Native fish to benefit from auto tidal floodgate

A new fish friendly version of the humble floodgate has been installed at Shoalhaven Heads as part of a project designed to help bring back fish to local waterways.

Industry & Investment (I&I) NSW’s Aquatic Habitat Rehabilitation Conservation Manager Scott Nichols said access to the upstream environment will improve feeding and recruitment opportunities for native fish, as well as helping them avoid predators.

“Many native fish need to migrate as part of their life cycle - accessing estuarine environments to breed, with adults and juveniles returning to freshwaters to grow and mature,” Mr Nichols said.

“The auto-tidal gate allows for fish passage into the waterway upstream, when by default the old flapgate would have been closed.

“Normal operation of the flapgate is retained so that under high catchment inflows, water can escape to the estuary, while high tides are prevented from entering the upstream waterway.

“The gate operates with the action of the tide, with a float and hinge mechanism opening a smaller opening within the flapgate to allow water exchange and fish passage.”

The float controls a hinge that opens the smaller gate on a falling tide.

As the tide begins to rise again, the float controls the amount of time before the smaller gate closes again.

“Because tidal exchange is increased from the installation, water quality in smaller waterways, such as Shoalhaven Heads will improve,” he said.

“It’s also hoped fish population numbers will also rise as previously restricted habitat becomes accessible once again.

“Native species like mullet, bream, eels, Australian smelt, and gudgeon species are likely to benefit from these structures, especially where there is a large area of waterway upstream of a flapgate.”

All sites have their water levels monitored as part of the project.

Another site is planned for installation of an auto-tidal floodgate in the coming months.

The project is funded by the Federal Government’s ‘Bringing Back the Fish’ project and supported by Shoalhaven City Council and the Southern Rivers Catchment Management Authority.

Further reading

Floodgate management