tilapia was close to 40cm long, so they can eat a fish almost half their size — which is great. "It's provided a lot of hope for people that are invested in healthy cod populations across the board." While the Mary River cod is considered an apex predator in the river system, it now occurs in less than 30 per cent of their former known range. Griffith University's Professor Mark Kennard, who works with the National Environmental Science Program, said the cod would eat a lot of different types of large animals. "We've collected cod that have regurgitated possums and lizards so they are a large, top-level predator in freshwater systems," Professor Kennard said. He said researchers believed tilapia would be a food source for the cod. "But there hasn't been much documented evidence of our large-body native species actually eating non-native fish like tilapia," Professor Kennard said. Environmental groups, researchers and traditional owners have been co-ordinating conservation efforts along the Mary River for decades. Professor Kennard said tilapia had increased in abundance in the Mary River, especially since the last big flood in 2022. Tilapia are so successful as an invasive fish that eradication is not considered possible with the species found in 26 of Queensland's 67 catchments. "Part of the solution is things like enhancing benefits for native species," Professor Kennard said. Professor Kennard was part of an extensive mapping of the unique river system, which runs south to north. It has led to innovative conservation ideas such as cod logs and tilapia fertiliser. "There's still a lot of work to do. The threatened species have not come back as much as we would like," he said. "They're still rare and restricted in certain parts of the catchment despite 30 years of on-ground work doing restocking of fish, that kind of thing. "So I think we do need to be making a concerted effort now and in the coming years." Mr Espinoza said the finding would "increase our resolve" to put in place short and long-term solutions for managing invasive species in the delicate system. "Hopefully in 10, 15, 20 years' time we've got a population of large cod that can do the rest of the job themselves," he said. "It's a real natural, sustainable solution."
ABC News
23-04-2025
- Science
- ABC News
Nests of endangered 'bum-breathing' white-throated snapping turtles found in new Baffle Creek habitat
A newly discovered population of endangered turtles found only in a small collection of Queensland waterways is not only surviving but seems to be thriving. Researchers have discovered several breeding sites of white-throated snapping turtles at Baffle Creek, about 400 kilometres north of Brisbane. The turtles, Elseya albagula , were thought to only live in the Mary, Burnett, and Fitzroy Rivers in Queensland and are known for their unique trait of "bum breathing" — absorbing oxygen through the anus. Researchers are optimistic about the white-throated snapping turtle species' future. ( Supplied: Burnett Mary Regional Group ) The catchment areas stretching from the Sunshine Coast to Rockhampton offer clear, well-oxygenated river systems with submerged boulders and log jams for shelter and sandy banks for nesting. Two years ago, researchers with the Burnett Mary Regional Group (BMRG) were shocked The Baffle Creek catchment is a long way from the established populations in the Mary, Burnett, and Fitzroy Rivers. ( ABC News ) They have now found five more turtles and several nesting sites. "The habitat is now facilitating breeding — that's really exciting, really positive," research manager Sydney Collett said. Ms Collett said their "two-phase incubation style" put the animals at risk because eggs were laid in winter and did not hatch until summer. Sydney Collett is part of the group that found the new population in Baffle Creek and the nesting sites. ( Supplied: BMRG ) "That means that for four, five, six months, they're really at risk of [predators] getting to them," she said. "The chances of them surviving the nesting period are really low. "They have similar rates to the sea turtles in that about 90 per cent of the nests that they lay in a season will be predated, trampled, or flooded." Ms Collett said it was unusual for clutches to survive without human intervention. "Maybe they just don't have foxes with very good smell or vision [at Baffle Creek]. I'm not entirely sure." Around 90 per cent of nests will be destroyed, thereby limiting hatchlings' survival rates. ( Supplied: Burnett Mary Regional Group ) 'Robust and resilient' Marilyn Connell has been involved in conservation work for freshwater turtles in the Mary River for 20 years. She said another reason why white-throated snapping turtles were endangered was that hatchlings took 15–20 years to mature. Marilyn Connell says discovering more freshwater turtles is positive news. ( ABC Wide Bay: Lucy Loram ) "There are lots of opportunities — like 20 years — for something to go wrong," she said. Ms Connell said finding new nests in new locations was positive news. "It's quite a special turtle species and we're really lucky to have it," she said. "If we didn't protect nests, which we can do quite successfully now, the recruitment would just be basically next to zero. "Even though their numbers are in decline, they are still very robust and resilient. They seem to be able to hang on even at much lower numbers." Researchers take genetic samples to learn more about the new population. ( Supplied: Burnett Mary Regional Group ) New location still a mystery Ms Collett said it was still a mystery how the population ended up in the Baffle Creek catchment in the first place. "It's hard to figure out how they would have gotten there naturally because they'd be walking several hundred kilometres if they were coming from another catchment," she said. The group found nesting sites and new turtles in the Baffle Creek catchment in March 2025. ( Supplied: Burnett Mary Regional Group ) Ms Collett said it was possible the turtles had been raised as pets and released into the catchment. "But there have been extensive surveys of the Baffle catchment, and they've never found them before," she said. " Maybe they weren't so critically endangered as we originally thought. " ABC Wide Bay — local news in your inbox Get our local newsletter, delivered free each Thursday Your information is being handled in accordance with the Email address Subscribe
