Thursday, August 18, 2022
Renewable Energy News

Australian-first eel bypass on northern Tasmania’s Trevallyn Dam to help downstream migration – ABC News

By Staff , in Hydropower , at July 29, 2020

A new $1 million eel bypass in the wall of a Tasmanian dam will soon give freedom to short-finned eels that often get stuck, but commercial fisherman say it will also result in less international eel exports from the island state.

The bypass — essentially a hole with a chute drilled through Trevallyn Dam at Launceston — has been constructed by Hydro Tasmania and is an Australian first for eel sustainability.

The hole will be closed during winter and water will only flow during the summer eel migration season.

Aquatic scientist David Ikedife said researchers spent two years tagging eels and tracking their behaviour to find the perfect spot to build the bypass.

“It’s been really carefully engineered, looking at velocity and pressure changes, so it’s been designed to be really fish friendly,” Mr Ikedife said.

Short-finned eels migrate from Tasmania to the Coral Sea off the coast of Queensland from December to April each year.

Mr Ikedife said the baby eels then travelled back to Tasmania in currents.


In the 1990s, an elver ladder was developed at the Trevallyn Dam to help baby eels climb upstream.

But that is where many got stuck and struggled to migrate downstream.

“The problem was they didn’t really have anywhere to go except for over the dam wall during spills or through the [Trevallyn Hydro] power station and the turbines,” Mr Ikedife said.

‘Look at pulling back on exporting’

But the eel bypass has caused complication for commercial eel fishers.

Shaun Finlayson above Trevallyn Dam wall on a sunny day
Shaun Finlayson and his family are no longer able to fish where the eel bypass has been constructed.(ABC Northern Tasmania: Manika Champ)

Shaun Finlayson from Tasmanian Eel Exporters said since work began on the bypass, his family’s business had been unable to fish in the area near the dam wall.

A Hydro Tasmania spokesperson said an agreement was being worked through with commercial eel fisherman “so they can operate safely within this exclusion zone and those discussions are ongoing”.

Mr Ikedife said commercial fisherman can still catch eels further upstream in Lake Trevallyn, but Mr Finlayson said that was unviable.

He said his family usually caught between 10 and 15 tonnes of eels annually in the area that is now off limits.

“They’re the prime eels we send overseas, so we’ll probably look at pulling back on exporting overseas and focus more on domestic markets.”

A waterfall of water rushing down a concrete dam wall surrounded by bushland
The eel bypass looks like a small waterfall rushing down the Trevallyn Dam wall.(ABC Northern Tasmania: Manika Champ)

Eels caught commercially in Tasmania are usually sent to Asia to be used in food.

Hydro Tasmania will monitor how many eels use the bypass through imaging sonar equipment.