To clarify the trophic relationship of important rock fishes, we analyzed trophic niche of three typical rockfish species (Oplegnathus fasciatus, Sebastiscus marmoratus and Conger myriaster) in the Zhongjieshan Islands in summer 2020, based on the carbon and nitrogen stable isotope techniques. We calculated the contributions of major carbon sources [macroalgae, phytoplankton, suspended particulate organic matter (POM) and substrate organic matter (SOM)]. The results showed that: 1) the δ13C values of the three species ranged from -21.44‰ to -15.21‰, with an average value of (-16.85±1.12)‰, while the δ15N values ranged from 8.32‰ to 10.96‰, with an average value of (9.69±0.66)‰. There were significant differences in carbon and nitrogen stable isotopes among the three species. 2) There was small niche overlap between O. fasciatus and S. marmoratus, indicating that the interspecific competition was not intense. There was no overlap between C. myriaster and the first two, indicating feeding differentiation. 3) The total ecotone area, corrected core ecotone area, and food source diversity of C. myriaster were the highest, indicating that it had a more generalized diet and richer food sources. 4) With Mytilus coruscus as a baseline organism, the trophic level of C. myriaster was the highest (3.38), followed by S. marmoratus (3.09), and the trophic level of O. fasciatus was the smallest (3.00). 5) Results of the stable isotope mixture model (SIAR) showed that POM was the main carbon source of the three species, contributing 57.4%, 57.9%, and 92.0% of the total, respectively. In addition, the contribution rate of SOM was also high for O. fasciatus and S. marmoratus, which was 21.5% and 33.9%, respectively. This study could provide basic information and reference for understanding trophic structure and marine food web in Zhongjiashan Islands.
为明确中街山列岛重要恋礁性鱼类的营养关系,本研究以中街山列岛的3种典型恋礁性鱼类条石鲷、褐菖鲉和星康吉鳗为对象,利用碳、氮稳定同位素技术分析了其在2020年夏季的营养生态位,并计算主要碳源(大型海藻、浮游植物、悬浮颗粒有机物、底质有机物)的贡献值。结果表明: 1)条石鲷、褐菖鲉和星康吉鳗的δ13C值范围在-21.44‰～-15.21‰,平均值为(-16.85±1.12)‰;δ15N值范围在8.32‰～10.96‰,平均值为(9.69±0.66)‰,三者之间的碳氮稳定同位素均有显著性差异;2)条石鲷和褐菖鲉的营养生态位重叠很小,说明其种间竞争并不激烈,而条石鲷和褐菖鲉与星康吉鳗之间均不存在生态位重叠,说明它们之间的摄食种类有所分化;3)星康吉鳗的生态位总面积、校正核心生态位面积和食物来源多样性均最大,表明星康吉鳗的食性泛化,食物来源更为丰富;4)以厚壳贻贝作为基线生物,星康吉鳗的营养级最大,为3.38,其次是褐菖鲉,为3.09,条石鲷的营养级最小,为3.00;5)稳定同位素混合模型(SIAR)显示,悬浮颗粒有机物是三者的主要碳源,贡献率分别为57.4%、57.9%和92.0%,此外,底质有机质对条石鲷和褐菖鲉的贡献率也较高,分别为21.5%和33.9%。本研究可为了解该生态系统营养结构以及构建中街山列岛海洋食物网提供基础资料和参考数据。.
Keywords: Zhongjieshan Islands; carbon source; stable isotope; trophic niche.