I’m a self-employed fish researcher based in Lake Cargelligo, in the middle of the Lachlan catchment – so pretty-much in the middle of NSW and also the middle of the Murray-Darling Basin.

To anyone reading this who’s thinking ‘nah, that’s not a real job’ and advising their kids against it – that’s what I thought too! However, it turns out it’s not that esoteric and eccentric after-all. I’m pretty-much run-off my feet. Then again – I’ve been at it for close to 30 years.

In April I was sampling fish in an on-again off-again lake close to Booligal (of all places – look it up if no idea), and the landowners – who have become great friends over the last 4 or 5 years – noticed I was more than a little surprised at what was falling out of the nets. This work was sponsored by the Commonwealth Environmental Water Office (CEWO) and the University of Canberra under the FlowMER program, but was for a project completely unrelated to finding weird animals in strange places.

Lower Lachlan River Olive perchlet. Photo credit: Warren Chad

One of the rarest fish species in the MDB nowadays is a small predator called the Olive perchlet. They get to about 50mm long, and are transparent, so I (and many other fish geeks) call them ‘glassfish’, but in all other respects they are like a miniature yellowbelly or cod – all mouth and attitude.

Adam Kerezsy with a Lachlan River yellowbelly prior to release. Photo credit: Mal Carnegie

From the mid-noughties we knew there was one population of olive perchlet left in the Lachlan: in the weirpool at Brewster, halfway between Lake Cargelligo and Hillston. Yet in April 2023 here/there they were dropping out of nets set in an ephemeral lake in…………….Booligal!

Adam Kerezsy setting fyke nets, a non-harmful way of sampling aquatic animals. Photo credit: Mal Carnegie

My experience and curiosity kicked in: I hauled out some vials pre-filled with ethanol and a small pair of scissors and took tiny slivers from the tails of the captured animals for genetic analysis. I was pretty sure they were part of the Brewster population that had been forced to find a new abode in the massive 2022/23 floods. But maybe they weren’t?

I knew exactly who to ask, for Dr Peter Unmack is a similarly individualistic fish nerd, but his expertise is far more white-coaty than mine, as he is into genetics and biogeography. In fact, Pete knows more about Aussie freshwater fish than just about anybody.

With samples sent to Dr Pete I returned to Booligal – this time supported by NSW DPE – in order to work out exactly how many lakes and dams the little critters were hiding in.

Refugee Olive perchlet from a drying lake prior to translocation to a safe habitat. Photo credit: Adam Kerezsy

But there was another issue by then, for we knew that one of the lakes where I’d found the fish was ephemeral: it filled during the floods but would dry down sooner or later. We collectively knew that if there was a population of an endangered species in such a place we probably needed to get busy and do something about it.

So during the coldest days of the year in June I waded and stumbled around in farm dams and any wetland I could find, because we needed a place that was safe from flooding, safe from carp, and – preferably – easy to manage with landholder cooperation. Following a freezing week and an unwelcome bite on the finger from a water rat I – luckily – found a location that ticked all the boxes: a beautiful 70 x 30m dam with a screened inlet. Perfect.

In the interim, Dr Pete had been busy doing what he does best and worked out – using genetic sequencing – that the Booligal glassfish and the Brewster glassfish were actually separate populations. In other words – the Booligal tribe had been hiding in plain sight for decades. This added a new level of urgency: not only was it desirable to ensure their safety, it was somewhat essential.

NSW Fisheries kicked in with permission – for they are the agency charged with actually looking after such things – and the Murray-Darling Basin Authority agreed to help with a bit of funding to actually do the work. I’m fairly cheap, but even so it takes a few days to catch and move a few endangered fish when they’re hard to find, and it’s also important to realise that if I suddenly die or win Lotto and move to a tropical island, somebody else might have to help out – and they might not be as cheap!

Fish country in the back country. Photo credit: Adam Kerezsy

It all came to fruition in late November. I headed off to Booligal with 24 nets and a boat on the top of the Hilux. Storms were forecast but I rode my luck – something I’ve done for as long as I can remember in outback Australia.

It took me most of the day to set the nets – all around the lake, which now has an average maximum depth of about a metre. By February it’ll be kaput.

I slept like a very large redgum log at the landowner’s place, mainly because 24 is A LOT of nets, but also because I knew I’d be racing the weather in the morning. There are 80 kilometres of black soil roads in the area I was working: basically a no-go after about 10mm of rain. And a lot more than that was predicted.

It all worked out. At 5:30am I headed back to the boat, and – hastily – around the nets. In the little punt I had a blue plastic bin and an aerator; on the back a trusty little 3.3hp Mercury motor. 30 glassfish here, then 22 at the next site, then only eight. I was really hoping for 100, but in the end got 74.

Not bad. I hurriedly loaded the nets and all the gear, then hoisted my old boat on the racks. Grey skies. Not good. Last, the bin with the fish and the aerator, tied on with an old rope.

Back up 20 kilometres of black soil roads under the darkening skies. A couple of gates. Then the tar, and 25 more kilometres until we – finally – liberated the little fish in their new home. One which won’t dry down and turn into a fish cemetery in late February.

And then it RAINED! Properly.

Adam Kerezsy with a big carp sampled during a similar survey in Booberoi Creek. Photo credit: Mal Carnegie

This article summarises how a co-operative effort involving state and federal agencies, independent researchers, a university and landholders has possibly saved a population of an endangered species of fish from becoming locally extinct.

Featured image: Olive perchlet habitat in far western New South Wales.

Photo credit: Adam Kerezsy

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