The Norwegian Institute for Nature Research, Trondheim, Norway.
Department of Biology, NTNU Centre of Fisheries and Aquaculture, Trondheim, Norway.
J Fish Biol. 2021 Sep;99(3):875-887. doi: 10.1111/jfb.14770. Epub 2021 May 24.
Brown trout (Salmo trutta) display extensive plasticity in marine migratory behaviours, with marine migrations considered to be an adaptive strategy which enables sea trout to maximize growth and reproductive potential. However, marine migrations are not without associated costs, including threats posed by ever-increasing salmon lice (Lepeophtheirus salmonis) infestations. In the present study, we used passive integrated transponder technology to characterize variability in sea trout migration behaviour amongst three catchments situated in a region of intensive salmon farming in central Norway. Specifically, we investigate how lice infestation, out-migration date and body size alter sea trout return rate and marine residence duration during the first out-migration to sea from each catchment. Distinct catchment-specific differences in sea trout out-migration size and the number of cohorts were observed, but larger body size did not guarantee the successful return of migrating trout. The marine residence duration of individuals that successfully returned to freshwater was positively correlated with lice infestation risk, suggesting for these individuals the lethal infestation threshold had not been reached. Our results also suggest that sea trout populations from lotic-dominated catchments are potentially at greater risk from size-related threats to their survival encountered during their marine migrations than sea trout from lentic-dominated catchments. The variability in sea trout migratory behaviour amongst catchments observed here emphasizes the challenges fisheries managers face when deciding the best actions to take to protect the anadromous portion of brown trout populations.
棕鳟（Salmo trutta）在海洋洄游行为方面表现出广泛的可塑性，海洋洄游被认为是一种适应性策略，使海鳟能够最大限度地提高生长和繁殖潜力。然而，海洋洄游并非没有相关成本，包括日益严重的鲑虱（Lepeophtheirus salmonis）感染带来的威胁。在本研究中，我们使用被动集成转发器技术来描述挪威中部一个鲑鱼养殖密集地区的三个集水区中海鳟洄游行为的可变性。具体来说，我们研究了鲑虱感染、洄游日期和体型如何改变每个集水区首次向海洋洄游时海鳟的返回率和海洋居留时间。观察到海鳟洄游大小和群体数量存在明显的集水区特异性差异，但较大的体型并不能保证洄游鳟鱼的成功返回。成功返回淡水的个体的海洋居留时间与鲑虱感染风险呈正相关，这表明这些个体尚未达到致命感染阈值。我们的研究结果还表明，来自流水型集水区的海鳟种群在海洋洄游过程中可能面临更大的与体型相关的生存威胁，而来自静水型集水区的海鳟种群则面临更大的威胁。这里观察到的集水区中海鳟洄游行为的可变性强调了渔业管理者在决定采取最佳行动保护棕鳟种群溯河部分时所面临的挑战。
