By Daniel Stoessel
(Cover image photographer: Dan Stoessel)
It was late September in the alpine reaches of Victoria. The air temperature was a brisk 13ᵒC, worse still, the stream water temperature was around 8ᵒC. Looking around at my trusty team, they stared shivering, dazed, and with some horror, at one of three streams I expected them to get into over the next three days in search of barred galaxias nest sites! Despite the hesitation, over the next three days the team found a total of 13 nests, which was pretty amazing considering only two had ever been previously located.
The species under question, barred galaxias, is a threatened native fish which grows to around 160 mm in length. The species is now restricted to only a handful of isolated sites in headwater streams of the Goulburn River system in Victoria. Knowledge of barred galaxias ecology is pretty sketchy. This study has helped to fill the information void by documenting details of nest sites, incubation and hatching of eggs, as well as the raising of larvae.
We confirmed that spawning of the species occurred from late winter to early spring in riffles immediately upstream of pools (Stoessel et al. 2015). Interestingly, there was also a suggestion that female barred galaxias deposited eggs at a number of sites rather than a single site (Stoessel et al. 2015), a behaviour which has only ever been documented for one other galaxiid, the flat-headed galaxias Galaxias rostratus (Llewellyn 1971). On return to the lab, eggs placed into incubators took a maximum of 48 days to hatch, and newly hatched larvae were approximately 9 mm in length (Stoessel et al. 2015).
Barred galaxias monitoring (photographer: Renae Ayres)
Knowledge gained of the species reproductive ecology, was used to breed several hundred barred galaxias, which, in addition to those hatched from the wild, were used to bolster parent populations badly affected by the devastating Black Saturday bushfires, and also to establish a small number of translocated populations. The success of the project is a real credit to the science employed, and in particular the team. For further information regarding the study, refer to: http://openjournals.library.usyd.edu.au/index.php/LIN/article/view/8635
Llewellyn, L.C. (1971). Breeding studies on the freshwater forage fish of the Murray-Darling River system. The Fisherman 3, 1–12.
Stoessel, D.J., Raadik, T.A. and Ayres, R.M. (2015). Spawning of threatened barred galaxias, Galaxias fuscus (Teleostei: Galaxiidae). Proceedings of the Linnean Society of New South Wales 137, 1–6.