Understanding the role of biological, environmental and human-impact factors on mercury concentrations in a demersal mesopredator shark

Abstract

Anthropogenic activities, including the increase in pollutants, are triggering significant impacts on marine ecosystems. Mercury (Hg) is a particularly toxic pollutant, which poses critical threats due to its persistence and bioaccumulation in marine food webs. Using generalized additive models, this study investigates the effect of the main factors influencing the variability of Hg concentrations in the small-spotted catshark (Scyliorhinus canicula), an abundant and largely distributed demersal predator across the western Mediterranean Sea. THg values measured ranged between 1.8 and 10.6 mg·kg⁻¹ (mean of 4.8 mg·kg⁻¹ dw). Our results revealed that Hg concentrations were influenced by latitude, distance to cities, and body size of individuals. Higher Hg concentrations were measured in the samples captured in the northern areas of the study. The health risk assessment based on estimated daily intake showed that at low values of consumption rates (AC for elasmobranch or other marine fish), there was no health risk from Hg exposure, with weekly intakes of 0.0009 and 0.17 μg/kg bw week, respectively. In contrast, higher consumption rates (general fish and demersal fish) led to measurements above recommended limits, indicating potential health risks. This study underscores the importance of understanding Hg dynamics in marine ecosystems and highlights the need for species-specific human consumption rates to better estimate risk exposure.