Movements associated with home-range establishment by two species of lowland river fish

Individuals that occupy restricted home ranges for long periods have little chance to sample surrounding habitats and may only be able to respond to changes in the distribution of resources at very local scales. Processes leading to the selection of a home range, therefore, potentially have an important bearing on individual fitness and, ultimately, on population structure. In this study, movements associated with the establishment of home ranges by golden perch (Macquaria ambigua) and common carp (Cyprinus carpio) in an Australian lowland river were examined using radiotelemetry. To examine behaviour associated with exploration and settlement into new home ranges, fish were artificially translocated into an unfamiliar river section. Although there was substantial intraspecific variation in patterns of movement, all fish tracked over the entire study period eventually settled into restricted home ranges. Several fish of both species either moved away from established home ranges and settled in new areas, or undertook large-scale movements and subsequently returned to the original home range. It is suggested that such movements may provide a mechanism by which fish can reap the benefits of home-range occupation whilst still being able to respond to changes in the distributions of spatially and temporally dynamic resources.