Mysteries of the bush (Part 2): the Lake Mears salmon

The southern end of Lake Mears, a small gem of the WA wheatbelt … and a place of mystery

Before I get started on Lake Mears and its mysteries, I need to backtrack a little and set the scene.

Back in the early 1960s I was working as a young forestry officer at Northcliffe, deep in the karri country of the lower south-west. One of my jobs was the survey and construction of a new road, the grandiosely-named “Northcliffe-Walpole Road”. It had been conceived as a direct route linking the two towns across trackless forest and coastal wilderness. It was federally funded, but the job was undertaken by the WA Forests Dept, for whom I was working, as it would provide greatly improved access for bushfire management.

The road was planned to take off from just south of Northcliffe and head off across the great scrubby heathlands found along the south coast (known locally as “flats”) towards the mouth of the Gardner River. It would then cross the river and head east, traversing the forests of the lower Gardner and Shannon River basins, until reaching Broke Inlet. There it would join up with the South-West Highway, just this side of Crystal Springs.

Coastal heathland on the flats south of Northcliffe, replete with ti-tree, grass trees and acacia scrub (photo by John Evans)

This, by the way, was one of several roading projects in the region at that time funded by a Federal Aid Road Grant emanating from the Commonwealth government that the Conservator of Forests had somehow managed to wrangle. We referred to the resulting roads as FARG Roads - sometimes pronounced “FAARRK! Roads” when the funds dried up half-way through a job, according to the whim of some faceless public servant in Canberra.

FARG roads were required to be built to tightly specified standards, meaning that I had to ensure the survey avoided steep pinches and tight curves, and that the road was trafficable all-year round. I never heard of anyone checking up on this, but we made the effort, and the result was a road of superior quality to the average forest track.

The project team consisted of a D7 bulldozer with driver, a young forestry cadet as my survey hand, my dog Cassius and me. The dozer driver was Bob Shelley, one of the toughest men I ever knew, handy with his fists and a hard drinker. But a good bloke, and able to handle his huge machine like a Ferrari. He also knew the job, having worked on its initial phases the previous summer and was an experienced bush engineer. Cassius’ contribution was to chase kangaroos and demolish the leftovers at crib time.

My blue heeler Cassius keeping his one black eye on progress with the new road

The first few km of the road crossed open heathland interspersed with scrubby sand dunes, occasional granite outcrops and small, ephemeral freshwater lakes. The soil was sandy, dry in summer and water-logged and boggy in winter. There was a network of shallow drainage gutters that barely ran even in winter, but which we had to accommodate by inserting culverts in the road wherever one was crossed. The whole area must have been submerged by the ocean at some time in the geological past, as the soil was full of marine fossils.

Bob Shelley at the controls of his D7, pushing up sand for the formation

To achieve an all-weather road, it was necessary to build up an embankment (which we called “the formation”, a term used by railway engineers) about a metre or so above the winter high-water level. This was accomplished by Bob bulldozing up sand from both sides of the survey line into an elevated roadway. This was later compacted, graded and gravelled.

As construction proceeded, the excavation and pushing up left behind a series of “borrow pits” on either side of the elevated formation.

 My forestry CJ5 jeep up on the completed formation, borrow pits in the foreground

Even before the next rain fell, the borrow pits began to fill with seepage and soon after the first heavy downpour they were brimming. Like all of the rivers and creeks in the karri country, the water in the pools was dark brown, almost black, due to tannins being dissolved out of the native vegetation.

Just then, Bob pointed out to me a surprising phenomenon. Within a day or so of the mini lakes forming in the excavations along the side of the new road, they swarmed with small fish.  I remember standing with Bob on the formation and watching them, tiny little things a few centimeters long, weaving about in the pools, myriads of them. We were mystified. Where had they come from and what were they?  I had never heard of such a thing before.

But I was not a fish man in those days (not one today either, for that matter) and besides we had a road to build and the site for a bridge over the Gardner River to survey. Winter was just around the corner when road building would come to a halt, we were pressed for time, and the Federal grant was holding.  We pushed on, and I failed to follow up on this mysterious and fascinating discovery.

I now wish I had reported it and maybe written it up for some publication like the newsletter of the WA Naturalists. Years later I heard that a young ichthyologist had “discovered” the fish in “roadside pools” south of Northcliffe and they turned out to be a rare species, a variant of the Shannon Mud Minnow (Lepidogalaxias salamandroides). My friend and ecological expert Dr Per Christensen studied and published a paper on them, but the young ichthyologist was credited with the discovery.

The Shannon mud minnow

Per Christensen explained the mystery of their sudden appearance. When the heathlands begin to dry out, as they do every year as mid-summer approaches, the minnows burrow down and form a sort of mud cocoon around them, in which they hibernate. Then, with the arrival of the winter rains the following year, and the flooding of the flats (or the construction of artificial pools by road engineers), they emerge to feed and breed. They breed rapidly, so that young fish are always replacing the older ones, the usual life expectancy of a mud minnow being only 2-3 years. I am not sure how the new ones learn the trick but as soon as the pools start to dry out, they retreat down into the subterranean cocoons, where they are easily able to survive.

The last time I was down there, fifty years later in 2015, it was hard to find those pools – the scrub had reclaimed them. Presumably the minnows are still there and come out when the flats are flooded, but I didn’t see any.

A sad note

Permit me a small digression here. Apart from the “discovery” of the fish, the other highlight of that 1964 summer was completing the road (now known as Chesapeake Road) down to and across the Gardner River. Here I oversaw the construction of a substantial bridge. Alas, it was a bridge to nowhere. The following year the funds were cut and although the road did eventually reach Broke Inlet, this was via existing and poorer quality forestry and logging tracks. Nor is it today (in 2025) the road it used to be. As always seems to happen when an area is declared a national park, as this area eventually was, the standards of maintenance and upkeep fell away. The aim seems to be to let the new national park regress into wilderness. The road across the flats that we took so much trouble to survey and build is now (in many places) corrugated, boggy and potholed. My beautiful bridge was never properly looked after and has been condemned.

The remnants of my ‘Bridge on the River Gardner’, photographed in 2015, no longer trafficable.

Getting back to Lake Mears (at last, I hear you cry)

About 40 years later I was remined of those days down on the Northcliffe flats. I was helping some enterprising young farmers with a scheme to rejuvenate Lake Mears at Aldersyde (in the Western Australian wheatbelt, east of Brookton). The lake had once been fresh but had become mostly salty since the 1940s.

Lake Mears is a lovely little almost circular lake about 200 hectares in size and over 2m deep when full. However, for most of the time it is empty, just a dry salt pan. But when conditions are right – a downpour from a major rain-bearing depression in summer followed by heavy winter rains - the chains of salt lakes in the upper catchment of the Salt River (itself the upper reaches of the Avon River) fill up and overflow. There is a low-lying channel known as Stock Pool Creek that normally by-passes the entry to Lake Mears but which, when in flood, overflows and fills the lake. Because the floodwaters derive from heavy rains, the inflow converts Lake Mears from a dry salt pan into a freshwater lake. Interestingly, once Lake Mears is full and the flooding is over, there can be a reverse flow with lake water moving back “up” the creek … until an equilibrium level is achieved.

The point of all this however, is that Lake Mears is also home to an indigenous species of fish that “hibernates” for years while the lake is dry and then swarms into great schools the moment it fills. There are other lakes nearby (known collectively as the Yenyenning Lakes) but to the best of my knowledge, none of them have fish.

I have talked about this with Mrs Betty Wilkinson (nee Thomson), who grew up on a farm on the edge of Lake Mears in the 1930s and 1940s.

“The Lake would be just about empty one day, and almost full the next” [Mrs Wilkinson told me], “and as soon as this happened the fish would appear. I would take a bucket down and when they swam and jumped in the creek I could get a bucketful. They were about the size of a large sardine. I would take them home and Mum would chop off the heads and fry them up in a pan. They were delicious eating.”

All of this is confirmed in the History of Aldersyde 1846-1946 by A Knox-Thomson, published in 1975, which says:

Lake Mears was a freshwater lake … but generally dried up in summer. When sufficient rain fell to make the Stock Pool Creek overflow, the lake filled to a depth of 6 feet, and if there were a series of wet winters, it stayed full for several years. When this happened it became alive with fish which grew to 5 - 7 inches in length. They were miniature salmon and were good eating while the lake had a fair depth of water in it.

The lake had its normal resident populations of ducks and swans, but when the fish swarmed, they would be joined by multitudes of predator birds who flew in from the west coast. According to Mr. Knox-Thomson: seagulls, cormorants and pelicans arrived there in thousands.

He went on:

Where the fish came from was a mystery, as they were all eaten or died when the water dried up. The lake would be absolutely dry for months and perhaps only have six inches to a foot of water in it for several winters … several small local creeks which drained the slopes around the lake would run briskly for a few hours after a heavy fall of rain or a thunderstorm. When this would happen, the fish would swarm out of the lake and swim upstream (as the salmon do in Canada).

The Thomson children used to drop a sapling across the creek, making a small waterfall. The little salmon would leap over this, just as Canadian salmon do over large waterfalls, and the children would run back and forth across the top side with an open kero can and get a bucketful in a few minutes.

I became involved in the Lake Mears project when local farmers (under the leadership of Todd Mills, who had also grown up on the farm adjoining the lake) came up with the idea of filling the Lake every winter via a gated channel from the creek into the lake and thus keeping the lake full and fresh, or at least fresh-ish. The plan was that the gates could be opened and shut in response to winter rainfall events, thus “harvesting” rainwater and diverting it into the lake.

I was engaged as wordsmith to draft a proposal and management strategy for submission to the authorities. This I did, and it ended up a pretty nice document (well, Todd was happy).

But I was not confident anything would come of it. I had dealt many times with the environmental bureaucrats down in Perth who ruled on this sort of proposal and their default response was almost always to say “NO”. So it was this time: the scheme was subjected to a feasibility study by a team of high-powered consultants (whose report, by the way, failed to mention the salmon) but nevertheless it was rejected. The trouble was that the lake and its surrounds are an A Class Nature Reserve, and any artificial manipulation of the creek and lake levels was regarded as fiddling with Mother Nature and therefore tantamount to environmental vandalism. The farmers lost heart and then interest … to the detriment of the lake, the wildlife and the landscape. In my opinion, the proposal would have had only beneficial environmental impacts.

But it was an interesting project, I met some admirable people and was exposed to two new mysteries of the bush. I didn’t ever see the Lake Mears salmon, but I heard all about them. The locals all had stories to tell me about the sudden appearance of the fish, and then the feeding frenzy when the predator birds flew in from the coast. They told me about the scores of pelicans, soaring in alone or in small flocks of three or four, of the dive-bombing cormorants and the chattering chaos of hundreds of seagulls feeding on schools of fish.

How the coastal birds knew the lake had filled and the fish had “germinated” (or whatever the correct term is), and where to find them was a wonderful mystery to everybody, compounding the mystery of the fish.

Once Lake Mears filled, it would stay full for a year or two, and the locals would fish, swim and go water-skiing on it. But eventually it would dry back to a salt pan, the birds would return to the Indian Ocean, and any surviving fish would burrow down to their subterranean cocoons, awaiting the next big Avon catchment flood. 

What is the Lake Mears salmon?

While it was always known locally as the “Lake Mears salmon” nobody I spoke to seemed able to tell me exactly what this animal was, its “official” name, as it were. Seeking expert advice I turned to Professor Stephen Beatty, the Director of the Centre for Sustainable Aquatic Ecosystems at Murdoch University.

“My money is on the western galaxias (Galaxias occidentalis), also called the western minnow” he told me. I looked it up, and discovered that the western minnow is:

… a small freshwater fish found only in southwestern Australia, can grow up to 170 mm (7 inches) in length, and tolerates brackish pools and acidic or tannin-stained water. It is also known to burrow and survive in underground cocoons, and to move upstream to spawn.

Galaxias occidentalis – the western minnow, or Lake Mears salmon

It is good to know all this of course, but the Latin name and the dry academic description fails to inspire. I prefer to think of it as The Lake Mears Salmon, and in my mind’s eye I see them coming from nowhere to school in their millions, to swarm up Stock Pool Creek, leaping barriers and doing their best to avoid the cavernous beaks of waiting pelicans or the insides of a cut-down kero tin.

But if the mystery of the fish is resolved the mystery of the birds remains.

An enduring mystery

How do birds know that an obscure little lake like Lake Mears, hundreds of km away, a mere pinprick on a vast landscape, is suddenly full of water and food? And how do they find it with such alacrity and precision?

Of course the phenomenon is well-known and has been intensely studied … but it remains an enduring mystery. Nobody knows, not the world’s best ornithologists, ecologists or animal behavioural scientists … and the birds are not telling.

Probably the best-known example is that of Lake Eyre (now known as Kati Thanda), the enormous ephemeral wetland in central Australia that fills up on rare occasions after torrential rain a thousand km away in Queensland. The flooding of Lake Eyre leads to a cornucopia of small crustaceans and fish, and then the arrival of millions upon millions of birds to feed on them and to breed and raise their young. Many of the birds fly thousands of km to get there, and some actually seem to be able to predict the flooding of the lake, arriving a day or two early.

The mystery of how birds know when the lake is full of water and food, and how to find it, is completely unsolved, although there are many theories. Some ornithologists suggest the birds can smell the flood waters from afar, or perhaps hear them, others that they follow floodwater pathways. I personally like the idea that they send out scouts who then report back, alerting the flock.

The scouts

I have experience of this, not with floods and fish, but with almonds. We once had an enormous almond tree in our backyard which flowered prolifically and produced thousands of almonds ever year … but we never got to eat one of them. Just before the almonds ripened to the point where they were suitable for human consumption I would look out the window one day and see a single white-tailed black cockatoo in the tree, giving the almonds a test run. He would hop around in the tree for 20 minutes or so, sampling almonds here and there, and suddenly depart. An hour or so later, a huge flock of cockatoos, maybe 50 or 60 birds, would arrive overhead, descend on the tree, and get to work.

A Carnaby’s white-tailed black cockatoo at work cracking open the woody fruit of a marri tree to get at the seed within, possibly checking whether it was time for the flock to be notified (photo by Rick Dawson)

I would watch them, cracking open the shells with their powerful beaks, extracting and eating the almond and then throwing the empty shells away. The feeding was accompanied by the flapping of heavy wings and a loud and happy cacophony of chortling and cackling. When the last almond had been consumed, they left as one bird, heading off (no doubt) to another almond tree in an adjoining suburb, leaving me to clean up the mess. Clearly these birds used a scout to survey the suburbs and then report back when it was time to get into it at 7 Palin Street, or wherever.

The idea that the birds arriving at Lake Eyre when it fills have been guided by a scout is just that – an idea. Nobody has established this, and nobody really knows how the birds do it.

Banded Stilts

I have also enjoyed a story told to me by my friend Denis Saunders, former Chief of Wildlife Research with the CSIRO and an authority on Western Australian birds. Denis studied birds on Rottnest Island (just off the coast of WA near Perth) for many years. One of the most common of Rottnest’s birds was the banded stilt.

Also known as the ‘Rottnest Snipe’ (in colonial times there was a Governor of Western Australia who used to go out with his shotgun and “bag a brace of snipe” before breakfast), the banded stilt is a pretty little bird usually seen bobbing about on the Peel Inlet or the lakes at Rottnest, or wading in the shallows pecking at things. They are also wonderful aerialists, flying in densely packed flocks often of thousands of birds, that twist, dive and turn in perfect unison.

During the summer of 1982/3 (Denis told me), he carried out an inventory of the banded stilts on Rottnest, and they numbered about 3000. Then one morning in March, he went out and found that the stilts were gone, having taken flight en masse during the night. Only a tiny handful remained. Where had the other thousands gone, and why?

It turned out that two days previously there had been widespread thunderstorms in the eastern Goldfields, perhaps 800 to 1000 km to the east. The salt lakes out there flooded, and filled with little brine shrimps, providing perfect conditions for stilts to feed and breed (the stilts do not breed on Rottnest). Somehow, they knew The Big Opportunity was on, and where to go to enjoy it, and wasted no time getting out there. I asked Denis for his explanation, but he did not have one.

My colleague Ian Kealley (at that time working in the Goldfields for the conservation department) also has an amazing story about banded stilts. When Cyclone Bobby dumped a poultice of rain on the eastern Goldfields in 1995, the huge salt lakes of the region filled to brimming almost overnight. Banded stilts knew about it and within days they descended on the area in uncountable thousands … soon to become uncountable millions as they bred unrestrainedly.  Ian remembers that in and around the lakes of the region there were stilts everywhere – on the lakes. on the islands, on the roads, in the air, feeding, breeding, hatching and incubating eggs, little ones, big ones, fat ones, thin ones … etc (you remember the poem). In some places there were stilt nests at a density of up to 15 per square metre.

Ian took to the air himself, carrying out aerial surveys of stilt nesting sites in and around Lake Ballard, a huge salt lake, usually dry, way to the north of Kalgoorlie, maybe 800 kms inland from the west coast and the islands where the stilts had been roosting and feeding. Ian was able to photograph and map the nesting colonies, but the birds were absolutely uncountable.

Banded stilt colonies on islands within Lake Ballard after Cyclone Bobby (photo by Ian Kealley)

Ian also reminded me of the words of his colleague, ecologist Andy Chapman (extracted here from Andy’s excellent book Journeys in a Promised Land):

I was fortunate to be involved with a small group of people …who documented a banded stilt breeding event on Lakes Ballard and Marmion after Cyclone Bobby left its rainfall legacy in March 1995 … We located one nesting colony on an island in Lake Ballard which had 2000 nests with 5000 adult birds in attendance. It is worth recording … that these birds had travelled up to 1000 km, put on condition, copulated, built nests and begun incubating eggs between 12 and 18 days of the rain falling. If this is not a biological marvel, I don’t know what is … the birds knew where to go from where they were, where it had not rained…

Yes, truly a marvel. And a mystery that endures …

To conclude: my favourite pelican story

Marvellous and mysterious stories about birds like stilts and pelicans remind me that I have always loved pelicans. Over a lifetime I have watched them perched on river posts or soaring, gliding and wheeling over the Swan River or inland lakes and south coast inlets, and I am fascinated to read about their wondrous skills as long distance aviators and navigators. But it is as aerialists that they seem to me to be supreme.

The English biologist Francis Ratcliffe recounts a wonderful pelican story in his 1930 book Flying Fox and Shifting Sand. This occurred during the time he was conducting his ground-breaking research into flying foxes in Queensland.

….. I once witnessed a magnificent display of soaring air mastery, and by birds which I, in my ignorance, had never suspected of such powers. They were pelicans. No one can observe without amusement a pelican lumbering across the surface of a lake in its clumsy efforts to take to the air. Their absurd heads are poked out; only when they are properly under way do they draw them in and settle them in a self-satisfied fashion well back between their shoulders.

To suggest that these incarnated jokes deserve a place beside such masters of the air as the eagle and the albatross seems ludicrous; but they do, nevertheless.

In Queensland I bought a baby movie camera, and quite naturally I decided to try and film the pelicans [on Lake Gracemere]. One sunny Sunday morning I took the boat from the bottom of the garden and rowed quietly over towards Pelican Point. There were a fair number of birds in residence and at first, they took little notice of my approach. When I had reached the middle of the mere, however, they suddenly woke up, and one by one flapped off over the water until the point was quite deserted.

I rather expected them to scatter over the lake, but the flock congregated above the line of gum trees on the bank. Once above the level of the tree-tops all flapping of wings completely stopped, and the big birds began to climb vertically into the heavens. They soared upward on pinions in a series of circles, wheeling in perfect unison. I watched them climb higher and higher. Soon they were a mere cluster of specks in the sky. Then even the specks faded, and the only indication left of their presence was a momentary faint flash as the sunlight caught their white underparts at one point of their circling. Finally, this too vanished, the sky swallowed them up completely.

I resumed the oars and rowed back to the house. As I stepped onto the landing stage the first pelican glided over the trees and settled on the point. Inside a minute the whole flock had reassembled. I could hardly believe my eyes. I had half expected never to see the birds again. They must have been keeping me under observation all the time. Evidently in power of sight as well as of flight the miscreated pelican can rival the king of birds.

I felt I was better able to understand the aerial mastery of the pelican when I was chatting one day with a friend who is a wildlife carer – someone who takes in injured animals and nurses them back to health. She had a pelican ‘under her wing’, as it were, at the time and told me how amazed she was the first time she picked up the bird. She had expected it to be heavy, like a goose. But while it was large and strong, it weighed almost nothing. Clearly the unique combination of strength and virtual weightlessness, plus a large wing span, means the pelican is perfectly adapted to riding the thermals and soaring on the wind, flying effortlessly without the need to flap.

A final thought

The mystery of the “germinating” fish on the Northcliffe flats and at Lake Mears is resolved. But the mystery remains of unbelievable bird navigation and their uncanny ability to “know” about hydrological conditions and feeding grounds far, far away, and then to set off and fly uneeringly to the perfect spot for feeding and breeding. The great annual international migrations of birds is similarly mystifying. There are a number of bird species, for example, that fly all the way from the Arctic circle to feed on the shores of the Swan River just down the road from me in Perth, always arriving on about the same day in spring and at the same spot, and then returning a few months later to Siberia, or wherever, for the northern summer, a round trip of 30,000 kms or so. Their navigation skills (and physical endurance) is beyond belief.

I am happy that these mysteries remain. As I have mentioned elsewhere in these chronicles, unresolved mysteries are the best and the most intriguing mysteries. Not everything in this world, or this life, needs to be understood, down to … the last full stop.