Using body mass index (BMI) to estimate mercury contamination of the blue shark (Prionace glauca) and the shortfin mako (Isurus oxyrinchus)
Blue shark (Prionace glauca) and shortfin mako (Isurus oxyrinchus) specimens were caught in the North-eastern Atlantic Ocean by Spanish and Portuguese longliners. They are considered as top-predators, particularly susceptible to bioaccumulate mercury (Hg). The Hg mean levels in blue shark and shortfin mako were 0.4 (SD = 0.3 mg kg-1) and 0.5 (SD = 0.9 mg kg-1), respectively. The body mass index (BMI) was tested to demonstrate the accumulation of Hg in these two top-predators, taking into account size (TL, cm) and mass (W, kg) simultaneously. The comparison of these three methods showed that the BMI could be a relevant biological indicator of the accumulative Hg process for sharks.