Abstract:
Tributary and mainstem connections represent important corridors for the movement of fish and other biota throughout river networks. We investigated the timing, frequency and environmental conditions associated with movements by adult golden perch (Macquaria ambigua) between the mainstem of the mid-Murray River and a tributary, the Goulburn River, in southeastern Australia, using acoustic telemetry over four years. Golden perch moved freely between mainstem and tributary habitats. The results of the study indicate that a spatially and temporally complex relationship between adult golden perch movement, river discharge and water temperature plays a key role in connecting mainstem and tributary populations of the species. The relatively common occurrence of movement across the mainstem–tributary junction suggests that this geographic feature does not function as an impermeable behavioural or demographic boundary between populations in the two rivers. This finding highlights the fact that fish populations do not necessarily conform to artificially constrained management units, and demonstrates the need to consider the spatial, behavioural and demographic interdependencies of aquatic fauna across riverscapes. Although they are often complex, the behavioural mechanisms and associated environmental conditions that influence connectivity across mainstem– tributary interfaces need to be understood and accounted for during development of models that underpin management actions for riverine fishes
