Biomarker analysis, especially fatty acids (FA) and stable isotopes (SI), has become a useful tool to elucidate the flow of energy and trophic interactions in an ecosystem and to analyse the diet of species that are hard to observe whilst feeding. Herein we compare FA profiles and SI composition (nitrogen, δ¹⁵N and carbon, δ¹³C) of muscle tissue from two sympatric Antarctic fish species—Notothenia rossii and N. coriiceps—that are key components in the inshore ecosystem of the South Shetland Islands. For both nototheniids, potential benthic food sources (algae, amphipods, polychaetes and gastropods) were screened in order to re-evaluate their trophic position (TP) and the energy flow. Significant differences in FA and SI composition between the two fish species were found. Notothenia rossii showed a higher total FA concentration, with high levels of polyunsaturated FA. Conversely, the potential food sources tested showed low concentrations of these FAs. This could indicate that both nototheniids are feeding mainly on another food source or that FA bioconversion takes place. While the FA results might suggest a possible trophic niche segregation between N. rossii and N. coriiceps, both species occupy a similar trophic position. Furthermore, we found a 50-times higher total concentration of monounsaturated FA in N. rossii than in N. coriiceps that can be related to the higher buoyancy capacity of the former. Trophic biomarkers did not elucidate the main prey item as lipid source for N. rossii and N. coriiceps, suggesting that other food sources and potential fatty acid bioconversion should be further investigated.

生物标志物分析，尤其是脂肪酸 (FA) 和稳定同位素 (SI)，已成为阐明生态系统中能量流动和营养相互作用以及分析进食时难以观察的物种饮食的有用工具。在此，我们比较了来自两种同域南极鱼类——Notothenia rossii和N. coriiceps——的肌肉组织的FA 谱和 SI 组成（氮、δ ¹⁵ N 和碳、δ ¹³ C）。它们是南设得兰群岛近海生态系统的关键组成部分。对于这两种nototheniids，潜在的底栖食物来源（藻类、片脚类动物、多毛类和腹足类动物）都经过筛选，以重新评估它们的营养位置（TP）和能量流。发现两种鱼类之间的 FA 和 SI 组成存在显着差异。Notothenia rossii显示出较高的总 FA 浓度，以及高水平的多不饱和 FA。相反，测试的潜在食物来源显示这些 FA 的浓度较低。这可能表明两种 nototheniids 主要以另一种食物来源为食，或者发生了 FA 生物转化。虽然 FA 结果可能表明N. rossii和N. coriiceps之间可能存在营养生态位分离，这两个物种占据相似的营养位置。此外，我们发现N. rossii中单不饱和脂肪酸的总浓度比N. coriiceps高 50 倍，这可能与前者较高的浮力有关。营养生物标志物并未阐明罗西猪笼草和牛头猪笼草的主要猎物为脂质来源，这表明应进一步研究其他食物来源和潜在的脂肪酸生物转化。