Spawning and Recruitment Ecology of Golden Perch (Macquaria ambigua Richardson 1845) in the Murray and Darling Rivers

Abstract

The golden perch (Macquaria ambigua Richardson 1845) is an iconic freshwater fish native to Australia’s Murray-Darling Basin. Like many other native fishes, golden perch have suffered declines in abundance and range since European settlement as a result of overfishing, habitat destruction, and dams that impede migration and regulate flows of the Murray-Darling river system. For more than four decades it has been widely considered that flow pulses and floods are proximate stimuli for spawning, and that floods enhance recruitment to sustain golden perch populations. It has, however, been shown recently that spawning and recruitment can occur in the absence of these conditions, that strongest recruitment events can occur outside of flood periods, and that both spawning and recruitment can occur during periods of low and even zero flows – at least in the dryland rivers of the Basin’s arid zones. Despite observations of golden perch spawning and recruitment across a range of hydrological conditions and locations, much speculation exists within the literature regarding the role of flow pulses and floods in the species’ life history, as there remain few observations of spawning in the wild and even fewer ecological studies of the early life history stages. The aims of this thesis are: to examine major aspects of golden perch life history with emphasis on the role of flows as stimuli to initiate spawning; to examine the role of floodplain habitats in the species’ early life history; to refine a conceptual model of the species’ life history and key life history events; and to evaluate the utility of this model by predicting and recording the role of river regulation in disrupting key life history processes for golden perch. The reproductive ecology of golden perch was examined in the Darling River throughout 2004-2006. During this period, temporal patterns of oöcyte maturity were examined to reveal that spawning could occur at almost any time of the year in the Darling River system. Distinct differences were also examined between the stages of oöcyte maturity observed for mature-aged females at various locations along a broad spatial gradient between Wilcannia and Menindee (~300 km), to reveal a prevailing spatial pattern in the occurrence of ‘ripe’, ‘transitional’ and ‘resting’ golden perch females within this reach of the Darling River.