Data from: Causes and consequences of repeatability, flexibility and individual fine-tuning of migratory timing in pike

1. Many organisms undertake migrations between foraging and breeding habitats and while it is assumed that reproductive timing affects fitness, little is known about the degree of individual consistency, and about the causes and consequences of individual variation in migratory timing in organisms other than birds. 2. Here, we report on a 6-year mark–recapture study, including 2048 individuals, of breeding migration in anadromous pike (Esox lucius), an iteroparous top-predatory fish that displays homing behaviour. By repeated sampling across years at a breeding site, we first quantify individual variation both within and between breeding events and then investigate phenotypic correlates and fitness consequences of arrival timing to the breeding site. 3. Our data demonstrate that males arrive before females, that large males arrive later than small males, that the timing of breeding migration varies among years and that individuals are consistent in their timing across years relative to other individuals in the population. 4. Furthermore, data on return rates indicate that arrival time is under stabilizing viability selection, and that individuals who are more flexible in their timing of arrival during the first reproductive years survive longer compared with less flexible individuals. Finally, longitudinal data demonstrate that individuals consistently fine-tune their arrival timing across years, showing that the timing of arrival to breeding sites is influenced by experience. 5. These findings represent rare evidence of how between- and within-individual variations in migratory timing across breeding events are correlated with phenotypic and fitness traits in an ecologically important keystone species. Our results emphasize the importance of considering variation in migratory timing both between and within individuals in studies investigating the fitness consequences of migratory behaviour and have implications for future management.

1. 诸多生物均会在觅食栖息地与繁殖栖息地之间开展迁徙，尽管学界普遍假定繁殖时机可影响个体适合度，但除鸟类外，学界对非鸟类生物的迁徙时机个体一致性程度，以及迁徙时机个体差异的成因与后果仍知之甚少。2. 本研究基于一项为期6年的标记重捕法（mark–recapture）研究，共纳入2048个个体，对象为具有归巢行为的多次繁殖型顶级捕食鱼类——溯河产卵白斑狗鱼（Esox lucius）。研究人员在繁殖位点开展跨年度重复采样，首先量化繁殖事件内部及繁殖事件之间的个体差异，随后探究繁殖位点抵达时机的表型关联与适合度后果。3. 本研究数据显示，雄性个体的抵达时间早于雌性；体型较大的雄性抵达时间晚于体型较小的雄性；繁殖迁徙时机存在年度间差异；且相较于种群内其他个体，各年度间个体的迁徙时机保持一致。4. 此外，回归率数据表明，抵达时机受到稳定性生存选择（stabilizing viability selection）的作用；且在首次繁殖年份中，抵达时机灵活性更高的个体，其存活寿命长于灵活性较低的个体。最后，纵向数据显示，个体在跨年度间会持续微调其抵达时机，这表明繁殖位点的抵达时机会受到个体经验的影响。5. 本研究结果为探明生态系统中关键物种（keystone species）的跨繁殖事件迁徙时机的个体间与个体内差异，如何与表型及适合度性状相关联提供了罕见的实证依据。本研究结果强调，在探究迁徙行为的适合度后果的研究中，需同时考虑迁徙时机的个体间与个体内差异，该结论对未来的物种管理具有参考意义。