Heavy metal contamination of European eel (Anguilla anguilla) and brown trout (Salmo trutta) caught in wild ecosystems in Spain.

In this study we analyzed the pattern of copper (Cu), cadmium (Cd), lead (Pb), and mercury (Hg) accumulation in liver (as a detoxifying organ) and muscle (as the most important tissue for human consumption) of brown trout (Salmo trutta) and European eel (Anguilla anguilla) caught in two wild Spanish rivers where both species are usually angled for human consumption. Cd, Pb, and Cu accumulated preferentially in the liver of both species. Hg accumulated both in the liver and muscle in brown trout, whereas it accumulated preferentially in muscle in European eel. Both high metal content and preferential accumulation of Hg in muscle suggest that European eel is more harmful than brown trout for human consumption.

Metallothionein as bioindicator of freshwater metal pollution: European eel and brown trout.

The aim of this work was to evaluate the potential of metallothionein (MT) as a bioindicator of heavy metal pollution in brown trout and European eel in the field situation. River Ferrerias (North Spain) provided a good gradient of metal contamination: concentrations of heavy metals were elevated both in water and in sediments at the downstream (polluted) site and were low at the upstream (unpolluted) site. MT levels of brown trout exhibited statistically significant differences between sites. Although European eel at the polluted site had a higher MT content, differences were not significant. It is concluded that MT is a good bioindicator of heavy metal pollution in brown trout.

Induction of micronuclei in eel (Anguilla anguilla L.) by heavy metals.

Micronucleus test was performed in situ on eels (Anguilla anguilla) from river sites with different levels of heavy metal pollution (cadmium and mercury). Cadmium content in eel liver but not micronuclei averages in kidney were associated with cadmium content in sediments. Mercury content in liver was not significantly associated with mercury content in sediments. Both cadmium and mercury induced micronuclei expression in eels when injected, the concentration tested being 1.7 mg metal/kg body weight and the micronuclei induction being 2.64 and 2.35 micronuclei per 1000 cells for cadmium and mercury respectively. It was concluded that these heavy metals are genotoxic for European eel, that eel liver metal content is a sensitive indicator for environmental monitoring of cadmium pollution, and that the micronuclei scores in eels are not a sensitive method to detect heavy metals pollution in freshwater ecosytems.

Metallothionein and heavy metals in brown trout (Salmo trutta) and European eel (Anguilla anguilla): a comparative study.

The levels and the cellular distribution of heavy metals, and the extent by which the metals binds to metallothionein (MT) in brown trout (Salmo trutta) and European eel (Anguilla anguilla), were analyzed in order to assess the natural conditions of MT and heavy metals in these two fish species. There were no differences in heavy metals and MT concentrations between males and females of brown trout in a nonreproductive status and between adult brown trout individuals. Brown trout presented higher Cu content than European eel. The cellular distribution of Cu was also different between the two fish species; while in brown trout most of the Cu was in the noncytosolic fraction, Cu was mainly located in the cytosol in European eel. However, the cellular distribution of Zn, Cd, and Pb was similar in the two fish species. There was also an important difference in the metal content of MT between both species. Whereas, in brown trout, Cu-binding MT represented 75% of total metal-binding MT, this value was 25% in European eel. The between-species differences found in this study are intrinsic characteristics not associated with environmental factors. These results establish the basis to use MT as a bioindicator.

Brown trout and European minnow as target species for genotoxicity tests: differential sensitivity to heavy metals.

Brown trout (Salmo trutta) and European minnow (Phoxinus phoxinus) were evaluated as target species to carry out genotoxicity tests. Assessment was made of their relative abundance in wild; their distribution areas; and their sensitivity to heavy metals, intraperitoneally exposing individuals of both species to a low dose (1.7 mg/kg body weight) of different heavy metals. Micronuclei were scored in renal erythrocytes 24 h after treatment. Cadmium chloride significantly induced micronuclei in both species whereas mercury nitrate induced micronuclei increase only in brown trout. Brown trout is abundant, present in all studied freshwater ecosystems, and more sensitive to toxic heavy metals than minnow; therefore it is presented as a target species for studies on heavy metal genotoxicity.

Brown trout as biomonitor of heavy metal pollution: effect of age on the reliability of the assessment.

Brown trout (Salmo trutta L.) is a native fish of the rivers of northern Spain. It is the dominant fish species in these rivers, and it is widespread over all the range of freshwater ecosystems in the area, including ecosystems potentially polluted with heavy metals. In this study, the potential of brown trout as biomonitor of heavy metal pollution and the effect of fish age on the reliability of the assessment are analyzed. Copper, lead, and cadmium concentrations of both abiotic compartments (water and sediments) and brown trout (S. trutta) from three northern Spanish rivers were analyzed. Significant correlations were found between sediment lead content and lead concentration in trout liver. One-year-old juvenile trouts were demonstrated to be useful as a biomonitor of copper and lead pollution, revealing between-location differences. Older trouts do not seem adequate to properly monitor heavy metal pollution. The effect of aging on the reliability of this species as biomonitor is discussed.

Micronuclei and fluctuating asymmetry in brown trout (Salmo trutta): complementary methods to biomonitor freshwater ecosystems.

In this work we measured both micronuclei number in kidney erythrocytes and fluctuating asymmetry in wild brown trout (Salmo trutta), caught in different fluvial ecosystems of Asturias (northern Spain) characterized by different levels of anthropic influence. Brown trout samples from rivers with high anthropic influence possessed significantly higher averages of both micronuclei and fluctuating asymmetry than brown trout samples from less anthropic-influenced rivers. These findings demonstrated the sensitivity of the micronucleus test in kidney erythrocytes to biomonitor freshwater ecosystems. The positive association found between micronuclei average and fluctuating asymmetry at the populational level suggests that fluctuating asymmetry tests could be potential indicators of environmental threat. Variation of fish asymmetry with ageing indicates that fluctuating asymmetry surveys of wild populations should be carried out in trouts of the same age class.

Eel (Anguilla anguilla) and brown trout (Salmo trutta) target species to assess the biological impact of trace metal pollution in freshwater ecosystems.

Copper, lead, and cadmium pollution were measured in water and sediments of two Northern Spanish rivers: Piles and Pigäeña. Liver contents of these heavy metals were analyzed in two fish species (eel, Anguilla anguilla, and brown trout, Salmo trutta) collected from the same locations. Significant levels of heavy metal pollution were found in a 38% of fish that are potential catches for sport fishermen. The results indicate that adult eel could be a good metal bioindicator if sampled at a homogenous age. In contrast, brown trout could be considered as a bioindicator only during the first year of life.