Trace metals pollution and trophic position of three sea urchin species in the Gulf of California.

Sea urchin species are ecologically important in the Gulf of California and are becoming popular as a local fishery due to their commercial value. The most abundant species are Echinometra vanbrunti, Eucidaris thouarsii, and Tripneustes depressus. The objective of this study was to evaluate cadmium, lead, copper, zinc, and iron concentrations, as well as stable isotope values in these sea urchin species in the Santa Rosalia mining area (STR), in three sites: Punta Gorda, Punta el Aterrizaje, and Punta Salina. The highest Fe concentration (100.2 mg kg-1) was found in E. vanbrunti, while the highest concentrations of Pb (15.1 mg kg-1), Cu (14.5 mg kg-1), and Zn (347.7 mg kg-1) were recorded in E. thouarsii, and the highest Cd concentration (10.8 mg kg-1) was found in T. depressus. The main health risk of trace metal pollution in STR may be caused by Cd and Pb. δ15N and δ13C values were higher in E. thouarsii and T. depressus, respectively; E. thouarsii has the highest trophic position. Specimen size was not related to metal concentrations, but a positive relationship was observed between specimen size and isotopic values in T. depressus. The three species showed different bioaccumulation patterns for the metals analyzed. Additionally, collection sites and seasons play an important role in the variability of metal concentration.

Stable carbon and nitrogen isotope values of dorsal spine age rings indicate temporal variation in the diet of striped marlin (Kajikia audax) in waters around Cabo San Lucas, Mexico.

RATIONALE: Billfishes, such as marlin, are top pelagic predators that play an important role in maintaining the stability of marine food webs. Notwithstanding the importance of these species, there remain gaps in our knowledge on their movements, foraging, and trophic status in the early stage of life. METHODS: We measured the δ(13)C and δ(15)N values in each annual growth band deposited in the dorsal spine from striped marlin caught off Cabo San Lucas, Mexico, to produce retrospective isotopic profiles that would enable us to detect any significant isotopic changes across development. The samples were analyzed using an elemental analyzer coupled to an isotope ratio mass spectrometer. RESULTS: There was no relationship between the size of striped marlin and the δ(15) N values. Differences in δ(15)N mean values across different age classes were not significant and the variation in δ(15)N values through the marlins' life cycle was less than 2‰. However, the mean δ(15)N values between individuals varied by up to 6‰. The δ(13)C values increased as a function of age, and the mean δ(13)C values varied significantly between age classes. CONCLUSIONS: Fin spines can be used to construct retrospective isotopic histories for the investigation of trophic dynamics and migratory histories in billfishes, for which population dynamics are often poorly known.