| Summary: | The spawning, pelagic and metamorphosis stage duration were evaluated in European flounder (<i>Platichthys flesus</i>) along a latitudinal gradient in the European Atlantic coast. The main objective was to determine latitudinal trends in the estuarine nursery habitat colonization processes, considering a wide geographical range: from the southernmost population in the Mondego estuary (Portugal), the French coasts (Vilaine and Slack estuaries), the Wadden Sea (Netherlands) to the northern populations in the Sørfjord (Norway). Flounder 0-group juveniles were captured in June/July 2010. Otolith microstructure was used to account for the duration of each stage by analysing daily growth increments. The spawning period took place between mid-January and early-July over the species’ distribution range, with a gap of nearly two months between the Mondego estuary and the Sørfjord populations, as a consequence of warmer water temperature earlier in the season in the southern areas. Both pelagic and metamorphosis stages were longer at the middle of the distribution range, and lasted in total up to two months after hatching. Results also suggested the existence of a counter-gradient growth compensation mechanism in the northernmost populations. Apart from temperature (proxy for the latitudinal gradient), which regulates species’ basal metabolic rates, differences between sites were also related with local features, such as the extension of the continental platform and adaptations to transport and retention mechanisms.
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