Predation effects on juvenile Atlantic salmon (Salmo salar) populations in changing riverscape

自然过程，如捕食，在所有种群中都在发挥作用。不同的人为行动(如渔业管理、水电、气候变化)可能会改变大西洋鲑鱼(Salmo Salar)种群由于捕食压力而实现的效果。由于许多大马哈鱼种群受到威胁，任何人类引发的变化都可能是有害的。本文提出的基于现场的研究集中于评估在三种情况下在自然水流和流量调节的河流中捕食对鲑鱼幼鱼的影响。第一个项目的重点是评估在新不伦瑞克(NB)的圣约翰河(SJR)大型水电管制下拟议的陷阱和卡车管理战略。我们之前的研究表明，深秋对水电站附近的大马哈鱼构成了捕食威胁。利用新颖的捕食标签声学遥测技术验证了这一假设的正确性。关于捕食事件的频率和位置的数据(来自捕食标签)将与来自常规声学标签的捕食者运动数据相结合(条纹石斑鱼、斑点石斑鱼和麝香石斑鱼)，并检查捕食频率作为水温的函数。第二个项目的重点是评估扩大的(100万)条纹石斑鱼种群对北卡罗来纳州米拉米奇河鲑鱼的捕食威胁。Project将在整个solt迁徙窗口按不同大小类别的条纹鱼在时间和空间上对捕食行为进行量化，并将这些数据与大马哈鱼的每日总游动大小相结合，以揭示按大小类别划分的潜在捕食威胁。这些信息将用于修订底层渔业的渔业管理建议。第三个项目将A)比较半水生哺乳动物在可涉水溪流和不同冰区(即无冰和复冰)中捕食的季节性水平，以及B)检验既定的假设，即捕食威胁是鲑鱼幼鱼在冷水温度下白天停止活动的驱动力。这两个研究部分都依赖于无源集成应答器技术的新发展，用于跟踪幼鲑鱼。P3A项目的实地研究将在北卡罗来纳州的小溪中进行，那里的冰过程是基于以前的研究而已知的。项目P3B将发生在格陵兰岛的卡皮西利特河，这是世界上唯一一条鲑鱼种群在没有哺乳动物捕食的情况下进化的河流。因此，预计鲑鱼的冬季行为反映了不同的活动模式，而不是在进化过程中存在冬季捕食的种群。拟议的研究将提供关于捕食在气候变化中季节性小育苗溪流中三文鱼种群调节中的作用的新信息，并将提供直接适用于更好地管理北美重要三文鱼河流中受威胁的和具有社会经济意义的三文鱼种群的建议。

Natural processes, such as predation, are at play in all populations. Different anthropogenic actions (e.g. fisheries management, hydropower, climate change) may alter the effect that Atlantic salmon (Salmo salar) populations realize due to predation pressure. With many A. salmon populations threatened, any human-induced change may be detrimental. The field-based research proposed herein focuses on assessing effects of predation on juvenile A. salmon under three case situations in natural-flow and flow-regulated rivers. The first project focuses on assessing a proposed trap-and-truck management strategy in a large hydropower regulated Saint John River (SJR), New Brunswick (NB). Our previous studies suggest late-autumn predation threat for pre-smolt A. salmon at the vicinity of a hydropower station. The validity of this hypothesis is examined by using novel predation-tag acoustic telemetry. Data on frequency and locations of predation events (from predation tags) will be combined with predator movement data from regular acoustic tags (striped bass Morone saxatilis and muskellunge Esox masquinongy) and the frequency of predation is examined as a function of water temperature. The second project focuses on assessing the predation threat of expanded ( >1 million) striped bass population on A. salmon smolts in the Miramichi River, NB. Project will quantify predation by different size categories of striped bass in time and space throughout the smolt migration window, and combine these data with the total daily run size of A. salmon smolts to reveal a potential predation threat by size category. The information will be used to revise fisheries management advice within bass fishery. The third project will A) compare seasonal levels of predation by semiaquatic mammals in wadable streams with contrasting ice-regimes (i.e. ice-free and ice covered) and B) examine the established hypothesis that threat of predation is the driving force of cessation of daytime activity in cold water temperature in juvenile A. salmon. Both research components rely on new developments in Passive Integrated Transponder technology for tracking juvenile A.salmon. Field research for project P3A will be undertaken in small streams in NB where ice processes are known based on previous research. Project P3B will occur in the Kapisillit River in Greenland; the only stream in the world where an A. salmon population has evolved in the absence of mammalian predation. Winter behavior of A. salmon is therefore expected to reflect different activity patterns than in populations where winter predation has evolutionarily been present. The proposed research will contribute novel information regarding the role of predation in regulating A. salmon populations in seasonal small nursery streams in changing climate, and will provide advice that is directly applicable for better managing threatened and socio-economically important A. salmon populations in significant North American salmon rivers.