By Geoffrey M Collins (above: the gorgeous Tully River, courtesy of G. Collins)
Running freshwater has and always will be a novelty for me. I am originally from the mallee country of northern Eyre Peninsula (near Warramboo, South Australia), a region which contains no permanent freshwater above ground (and very little below it). The name Warramboo is from the local Nauo aboriginal language and means ‘place of water’, but this refers to ephemeral samphire swamps and not to any drinkable water. The Great Australian Bight is nearby and I regularly went swimming or fishing in the salt, however the absence of freshwater gave it a strange appeal.
I moved to North Queensland some 2 ½ years ago to further my education in the realm of fish biology at JCU. It wasn’t long before I experienced the first of many fishing trips to the rivers of both the wet and dry tropics, beginning with the Herbert River. I didn’t know the local fish fauna very well, but soon discovered the Herbert to be full of ‘sooties’, ‘junglies’, ‘poons’ and ‘barra’.
Following several successful trips to the Herbert, I got my first real experience of the wet tropics in Tully Gorge. Fishing the Tully by foot is not at all like fishing the Herbert or Burdekin rivers, and I was informed before we set out that stumbling, falling over and getting wet up to my shoulders was par-for-the-course at this locality. This was certainly the case as casting a fly-line required wading in waist-deep in order to reach the far bank, where all the fish are located. All this proved to be worth it though as, up in the Gorge section, the Tully is an extremely healthy ecosystem, despite the altered flow from the hydro plant, and is chockas full of fish. I was told that the Tully contains two types of sooty: the regular ‘sooty’ (Hephaestus fuliginosus) that is distributed throughout much of north-eastern Australia’s tropical rivers, and the ‘Tully sooty’ (H. tulliensis). After casting the fly to a few likely looking locations, I hooked and landed the first of several of these enigmatic fish. The difference between the two closely related species of sooty became immediately apparent when seen up close: the Tully sooty has a sharper snout, relatively smaller mouth-gape, sightly darker colour, more prominent dorsal and pectoral fins and a dark, red eye.
Fig 1 – Adult Tully sooty (Russell River), approx. length = 350mm, (https://www.youtube.com/watch?v=UjxFFRltguo)
Of the 24 recognised species of Terapontids (grunters) in the rivers of Australia, the Tully sooty is unique in being endemic to the wet tropics of north Queensland (Allen et al., 2002). The major rivers of the wet tropics are clear and fast flowing for much of the year, and the Tully sooty is adapted to these conditions by being an exceptionally strong swimmer (personal obs.). Despite their limited range, they are extremely abundant and being one of the larger fish species of the wet tropics, they are one of the first species observed when snorkelling (where it is safe to do so). They regularly form schools with the closely related ‘sooty’ where the range overlaps (personal obs.) and while I have been able to immediately tell the difference between the two species, it is possible that a hybrid of these two exists in some regions (Pusey et al., 1995). Adding to the mystery here, a recently completed genetic study found that H. tulliensis groups more closely with species in the genera Syncomistes and Scortum than with others in the ascribed genus Hephaestus (Davis et al., 2014). Another characteristic I have noticed that may be used to distinguish the two species is the prominence of dorsal spines in H. tulliensis (the webbing between spines on the anterior dorsal fin extends between the tips of fins in H. fuliginosus, but takes more of a serrated appearance in H. tulliensis) (personal obs.).
Fig 2 – Juvenile Tully sooty (Russell River), approx. length = 80 mm
Other distinguishing characteristics of this species, are the mottled body colourations (seen only in certain individuals and differing from river to river) (Pusey et al., 2004; personal obs.) and an unusual condition where the lips protrude from the mouth and exhibit a fleshy, blubbery (hypertrophied) condition (correlated with dietary shifts in H. fuliginosus) (Pusey et al., 1995).
Fig. 3 – Sub-adult Tully sooty (Tully River), blubber-lipped condition, approx. length = 200 mm
I should state here that I am not actively researching the Tully sooty: my PhD focusses on the effects of hypoxia and temperature on physiological responses in genetically-distinct populations of barramundi (Collins et al., 2013). Growing to over a metre in length, and having significant commercial value (as well as being great to eat) barra have attained an iconic status in tropical Australia. This species displays habitat affinity with the natal river (not quite as strong as Pacific salmonids) and is distributed from Onslow (WA) to Maryborough (QLD). Environmental conditions (temperature and dissolved O2) vary enormously across the species’ distribution (Butler & Burrows, 2007 ; Walker et al., 1984), and while genetic differences between populations have been well established (Jerry et al., 2013), it remains unclear just how phenotypically and physiologically different the populations are.
Barra occupy most of my 9-to-5 time, but I still enjoy investigating my favourite Aussie freshwater native in its natural environment (which just happens to be some of the most stunning country in all Australia). While significant progress has been made in understanding the physiology and environmental tolerance of barra, similar information is lacking for not only the Tully sooty, but for many other species endemic to the wet tropics and provides scope for future research.
Fig. 4 – Dorsal fins of sooty grunter (H. fuliginosus; A & B) and the Tully sooty (H. tulliensis; C &D)
Geoffrey can be contacted at: [email protected]
Allen GR, Midgley SH, Allen M (2002) Field Guide to the Freshwater Fishes of Australia, CSIRO Publishing, Collingwood, VIC, Australia.
Butler B, Burrows D (2007) Dissolved oxygen guidelines for freshwater habitats of northern Australia. ACTFR Report No. 07/32. Australian Centre for Tropical Freshwater Research, James Cook University, Townsville, QLD, Australia, pp. 51.
Collins GM, Clark TD, Rummer JL, Carton AG (2013) Hypoxia tolerance is conserved across genetically distinct sub-populations of an iconic, tropical Australian teleost (Lates calcarifer). Conservation Physiology, 1.
Davis AM, Unmack PJ, Pusey BJ, Pearson RG, Morgan DL (2014) Effects of an adaptive zone shift on morphological and ecological diversification in terapontid fishes. Evolutionary Ecology, 28, 205-227.
Jerry DR, Smith-Keune C, Hodgsone L, Pirozzi I, Carton AG, Hutson KS, Brazenor AK, Gonzalez AT, Gamble S, Collins GM, VanderWal J (2013) Vulnerability of an iconic Australian finfish (barramundi – Lates calcarifer) and aligned industries to climate change across tropical Australia. Fisheries Research and Development Corporation and James Cook University, Townsville, QLD, Australia, pp. 222.
Pusey B, Read M, Arthington A (1995) The feeding ecology of freshwater fishes in two rivers of the Australian wet tropics. Environ. Biol. Fish, 43, 85-103.
Pusey BJ, Kennard MJ, Arthington AH (2004) Freshwater Fishes of North-Eastern Australia, CSIRO Publishing, Collingwood, Vic, Australia.
Walker TD, Waterhouse J, Tyler PA (1984) Thermal stratification an the distribution of dissolved oxygen in billabongs of the Alligator Rivers region, Northern Territory (Final Report). In: A limnological survey of the Alligator Rivers region, Northern Territory. Department of Botany, University of Tasmania, Hobart, pp. 181.