IntroductIon The European eel, Anguilla anguilla (L., 1758), is a widely distributed species that colonises almost all types of waters across Europe and northern Africa (Moriarty & Dekker 1997). Since the early 1980s, the population has been drastically declining in all its distribution area (Feunteun 2002) and its stock is considered outside safe biological limits (ICES 2010). Presently, the species is listed as endangered (Appendix II, CITES 2007) and is subject to an EU Council Regulation (EC) No. 1100/2007 establishing measures for the recovery and protection of the stock. Among the management measures that aim at the recovery of A. anguilla, special focus is being put on contamination by metals and their negative impacts on spawners quality (Robinet & Feunteun 2002, Maes et al. 2005, Belpaire & Goemans 2007a). These contaminants may affect the endocrine system and disable the normal development of gonads as well as interact with embryonic development, hatching and growth of larvae (for details, see Geeraerts & Belpaire 2010). It is during their conti- nental phase that eels are considered extremely prone to bioaccumulation of metals as a result of several eco- logical and physiological features: long life span, high fat content, benthic and relatively sedentary behaviour, high trophic level, resistance to water degradation and absence of annual reproductive cycles along with associated changes in lipids metabolism (Bruslé 1990, Belpaire & Goemans 2007a). Assessing the contamination load of the European eel could be a valuable tool for environmental monitoring as it is believed to faithfully characterise con- tamination pressure for a variety of harmful substances in both local and international scales (Belpaire & Goemans 2007a). This implies that besides contributing to establish measures to protect this species under the requirements of the EU eel recovery plan, monitoring A. anguilla contam- ination burden could also be useful to assess the chemi- cal status of the environment in a wider perspective, such as the Water Framework Directive (Belpaire & Goemans 2007a, b, Belpaire et al. 2008) and the Marine Strategy Framework Directive. Estuaries and coastal lagoons are particularly vulner- able ecosystems that receive considerable urban and industrial effluent discharges from adjacent areas as well as inputs from agricultural runoff yielding substantial quantities of anthropogenic pollutants that include several metals (Ribeiro et al. 2005, Has-Schön et al. 2006). Due to the presence of impassable dams in water courses and subsequent changes in the European eel natural distribu- tion patterns, the abundance of eels is relatively higher in these brackish waters (e.g., Domingos et al. 2006, Costa Vie et milieu - life And enVironment, 2011, 61 (3): 167-177 METAL CoNCENTRATIoNS IN THE LIvER oF THE EURoPEAN EEL, AnguillA AnguillA, IN ESTUARIES AND CoASTAL LAGooNS FRoM PoRTUGAL A. f. neto 1 , d. PAssos 1 , J. l. CostA 1,2,3 , m. J. CostA 1,3 , i. CAçAdor 1,4 , m. e. PereirA 5,6 , A. C. duArte 5,6 , m. PACheCo 6,7 , i. domingos 1,3* 1 Centro de oceanografia, faculdade de Ciências da universidade de lisboa, Campo grande, 1749-016 lisboa, Portugal 2 universidade lusófona de humanidades e tecnologias, Campo grande, 1749-024 lisboa, Portugal 3 departamento de Biologia Animal, faculdade de Ciências da universidade de lisboa, Campo grande, 1749-016 lisboa, Portugal 4 departamento de Biologia Vegetal, faculdade de Ciências da universidade de lisboa, Campo grande, 1749-016 lisboa, Portugal 5 Centro de estudos do Ambiente e do mar, universidade de Aveiro, Campus de santiago, 3810-193 Aveiro, Portugal 6 departamento de Química, universidade de Aveiro, Campus de santiago, 3810-193 Aveiro, Portugal 7 departamento de Biologia, universidade de Aveiro, Campus de santiago, 3810-193 Aveiro, Portugal * Corresponding author: idomingos@fc.ul.pt (isabel domingos) ABSTRACT. – The concentration of Cd, Cu, Hg, Pb and Zn in the liver of the European eel (Anguilla anguilla) was determined to evaluate the contamination burden of this species in Por- tuguese brackish water systems (Aveiro lagoon, Óbidos lagoon, Tagus estuary, Santo André lagoon and Mira estuary) and relate it to anthropogenic pressures within those ecosystems. The highest levels of most metals were found in eels from the Tagus estuary, in opposition to speci- mens from Santo André lagoon, which exhibited the lowest values. These results confirmed that eels from the most impacted areas show higher metal concentrations in their liver. Although lit- tle variability in metal load was observed within each brackish water system, some heterogene- ity in contamination profiles among sampling stations was detected, demonstrating the efficacy of using the European eel as a sentinel species to monitor metals contamination at both large and small spatial scales. EURoPEAN EEL AnguillA AnguillA METALS MoNIToRING BRACKISH WATER SYSTEMS SPATIAL vARIATIoNS SENTINEL SPECIES PoRTUGAL