Longitudinal and lateral connectivity is important for mobile aquatic species in rivers for reproductive migrations, recruitment, gene flow and access to food resources across habitat types. Water resource developments such as dams and levees may disrupt these connections, causing river fragmentation and loss of access to highly productive habitats such as floodplain wetlands. We used sulfur stable isotopes as a tracer to estimate patterns of fish movement in an unregulated river in tropical northern Australia, taking advantage of observed spatial variation in sulfur isotope values of their food resources across the catchment. We also modelled the flow and barrier related impacts of potential dam development scenarios on fish movement. Fish with isotope values significantly different from local prey values were determined to be migrants. In the ‘no dams’ scenario, movement varied among fish species (0–44% migrant fish within species where n > 5) and sites (0–40% migrant fish within sites where n > 5), and immigration was higher in more connected sites. Impacts of water resource development on fish movement varied between dam scenarios, with predictions that a dam on the main channel of the Mitchell River would have the highest impact of the three individual dam scenarios. This study provides critical information on how flow-mediated connectivity supports patterns of fish community movement in an unregulated river system. The generic quantitative approach of combining tracers of fish movement with connectivity modelling provides a powerful predictive tool. While we used sulfur stable isotopes to estimate fish movement, our approach can be used with other tracers of movement such as otoliths and acoustic telemetry, making it widely applicable to guide sustainable development in other river systems.

纵向和横向连通性对于河流中的水生生物物种进行生殖迁移，募集，基因流动以及获得跨生境类型的粮食资源至关重要。诸如水坝和堤防之类的水资源开发可能会中断这些连接，导致河流支离破碎，并丧失对洪泛区湿地等高产生境的访问。我们利用硫稳定同位素作为示踪剂，估计了整个澳大利亚流域食物资源的硫同位素值在空间上的变化，从而估算了澳大利亚北部热带未经管制的河流中鱼类的运动方式。我们还对潜在的大坝发展情景对鱼类运动的流量和障碍相关影响进行了建模。同位素值与当地猎物值显着不同的鱼被确定为移民。在“无水坝”情况下，鱼类（n> 5的物种中0–44％的迁徙鱼）和地点（n> 5的部位中0–40％的迁徙鱼）之间的运动各不相同，而迁徙率更高。连结的网站。在大坝情景中，水资源开发对鱼类运动的影响各不相同，据预测，在米切尔河主河道上的大坝将在三个大坝情景中产生最大的影响。这项研究提供了有关流量介导的连通性如何在不受管制的河流系统中支持鱼类群落运动模式的重要信息。将鱼类运动的示踪剂与连通性建模相结合的通用定量方法提供了强大的预测工具。虽然我们使用硫稳定同位素来估计鱼类的活动，