Tasmania has 25 species of native freshwater fish, including two species of eels: the short-finned eel and the long-finned eel. These two species are diadromous, that is, they migrate between fresh and marine waters to complete their life cycle.
Eels are found in many of Tasmania’s river catchments and are the state’s largest, native, predatory freshwater fish. While some species of freshwater eels are considered at risk in other parts of the world – that’s not the case in Tasmania.
During migration in the South Esk catchment, mature freshwater 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 as possible for migration to occur.
We work collaboratively with the Inland Fisheries Service (IFS) to assist upstream 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 reduce the number of eels travelling through the power station. Many thousands of eels safely navigate this bypass each year on the downstream migration towards their spawning grounds in the Coral Sea.
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 freshwater 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 flow of water cascading down the dam’s western side.
Just as we’ve worked hard to ensure freshwater 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 and into Lake Trevallyn.
We also work with the IFS to capture elvers from the Kanamaluka/Tamar Estuary and transport them upstream past the dam. Elvers that the IFS capture are also restocked into other key catchments within Tasmania.
At Meadowbank, just north of New Norfolk, we collaborate with the IFS to facilitate upstream passage. A short ladder and large fish trap at the base of the dam collect elvers and allow them to be safely moved upstream into Lake Meadowbank. The system also supports adult lampreys (primitive jawless eel-like fish) which migrate upstream in early spring.