Smallmouth Hardyhead, Atherinosoma microstoma (Günther 1861)
Smallmouth Hardyheads, Atherinosoma microstoma, in Wirrina Cove, South Australia, January 2018. Source: David Muirhead / iNaturalist.org. License: CC By Attribution-NonCommercial
Small silvery schooling fishes with two widely separated dorsal fins, a forked tail, large eyes, a tiny mouth and jaws with large canine teeth. During the breeding season, males develop bright orange stripes along their sides.
Smallmouth hardyheads are usually iridescent silvery to olive-green above and paler below, with a distinct mid-lateral stripe. They can tolerate a wide salinity range and are often seen swimming in schools in south-eastern Australia, especially in brackish waters.
Smallmouth Hardyhead, Atherinosoma microstoma (Günther 1861)
More Info
|
Distribution |
Endemic to temperate streams, inland lakes, estuaries and adjacent marine areas of south-eastern Australia, from Tuggerah Lakes, New South Wales, to Lake George, South Australia, including coastal and Bass Strait regions of Tasmania and Victoria. Smallmouth Hardyheads inhabit the lower reaches of coastal drainages and adjacent marine waters, including estuaries and occasionally the lower freshwater reaches of rivers. They often form large schools and prefer estuarine sea-grass habitats, or areas with aquatic vegetation. |
|
Features |
Dorsal fin V-IX, I, 8-11; Anal fin I, 8-13; Caudal fin 17; Pectoral fin 12-16; Pelvic fin I, 5; Gill rakers 12-15; Vertebrae 37-42; Midlateral scales 36-41; Transverse scales 7. Head and body: Body long and slender, dorsal profile almost flat, ventral profile convex; caudal peduncle long, slender. Head moderately large, snout pointed to slightly rounded, eye large, positioned high on side of head near dorsal profile. Mouth small, terminal, upturned, barely protrusible, lips thin, gape not quite reaching eye. Jaws teeth fine, with larger and distinctly fang-like canines; vomer and palatines usually with obvious teeth. Scales: head and body covered with large cycloid scales, lateral line absent. Fins: Two short-based dorsal fins, first small, centred on back, originating three to six scales in front of vertical through pelvic-fin tips, widely separated from second dorsal fin by six to ten scales. Second dorsal fin high, tapering sharply posteriorly, base longer than that of first dorsal fin. Anal fin similar to and nearly opposite second dorsal fin. Caudal fin forked, fin tips pointed, upper lobe slightly longer than lower lobe. Pectoral-fin base mostly above middle of side. Pelvic fins small, abdominal, originating below or just behind pectoral-fin tip; pelvic-fin tips reaching just before to just beyond anus. |
|
Size |
To 10.7 cm standard length |
|
Colour |
Translucent green to olive green above, pale green, yellowish or silvery below; midlateral stripe broad, silvery, brown or coppery red; abdomen, opercle and preopercle usually silvery with blue or green iridescent sheen; fins transparent; operculum bright silver, eye silver. During the breeding season, males develop bright orange stripes along their sides. |
|
Feeding |
Feed mostly on small benthic crustaceans, insects, gastropods and polychaete worms. |
|
Biology |
Smallmouth Hardyheads are short-lived and breed from September to October before dying shortly afterwards. The sexes are separate and fertilisation is external. They spawn in pairs, and females lay demersal eggs amongst aquatic vegetation. The pelagic larvae hatch after 5-7 days. |
|
Fisheries |
Although there is no fishery for Smallmouth Hardyheads, they are often used as bait by recreational anglers. |
|
Conservation |
Not evaluated |
|
Remarks |
Smallmouth hardyheads are remarkably euryhaline, able to tolerate a broad range of salinities. They live in almost pure freshwater in Tasmania, as well as in some highly saline Victorian lakes. |
|
Similar Species |
The similar Elongate Hardyhead, Atherinosoma elongata, differs in having 3 scale rows above the lateral line, no tooth patches on the tongue, and a slightly more slender body - vs 2 scale rows above the lateral line and oval tooth patches on the tongue, and occurring in freshwater to marine habitats. |
|
Etymology |
Atherinosoma is from Greek meaning pointed body and microstoma is from Greek meaning small mouth. |
|
Species Citation |
Atherina microstoma Günther 1861, Cat. Fishes Brit. Mus. 3: 401. Type locality: Tasmania. |
|
Author |
Bray, D.J. & Thompson, V.J. 2017 |
|
Resources |
Smallmouth Hardyhead, Atherinosoma microstoma (Günther 1861)
References
Allen, G.R., Midgley, S.H. & Allen, M. 2002. Field guide to the freshwater fishes of Australia. Perth : Western Australian Museum 394 pp.
Cadwallader, P.L. & Backhouse, G.N. 1983. A Guide to Freshwater Fish of Victoria. Victorian Government Printing Office, Melbourne.
Castelnau, F.L. de 1872. Contribution to the ichthyology of Australia. 1. The Melbourne fish market. Proceedings of the Zoological and Acclimatisation Society of Victoria 1: 29-242 1 pl. (as Atherinichthys modesta in part, and Atherinosoma vorax)
Günther, A. 1861. Catalogue of the Acanthopterygian Fishes in the Collection of the British Museum. London : British Museum Vol. 3 586 pp.
Hammer, M.P., Adams, M. & Foster, R. 2012. Update to the catalogue of South Australian freshwater fishes (Petromyzontida & Actinopterygii). Zootaxa 3593: 59–74
Higham, J., Ye, Q. & Smith, B. 2005. Murray-Darling Basin Drought Monitoring: Monitoring Small-bodied Fish in the Lower Murray During and After Drought Conditions in 2003-2004. SARDI Research Report Series No. 73. SARDI Aquatic Sciences, Adelaide.
Ivantsoff, W. 1978. Taxonomic and systematic review of the Australian fish species of the family Atherinidae with references to related species of the Old World. Unpubl. Ph.D. Thesis Sydney : Macquarie Univ. 701 pp. 118 figs
Ivantsoff, W. & Crowley, L.E.L.M. 1996. Family Atherinidae, Silversides or Hardyheads, pp. 123-133. In McDowall, R.M. (ed.) Freshwater Fishes of South-eastern Australia. Second edition. Reed Books, Sydney.
Kuiter, R.H. 1993. Coastal fishes of south-eastern Australia. University of Hawaii Press, Honolulu. i-xxxi + 1-437.
Kuiter, R.H. 1996. Guide to sea fishes of Australia. A comprehensive reference for divers and fishermen. New Holland Publishers, Frenchs Forest, NSW, Australia: 1-434.
McCulloch, A.R. 1911. Report on the fishes obtained by the F.I.S. Endeavour on the coasts of New South Wales, Victoria, South Australia and Tasmania. Part 1. Zoological (Biological) Results. Endeavour 1(1): 1-87 figs 1-20 pls 1-16 (as Taeniomembras microstoma)
McDowall, R.M. (ed.) 1996. Freshwater fishes of south-eastern Australia. Sydney : Reed Books 247 pp.
Molsher, R.L., Geddes, M.C. & Paton, D.C. 1994. Population and reproductive ecology of the small-mouthed hardyhead Atherinosoma microstoma (Günther) (Pisces: Atherinidae) along a salinity gradient in the Coorong, South Australia. Transactions of the Royal Society of South Australia 118: 207-216.
Pavlov, A., W. Ivantsoff, P.R. Last & L.E.L.M. Crowley. 1988. Kestratherina brevirostris, a new genus and species of silverside (Pisces: Atherinidae) with a review of atherinid marine and estuarine genera of southern Australia. Australian Journal of Marine and Freshwater Research 39: 385-397.
Potter, I.C., Ivantsoff, W., Cameron, R. & Minnard, J. 1986. Life cycles and distribution of atherinids in the marine and estuarine waters of southern Australia. Hydrobiologia 139: 23-40.
Raadik, T.A. 2008. Family Atherinidae. pp. 395-400 in Gomon, M.F., Bray, D.J. & Kuiter, R.H. (eds). Fishes of Australia's Southern Coast. Sydney : Reed New Holland 928 pp.
Stuart, I., Ye, Q., Higham, J. & O’Brien, T. 2005. Fish Migration at Tauwitchere Barrage: New Options for Fish Passage. Murray-Darling Basin Commission, Canberra. 33 pp.
Wedderburn SD, Bailey CP, Delean S, Paton DC. 2015. Population and osmoregulatory responses of a euryhaline fish to extreme salinity fluctuations in coastal lagoons of the Coorong, Australia. Estuarine, Coastal and Shelf Science 168: 50-57. doi:10.1016/j.ecss.2015.11.015 Abstract
Wedderburn, S. & Hammer, M. 2003. The Lower Lakes Fish Inventory: Distribution and Conservation of Freshwater Fishes of the Ramsar Convention Wetland at the Terminus of the Murray-Darling Basin, South Australia. Native Fish Australia (SA) Inc., Adelaide. 38 pp.
Whitley, G.P. 1934. New fish from Victoria. Victorian Naturalist 50(10): 241-242 1 fig. (as Pranesella endorae)
Whitley, G.P. 1943. Ichthyological descriptions and notes. Proceedings of the Linnean Society of New South Wales 68(3, 4): 114-144 figs 1-12
