The European eel, a catadromous endangered species, displays plasticity in phenotypic traits and in trophic behaviour, features that can eventually affect growth. The aim of this study was to compare variation in carbon (δ¹³C) and nitrogen (δ¹⁵N) stable isotopes in muscle tissue of the adult eel life stages (i.e. yellow and silver eel), as function of growth. Eel samples were obtained from nine sites across the Mediterranean region, that included seven coastal lagoons of different size and ecological structure, and two freshwater habitats corresponding to one river and one lake. A large variability was found in both δ¹³C and δ¹⁵N values, suggesting that eels fed over a broad range of potential food sources. Eels from each location showed specific range values of δ¹³C, in most sites irrespective of stage, reflecting lagoon- or freshwater-specific carbon sources. A positive correlation was found between individual δ¹⁵N values and annual growth rates, suggesting that eels generally seem to feed on prey of higher δ¹⁵N values among the trophic resources available in each foraging habitat. This allows individuals to grow faster and to attain earlier the pre-spawning phase (i.e. the silver stage). A better understanding of eel trophic ecology across different life stages and different habitats is one of the prerequisites for the effective management of local stocks.

欧洲鳗是一种濒临灭绝的濒危物种，在表型性状和营养行为上表现出可塑性，这些特征最终会影响生长。本研究的目的是比较在碳变化（δ ¹³ C）和氮（δ ¹⁵成年鳗鱼生命阶段（即黄色和银鳗）的肌肉组织中的N）稳定同位素，如生长的功能。从整个地中海地区的9个地点获得鳗鱼样本，其中包括7个大小和生态结构不同的沿海泻湖，以及与1条河流和1条湖泊相对应的2个淡水栖息地。一个大的变化是在δ都发现¹³ C和δ ¹⁵N值，表明鳗鱼有广泛的潜在食物来源。从每个位置鳗鱼显示δ的特定范围内的值¹³ ℃，在大多数网站无关的阶段，反射lagoon-或特定淡水碳源。正相关个体δ之间发现¹⁵的N值和年增长率，这表明一般鳗鱼似乎较高δ的猎物进料¹⁵的N个值中的每个觅食栖息地可用的营养资源之一。这使个体能够更快地成长，并能更快地达到产卵前阶段（即白银阶段）。更好地了解不同生命阶段和不同栖息地的鳗营养生态是有效管理当地种群的先决条件之一。