Fish contains considerably higher selenium (Se) concentrations than other kinds of meats, and thus it is considered a major dietary source of this nutrient. At the same time, fish is also the major source of mercury (Hg) in the human diet, whose toxicity can be reduced by the Se through the interaction between both compounds. In consequence, the biological availability of Se is reduced. In the current study, the occurrence of Se was evaluated in commercially available Brazilian marine species, and the retention of Se in sharks (sand tiger shark) was determined. The average levels of Se found in bony fish, gutted corvina (Micropogonias furnieri), triggerfish (Balistes capricus), hake and sardine (Sardinella brasiliensis), 0.48 ± 0.18 μg.g-1, and in cartilaginous fish, small shark (squantina Guggenheim), hammerhead shark, spinner shark, and sand tiger shark, 0.36 ± 0.07 μg.g-1, did not differ from one another (p > 0.05). In fact, their occurrence was in accordance with the literature data on marine fish. The levels of Se found in the sharks (predatory species) are not enough to establish a stoichiometric relation for the interaction with Hg focusing on the desired toxic protection. The effective Se retention evaluated in the sand tiger shark, after extraction with water, was considered high (minimum of 68.81%) and important taking nutritional and toxicological aspects into account.
selenium; marine fish; mercury
