The Atlantic salmon, Salmo salar Linnaeus 1758, is a charismatic, anadromous species that has faced dramatic declines throughout its range. There is currently a lack of information on the effect of free-standing bodies of water on a key life event, sea migration, for the species. This study extends our understanding in this area by combining acoustic telemetry with a correlated random walk model to try to examine potential morphological and behavioural factors that differentiate successful from unsuccessful migrants through Scotland’s largest lake. Consistent with other studies, we found that smolts experienced a high rate of mortality in the lake (~ 43%), with approximately 14% potentially predated upon by birds and 4% by Northern pike. Migration speed in the lake was slow (the mean minimum movement speed between centres of activity was 0.13 m/s), and pathways frequently deviated away from the outlet river. There was no evidence of a morphological or behavioural trait or migratory pathway that distinguished successful from unsuccessful smolts. This suggests that migration movement direction in the main body of Loch Lomond appeared to be random. This was further supported by the output of a correlated random walk model which closely resembled the pathway and migration speed and distance patterns displayed by successful migrants. However, once successful smolts came within ~2 km of the lake exit, a high proportion remained in this region prior to entering the River Leven. We suggest that this “goldilocks zone” is where directional cues become apparent to migrating fish. Future studies should combine random walk models with environmental variables to determine if external factors are driving the apparently random movement patterns exhibited by smolts in lakes.

大西洋鲑鱼，Salmo salarLinnaeus 1758 是一种富有魅力的溯河物种，在其整个范围内都面临着急剧下降。目前缺乏关于独立水体对物种的关键生命事件——海洋迁徙的影响的信息。这项研究通过将声学遥测与相关随机游走模型相结合，尝试检查潜在的形态和行为因素，这些因素将成功与通过苏格兰最大湖的不成功移民区分开来，从而扩展了我们对这一领域的理解。与其他研究一致，我们发现小鲑鱼在湖中的死亡率很高（约 43%），大约 14% 可能被鸟类捕食，4% 被北梭鱼捕食。湖内迁徙速度缓慢（活动中心间平均最小移动速度为0.13 m/s），和路径经常偏离出口河流。没有证据表明形态或行为特征或迁徙途径可以区分成功与不成功的幼崽。这表明洛蒙德湖主体的迁移运动方向似乎是随机的。相关随机游走模型的输出进一步支持了这一点，该模型与成功移民显示的路径、迁移速度和距离模式非常相似。然而，一旦成功的小鲑鱼进入湖出口约 2 公里范围内，在进入利文河之前，该地区仍有很大比例。我们建议这个“金发区”是迁徙鱼类明显的方向线索。