INTRODUCTION It is generally conceded that the impounding of rivers creates physical barriers to the migration of ﬁsh and other aquatic animals, and alters natural ﬂow, water quality and the thermal regime of river environments. The resulting changes convert the riverine or lotic environment to a lacustrine or lentic one. The survival of natural riverine freshwater ﬁsh populations in impoundments depends on the reproductive success of the species in the newly created environment. Sur vival may be achieved through the ability to use suitable spawning habitats in the inﬂuent river above the lake and/or by recruit- ment success from riverine populations, or combinations of these factors. The reproductive strategies of riverine species in impounded waters have been studied in a number of instances. For example, the reproductive strategies of species of Barbus were studied in Lake Le Roux on the Orange River in South Africa (Cambray & Bruton 1984; Tomasson et al. 1984) and De Silva (1983) discussed the reproductive strategies of introduced and indigenous species in the Parakrama Samudra reser voir in Sri Lanka. The inﬂu- ence of human-induced changes on reproductive traits was studied by Noakes and Balon (1982). Macquarie perch were once widely distributed through- out the cooler upper reaches of the Murray–Darling River system in south-eastern Australia, but their distribution did not often extend to the sources of these rivers (Bishop & Lakes & Reservoirs: Research and Management 2000 5: 281–291 Effects of river impoundment on body condition and reproductive performance of the Australian native ﬁsh, Macquarie perch (Macquaria australasica) Scott C. Gray, 1 Sena S. De Silva, 1 * Brett A. Ingram 2 and Geoff J. Gooley 2 1 School of Ecology and Environment, Deakin University, PO Box 423, Warrnambool, Victoria 3280 and 2 Marine and Freshwater Resources Institute, Snobs Creek, Private Bag 20, Alexandra, Victoria 3714, Australia Abstract This study attempts to evaluate the inﬂuence of the impounding of Lake Dartmouth (36°35'S, 147°31'E; on Mitta Mitta River in Victoria) on the Macquarie perch (Macquaria australasica, Cuvier 1830), an Australian percichthyid ﬁsh of riverine origin. In this study the yearly changes in body condition and spawning performance of adult populations in the impoundment were evaluated in relation to lake features, in particular the water level. Body condition of the spawning population of Macquarie perch in Lake Dartmouth, in year n was related to mean annual storage volume of the lake, with a time lag of one year during the post-ﬁlling phase of the lake (1991–1997). The inﬂuence of condition on the reproductive performance of captive female Macquarie perch from Lake Dartmouth using artiﬁcial propagation techniques was evaluated over the period 1991–1997. The mean relative fecundity (mrf), expressed as the number of eggs produced per kilogram of body weight of hypophysed ﬁsh, showed a decrease over the period, but the mean weight of hypophysed ﬁsh did not decrease over the same time period. The mrf (Ymrf) was positively correlated to yearly mean relative condition factor (XRc), the relationship being: Ymrf = 68692 XRc –43955 (R 2 = 0.58, P < 0.05). The spawning variables, mean percentage fertilization (Yfn) (1991–1997) and mean larval production (Yln) (1992–1996) in each year (n) were also related to the mean relative condition factor (XRc) of female ﬁsh that spawned after hypophysation in each year. It is suggested that the declining success in the artiﬁcial propagation of this species is caused by a declining maternal condition of female ﬁsh collected from the impoundment, resulting from poor nutrition. Key words body condition, Macquarie perch, reproduction, reservoir. *Corresponding author. Email: sena@deakin.edu.au Accepted for publication 18 September 2000.