Distribuição de mercúrio em atuns (thunnus obesus e thunnus albacares) capturados no oceano atlântico oeste equatorial

Abstract

Tuna are prized delicacies in the world and in Brazil is no different. They are widely consumed in different shapes and looks, are notorious species of high ecosystem importance, occupy usually the top of the marine trophic chain, and therefore present high bioaccumulation and biomagnifications mercury throughout their lives. Since Hg is a highly toxic metal, even in small concentrations, ingestion of tuna can augment human exposure to Hg. Assimilation of Hg in humans occurs primarily by diet and tuna is one of the most consumed marine fish, thus taking this into consideration, the present study assessed the levels of Hg in muscle tissue of two species of tuna caught in the northeast of Brazil, as well as estimate the environmental risk associated with the consumption of these species for the general population. Average total Hg concentrations measured in muscle tissue of two species of tuna (Thunnus obesus and Thunnus albacares) and in muscle tissue of the flying fish (Hirundichthys affinis) range to 95,4 a 1.748,1 ng.g-1 ( average 545,2±338,2 ng.g-1 wet weight) in T. obesus and 48-500 ng.g-1 (average 159,2±79,4 ng.g-1 wet weight) in T. albacares and 49-83 ng.g-1 wet weight in H. affinis. Smaller individuals of both species of tuna showed the lowest concentrations, but a significant relationship between the size of fish and concentrations of Hg was found for T. obesus, but not for T. albacares. Some of the (> 30 kg) biggest individuals of T. obesus presented Hg concentrations > 1,000 ng.g-1, exceeding the legal limits for human consumption, although the average concentration for this species was much lower (545 ng.g-1). Concentrations in T. albacares captured Eastern Brazilian equatorial waters were lower than those found in the Eastern Atlantic Ocean and in the North Atlantic. No comparison can be made to T. Obesus in the Atlantic Ocean, because no studies were found with this species in the region. According to the Hg values observed in both species it was possible to calculate the recommended intake among adults with approximately 70kg body weight, both in the general population, as in risk groups (pregnant women, nursing mothers and children < 10 years). The intake was measured by meals of 250g muscle of the animals studied.