By Chris Bice
Written 17 December 2013, Posted April 2014
The Congolli as it is known in South Australia (or Tupong if you’re from Victoria or Sandy if you’re Tasmanian), is a small-medium sized fish (up to about 350 mm) native to coastal streams of south eastern Australia (McDowall 1996). Body colouring can vary between individuals and habitats, but it is typically light brown with dark brown blotches or bars on the sides and dorsal surface, and white on the ventral surface. A benthic species, the Congolli has a flattened head with a pair of high set eyes and a large mouth. It also doesn’t have a swim bladder like most other ray-finned fishes. The Congolli is an ambush predator, commonly burying itself in the substrate with just its eyes protruding, before bursting out and preying upon unsuspecting small fish, crustaceans and aquatic insects.
The Congolli is a catadromous species meaning it resides in freshwater habitats as an adult, but spawns in the ocean. As such, the ability of adults to migrate from freshwater to marine habitats to spawn and then for juveniles to migrate upstream into freshwater habitats is fundamental for the persistence of populations of this species. Subsequently, barriers to migration in the form of barrages, weirs, culverts, etc. represent a significant threat to this species throughout its range.
Interestingly, Congolli display marked sexual dimorphism. All fish over 200 mm are invariably mature females, whilst male size maxes out at only 150 mm. Furthermore, there appears to be sexual segregation in habitat use with mature females most common in freshwater habitats and the smaller males more common in brackish and estuarine habitats. In the Lower Lakes of the River Murray, adult females migrate downstream to meet up with the males and spawn in winter (Zampatti et al. 2011).
When they decide to migrate, their desire for a rendezvous with the males is surprisingly strong – one female, tagged with an acoustic transmitter, was observed to migrate downstream a distance of 35 km in one night; not a bad effort for a small fish that doesn’t have a swim bladder! Studies on the movement of female Congolli in both South Australia and Victoria (Crook et al. 2010) did not detect return movements of adult female Congolli from the ocean, suggesting the species is semelparous – that is the adult females die after spawning.
Congolli were much more abundant throughout their range prior to the damming and regulation of south eastern Australia’s coastal rivers. Indeed they once comprised a significant proportion of the commercial fishery in the Lower Lakes and Coorong in South Australia, and were commonly used as live bait by the same commercial fishers when targeting mulloway at the Murray Mouth (Evans 1991). Nonetheless, increased knowledge of the life-history of Congolli has highlighted key issues (notably connectivity between riverine and marine environments to allow migrations) to be addressed by environmental managers to ensure the conservation of this unique species.
Chris Bice is a fish ecologist based in Adelaide, South Australia. Chris’s areas of expertise include threatened species ecology, fish movement and the response of fish to altered flow regimes.
Crook, D. A., W. M. Koster, J. I. Macdonald, S. J. Nicol, C. A. Belcher, D. R. Dawson, D. J. O’Mahony, D. Lovett, A. Walker and L. Bannam (2010). Catadromous migrations by female tupong (Pseudaphritis urvillii) in coastal streams in Victoria, Australia. Marine and Freshwater Research 61: 474-483.
Evans, D. (1991). The Coorong. A multi-species fishery. Part 2. Fishing Methods, Technology and Personal Experiences 1930-1966 and Gear Statistics 1972-1989, Fish Research Paper, Department of Fisheries South Australia. McDowall, R. M., Ed. (1996). Freshwater fishes of south-eastern Australia. Sydney, Reed.
Zampatti, B. P., C. M. Bice and P. R. Jennings (2011). Movements of female Congolli (pseudaphritis urvillii) in the Coorong and Lower Lakes of the River Murray South Australian Research and Development Institute (Aquatic Sciences), Adelaide. SARDI Publication No. F2011/000333-1. SARDI Research Report Series No. 577. 32pp.
Hey Ebb, Tough question, I suppose they are one of my favourite fish species for a few reasons, firstly they aren’t particularly common (it’s easier to like the species that are a little more rare), secondly, I find the catadromous life-history pretty interesting and last, whilst physically they are very tough fish – you can directly transfer them between freshwater and marine water and vice versa with apparently no impact, and they seem more or less impervious to handling – they are highly vulnerable to the impacts of river regulation due to their migratory life history. Sounds pretty artsy, but I think it’s this contrast between ‘toughness’ and vulnerability that makes them appealing. Feel free to incorporate this however you like
Editor’s note: I think your email says it just fine.