A fishway close to Ingham’s town centre is the newest addition in a project that’s helping more than 100 species of fish – including barramundi, mangrove jack and jungle perch – to breed up in Wet Tropics waterways.

Terrain NRM and Catchment Solutions recently completed the 250 metre fishway at Gedges Crossing which will help fish to move through a weir. The structure is one of five fishways that have recently been built and one of 18 projects removing barriers to fish in the Murray and Herbert river catchments between Tully and Ingham.

Terrain NRM’s Deb Bass said other solutions have included bed-level creek crossings to replace causeways, culvert modifications and the removal of several creek crossings.

“We’ve also been working on invasive weed and feral pig control in these areas, and revegetation in an area where fish passage works were completed.

“This newest fishway is a curved rock ramp that’s at the side of Gedges Crossing on Pump Station Road, and is designed for lower flow conditions when smaller fish can’t get over the weir.

“It’s opening up more than 50km of upstream habitat to many different fish species.

“Fishways slow the water and create resting pools. The idea is juvenile fish can move upstream a couple of metres, then take a rest, then move up further and rest and so on.”

Terrain NRM has partnered with Catchment Solutions and OzFish Unlimited on the Fish Homes and Highways project, which is funded by the Australian Government’s Reef Trust program.

All the fishways were constructed in the dry season and the last one was completed just weeks before Cyclone Jasper crossed the Far North Queensland coast, bringing flooding rain.

“We’d already seen hundreds of empire gudgeons and shrimp species using the fishway at Lagoon Creek, moving up with the tide,” Deb said.

“OzFish Unlimited will be monitoring the fishways over the next six months to see the number and type of native fish moving through them.”

The construction phase followed extensive surveying in the Herbert and Murray River catchments. More than 3500 potential fish barriers were identified, leading to short-listing and on-ground inspections of over 300 sites to prioritise work based on the landscape, landholder willingness, accessibility, cost and development approvals.

More than 22,000 pond apple trees have been hand treated along creeks in the Upper Murray region this year in an effort to blitz the invasive species that is being spread by flood. Following the treatment of 115 hectares last year, ground teams have expanded their search to take in Corduroy and Boar Creeks in the Murray catchment.

A weed of national significance, pond apple was introduced to Australia in 1912 as grafting stock for commercial custard apple crops and is now a major environmental weed in the Wet Tropics. Removal work is part of Terrain NRM’s “Fish Homes and Highways” project and is funded by the Australian Government’s Reef Trust.

Terrain’s Deb Bass says the spread of pond apple is especially worrying for its potential to impact mangroves.

“Pond apple forms dense stands in swampy areas and is capable of replacing mangrove or freshwater wetland ecosystems if left unchecked. We’ve treated approximately 150 hectares this year.”

Seeds are usually spread in big quantities in flood waters so the ground team is working from the upstream reaches out toward the coast. Feral pigs are also proving to be prolific seed spreaders.

“Whilst pond apple is not considered good to eat by humans, feral pigs think the fruit is pretty tasty.  The weed team are guaranteed to find big clumps of pond apple when they follow the pig tracks into the forests,” said Ms Bass.

The silver lining is that the seed bank is only viable for two years. Some weeds have seeds that will germinate many years later, but pond apple can be effectively controlled by treating the same area two years in a row.

Ms Bass said it is critical that weed management programs are properly funded and managed.

Native fish will be able to access more habitat for more of the year, when eight of the highest priority fish barriers in the Murray and Lower Herbert catchments are remediated later this year.

These catchments are a diversity hotspot for diadromous freshwater fish species – which means the adults spawn in estuaries, and the juveniles migrate upstream where they mature into adults.

After extensive surveying work, hundreds of barriers preventing fish movement were assessed and prioritised for remediation work as part of the Fish Homes & Highways project being delivered by Terrain NRM and funded by the Australian Government’s Reef Trust.

Now, design work is being finalised with one barrier set for work to start shortly.

Trent Power from Catchment Solutions is a specialist in fish passage designs. He says that working in creeks and rivers is difficult at the best of times.

“Work has to be done in dry season when the water flow is at its lowest, and it needs to be complete before wet season starts which can potentially wash a remediation site away if it’s unfinished.”

One of the remediation sites is a rock weir on the lower part of the Herbert River, known as Gedges Crossing, which cuts off 250km of potential upstream habitat for small fish during certain parts of the year.

“Things that stop fish aren’t necessarily a barrier all year round. For instance, the water level at Gedges Crossing only drops enough to create a barrier in the late wet and through the dry season. But those really small fish like baby barras and empire gudgeon certainly can’t get through when flows are low. They can’t jump, and at this size their swimming ability is poor. Anything more than a 10-20 cm drop can stop them in their tracks” said Trent.

A rock ramp fishway design is being considered for the weir. This is a common solution to barriers under three metres in height.

Rocks are strategically placed to influence the flow of the water in a way that makes it possible for a small fish to swim upstream. If you think of it as an underwater staircase, the fish can rest on top of each stair before tackling the next.

Cane growers in the Murray River catchment have help at hand to address productivity constraints.

Sugar Research Australia is working with growers as part of a new project to support the industry’s long-term sustainability.

Project Manager Cathy Mylrea said the project would include extension officer support, financial incentives, demonstration sites and field days with practical demonstrations in the paddock.

She said previous programs had targeted specific practices to improve nutrient management.

“We want to find out what constraints growers have and what they see as the issues, and then support them to address those. For example, if a grower has blocks that are continually low-yielding, we want to work together to figure out why,’’ she said. “It might be due to soil type, drainage issues, or pests and disease. When we know what the root cause is, we have an opportunity to provide services or financial support to address the issue.”

The project will include grower support to create whole-of-farm management plans and to update existing nutrient management plans.

Increases in farm efficiencies and productivity will also bring reef water quality benefits.

James Donaldson from Wet Tropics Waterways said the Murray River catchment had made good progress towards dissolved inorganic nitrogen reduction targets, as reported in the recently released Reef Water Quality Report Card 2020.

“These results reflect the hard work being undertaken by the agricultural industry, and farmers should be congratulated,’’ he said. “While progress towards targets is positive, we know we’ve still got work to do.”

The project in the Murray catchment is part of a broader “Mobilising the Mossman and Murray” project, which is funded by Terrain NRM through the Australian Government’s Reef Trust.

Can a small fish navigate the Murray and Herbert rivers and tributaries? That’s the basis for a new project to remove barriers preventing juvenile fish – including barramundis and jungle perch – from moving upstream to nursery grounds.

More than 3500 potential fish barriers have been identified in the Murray and Lower Herbert basins and a field team is now inspecting hundreds of them to prioritise work at causeways, culverts and areas with weed and feral pig problems.

The new Fish Homes and Highways project is being delivered by Terrain NRM to address threats to nationally significant wetland areas and coastal ecosystems.

Terrain’s Deb Bass said constructed barriers like weirs, causeways, pipe and box culverts could stop freshwater fish species that spawn in estuaries from safely moving upstream to wetlands to mature into adults. Not being able to reach nurseries to mature impacted fish populations and diversity.

She said constructed barriers were just one of the challenges for fish.

“Aquatic weeds like hymenachne can build up, creating a physical choke as well as a chemical barrier where there’s simply not enough oxygen left for fish to move through safely. Add feral pigs to the mix, which tear up waterways and create physical barriers, and you have a serious problem.

“Impacted fish include iconic species like jungle perch, barramundi, mangrove jack and tarpon.”

Experts have used high resolution imagery and desktop analysis to identify the potential barriers in the Murray and Herbert catchments. Three hundred barriers, considered the top-priority ones, are now being physically investigated by a field team.

Ms Bass said other factors including stream movement, flow rate, distance from the coast, physical specifications of barriers, and ease of modification are then considered.

“This way we can find out what interventions will have the best bang for buck as well as the best ecological outcomes for fish,” she said.