Marine and Freshwater Research Marine and Freshwater Research Society
Advances in the aquatic sciences

Salinity may cause fragmentation of hardyhead (Teleostei: Atherinidae) populations in the River Murray, Australia

Scotte D. Wedderburn A C , Keith F. Walker A and Brenton P. Zampatti B
+ Author Affiliations
- Author Affiliations

A School of Earth & Environmental Sciences DX650 312, The University of Adelaide, SA 5005, Australia.

B SARDI Aquatic Sciences, PO Box 120, Henley Beach, SA 5022, Australia.

C Corresponding author. Email:

Marine and Freshwater Research 59(3) 254-258
Submitted: 31 October 2007  Accepted: 28 February 2008   Published: 30 April 2008


Salinisation in lowland areas of the Murray–Darling Basin, Australia, has had noticeable effects on fish. The endangered endemic Murray hardyhead Craterocephalus fluviatilis is distributed patchily and confined mainly to saline waters (0.4–20 g L–1), whereas the unspecked hardyhead C. stercusmuscarum fulvus has a more continuous distribution but is absent from high salinities (>10). Osmoregulation was compared in these two congeners and an estuarine atherinid, the small-mouth hardyhead Atherinosoma microstoma, over a wide salinity range (0.03–85). All three species are euryhaline, although the osmoregulatory ability of C. s. fulvus falters above ~35 salinity. In low salinity (<1), C. fluviatilis is a better osmoregulator than A. microstoma, but both species tolerate hypersaline conditions (85). These data imply a physiological reason for the predominance of C. fluviatilis in inland saline waters, but the reasons for its absence from freshwater habitats (<0.4) remain unclear. The findings have implications for other freshwater fish, especially populations of closely related species, subjected to the effects of salinisation or other stressors.

Additional keywords: Atherinosoma, Craterocephalus, endangered species, osmoregulation, salinity tolerance.


The present study is from PhD research by S.D.W., co-supervised by K.F.W., B.P.Z., Associate Professor David Paton and Dr Michael Geddes. It was funded by the South Australian Murray–Darling Basin Natural Resources Management Board, the Goolwa to Wellington and Coorong and Districts Local Action Planning boards and the University of Adelaide’s Faculty of Science. We thank Michael Hammer, Nadine Kilsby, Karl Hillyard, Eric Nicholson and Associate Professor Robert Reid for field and laboratory assistance. We are grateful to Dr Wayne Robinson and Dr Lorenzo Vilizzi for statistical advice, and to three anonymous reviewers, and the Editor, for their very helpful comments.


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