The river that knew

Mist and sky above Mooney Mooney Creek better

Looking upriver from the junction with Floods Creek

If I want a quiet morning on the Hawkesbury, my best bet is a paddle up Mooney Mooney Creek.  It’s a jet ski free zone, and that’s a very fine thing. In maybe ten jaunts on various reaches of Mooney Mooney, I’ve seen a handful of kayaks, a few fishermen and one very slow moving yacht.  Unlike Cowan Creek or Patonga, there’s no sandy beaches for frisking about on, and the oysterfarms can be navigational hazard at low tide. But if you prefer hanging out with eagles and herons to spending time with humans in charge of powerboats, Mooney Mooney Creek’s the go.

Azure kingfisher profile crop

An uncharacteristically still azure kingfisher

There are really three Mooney Mooneys, for my purposes anyway.  There’s the upper reaches, a pleasant morning’s paddle if you throw in tranquil tributary Flood Creek, lined with casuarinas and decorated with the blue and green streaks of kingfishers hunting (more on the scenes and ecosystems there in a future post).  The put-in for that trip is where the switchbacking Pacific Highway crosses the river, though if you paddle upstream you pass under the highest bridge in Australia, a symphony in soaring concrete.

Or you can go downstream, towards Lemon Tree Bay and maybe on a low-ish tide, see, on every bend and mudflat herons feasting, and if you’re lucky, spot a wedge-tailed eagle soaring overhead.

Herons in parallel back in focus

White faced herons hunting at low tide

Up there in the headwaters, you’ll often see other kayakers – there are sometimes guided tours to the area – and occasionally people camping, rather naughtily, by the side of the river.  The Great North Walk, that links Sydney and Newcastle, via most of the lovely places along the way including Berowra (of course), flanks the upper reaches of the river and once or twice I’ve heard voices of hikers walking along the track or crossing the suspension bridge that spans the top of Piles Creek.

Snake island backlit 3

Snake Island and Brisbane Water National Park

But I’d prefer to be paddling than driving and I’m a little bit lazy, so I usually put in my boat in closer to home, at Deerubbin, where the freeway crosses the Hawkesbury.  From there I paddle under the freeway and past Spectacle Island, stopping off to check out the Mooney Mooney spoonbill colony, and then upstream.  Once you get past Snake Island and Sailor’s Chest Point, there’s not much sign of human activity, apart from oyster poles.

But there’s plenty going on, even without too many of us humans around.  Last week’s outing was particularly rich in feathery encounters.  A masked lapwing family enjoying a day out by the water by the Mooney Mooney public wharf.

Comedy silver gulls ducking for crabs in the shallows near Spectacle Island.

Silver gull with crab square amend

A sacred kingfisher  in the morning sun near her burrow in an abandoned arborial termite nest.  She got so bored with me clicking away she had a nap.

A striated heron, one of the river side regulars, pretending to be a particularly striking bit of sandstone.

And further up the creek, the predictable but still wonderful sight of a pair of young sea eagles perched amongst the mangroves in the shallow waters of Fox Bay.

The young ones seem to be easier to get close to.  A bit curious and a bit clueless, perhaps, about strange legless creatures that float downstream with the tide.

Even in the peace and quiet, there’s a feeling that all the inhabitants of Mooney Mooney Creek know about us.  They know we’re there – mostly out of sight, maybe, but not entirely out of mind.  The freeway passes just behind the ridge much of the way up the valley. You see it as you pass Snake Island, the trucks and cars  appear briefly, lifted above the rocky escarpment.  Sometimes, further up the creek,  the wind shifts and you can hear the sound of the traffic.

I recently found out that the freeway’s original route went right through my tranquil paddling territory – along Pile Creek, to cross the river south of where the Pacific Highway runs.  Right through kingfisher country.

But someone in the National Parks and Wildlife Service in the late 60s or 70s stood up to the road builders and just said “No”.  No, you can’t build a bloody great big road right through the (then recently established) Brisbane Water National Park.  We’re not having it.  In the words of the surprisingly fascinating “OzRoads” website

This new route had a more expensive bridge and steeper grades than the preferred route but there was nothing the DMR could do about it.

And it’s not often you hear freeway builders say that.  I’d love to  know the full story of who in Parks fought the good fight with the Roads folk.  Everytime I paddle up Mooney Mooney Creek now, I’ll be thinking about them and saying a little thank you.

Sea eagle facing away profile crop

Other paddles from Deerubbin Reserve

Up the Hawkesbury to Bar Island

For the ambitious, further in the same direction to Marramarra Creek

Into the heart of Muogamarra National Park up the winding Kimmerikong Creek

Downriver under the gorgeous if structurally challenged Hawkesbury River Bridge

 

Further references

Boon, Paul (2017) The Hawkesbury River: a social and natural history CSIRO Publishing

 

 

Broken Bay at low ebb

Last weekend I decided to explore the lower reaches of Mooney Mooney Creek from its meeting point with the Hawkesbury, riding on a rising tide. After my spooky solo paddles in Mangrove Creek, I had a hankering for the open horizon and a bit of human life around me. From my put-in at Deerubbin Reserve beside the freeway, and all the way round Spectacle Island, a nature reserve in the mouth of the creek, the constant hum of the traffic and the echoing rumble of trains crossing Brooklyn Bridge remind you that “civilisation” isn’t far away.

Low tide at Mooney Mooney Creek means mud and oyster leases.  The lingering blue haze from last week’s hazard reduction burns descended on the poles and frames, forlorn in the shallows, blurring them into beautiful abstracts.

The story of oyster farming in the Hawkesbury in recent times is a sad one, full of strange historical ironies.

People have been harvesting shellfish from the shores of the river for a very very long time and Sydney rock oyster has been farmed in Broken Bay since the 1880s.  In those days oysters were dredged from the estuary floor and after the meat was eaten, the shells, along with those from ancient middens, were burnt to make lime for mortar.

But in 2004, after a hundred years of farming oysters here, Qx disease hit the Hawkesbury.

The “Q” in the name stands for Queensland.  The Sunshine State produces a 10th of the oyster harvest it did in the nineteenth century, thanks to Qx and to the oyster-infesting mudworm (introduced from New Zealand in the 1880s along with imports of oyster spat). The “x” was a scientific shorthand for “what the hell is this anyway?  We really don’t know”.   Since then, researchers have figured out that Qx is caused by Marteilia sydneyi, a single-celled organism that during the summer infects oysters, causing them not just to slowly starve to death, but also to reabsorb their own gonads (nasty!).  The parasite then releases spores that cycle their way through a polychaete worm, Nephtys australiensis, in the winter, before reinfecting the oysters the following season.

M. sydneyi isn’t always the kiss of death.  The parasite is found in estuaries all along the coast of NSW and Queensland, even in “low risk” areas where Sydney rock oysters are still being commercially grown. Environmental stress, it seems, triggers outbreaks of Qx and surprisingly few wild Sydney rock oysters, the ones I saw lining the rocky shores of Mooney Mooney Creek, die from Qx. Which is good, if mysterious, news.

So, facing of losses of over 90% of the harvest, what could save the oyster industry in the Hawkesbury?

It was noxious pest to the rescue.

The Pacific oyster, farmed in Japan for centuries, was smuggled into Port Stephens in the eighties and spread quickly through the intertidal zones of New South Wales.  It’s a fecund and fast growing bivalve, planktonic eggs and larvae travelling far and wide, crowding, outgrowing, and sometimes settling on and smothering native rock oysters. A “selfish shellfish”, in the words of one inspired Tasmanian subeditor.

The very qualities that have made the Pacific oyster such a hateful invader came to the rescue of the Hawkesbury farmers in 2005.  A process for producing sterile “triploid” Pacific oysters had been developed in North America in the 1980s, with the aim of pumping out meatier shellfish fast. When fertility mean spawning 40 million eggs in a season (not to mention changing sex several times over a lifetime) avoiding reproduction saves a lot of energy.

Local farmers restocked with these “triploid” Pacific oysters.  As well as being immune to Qx, they were ready to harvest in less than two years compared to the three and a half years it takes rock oysters to reach the table.  The new “tamed” Pacific oysters took the Hawkesbury by storm.

And then in 2013 disease struck again. Millions of oysters were wiped out overnight by a virus that affected Pacific oysters and Pacific oysters alone.

Like the oyster itself, the scientifically spawned sterile “triploids”, and indeed the settlers that farm them, “oyster herpes” or POMS (Pacific Oyster Mortality Syndrome), first seen in France in the late noughties, had circled the globe to Broken Bay.

Only three oyster farming businesses are still going in the Hawkesbury these days, hanging on for scant supplies of Qx resistant rock oyster spat, first found amongst the survivors of the Georges’ River outbreak in the mid 1990s.

Right now, the derelict oyster farms are mostly places for posses of pied cormorants to hang out.

But there’s still plenty of life to be found at Mooney Mooney at low water: globe trotters like the eastern curlew, exhausted after a long flight south, and locals like the rock warbler that only lives on Sydney sandstone, compensating for its drab colours and homebody ways with a goth-style nest of grass and spider webs it hangs in the darkness of caves and crevices. And I clocked a new heron record – twenty at least, catching crabs in the mud of low tide.

References

Michael C Dove, John A Nell, Stephen Mcorrie and Wayne A O’Connor “Assessment of Qx and Winter Mortality Disease Resistance of Mass Selected Sydney Rock Oysters” Journal of Shellfish Research 32(3) 681-87 doi: http://dx.doi.org/10.2983/035.032.0309

Wayne A O’Connor and Michael C Dove “The changing face of Oyster Culture in New South Wales, Australia” Journal of Shellfish Research, Vol. 28, No. 4, 803–811, 2009.

J.A. Nell “The history of oyster farming in Australia” Marine Fisheries Review 63(3), 14-25

Nine herons hunting

Nine herons hunting… could it be the beginning of a carol for Christmas-in-July?  Not a bad sound track, perhaps, for a paddle on a wintry 25th down Mooney Mooney Creek.

There were (roundabout) eight cormorants, some of them cacking….

… three posing pelicans

… two eagles soaring

And a kingfisher in a mangrove tree (no photo, naturally).

But realistically, I could only get all the way through the twelve days of anti-Christmas by including the many invisible mud-loving animals that all those herons were stalking.  And I’m not quite sure if I have the alliterative and euphonious verbs to use for them.  Twelve isopods…. idling? Eleven worms a-wobbling? Ten crustaceans crawling?

Even if it can’t offer swans a-swimming or geese a-laying, Mooney Mooney does pretty well for both visible and invisible animals, considering how damn noisy it is.

I first started dreaming about paddling this creek as we swooped above it, across the lofty freeway bridge.  It’s a gorgeous structure, if you are partial to well-formed concrete: elegantly curved, arching vertiginously above the treetops of Brisbane Water National Park.  An endless stream of cars and semis cross the valley on the F1, the main route north from Sydney, on the tallest road bridge in Australia, the still water 75 metres below.

The Pacific Highway, looping its way down to its own modest crossing point, has plenty of traffic too: bikers switchbacking their way up the old road. This Saturday, I didn’t see a soul in three hours on the river, but for a mile or more I could hear the hiss of compression brakes and the revving of engines.

And yet, if I had to pick a place, of all the waterways I’ve paddled so far, to find and fail to take a picture of a kingfisher, this rowdy river is the one I’d choose.  The traffic noise seems to keep the humans at bay, but not the herons.  What’s going on with the wildlife around here?

There’s plenty of evidence that traffic noise bothers birds.  I particularly like a recent experiment where researchers planted speakers in a long line to create a phantom road.  That’s just what the freeway feels like from Mooney Mooney Creek – a road you can hear all over but mostly can’t quite see.  The phantom road, with its invisible traffic masking mating and alarm calls and the sound of approaching predators, cut numbers by a quarter, and drove two species away from the area entirely.

Some cope better than others.  High pitched songs are less likely to be blocked out by the roar of traffic, and so squeaky voiced birds are more likely to hang around in noisy places.  Species with a little vocal versatility often start to sing a bit higher, a little slower or in purer tones, just to be heard.

If you’re carnivorous, being able to hear the critters scuttling around in the bushes is a boon. Seeds and nectar are less likely to make a break for it, so background noise seems to be less of a big deal for the plant-eaters.  Also, birds that feed on the ground seem to mind the noise less – perhaps there’s more obstacles between them and the din.

Everyone agrees that in loud places, birds spend more time on the alert for predators – a high maintenance lifestyle.  That said, some nest-robbers are also put off by the rumble of traffic, so for some species, chicks hatching in noisy nests have a better chance of survival.  If you can handle the decibels, you may have a competitive advantage.

What does all this tell me about the plentiful birdlife of Mooney Mooney Creek?  Thinking about it, I saw high-pitched squeakers, mud-hugging stalkers and sharp-eyed hunters (see, I’m getting into the swing of this avian carol singing thing!)  I’m guessing striated herons don’t echolocate for crabs.  This white-faced pair were happy to ignore not just the distant thunder of trucks but the much more immediate annoyance of a nosy canoeist with a camera.

“The mud is like a Christmas tree”, my eight year old said, hearing the story of my low-tide adventures, “and the bird were excited to find all their presents”.

When the eating is this good, it seems, the soundtrack scarcely matters.

References

Francis, C.D. (2015) “Vocal traits and diet explain avian sensitivity to anthropogenic noise” Global Change Biology 21(5), 1809-1820

Francis, CD and Jesse R Barber (2013). A framework for understanding noise impacts on wildlife: an urgent conservation priority. Frontiers in Ecology and the Environment 11: 305–313. http://dx.doi.org/10.1890/120183

Francis, CD, Ortega, C and Cruz, A. (2009) “Noise Pollution changes avian communities and species interactions” (2009) Current Biology 19(16) pp.1415-19

Patricelli, Gail L. and Jessica L. Blickley (2006) “Avian communication in urban noise: causes and consequences of vocal adjustment” from The Auk 123(3): 639-49