This study analyzed the spatial variation of stable isotopes (${\delta }^{15}$N and ${\delta }^{13}$C) and the trophic position of three rocky reef fishes, Balistes polylepis, Stegastes rectifraenum and Kyphosus vaigiensis. According to previous feeding studies, these species are categorized as a benthic carnivore, an omnivore, and an herbivore, respectively. Specimens were sampled in two locations on the western Gulf of California: Bahía de La Paz and Santa Rosalía. For ${\delta }^{15}$N, the mean value recorded in S. rectifraenum was 18.1‰, followed by B. polylepis (17.7$‰$), and K. vaigiensis (16.7‰): omnivore–carnivore–herbivore. The mean ${\delta }^{13}$C value recorded for K. vaigiensis was –13.6‰, followed by S. rectifraenum (–14.9%) and B. polylepis (–16.1‰): herbivore–omnivore–carnivore.​ ${\delta }^{15}$N and ${\delta }^{13}$C values differed significantly between locations, except for ${\delta }^{15}$N for K. vaigiensis and ${\delta }^{13}$C for S. rectifraenum. Differences in ${\delta }^{15}$N may probably be related to oceanographic differences in productivity between the areas or to discharges of anthropogenic compounds. In general, the differences in ${\delta }^{13}$C between La Paz and Santa Rosalía suggest that fishes have different feeding grounds in each of the locations studied. The mean trophic position, estimated from both isotopes, varied between 2.91 in K. vaigiensis and 3.65 in S. rectifraenum. In La Paz, the isotopic niches of the three species overlapped, while in Santa Rosalía this overlap was observed only between B. polylepis and S. rectifraenum. This study is one of the first to apply stable isotopes as a tool to depict the trophic structure of the diverse biota associated with rocky reefs in the Gulf of California.

本研究分析了稳定同位素的空间变化（${\delta }^{15}$N 和 ${\delta }^{13}$C) 以及三种岩礁鱼类的营养位置，Balistes polylepis、Stegastes rectifraenum和Kyphosus vaigiensis。根据之前的饲养研究，这些物种分别被归类为底栖食肉动物、杂食动物和草食动物。样本在加利福尼亚湾西部的两个地点取样：拉巴斯巴伊亚和圣罗莎利亚。为了${\delta }^{15}$N，记录在S 中的平均值。rectifraenum为 18.1‰，其次是B。息肉(17.7$‰$) 和K。vaigiensis (16.7‰)：杂食动物-肉食动物-草食动物。均值${\delta }^{13}$为K记录的 C 值。vaigiensis为 –13.6‰，其次是S。rectifraenum (–14.9%) 和B . polylepis (–16.1‰)：草食动物-杂食动物-肉食动物。${\delta }^{15}$N 和 ${\delta }^{13}$C 值在不同地点之间存在显着差异，除了 ${\delta }^{15}$N 代表K. vaigiensis和${\delta }^{13}$C 代表S. rectifraenum。差异${\delta }^{15}$N 可能与区域之间生产力的海洋学差异或人为化合物的排放有关。一般来说，区别在于${\delta }^{13}$拉巴斯和圣罗莎利亚之间的 C 表明鱼类在每个研究地点都有不同的觅食场所。根据两种同位素估计的平均营养位置在K. vaigiensis 的2.91和S. rectifraenum 的3.65之间变化。在拉巴斯，这三个物种的同位素生态位重叠，而在 Santa Rosalía，这种重叠仅在B. polylepis和S. rectifraenum之间观察到。这项研究是最早应用稳定同位素作为工具来描绘与加利福尼亚湾岩礁相关的各种生物群的营养结构的研究之一。