Partial migration, or variation in migratory propensity within populations, has been reported across a range of taxa, including fish. Otolith microchemistry has revealed a high degree of life history plasticity in many amphidromous species, with diadromous and non-diadromous recruitment occurring. We examined this plasticity and its effect on population structure, dispersal and recruitment in Galaxias brevipinnis, an amphidromous fish widespread around New Zealand. We used otolith microchemistry analyses to examine recruitment sources and fish surveys to assess abundance and size structure in two large river systems, each containing naturally formed lakes and no obvious physical barriers to migration. Otolith analyses revealed discrete recruitment sources for stream-resident populations, with marine recruitment supporting populations downstream from lakes and exclusively lake-derived recruitment for populations upstream of lakes. Although diadromous G. brevipinnis were abundant within 10km of the sea, the abundance and relative proportion of younger fish declined as distance upstream increased, until a lake was reached, at which point abundance and the proportion of small individuals increased. The results provide a strong indication that supply is limiting recruitment for G. brevipinnis as distance from pelagic larval habitat increases, and that discrete recruitment sources and population structuring exist even within drainages.

中文翻译：

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生活史可塑性影响广泛的洄游鱼类Galaxias brevipinnis的种群结构和分布

部分迁移，或种群内迁移倾向的变化，已在包括鱼类在内的一系列分类群中报告。耳石微化学揭示了许多两栖物种具有高度的生活史可塑性，发生了双向和非双向募集。我们研究了这种可塑性及其对 Galaxias brevipinnis（一种广泛分布于新西兰各地的两栖鱼类）的种群结构、扩散和补充的影响。我们使用耳石微化学分析来检查补充来源和鱼类调查，以评估两个大型河流系统的丰度和大小结构，每个河流系统都包含自然形成的湖泊，并且没有明显的迁移物理障碍。耳石分析揭示了流居民人口的离散招募来源，海洋补充为湖泊下游的种群提供支持，而湖泊上游的种群则完全来自湖泊。虽然离海10km以内的G. brevipinnis丰富，但随着上游距离的增加，幼鱼的丰度和相对比例下降，直到到达湖泊，此时丰度和小个体的比例增加。结果有力地表明，随着与远洋幼虫栖息地的距离增加，供应限制了 G. brevipinnis 的补充，并且即使在排水系统中也存在离散的补充来源和种群结构。随着上游距离的增加，幼鱼的丰度和相对比例下降，直到到达一个湖泊，此时小鱼的丰度和比例增加。结果有力地表明，随着与远洋幼虫栖息地的距离增加，供应限制了 G. brevipinnis 的补充，并且即使在排水系统中也存在离散的补充来源和种群结构。随着上游距离的增加，幼鱼的丰度和相对比例下降，直到到达一个湖泊，此时小鱼的丰度和比例增加。结果有力地表明，随着与远洋幼虫栖息地的距离增加，供应限制了 G. brevipinnis 的补充，并且即使在排水系统内也存在离散的补充来源和种群结构。