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From cane paddock, to barramundi-filled wetland.

Wetlands constructed on sugarcane farms two decades ago are helping to boost fish populations in Tully’s freshwater systems

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Surveys found that 36 native fish species and three invasive species now inhabit these wetlands, including popular migratory fish like barramundi and mangrove jack.

Research has found the lagoons are capturing and regulating floodwaters, supporting native fish and improving cane productivity.

Dr Nathan Waltham, a scientist at James Cook University’s Tropwater Research Centre, says surveys found 36 native fish species and three invasive species now inhabit these wetlands, including popular migratory fish like barramundi and mangrove jack. 

“Good connectivity between freshwater and saltwater is necessary for the life cycle of many fish,’’ he says. “Finding these migratory species means fish are using these lagoons as nurseries, as well as moving across the floodplain during the wet season to spawn in marine waters.”  

CANEGROWERS’ Peter Lucy said the farmers involved were proud of the outcomes and well aware of the important role the lagoons have as fish habitat. 

“The wetlands have been a win-win outcome for the growers involved. Soil excavated during construction can be used to improve low lying areas, and the wetlands create all year-round habitat and filtration systems,” he said.  

Well-designed and constructed wetlands in areas of boggy, low-production farmland can play an important role in supporting the growth of fish species and improving water quality.    

Unfortunately, many wetland areas in the Wet Tropics have been cleared or modified. The good news is more projects are using constructed wetlands to improve reef water quality. 

Dr Waltham says these wetlands are vital to help fulfill the functions that impacted natural wetlands can no longer perform.

“We need wetlands. They are essential for protecting our coastline, buffering against flood waters, contributing to fisheries’ productivity and acting as powerful carbon sinks to help tackle climate change.” 

Tropwater’s Dr Adam Canning, who co-led the research, says 29 wetlands were constructed across 10 cane farms, with farmers taking responsibility for maintenance.    

“The farmers are really proud of these lagoons and what they have accomplished in supporting fisheries and biodiversity more generally, and rightly so,” he says.  

“Tully is one of North Queensland’s most sugarcane-dominated catchments. There’s a lot of work being done in this region and farmers are motivated to be involved in more initiatives to help improve water quality and to support biodiversity.”  

Wetland fast facts 

  • Wetlands include swamps, marshes, mudflats and mangroves – all of which are important parts of our coastal ecosystems that filter water flowing off the land to the reef.  
  • Queensland has more types of wetlands than any other state in Australia. 
  • Since colonisation, many wetland areas have been modified for agriculture, industry and urban development.  
  • Almost 50% of swamps and 40% of river wetlands have been cleared in the Wet Tropics.

Wetland research was funded through the Australian Government National Environment Science Program Tropical Water Quality Hub.  

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