Mercury and Selenium Levels in Blue Shark (<em>Prionace glauca</em>) Along the California Current Ecosystem: Assessing Human Health Risks

Research on trophic transfer of trace elements in food chains, particularly toxic elements like mercury (Hg) and essential elements like selenium (Se), is crucial for understanding their impact on human health. In this work, we assessed the transfer of Hg and Se in the blue shark (Prionace glauca), a top predator with economic importance. Muscle samples from 23 sharks, as well as their main prey (squid, red shrimp, sardine, and mackerel), were analyzed for Hg and Se concentrations. The mercury levels of sharks were below the recommended legal limit for seafood consumption in Mexico (1 µg.g-1 ww), while selenium levels were significantly lower than previously reported for the species. The biomagnification was evaluated in this species by calculating biomagnification factors (BMF) for mercury (Hg) and selenium (Se) based on predator-prey element concentrations. Hg showed a BMF of 2.8, indicating biomagnification, while Se had a BMF of 0.2, suggesting biodilution. Trophic transfer factor models supported these findings, showing a positive correlation of Hg concentration with trophic level and a negative correlation with Se. Consumption of blue shark muscle poses no risk based on hazard quotient analysis, but caution is advised due to Hg biomagnification.