Tasmania has 25 species of native freshwater fish. Some of these are diadromous, that is, they migrate between fresh and marine waters to complete their life cycle.
Short-finned eels are found in many of Tasmania’s river catchments, and are the state’s largest, native, predatory freshwater fish. While short-fined eels are considered at risk in other parts of the world – that’s not thought to be the case in Tasmania.
During migration in the South Esk catchment, mature short-finned eels travel downstream to breed, sending them on a journey all the way from the Tamar Estuary / kanamaluka to the Coral Sea off the coast of Queensland. Juvenile eels then eventually return to rivers to mature.
It’s an arduous journey and we recognise the impact that our dams have on these species and work hard to make it as safe possible for migration to occur.
We work collaboratively with the Inland Fisheries Service (IFS) to assist eel passage past barriers that may block their migration, and our award-winning eel bypass at Trevallyn Dam helps thousands of eels migrate safely downstream each year
In 2020, Hydro Tasmania commissioned a world-first eel bypass at Trevallyn Dam to further reduce the number of eels travelling through the power station.
Since the bypass was commissioned, over 5,000 short-finned eels have been able to safely migrate downstream.
Without the bypass in place, eel migration and breeding would be impeded and more eels would pass through the dam intake, a dangerous journey that can cause death. Hydro Tasmania remains committed to supporting the long-term sustainability of short-finned eels in Tasmania.
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In late 2020, our eel bypass received the Australian Water Association’s (AWA) Regional Infrastructure Project Award.
Visitors to Trevallyn Dam between December and April will see the bypass operating as a small spray of water cascading down the dam’s western side.
Just as we’ve worked hard to ensure short-finned eels have safe passage downstream, our fish traps and elver (juvenile eels) ladders help complete the migration cycle by enabling juvenile eels to return upstream.
Eels are prolific ‘climbers’, and the elver ladders in operation at Trevallyn and Meadowbank dams have proven incredibly successful, helping hundreds of thousands of juvenile eels migrate upstream each year.
Our elver ladder at Trevallyn is arguably the busiest ladder in the southern hemisphere. The ladder passes through the dam’s internal galleries and enables elvers to climb and swim their way upstream past Trevallyn Dam into Lake Trevallyn
We also work with the IFS to capture elvers from the Tamar Estuary and transport them upstream past the dam.
At Meadowbank, just north of New Norfolk, we use a short ladder and large fish trap to collect elvers and move them safely upstream into Lake Meadowbank.The system also supports adult lampreys (primitive jawless eel-like fish) which migrate upstream in early spring.
Eel movements during peak migration periods are unpredictable. Eels have an instinctual desire to travel with flow downstream and this means that sometimes, despite our best efforts, some eels travel through the power station intake.
Whilst some eels survive this journey, in the past a number of deceased eels have been found around the tailrace in the Tamar Estuary.
There’s no one-size-fits-all solution to this problem, and Hydro Tasmania has invested significant time and resources to develop tailored solutions that deliver the best conservation outcomes for eels.
We’re actively working to have additional mitigation measures in place to work alongside our eel bypass and elver ladders and reduce eel passage through the power station intake.
These mitigations require investigation to ensure we’re using the most effective method and may include:
Hydro Tasmania takes this issue seriously. Our eel bypass, elver ladders, and fish traps are a testament to our ongoing commitment to helping safe migration in our catchments.