Ciraane Utashi D, Sonny Damien, Lerquet Marc, Archambeau Pierre, Dewals Benjamin, Pirotton Michel, Sacré Pierre, Benitez Jean-Philippe, Ovidio Michaël, Erpicum Sébastien
UR-UEE, Laboratory of Hydraulics in Environmental and Civil Engineering (HECE), University of Liège, Belgium.
PROFISH, Belgium.
Sci Total Environ. 2025 Jun 20;982:179556. doi: 10.1016/j.scitotenv.2025.179556. Epub 2025 May 12.
Knowledge gaps persist regarding the influence of river hydrodynamics (e.g., flow velocity, depth, temperature, pressure) on the seaward migration of young Atlantic salmon (smolts). These gaps are reflected in rivers by the reduction of safe migration routes for salmons caused by the artificial flow alteration from hydraulic structures such as dams. The situation has long contributed to the disappearance of Atlantic salmon in many rivers and hinders their sustainable reintroduction. To better understand the hydrodynamic factors influencing smolt migration speeds, this study examines the downstream migrations of 491 hatchery smolts over three years (2017, 2021, and 2023) characterized by contrasting hydrological conditions and distinct flow patterns. The study covers 82 km of the Meuse River in Belgium, where smolts crossed six reaches delimited by movable weirs. Smolt trajectories were tracked using acoustic telemetry from 12 detection sites. A one-dimensional hydrodynamic model calculated the water velocities encountered by smolts, while water temperature and the diurnal pattern were also monitored. The results confirm the positive correlation between flow velocities and smolt migration speeds suggested in the literature. Flow velocities below one body length per second (approximately 0.15 m/s) disorient smolts. However, smolts slowed at relatively high velocities, as shown by the negative correlation between flow velocities and relative migration speeds. Additionally, migration speed increased with distance travelled and daytime but decreased with water temperature. These findings pave the way for the implementation of more science-based environmental flow conditions in human-altered rivers during the migration season of smolts.
关于河流水动力学（如流速、深度、温度、压力）对大西洋鲑幼鱼（稚鱼）向海洄游的影响，仍然存在知识空白。这些空白在河流中表现为，诸如大坝等水工建筑物造成的人工水流改变，导致鲑鱼安全洄游路线减少。长期以来，这种情况导致许多河流中的大西洋鲑消失，并阻碍了它们的可持续重新引入。为了更好地理解影响稚鱼洄游速度的水动力因素，本研究考察了491尾孵化场稚鱼在三年（2017年、2021年和2023年）中的下游洄游情况，这三年的水文条件不同，水流模式也不同。该研究涵盖了比利时默兹河82公里的河段，稚鱼在这段河流中穿过了由活动堰界定的六个河段。使用声学遥测技术从12个检测点跟踪稚鱼的洄游轨迹。一个一维水动力模型计算了稚鱼遇到的水流速度，同时还监测了水温及昼夜模式。结果证实了文献中提出的流速与稚鱼洄游速度之间的正相关关系。每秒低于一个体长（约0.15米/秒）的流速会使稚鱼迷失方向。然而，如流速与相对洄游速度之间的负相关所示，稚鱼在相对较高的流速下会减慢速度。此外，洄游速度随游程和白天时间增加，但随水温降低。这些发现为在稚鱼洄游季节，在人类改造的河流中实施更具科学依据的环境水流条件铺平了道路。
