Oral Presentation Australian Society for Fish Biology Conference 2017

River flows support key life-history events of spotted galaxias (Galaxias truttaceus) in south-western Australia (#46)

Paul G Close 1 , David L Morgan 2 , Stephen J Beatty 2 , Mark G Allen 2
  1. Centre of Excellence in Natural Resource Management, University of Western Australia, Albany, WA, Australia
  2. Freshwater Fish Group & Fish Health Unit, Centre for Fish & Fisheries Research, Murdoch University, Murdoch, Western Australia, Australia

Western Australian populations of the spotted galaxias (Galaxias truttaceus) have recently been proposed as an ‘ecologically significant unit’. Conservation of the species is supported by a recovery plan, however knowledge of recruitment dynamics constrains implementation of management strategies. Unlike the diadromous life cycle of most populations in south-eastern Australia, those in south-western Australia are landlocked and potamodromous: adults remain in rivers and migrate upstream to spawn in autumn, larvae drift downstream to lakes which they use as nurseries with juveniles undertaking upstream recruitment migrations in spring. Because rivers in south-western Australia are experiencing substantial changes in river flow, knowledge of the relationship between flow and key life history events will be critical for the development of appropriate management. In the case of G. truttaceus, this is poorly understood. This study examined the timing of spawning, downstream drift of larvae and upstream recruitment of juveniles in relation to river flows over two years. Each of these key life-history events occurred in response to specific seasonal flow conditions. Fish spawned once during autumn, although asynchronously depending on the timing and magnitude of elevated flow events. In winter, larvae drifted downstream ‘en-mass’ during elevated flow events, that presumably created sufficient velocity through pools to incorporate newly hatched larvae into the drift. Upstream recruitment migration by juveniles was protracted and occurred on lower flows in spring and early summer. This new knowledge regarding the relationship between specific flows and life-history events will benefit the conservation of this critically endangered fish in Western Australia.