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The Last Olive Perchlet


The very year they could be rightfully declared extinct, something was stirring in the bottom of Rexy Conallin’s bucket…..was it…..THE LAST OLIVE PERCHLET!?!

What else is hiding out there? Who is looking? How are they looking? Who is funding our ongoing need for inventory knowledge?

During one of the greatest ever bush fishing adventures of the modern era, a team of scientists, NRM people and commercial fishos from NSW, SA and Vic all got together in the Lower, lower Lachlan (Where even Clancy of the overflow was unreachable) to try out some ideas about controlling carp. This trip was the Kokoda trail of fish research expeditions and whilst all survived, none that were there will ever forget the Lachlan blues. But that is another story for later on.

Whilst testing Rex Conallin’s portable Williams carp cage below a small weir in the Lake Brewster outflow channel, Cam McGregor made two important discoveries.

1: Rex wasn’t processing the small fish catch from the fyke nets like he said he would and

2: In a small tin bucket where Rex was storing the catch for “later” lurked a different looking fish.
Cam’s sharp eyes had picked out the first olive perchlet (Ambassis agassizi) caught in the Lachlan River for nearly fifty years, commonly considered the threshold for declaring something extinct. Like Plato once stated, “where there’s one olive perchlet, there must be at least two more olive perchlets” (although the Bible’s Genesis seems to disagree with this conclusion assuming Adam and Eve were not Tasmanian).


A catch of perchlet and the net from whence they were re-discovered in the Mountain Creek outlet channel, lower, lower, Lachlan. Note Rexie’s carp cage at the right.

A follow up survey revealed a massively abundant population of olive perchlet through the local waterways with the species completely dominating the catch in many nets (3000+ individuals per fyke) and co-existing happily in shallow, isolated pools with yellowbelly, carp, redfin, gudgeons and smelt…….

…….And cute little turtles…………


…………..And this freak of a hardyhead (top one) with no face whatsoever!!!


Indeed this was the only known population of olive perchlet in the entire Murray Catchment. And it was going OFF! What was unique about this place that the olive perchlet should be here and why didn’t we know they were there? The habitat where they were first found is at the bottom end of a puny little channel with in-stream barriers galore, poor water quality and every now and then State Water would unleash a Biblical flood of pelican crap infested green water that would shake the very leaves off the redgums downstream through that channel. “These fish should be flourishing in the Murray”. But on reflection, the key things that seemed to be there for these perchlet was a combination of low flow habitats and instream macrophyte beds like this……

At the bottom of the Lachlan, most irrigation flows don’t arrive, increasingly since more water has become diverted up Willandra Creek rather than the bottom of the main channel. So the drought processes that would have occurred regularly in these Murray River catchments, that is summer low flows and regular flow variability to maintain macrophyte bed growth and diversity. In fact, a large part of the population existed within an area that was between where we drain the summer flows off to fill lake Brewster and where we smash them back in via the Mountain Creek outlet. In addition, the water takes so long to get down the Lachlan from the upper catchments (where it rains) that water arrives warm and there is no big mass of water moving through to other places (Lachlan water stays in the Lachlan!). So they may have an ideal little refuge where they are sheltered from the regular reversals of hydrology and water quality that predominate throughout their former range.


How to design a perchlet refuge. Original artist’s rendition of the purpose built perchlet refuge.
As scientists what are want to do, we pulled some of the perchlets heads apart, ethically, to look at their otoliths – ear bones that record their growth like the rings of a tree. Low and behold, these fish were all from a single year class that seemed to link back to a pulsed flow event during spring that year, But No; otolith aging revealed that the spawning STOPPED once the flow pulse hit. All of the fish were in fact spawned in the period preceding the flow pulse at the exact point that water temperature reached 23 degrees C and stopped once the flow pulse dropped the temperature again. This is EXACTLY the temperature that Angela Arthington and …ahh….Milton said they would spawn at in Queensland during the eighties (Milton and Arthington 1985). So there we have it, water temperature, low flow habitat and macrophyte beds, all combined with a unique little refuge from many of the impacts of the water regulation going on all around and you can still have olive perchlet.


The spawning period of olive perchlet in relation to water temperature of the Lachlan River (McNeil et al. 2008).


So there ARE hidden little gems out there! The last remaining bastions of a Murray that was, unique linkages to our past, heritage places and conservation hot-spots. But serendipity does not come to those who stay at home playing the x-box or indeed writing conservation and recovery plans in Canberra or those that effectively manage budgets to protect asssets identified using risk assessment methodologies supported by baysian belief networks and decision support models. Or even those, it appears, that run national monitoring programs designed to monitor the population structure of fish in the Murray-Darling Basin.

In fact all past monitoring had missed this population completely, could this be happening elsewhere? Could there be other populations of perchlet lurking, waiting, could there be other species? Purple spotted gudgeons? Murray hardyhead? Pigmy perch? Purple helmeted pocket gudgeons? OK, Tarmo Raadik made that last one up, but you see the point?

The answer is yes. Mike Hammer a while back woke up in the middle of the night after a vivid dream, muttered, “I know where they are” and slipped out of bed and off to the Murray where he found a robust little population of purple spotted gudgeon waiting for him, calling him. Again, the only one in the Murray catchment. The yarra pigmy perch called out to him on another moonlight night and somnambulated down to the Barrages to discover populations down there. But its never big government programs that find these guys, and why not? I personaly believe that two things are driving this problem

1: A focus on big fish for conservation and community and

2: A love of electrofishing in big rivers as a fish monitoring strategy.

After the discovery of the olive perchlet we asked, How did we miss these guys and are we missing them everywhere we monitor? So we ran a whole heap of SRA (Sustainable Rivers Audit) samples through the known population. We caught olive perchlet, but not many and we know from the netting they were thick in the water. But the SRA and similar monitoring programs want to catch big fish and so they do. Bony bloody herring, carp but importantly golden and silver perch and Murray cod – EPBC listed GODS of fish. Common as bloody muck. But are the perchlet EPBC listed? Are Galaxias rostratus EPBC listed? Are southern pigmy perch EPBC listed? Are the Southern Purple spotted gudgeon listed?


A Jamie Oliver style smattering of olive perchlet on seasonal greens…Oliver perchlet anyone???

No, its just big fish and a heap of species that have been naturaly locked into tiny little ranges for thousands of years due to their natural inability to cope with the world around them. I reckon half the big fish are listed because people use the wrong bait. But hands up who has caught a shitload of Galaxias rostratus lately? The silence is deafening. And here is the real problem, there is NO focus on studying, listing and planning for the restoration of small bodied, wetland oriented fish, unless you are already a useless species at the end of your natural shot at the evolutionary title (I’m looking at YOU Mogurnda clivicola). The water industry delivers flows for inundating wetlands with little to no strategies for how their flows are targeting and tailored towards the recovery and sustainance of these wetland fish species. We raised these concerns a decade ago (see Closs et al. 2005) and since that time the little rare species have just about disappeared from floodplains across The Murray catchment. Are they headed for the olive perchlet and purple spotted gudgeon world of “oh, when did they dissappear? I wasn’t watching!”

NO, we Must look for these populations using appropriate methods and targeting the appropriate habitats. We need to monitor the Killawarra Floodplain on the Ovens, We need to monitor the Werai Forest on the Edward/Wakool, and the olive perchlet have taught us that we need to monitor that crappy little outlet channel at Lake Brewster, the purple spotted gudgeon has taught us that we need to monitor those crappy little wetlands that run through caravan parks on the Murray and mostly we need to monitor that little patch where no one has looked and where the next exciting discovery is waiting to help us bring back the fish to the Murray catchment.



Help cheer up Janice Kerr’s little Oliver perchlett, find him some friends, find and revive the small fish! (original artwork by Janice Kerr).

Editor’s note: Thanks Dale for an insightful and inspiring article. It would be really interesting to hear the thoughts of other fish survey folk on related issues, maybe via some brief comments/letters………