NATIVE SPECIES Common Name Darling River hardyhead Scientific Name Craterocephalus amniculus Crowley & Ivantsoff, 1990 Photo: Gunther Schmida Identification head of pools. Almost nothing is known of A small, laterally compressed fish with a its life history. Small subadult specimens have small protrusible mouth, thin lips, large been collected in September, but the breeding silvery eye and moderately short, blunt gill details are unknown. It can be found singly rakers. Maximum size 55 mm. There are or in small or large schools (50+ fish). In the two small, short-based dorsal fins, with the Macintyre River, spawning appears to span at second directly above the anal fin. The tail least September to February. is forked, the pectoral fins are positioned Distribution and Abundance high on the body and the anal fin has 5–8 rays. The scales are small and rarely overlap; This hardyhead is found in the northern the midlateral scale count is 37–38 and the Murray-Darling Basin in the upper tributaries transverse count 14–18. There are usually no of the Darling River near the Qld–NSW scales on top of head, but if present they are border. It is also known from the headwaters small and circular. The back is dusky gold, of the Hunter system in coastal NSW. In the midlateral stripe is dark and silvery with the Basin it is patchily distributed, and silvery gold below, and the ventral surface known from the Condamine, Peel, Namoi, is always paler, with a silvery sheen. The Macintyre and Cockburn rivers and Boiling opercula are bright silver. Down and Warialda Creeks. It is reportedly relatively common in these locations. Recent Biology and Habitat fish sampling in the upper Dumaresq, Mole The Darling River hardyhead is found in and Severn rivers in northern NSW found slow-flowing, clear, shallow waters or in Un-specked hardyheads in abundance and aquatic vegetation at the edge of such waters. a concomitant absence of C. amniculus, It has also been recorded from the edges of while the reverse was true for the upper faster-flowing habitats, such as runs at the Macintyre River. Although abundant at sites where riparian cover is moderate to good 58 FISHES OF THE MURRAY-DARLING BASIN AN INTRODUCTORY GUIDE 59 ID VALLEY 1 Avoca 2 Border Rivers 3 Broken 4 Campaspe 5 Castlereagh 6 Central Murray 7 Condamine 8 Darling 9 Goulburn 10 Gwydir 11 Kiewa 12 Lachlan 13 Loddon 14 Lower Murray 15 Macquarie 16 Mitta Mitta 17 Murrumbidgee 18 Namoi 19 Ovens 20 Paroo 21 Upper Murray 22 Warrego 23 Wimmera in the Macintyre, it is not known whether General References hardyheads also occur further upstream where Crowley & Ivantsoff 1990; Ivantsoff & the riparian cover is either poor or dominated Crowley 1996; Morris et al. 2001; Harris & by willows and other exotic species. The NSW Gehrke 1997; Gehrke & Harris 2004; (P. Rivers Survey failed to record any individuals. Unmack unpubl. data) (G. Wilson unpubl. The Pilot Sustainable Rivers Audit also failed data). to record any individuals at the ‘best available’ sites in the northern Basin and at the assessment sites in the Condamine drainage. In the first two sampling rounds of the Audit, a total of 39 individuals were recorded: 1 from the Border Rivers and 38 from 3 sites in the Namoi. In NSW the species has been recorded between about 250–900 m altitude. Potential Threats The relatively recent recognition of this species means that any declines have not been documented. Water abstraction may be an issue in the smaller creeks that it occupies. Other hardyheads are potentially threatened by habitat degradation, altered flow regimes and impacts of alien species such as Eastern gambusia. 58 FISHES OF THE MURRAY-DARLING BASIN AN INTRODUCTORY GUIDE 59 Published by the Murray-Darling Basin Commission Postal address: GPO Box 409, Canberra ACT 2601 Office location: Level 3, 51 Allara Street, Canberra City ACT Telephone: (02) 6279 0100, international + 61 2 6279 0100 Facsimile: (02) 6248 8053, international + 61 2 6248 8053 Email: [email protected] Internet: http://www.mdbc.gov.au For further information contact the Murray-Darling Basin Commission office on (02) 6279 0100 This fish fact sheet is an extract derived from the report: Lintermans, M. 2007, Fishes of the Murray-Darling Basin: An introductory guide. MDBC Publication No. 10/07 ISBN 1 921257 20 2 © Murray-Darling Basin Commission 2007 This work is copyright. 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