Mesopredator species play an essential role in balancing and sustaining ecosystems through their interactions with various species and with their habitats. In ecosystems that have been subjected to overfishing, it is essential to obtain information on the trophic ecology of such predators. Based on this motivation, this study aimed to investigate the feeding strategies and trophic roles of four demersal sharks (e.g., Mustelus mustelus, Mustelus asterias, Squalus acanthias, and Scyliorhinus canicula) by analyzing their stomach contents and using stable isotope (δ¹³C and δ¹⁵N) analysis. These shark species are subject to overfishing, and their landings have decreased by 98% over the last 18 years in the Sea of Marmara. The results demonstrated that interspecific differences in the main prey resources exist among those sharks. Mustelus mustelus and Mustelus asterias feed mainly on crustaceans, and their diets are very similar. However, Mustelus asterias utilizes a specialist feeding strategy while Mustelus mustelus utilizes a medium-state generalist strategy. Squalus acanthias occupies a high trophic level and mainly feeds on teleosts over both short and long time scales. The probability of isotopic niche overlap of Scyliorhinus canicula with the isotopic niches of S. acanthias was the highest (70.7%), which indicates that both species exploit similar food resources within the same environment. These results contribute to the knowledge of the ecological role of these highly vulnerable cartilaginous species and may help to improve conservation programs in the Sea of Marmara, a lesser-known part of the northeast Mediterranean.

Mesopredator 物种通过与各种物种及其栖息地的相互作用，在平衡和维持生态系统方面发挥着重要作用。在遭受过度捕捞的生态系统中，获得有关此类捕食者的营养生态的信息至关重要。基于这一动机，本研究旨在通过分析四种底栖鲨鱼（例如，Mustelus mustelus、Mustelus asterias、Squalus acanthias 和 Scyliorhinus canicula）的胃内容物和使用稳定同位素（δ ¹³ C 和δ ¹⁵N) 分析。这些鲨鱼物种受到过度捕捞的影响，在过去的 18 年中，它们在马尔马拉海的上岸量减少了 98%。结果表明，这些鲨鱼的主要猎物资源存在种间差异。Mustelus mustelus和Mustelus asterias主要以甲壳类动物为食，它们的饮食非常相似。然而，Mustelus asterias采用专家喂养策略，而Mustelus mustelus采用中等状态的通才策略。Squalus acanthias占据高营养级，主要以硬骨鱼为食，无论是短期还是长期。Scyliorhinus canicula同位素生态位重叠的概率S. acanthias的同位素生态位最高（70.7%），这表明这两个物种在同一环境中利用相似的食物资源。这些结果有助于了解这些高度脆弱的软骨物种的生态作用，并可能有助于改善马尔马拉海（地中海东北部鲜为人知的部分）的保护计划。