Elasmobranchs are among the species most threatened by overfishing and a large body of evidence reports their decline around the world. As they are large predators occupying the highest levels of marine food webs, their removal can alter the trophic web dynamic through predatory release effects and trophic cascade. Suitable management of threatened shark species requires a good understanding of their behaviour and feeding ecology. In this study we provide one of the first assessments of the trophic ecology of the “vulnerable” smooth-hounds Mustelus mustelus and M. punctulatus in the Central Mediterranean Sea, based on stomach contents and stable isotope analyses. Ontogenetic diet changes were addressed by comparing the feeding habits of three groups of individuals: juveniles, maturing and adults. Our results highlighted that the two species share a similar diet based mostly on the consumption of benthic crustaceans (e.g. hermit crabs). Their trophic level increases during ontogeny, with adults increasing their consumption of large-sized crustaceans (e.g. Calappa granulata, Palinurus elephas), cephalopods (e.g. Octopus vulgaris) and fish (e.g. Trachurus trachurus). Our results provide also evidence of ontogenetic shifts in diet for both species showing a progressive reduction of interspecific trophic overlap during growth. The results of this study contribute to improve the current knowledge on the trophic ecology of these two threatened sharks in the Strait of Sicily, thus providing a better understanding of their role in the food web.

软骨鱼是受过度捕捞威胁最严重的物种之一，大量证据表明它们在世界各地的数量正在减少。由于它们是占据海洋食物网最高层的大型捕食者，它们的清除可以通过捕食释放效应和营养级联改变营养网动态。对受威胁的鲨鱼物种进行适当的管理需要充分了解它们的行为和摄食生态。在这项研究中，我们根据胃内容物和稳定同位素分析，对地中海中部“脆弱”光滑猎犬Mustelus Mustelus和M. punctuatus的营养生态进行了首次评估。通过比较三组个体（青少年、成年个体和成年个体）的饮食习惯来解决个体发育饮食变化。我们的结果强调，这两个物种具有相似的饮食，主要基于底栖甲壳类动物（例如寄居蟹）的消耗。它们的营养水平在个体发育过程中增加，成虫增加了对大型甲壳类动物（例如细粒藻、Palinurus elephas）、头足类动物（例如章鱼）和鱼类（例如Trachurus trachurus）的消耗。我们的结果还提供了两个物种饮食个体发生变化的证据，表明生长过程中种间营养重叠逐渐减少。这项研究的结果有助于提高目前对西西里海峡这两种受威胁鲨鱼的营养生态学的了解，从而更好地了解它们在食物网中的作用。