NATIVE

Common Name Short-headed

ScientificN ame mordax (Richardson, 1846) Photo: Michael Hammer Photo: Michael

Identification Small to medium sized, slender and elongated, with a scaleless, -like body. Adults are commonly 300–440 mm long in freshwater situations (maximum size ~500 mm). Two low dorsal fins are situated well back on the body near the rounded caudal fin, Photo: Michael Hammer Photo: Michael and paired pectoral and pelvic fins are absent. Lampreys lack jaws; instead adults have a well-developed suctorial oral disc with sharp, the body surface. A large, hood-like upper radially arranged tooth plates. There aretwo lip overhangs the small mouth. Brownish in large tricuspid teeth on the oral disc above the colour, ammocetes are darker on the dorsal mouth and no fimbriae (fringing filaments) surface and reddish around the gills because surrounding the oral disc. In mature adults, of the underlying blood vessels. They can be the radial toothplates disappear. The eyes of distinguished from ammocetes of the Pouched adults are dorsolateral, and both adults and lamprey by the position of the vent, which is ammocetes have seven small oval gill apertures below a point about halfway along the length on each side of the body behind the head. of the second dorsal fin. Adults are bluish-grey dorsally just before and after their marine phase; during their Biology and Habitat spawning migration they are a duller grey. Most of the adult life is spent at sea or in The larval juvenile life phase (ammocete) is estuaries. Young adults migrate upstream usually less than 140 mm long, worm-like, from the sea in spring and summer to breed lacks eyes and tooth plates, and the dorsal in rivers. The spawning run lasts for about fins are very low, not extending far above a year, before they spawn the following

28 Fishes of the Murray-Darling Basin An introductory guide 29 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

spring, from August–November. During the even Narrandera on the Murrumbidgee), spawning run, individuals are usually active but otherwise found in coastal rivers in Vic, nocturnally, and burrow into the substrate NSW, SA and Tas. In recent times adults are during the day. Females have 3,800–13,400 rarely seen, but formerly they could be seen in small eggs, (0.3–0.5 mm diameter), which are large numbers in the lower Murray on their deposited in a shallow nest (small depression) spawning run at migration barriers such as in the substrate, often in shallow, relatively weirs. There are recent records of this species fast water. Adults die shortly after spawning. from below the Goolwa Barrage. Ammocetes Ammocetes are sedentary and live in slow- are reasonably common in suitable silty flowing streams, burrowing in silt or mud, for habitats. about three years before metamorphosing (at around 100–140 mm length) and migrating Potential Threats down to the sea, usually in spring. Barriers to fish movement can interfere with The ammocetes are toothless, feeding on spawning migrations, although the species can algae, detritus and micro-organisms filtered climb wet vertical surfaces. from the water. After metamorphosis to General References adulthood, they become parasitic on other fish, rasping a hole in the side and feeding on Allen et al. 2002; Cadwallader & Backhouse blood and/or muscle. Adults cease feeding 1983; Gilligan 2005a,b; Hughes & Potter prior to their spawning migration. 1968; Koehn & O’Connor 1990; Potter 1970, 1996a; Wedderburn & Hammer 2003. Distribution and Abundance Generally restricted to the lower to mid Murray River in the Basin (occasionally recorded as far upstream as Yarrawonga and

28 Fishes of the Murray-Darling Basin An introductory guide 29 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. Graphical and textual information in the work (with the exception of photographs, artwork and the MDBC logo) may be stored, retrieved and reproduced in whole or in part provided the information is not sold or used for commercial benefit and its source (Fishes of the Murray-Darling Basin) is acknowledged. Such reproduction includes fair dealing for the purpose of private study, research, criticism or review as permitted under the Copyright Act 1968. Reproduction for other purposes is prohibited without the permission of the Murray- Darling Basin Commission or the individual photographers and artists with whom copyright applies. To extent permitted by law, the copyright holders (including its employees and consultants) exclude all liability to any person for any consequences, including but not limited to all losses, damages, costs, expenses and any other compensation, arising directly or indirectly from using this report (in part or whole) and any information or material contained in it.

ii Fishes of the Murray-Darling Basin