Evidence for Interrupted Biomagnification of Cadmium in Billfish Food Chain Based on Stable Carbon and Nitrogen Isotopes from Southwestern of Gulf of California

We report cadmium (Cd) concentrations in muscle, liver, and blood of striped marlin (Kajikia audax) and blue marlin (Makaira nigricans), caught in the southwest of the Gulf of California. The average Cd concentration was higher in the liver followed by blood and muscle in descending order. This pattern of Cd concentration may be related to the differences in the physiological function of these tissues. In K. audax, the Cd concentration in muscle and liver increased proportionally with body size, but only in animals that have reached the body size corresponding to first sexual maturity (animals exceeding 155 cm of postorbital length). Interspecific differences in dietary composition and Cd content evidenced that food preferences have a significant effect on the bioaccumulation of Cd. No evidence of Cd biomagnification (progressive bioaccumulation of an element along the food web) was found, as the correlation between logarithmic Cd concentrations and delta N-15 values was not significant when both billfish and their prey items were included in the calculations. Furthermore, the calculated biotransference factor (transfer of an element from food to consumer) suggested that Cd transference is interrupted from prey to marlins.