Movement patterns and habitat selection of the Endangered eastern freshwater cod Maccullochella ikei in the Mann River, Australia

Abstract

Movement and migration are fundamental activities in the life history of fishes. It is therefore critical in species conservation that there is a clear understanding of why movements or changes in habitat occur. The aim of the present study was to quantify the movement patterns and habitat selection of the Endangered eastern freshwater cod Maccullochella ikei in relation to river discharge, water temperature and season. Twenty-five adult M. ikei were implanted with radio tags and tracked for 12 mo in the Mann River, Australia. Fish were located manually once a week, whilst larger inter-pool movements were monitored continuously by automated tracking stations. Ten 24 h continuous tracking events were undertaken to quantify diel movement patterns. Under- water cameras were used to verify fixes and observe behaviour. Based on weekly fixes and track- ing station data, 2 main types of behaviour were observed: extended periods of restricted move- ment and strong home-site fidelity, and short periods of relative high mobility and home-site shifts. Larger intra- and inter-pool movements were most often related to rises in river discharge. There was also increased movement and home-site shifts by males but not females during the breeding season. Diel behaviour was typified by sedentariness during the day and increased cre- puscular and nocturnal activity. Habitat selection was for deep pools, and large boulders and woody debris were preferred as cover. These results suggest that the maintenance and restoration of quality habitat and natural flow regimes are essential for the ongoing conservation of remnant populations of M. ikei and for the successful reestablishment of the species in areas where it has become extirpated.