Research Institute for the Environment and Livelihoods, Charles Darwin University, Darwin, NT, Australia.
School of BioSciences, The University of Melbourne, Melbourne, VIC, Australia.
Oecologia. 2019 Oct;191(2):253-260. doi: 10.1007/s00442-019-04460-7. Epub 2019 Jul 6.
Diadromy is a form of migration where aquatic organisms undergo regular movements between fresh and marine waters for the purposes of feeding and reproduction. Despite having arisen in independent lineages of fish, gastropod molluscs and crustaceans, the evolutionary drivers of diadromous migration remain contentious. We test a key aspect of the 'productivity hypothesis', which proposes that diadromy arises in response to primary productivity differentials between marine and freshwater habitats. Otolith chemistry and biochronology data are analysed in a facultatively catadromous tropical fish (barramundi, Lates calcarifer) to determine the effect of freshwater residence on growth rates. Individuals that accessed freshwater grew ~ 25% faster on average than estuarine residents in the year following migration, suggesting that catadromy provides a potential fitness advantage over non-catadromous (marine/estuarine) life histories, as predicted by the productivity hypothesis. Although diadromous barramundi exhibited faster growth than non-diadromous fish, we suggest that the relative reproductive success of diadromous and non-diadromous contingents is likely to be strongly influenced by local environmental variability such as temporal differences in river discharge, and that this may facilitate the persistence of diverse life history strategies within populations.
洄游是一种迁移形式，水生生物为了觅食和繁殖，在淡水和海水之间进行定期移动。尽管鱼类、腹足纲软体动物和甲壳类动物中的洄游已经在独立的进化支系中出现，但洄游迁移的进化驱动因素仍存在争议。我们检验了“生产力假说”的一个关键方面，该假说提出，洄游是对海洋和淡水生境之间的初级生产力差异的一种响应。我们分析了一种兼性洄游的热带鱼类（巴沙鱼，Lates calcarifer）的耳石化学和生物年代学数据，以确定淡水停留对生长速度的影响。与在河口栖息的个体相比，洄游后一年进入淡水的个体的生长速度平均快了约 25%，这表明，正如生产力假说所预测的那样，与非洄游（海洋/河口）生活史相比，洄游提供了一种潜在的适应性优势。尽管洄游的巴沙鱼比非洄游的鱼生长速度更快，但我们认为，洄游和非洄游群体的相对繁殖成功率可能会受到当地环境变化的强烈影响，例如河流流量的时间差异，这可能会促进种群内多样化的生活史策略的持续存在。
