Fish barriers impact FNQ’s fish stocks

FNQ’S FISH STOCKS IMPACTED BY BARRIERS

19 JULY 2023

Thousands of fish barriers – from weirs to causeways and culverts – are affecting native fish populations in the Wet Tropics and impacting commercial and recreational fishing.

A recent study in the Daintree, Mossman and Barron River estuaries identified more than 1600 potential barriers for fish, and earlier studies of the Herbert and Murray River estuaries identified more than 3000.

Terrain NRM’s Lana Hepburn said results have led to work at 18 sites in the Herbert and Murray catchments to modify causeways, retrofit fish passageways and control weeds, but a lot more work needs to be done.

The natural resource management organisation is calling for more funding to improve fish populations across the Far North.

“More than half of Australia’s fish species, including barramundi and jungle perch, spawn in estuaries and need to move upstream to breed and complete their life cycles,” Ms Hepburn said.

“As small fingerlings, it’s impossible to get past road crossings and weirs, dams, drop-offs and fast-flowing water. Even weeds and a lack of light can impact fish migration.”

Ms Hepburn said fish barriers were identified through geospatial mapping and aerial photography, before field trips to do the ‘ground truthing’.

So far, about 200 of the 1600 sites identified in northern waterways have been visited by a team from Terrain NRM, Wet Tropics Waterways, Catchment Solutions and the Dawul Wuru Aboriginal Corporation’s Yirrganydji Land and Sea Rangers.

“About 60 per cent of the sites we’ve visited have significant barriers to fish migration,’’ she said. “The goal is to open up as much upstream habitat as we can.’’

Terrain NRM is prioritising barriers for fixing, based on the best return on investment. At this stage, there is no fish barrier funding for the Daintree, Mossman and Barron catchments beyond the barrier identification project.

“Our priorities are usually the sites closest to an estuary and on larger waterways with more riparian areas,’’ Ms Hepburn said. “The closer a barrier is to the coast, the more upstream habitat it is blocking. The distance between each barrier is important too.

“These days, infrastructure like bridges and culverts are better designed to allow for fish passage. But with older infrastructure, we are looking at options ranging from building rock ramp fishways to replacing pipe culvert causeways with bed-level crossings or retrofitting other fish-friendly solutions.”

Dr Greg Vinall, aquatic ecologist and Chair of Wet Tropics Waterways, said fish populations and fish diversity are an important indicator of waterway health and are part of the annual Wet Tropics Waterway Health Report Card.

“We are building a more comprehensive picture of the impacts of fish barriers across the region,’’ he said. “Studies have identified and prioritised barriers in the Herbert, Murray, Daintree, Mossman and Barron estuaries. Now we need to secure funding to complete the remaining catchments – Trinity Inlet, Mulgrave, Russell, Johnstone and Tully – and to get to work fixing some of the highest priority barriers that have the most impact on our fish stocks.

“By removing barriers, we enable native fish to restock and become self-recruiting. More fish moving up into the headwaters will make our wetlands and freshwater environments healthier and, in turn, make our commercial and recreational fishing more sustainable downstream.”

The ‘Connecting Wet Tropics Waterways for Sustainable Recreational Fishing’ project is funded by Terrain NRM through the Australian Government’s Fisheries Habitat Restoration Program and the ‘Fish Homes and Highways’ project is delivered by Terrain NRM through funding from the Australian Government’s Reef Trust.

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