Seasonal movements with shifts in lateral and longitudinal habitat use by common bream, Abramis brama, in a heavily modified lowland river

Acoustic telemetry was used to investigate the longitudinal and lateral movements and distribution of adult common bream, Abramis brama (L.), over 43months in a heavily modified lowland river in eastern England. A positive relationship between activity and temperature was found, with bream moving greater cumulative distances during the warmer months and distributed over a greater longitudinal proportion of the main channel. The occupancy of tributaries was related to temperature, with bream entering shallow tributaries during rising temperatures in the spring, whilst a deeper, slow-flowing tributary was used more frequently during the cooler autumn/winter months. During the autumn, occupancy of this deeper tributary was positively related to flow rate in the main channel, suggesting that bream use this tributary for flow refuge. The functions of these behaviours are discussed along with potential management of heavily modified lowland rivers.