Regional Studies in Marine Science | 2021
Diet and trophic position of three common rocky reef fish at two locations in the Gulf of California
Abstract
Abstract This study analyzed the spatial variation of stable isotopes ( δ 15 N and δ 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: Bahia de La Paz and Santa Rosalia. For δ 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 δ 13 C value recorded for K. vaigiensis was –13.6‰, followed by S. rectifraenum (–14.9%) and B. polylepis (–16.1‰): herbivore–omnivore–carnivore.\u200b δ 15 N and δ 13 C values differed significantly between locations, except for δ 15 N for K. vaigiensis and δ 13 C for S. rectifraenum. Differences in δ 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 δ 13 C between La Paz and Santa Rosalia 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 Rosalia 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.