The quest for a ‘fat-gut’

By Aaron Davis

I guess like most fish researchers, I have several ‘favourite fish’, so when asked to nominate a favourite terapontid grunter, I had to put some thought into it. I love watching Coal grunter (Hephaestus carbo) in their natural habitat, they’re a stunning fish found in beautiful environments, and at the risk of anthropomorphism, have genuine personality (being totally unafraid of swimming up and giving the clumsy two-legged intruders into their habitats a thorough checking-over). But my favourite terapontid would probably be something a bit different, the Small-headed grunter, Scortum parviceps. Endemic to the Burdekin River catchment, I’ve found them a somewhat elusive fish. My first real encounter with them took place in the very early stages of my PhD, when my supervisor (Brad Pusey) suggested if I needed some specimens for dietary and morphometric analysis, that my best bet would be the upper Burdekin catchment, at the same time warning me they could be a bit ‘hit and miss’ to find. I was soon at Reedy Brook station (my father in tow as a field assistant) in the picturesque basalt country of the upper Burdekin River, trying to describe to the somewhat bemused grazier the specific fish I was after (most people head up there to catch Sooty grunter, Hephaestus fuliginosus). Then he stated ‘Ah, I know what you mean, you want some ‘Fat-guts’. I know a spot where we get them, but they taste like sh&t.’ (if they taste anything like their congener S. ogilbyi, this is a fair assessment).

An hour or so later (after some navigational issues) we were at a beautiful, essentially untouched lagoon nestled against a hill side, setting up camp. I soon caught my first Fat gut on a strip of meat (despite subsisting mainly on plants, they do opportunistically take animal prey), and once in hand saw the reason for the grazier’s description. They’re built like footballs, almost as wide as they are long (being a specialised herbivore they have a characteristically long intestine, giving them their local ‘fat-gut’ moniker), and are a surprisingly powerful fish on a fishing line, especially larger models pushing 400 mm total length (a couple busted off my father’s line, which was pointed out as obviously due to his poor knot-tying abilities). I’d strung up a gillnet and within a ½ hour had 25 fish on ice, so my first field collection was off to a flyer. I’m not even sure why I like this fish so much, but their contrast to the closely related sooty grunter piqued my interest in evolutionary drivers of morphological diversification straight away (which then became a central theme of my PhD). Some of the appeal may be the beautiful country I chased them in (with the ‘old man’, which is always nice), or the fact this initial success gave me much needed confidence at the early stages of the PhD (when you really do wonder if you’re making the right move). I caught quite few more Fat-guts over the next few years, but never with so much success. Being a specialised herbivore (quite rare for Australian fish), they became one of the stars of my research.

About me: I’m not even sure how to describe myself professionally (some of my colleagues joke about my professional identity crisis). My ‘real’ job (that pays the bills) deals mainly with water quality in the Great Barrier Reef, which is interesting, challenging and rewarding in the sense of feeling you can make a difference. Fish are almost a sideline hobby, but something I enjoy immensely (its nice, but uncommon, when these two threads meet), although, my favourite fish evolutionary research topics admittedly don’t have much of an applied basis. I guess I could be classified broadly as a freshwater ecologist, dabbling across water quality, fish, even ‘bugs’ (macroinvertebrates). I actually started out as a bug person, spent a few years staring down a microscope, saw the light, got into fish diet, and then proceeded to spend 5 years staring down microscopes at the bugs fish ate (though the macroinvertebrate ID skills I gained were probably the best grounding I could have had for my PhD in hindsight).

Photo: One of my first ‘Fat-guts’. The picture doesn’t really give justice as to how ‘broad across the beam’ these fish are.

Aaron Davis mug shot
Editor’s note: Dr Aaron Davis does not act like a doctor, in the nose-up kind of way at least. But gee he publishes some great research papers on the grunters.