Age, morphology, and environmental variation shape movement behaviour syndromes in a riverine fish - golden perch...

Understanding the scale and characteristics of animal movements allows for effective species management. These movement characteristics can vary widely within a species, so there is a need to understand and account for the spectrum of movement behaviours within a population. Movement ecology studies of freshwater fish predominantly aim to uncover environmental correlates of population-wide movement behaviours. However, few studies consider the specific movement types that may exist within a species or population. This is somewhat surprising considering the importance of fish movement and migration in determining population characteristics and species persistence over time. In this study, we used acoustic telemetry to investigate the role and extent of intrapopulation variation in the movement behaviour of golden perch (Macquaria ambigua, Percichthyidae) in the Condamine-Balonne River system, Australia. After tracking 132 individuals between 2018 and 2025, we employed a novel approach to characterise annual fish movement behaviour into distinct movement groups using a suite of movement data metrics. These groups were then compared to morphological and environmental variations, assessing group membership. We found strong variation in the movement behaviour of golden perch and identified five distinct movement groups. The proportion of individuals in each movement group varied with hydrological alteration and demonstrated behavioural plasticity within the population, possibly in response to the increased density within weir pool habitats. Fish that exhibited strong home-site residency and low mobility (under 5 km linear range) were most prevalent, and only a small number of fish (n = 18) moved more than 50 km per year. Higher mobility was associated with larger body size (length and weight) and increased age. Future management actions for freshwater fish may benefit from recognising the diverse movement syndromes present within a population. Integrating these behavioural groups, and their differing requirements, into environmental flow management could better preserve key ecological functions and strengthen population resilience.