The freshwater threespine stickleback (Gasterosteus aculeatus) shows tremendous interpopulation variation in a variety of phenotypic traits, including reproductive characteristics. We investigated individual-level reproductive patterns in the freshwater Ono population in Japan, which occurs nearly at the southern global range limit for this species. Although G. aculeatus populations generally only reproduce in spring and/or summer, we directly observed tagged individuals in semi-natural enclosures and found that both males and females reproduced almost the year long. We observed two peaks in reproductive activity, spring to early summer and autumn to early winter, at both the population and individual levels. Thus, we found unique features in the timing and duration of reproduction of this freshwater population, which inhabits spring-fed areas with constant year-round water temperatures.

中文翻译：

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日本淡水三刺棘鱼种群的个体几乎全年繁殖

淡水三刺棘鱼 (Gasterosteus aculeatus) 在各种表型特征（包括生殖特征）中显示出巨大的种群间变异。我们调查了日本淡水小野种群的个体水平繁殖模式，该种群几乎发生在该物种的全球南部范围限制处。虽然 G. aculeatus 种群通常只在春季和/或夏季繁殖，但我们直接观察了半自然围栏中的标记个体，发现雄性和雌性几乎一年都在繁殖。我们在种群和个体水平上观察到生殖活动的两个高峰，春季到初夏和秋季到初冬。因此，我们发现了这个淡水种群繁殖时间和持续时间的独特特征，