DECOD (Ecosystem Dynamics and Sustainability), INRAE, Institut Agro, IFREMER, Rennes, France.
U3E, Experimental Unit of Aquatic Ecology and Ecotoxicology, INRAE, OFB, Rennes, France.
J Fish Biol. 2024 Jan;104(1):125-138. doi: 10.1111/jfb.15567. Epub 2023 Oct 2.
This study provides a regional picture of long-term changes in Atlantic salmon growth at the southern edge of their distribution, using a multi-population approach spanning 49 years and five populations. We provide empirical evidence of salmon life history being influenced by a combination of common signals in the marine environment and population-specific signals. We identified an abrupt decline in growth from 1976 and a more recent decline after 2005. As these declines have also been recorded in northern European populations, our study significantly expands a pattern of declining marine growth to include southern European populations, thereby revealing a large-scale synchrony in marine growth patterns for almost five decades. Growth increments during their sea sojourn were characterized by distinct temporal dynamics. At a coarse temporal resolution, growth during the first winter at sea seemed to gradually improve over the study period. However, the analysis of finer seasonal growth patterns revealed ecological bottlenecks of salmon life histories at sea in time and space. Our study reinforces existing evidence of an impact of early marine growth on maturation decision, with small-sized individuals at the end of the first summer at sea being more likely to delay maturation. However, each population was characterized by a specific probabilistic maturation reaction norm, and a local component of growth at sea in which some populations have better growth in some years might further amplify differences in maturation rate. Differences between populations were smaller than those between sexes, suggesting that the sex-specific growth threshold for maturation is a well-conserved evolutionary phenomenon in salmon. Finally, our results illustrate that although most of the gain in length occurs during the first summer at sea, the temporal variability in body length at return is buffered against the decrease in post-smolt growth conditions. The intricate combination of growth over successive seasons, and its interplay with the maturation decision, could be regulating body length by maintaining diversity in early growth trajectories, life histories, and the composition of salmon populations.
本研究通过跨越 49 年和 5 个种群的多群体方法，提供了大西洋鲑在分布南端长期生长变化的区域图景。我们提供了经验证据，表明鲑鱼的生活史受到海洋环境中共同信号和种群特有信号的共同影响。我们发现，从 1976 年开始，鲑鱼的生长突然下降，之后在 2005 年之后又出现了更为明显的下降。由于这些下降也在北欧种群中被记录下来，因此我们的研究极大地扩展了海洋生长模式下降的模式，将其包括了南欧种群，从而揭示了近 50 年来海洋生长模式的大规模同步性。在其海洋逗留期间的生长增量具有明显的时间动态。在粗糙的时间分辨率下，研究期间第一冬在海上的生长似乎逐渐改善。然而，对更精细的季节性生长模式的分析揭示了鲑鱼在海洋中的生活史在时间和空间上存在生态瓶颈。我们的研究加强了早期海洋生长对成熟决策的影响的现有证据，表明在海上度过第一个夏天末期的个体较小，更有可能延迟成熟。然而，每个种群都具有特定的概率成熟反应规范，并且海洋中生长的局部成分，其中一些种群在某些年份的生长更好，可能会进一步放大成熟率的差异。种群之间的差异小于性别之间的差异，这表明鲑鱼成熟的性别特异性生长阈值是一个经过良好保护的进化现象。最后，我们的研究结果表明，尽管大部分长度增益发生在第一个夏天在海上，但在返回时的体长时间变异性可以缓冲在幼鱼后期生长条件下降的影响。在连续几个季节的生长的复杂组合及其与成熟决策的相互作用，可以通过维持早期生长轨迹、生活史和鲑鱼种群组成的多样性来调节体长。
