13 December 2018
This is an amazing story of survival in the complex universe that exists in the fresh waterways we manage. It’s not to be confused with The Hitchhiker’s Guide to the Galaxy which is a completely different story in a much larger universe. The two are similar only in that they contain important lessons about life, the universe and everything, so make yourself a solid cup of tea and don’t forget your towel.
First let’s introduce the galaxiids. They are about the same size as a Babel Fish but they won’t help you understand foreign languages and we do not recommend you put them anywhere near your ear. In fact, we would prefer you to just leave them alone. They’re precious.
If you’ve spent any time in Tasmania’s fresh waterways you might have seen them. They’re usually less than 20 cm long and are known as minnows, whitebait, jollytails, mountain trout and many other names depending on where you are and which species are in residence.
We have five threatened species of galaxiid in our lakes in Tasmania’s central highlands, and four of these occur in Arthurs Lake and yingina / Great Lake. We pulled together a team of freshwater scientists to improve our knowledge of these tiny species of fish which are an essential part of the ecosystem - and therefore the universe - and everything. The team of scientists from Hydro Tasmania, Entura, the Inland Fisheries Service (IFS) and Tasmania’s research community, have been building our understanding of what makes these species tick, with the aim of better protecting them. But protecting these vital species hasn’t always been smooth sailing.
This is a story about the Pedder galaxias which, paradoxically, does not now exist in Lake Pedder.
Lake Pedder lies in the state’s south west and is home to a number of rare and newly discovered species. The lake was the original home of the Pedder galaxias, the country’s most endangered freshwater fish.
When the species was first discovered the Pedder galaxias only lived in Lake Pedder and its rivers and streams but its numbers dropped sharply after the impoundment of the natural lake in the early 1970s.
In the early 90s, the Inland Fisheries Service released 34 fish into the much smaller Lake Oberon approximately 10 kilometres south of Lake Pedder in an attempt to find the species a new home where they could build a new breeding population. It was a success. The Pedder galaxias thrived in its new home.
To further safeguard the species, ten years later another 74 fish were taken from Lake Oberon to the nearby Strathgordon water supply dam forming a second breeding population outside of Lake Pedder. The water supply dam is owned by Hydro Tasmania, and we worked closely with the IFS to modify the dam to make it suitable for this very special fish. Initially they were slow to take to their new home, however subsequent habitat improvements resulted in the establishment of a healthy, self-sustaining population.
This work was critical for the longevity of the species as they are no longer found in Lake Pedder, and now only occur in Lake Oberon and the Strathgordon dam.
During the 2015/16 energy supply challenge the water level in yingina / Great Lake dropped to almost record low levels and we needed to act quickly to protect the lake's threatened galaxiids (Shannon paragalaxias and Great Lake paragalaxias) and their precious eggs during spawning season. If the water level fell too much or too quickly the eggs would risk becoming exposed to the air, dry out and die.
The information collected previously by our researchers enabled us to understand the risks of drawing the lake below critical levels, and the potential impact on galaxiid populations. However, the unexpected failure of the Basslink cable and inability to import power meant that our options to reduce the pressure on Great Lake’s water level were severely limited. Fortunately we were able to use alternate generation sources so that we could to protect water levels in yingina / Great Lake.
When the challenge was over and water levels were replenished around the middle of 2016, we checked on the galaxiid population we worked so hard to protect. Our freshwater biologists made a careful count and we were happy to find the species was largely unaffected. The hard work of our research team had paid off.
Since then we have come up with some other ways to protect this unique species. Over the last three years (2016-18) we have successfully trialled the use of artificial spawning habitats at Swan Bay at the southern end of yingina / Great Lake. We’re also in the process of trialling transportable artificial spawning habitats in yingina / Great Lake and Shannon Lagoon. These give us more ways to protect these precious little fish.
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