The Todd River in Alice Springs; in flood on the 8th January 2015 (Photo Bridget May), and its normal dry self just two weeks earlier (MH)
Why did the fish cross the road? My cheeky kids informed me it was because the chickens were too wet! I’d just received an iPhone photo from a reporter in Alice Springs, an amazing right-place right-time shot of a pair of Spangled Perch navigating a road crossing on a tributary to the Todd River. The arid interior had over the last week received a widespread rain dump in the order of 100-200 millimetres; this had leaked down from the northern monsoon as a new year’s treat. These rare events (typically every few years but up to ten or so years apart) signal flash flooding over hundreds of kilometres of normally dry streams and rivers. The Todd which runs through the heart of Alice Springs ran a ‘banker’ following the rain, cutting the town in half for a couple of days. Just two weeks earlier I had visited Alice and observed with interest the dry river bed who’s trees and bushes were on a permanent slant from occasional flood force trauma, and remember thinking I wonder how many years it would be before it would be flowing again…
Map of recent rainfall across Central Australia (BoM) and a Spangled Perch from the Barkly Tablelands (MH)
The reporter who had spotted the perch crossing the road, like many that come across fish in the desert, marvelled at the presence and tenaciousness of these little guys. Spangled Perch Leiptherapon unicolor a non-grunting member of the grunter family Teraponitdae (aka Bobby Cod, Perch or Spangs – see Iain Ellis’s great article hyperlink) are a truly remarkable fish. They occur in almost every permanent or semi-permanent waterhole across inland Australia and are fast swimmers, needing only a small amount of water to travel vast distances across the desert. I occasionally field public and media queries about rains of fishes involving Spangled Perch, where they were purportedly sucked up by a storm from a waterhole and released at some unassuming site far from a river. While we can’t rule these scenarios out,given the species’ amazing swimming ability its most plausible that they swim to the areas where they are observed (how a marine mullet came to be on the roof of my suburban Darwin home, however is another matter).
The Spangled Perch is the only native fish known from the Todd River catchment, but a much richer fauna is found in the larger Finke Catchment running parallel to the west. Nine species, including three found nowhere else (Finke Hardyhead, Finke Purple-spotted Gudgeon and Finke Goby) are spread along the ~600km of river (albeit only as occasional residents in the lower reaches), beginning in the spectacular WestMacDonnell Ranges then heading southeast towards Lake Eyre. The Finke loop is a great day trip from Alice Springs to see the Finke River at a couple of sites including four-wheel-driving along the river to Palm Valley, and at waterholes like Ellery Creek Big Hole where you can quietly observe some of the local native fish going about their business.
I must be good luck as far a desert precipitation goes, as it rained on my last sojourn to the desert too, as part of a Bush Blitz Species Discovery Expedition hunting for fish along the central Finke River and West MacDonnell Ranges. This was not flooding rain, but enough to refresh refuge waterholes, and to make station tracks turn to mud leaving us immobilised for few days. Seeing burrowing frogs materialise and claypans come to life with ancient looking shield shrimps more than made up for it though. On this trip I was fortunate to be able to access some remote sites by helicopter, which gave a great perspective on how much dry riverbed is out there, and how important the occasional refuge waterholes is between the flood times.
Michael is the Curator of fishes at the Museum & Art Gallery of the Northern Territory in Darwin [email protected]
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Bostock BM, Adams M, Austin CM & Laurenson LJB (2006) The molecular systematics of Leiopotherapon unicolor (Günther, 1859): testing for cryptic speciation in Australia’s most widespread freshwater fish. Biological Journal of the Linnean Society, 87, 537–552.
Ellis, I (2014). Species profile: Spang, Leioptherapon unicolor (Günther, 1859). www.themorayslair.org/spang-leioptherapon-unicolor-gunther-1859, accessed January 2015.
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