Understanding the causes of variation in recruitment of marine fishes has been a central goal over the last century. However, the relationship between year class strength and larval growth and survival is poorly known for most species. The main goal of this study was to investigate the relationships between larval traits and year class strength of two flatfish species in an nursery estuary. We examined the effects of the variation in the early life characteristics (pelagic larval growth, pelagic larval duration, size-at-hatching and size-at-settlement) on post-settlement survival of flounder and common sole in the Mondego estuary (Portugal) over a 5-year period (2011–2015). The two flatfish species showed distinct larval traits variation during the study period, mainly related with location of the spawning ground and intrinsic biologic patterns. Flounder was able to delay metamorphosis while gathering energy and/or waiting for suitable environmental cues from estuarine origins while sole take advantage of better environmental conditions due to a later hatching. Early fast growth were strongly related with subsequent growth, affecting larval survival. Both growth and larval traits variation during the studied period were strongly related with temperature. This study highlights the importance of early growth for fish survival and contributes with key information on fish early life stages that will support a better management of fish stocks.

中文翻译：

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两种比目鱼早期生命阶段生长和生存之间的对比联系

了解海洋鱼类补充变化的原因一直是上个世纪的中心目标。然而，对于大多数物种来说，年级强度与幼虫生长和存活之间的关系知之甚少。本研究的主要目的是调查育苗河口两种比目鱼的幼体性状与年级强度之间的关系。我们研究了早期生命特征（中上层幼体生长、中上层幼体持续时间、孵化时大小和定居时大小）​​的变化对蒙德戈河口比目鱼和鳎鱼定居后生存的影响（葡萄牙）为期 5 年（2011 年至 2015 年）。两种比目鱼在研究期间表现出明显的幼体性状变化，主要与产卵场的位置和内在的生物学模式有关。比目鱼能够在收集能量和/或等待来自河口起源的合适环境线索的同时延迟变态，同时由于较晚的孵化而单独利用更好的环境条件。早期快速生长与随后的生长密切相关，影响幼虫的存活。研究期间的生长和幼虫性状变化均与温度密切相关。这项研究强调了早期生长对鱼类生存的重要性，并提供了有关鱼类早期生命阶段的关键信息，这将支持更好地管理鱼类资源。