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Hole in dam wall saves epic eel journey

Patrick Gee, July 29, 2020 6:45PM The Launceston News

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Drilling a bypass in the Trevallyn Dam for short-finned eels. Picture: Hydro Tasmania media_cameraDrilling a bypass in the Trevallyn Dam for short-finned eels. Picture: Hydro Tasmania

environment

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Eels in Launceston, Tasmania can now swim through a hole drilled in a dam wall to help them on their incredible 3000km migration to New Caledonia.

Hydro Tasmania announced the completion of the Australian-first project on Tuesday, which was World Nature Conservation Day.

The hole, called an eel bypass, cost $1 million and will help protect the slippery short-finned eel species and relieve stress on its breeding cycle.

Tiny larval* eel babies – known as glass eels because of their transparency* – drift down to New Zealand, Tasmania and other parts of Australia on currents from the Coral Sea.

Fish eel study Department of Inland Fisheries   technical officer Andrew Taylor with baby glass   eels they have collected from the Derwent   and Tamar Rivers for studies media_cameraGlass eels drift down to New Zealand, Tasmania and other parts of Australia on currents from the Coral Sea. These were collected by Tasmanian Department of Inland Fisheries officers from the Derwent and Tamar Rivers.

When they sense freshwater, they swim upstream, metamorphose* into the typical eel shape and colour and become juvenile* elvers*.

They live in dams and streams for 10-35 years until they mature, before making the almost 3000km journey out to sea and north to spawn* before they die.

An eel ladder was installed at the Trevallyn Dam on the South Esk River in Launceston in the 1990s so juvenile eels could get upstream.

But, until now, the eels have relied on either the dam spilling or have tried to pass through the Trevallyn Power Station intake to get back down stream for their migration.

The former is uncommon and the latter can be fatal for the eels.

Hydro Tasmania aquatic scientist David Ikedife said this was the first time any dam in Australia had been fitted with an eel bypass for downstream migration.

The organisation tagged and tracked the movements of eels looking for a way downstream before drilling a hole in the dam wall in a corner regularly explored by the eels and installing a chute*.

Supplied Editorial Water flowing through a bypass in the Trevallyn Dam wall for  migrating short-finned eels. Picture: Supplied/Hydro Tasmania media_cameraWater flowing through a bypass in the Trevallyn Dam wall for migrating short-finned eels. Picture: Hydro Tasmania

“A lot of research and development has gone in to this, and population numbers will be carefully monitored to see what effect it has,” Mr Ikedife said.

“During the eel’s downstream migration from December to April each year, visitors to Trevallyn Dam will see the small cascade* of water from the eel bypass in operation and will know Hydro Tasmania is helping this native species on its long journey.”

Supplied Editorial Short-finned eel. Picture: Supplied media_cameraAn adult short-finned eel.

Hydro Tasmania CEO Steve Davy said part of the organisation’s duty was to look after the waterways in its care, including the species that live in them.

“Though not endangered in Australia, similar species of eels are listed as threatened in the Northern Hemisphere, so the responsibility is on water managers like Hydro Tasmania to take action,” Mr Davy said.

Tasmania’s Energy Minister Guy Barnett said Hydro Tasmania should be congratulated for assisting the migration of the eels and helping to maintain the biodiversity* of the river system.

“It’s an Australian first, it’s a million dollar investment and on Nature Conservation Day, it’s a great initiative* to announce,” he said.

Supplied Editorial Energy minister Guy Barnett and Hydro Tasmania aquatic scientist  David Ikedife at Trevallyn Dam. Picture: PATRICK GEE media_cameraTasmania’s Energy Minister Guy Barnett and Hydro Tasmania aquatic scientist David Ikedife at Trevallyn Dam. The eel bypass chute is in the background on the left. Picture: Patrick Gee

GLOSSARY

  • larval: relating to the immature part of the lifespan of some insects and other animals
  • transparency: quality of being see-through
  • metamorphose: change form
  • juvenile: young, immature
  • elvers: young eels at a particular stage of their development
  • spawn: release or deposit eggs or lots of offspring
  • chute: sloping channel or slide
  • cascade: tumble down, as in a waterfall
  • biodiversity: the range of plants and animals in a habitat
  • initiative: an action or plan

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QUICK QUIZ

  1. How did Hydro Tasmania (which runs the dam) decide where to put the hole?
  2. What is the species of eel called?
  3. Which months of the year will the eels use the bypass?
  4. Without the hole, how did the eels get past the dam wall?
  5. Where are the adult eels headed on their big migration?

LISTEN TO THIS STORY

CLASSROOM ACTIVITIES
1. Write an Adventure Story
This is not merely a hole in a wall an eel can go through. This is an adventure story of an epic eel journey. Write an exciting adventure story based on the experiences or adventures of an eel using the bypass.

Time: allow 30 minutes to complete this activity
Curriculum Links: English, Visual Communication Design, Visual Arts

2. Extension
Design a storyboard or write a script for an advertisement about the new eel bypass. Your audience is eels. Your purpose is to encourage them to use the bypass and learn about it.

Time: allow at least 40 minutes to complete this activity
Curriculum Links: English, Media Arts, Critical and Creative Thinking

VCOP ACTIVITY
Opener Up-Level It
Make a list of all the openers in the article. Pick three that repeat and see if you can replace them with another word, or shuffle the order of the sentence to bring a new opener to the front.

Don’t forget to re-read the sentence to make sure it still makes sense, and that it actually sounds better.

HAVE YOUR SAY: How important is it to you that the eels can now safely complete their journey?
No one-word answers. Use full sentences to explain your thinking. No comments will be published until approved by editors.

Extra Reading in environment