Abstract
Thirty-five European eels (Anguilla anguilla), caught in 2007 in the river Thames upstream and downstream of both London and the tidal limit, were analysed for PCBs and organochlorine pesticides. Most chemicals were detectable in every fish, although they have been banned or severely restricted for many years. In general, the tidal eels were more contaminated than upstream ones, which was related to their higher lipid contents.The ICES7 indicator PCB concentrations ranged overall from 4.2 to 124μgkg−1 fresh weight with averages of 33 and 56μgkg−1 for the upstream and tidal eels; 3.5–104μgkg−1, average 26 and 48μgkg−1 of that were ICES6 PCBs. Total DDT was on average 16μgkg−1 (1.7–38μgkg−1) upstream and 18μgkg−1 (8.6–35μgkg−1) downstream with about half of that provided by pp′DDE. Lindane (γ-HCH) was found at up to 2.8μgkg−1 (averages 0.58 and 1.1μgkg−1 upstream and downstream) and hexachlorobenzene (HCB) was on average 1.9 and 2.5μgkg−1 in the two groups with a maximum of 6.4μgkg−1 in each. Therefore all individuals passed the European Environmental Quality Standard (EQS) of 10μgkg−1 for HCB. PCB contamination was fairly typical for recent UK eel data, whilst DDE and lindane concentrations were lower than most previous UK eel studies, perhaps reflecting a downward trend.Although not as highly contaminated as some eels from previous UK and European studies, the presence of so many of these chemicals, with their known health effects may represent a stress for the fish or higher predators, such as birds.
Highlights
IntroductionThe European Eel (Anguilla anguilla) is an important species for commercial fisheries
They were assessed for parasite infections by dissection and microscopy in a commercial laboratory (Thames Valley Aquatic Services, 2007) and sections of eel were frozen in fluoro-ethylene-propylene bags and stored at À80 °C for 16 months until analysis
About half of the estuary eels and all but two of the 11 non-tidal ones were infected with adult or juvenile stages of the nematode A. crassus, no larval stages were found
Summary
The European Eel (Anguilla anguilla) is an important species for commercial fisheries. There is, much concern over sharply declining numbers from about 1980 onwards (ICES, 2011). The European eel is on the IUCN Red List classified as a ‘‘critically endangered species’’ (Freyhof and Kottelat, 2010). All European Union countries where eels occur, have to produce eel management plans, with the long term aim of ensuring silver (mature) eel escapement to the sea recovers to at least 40% of what it would be if there were no anthropogenic influences (European Union, 2007). Successful recovery plans are hindered by a lack of certainty about the main cause(s) of the decline. Climate change leading to reduced ocean productivity (Bonhommeau et al, 2008), and to variations in ocean currents (Baltazar-Soares et al, 2014), overfishing and loss of habitat perhaps in coastal areas relatively near to the Sargasso Sea (Kettle et al, 2011), infections-especially with the nematode Anguillicola crassus (Palstra et al, 2007), barriers to migration (Chadwick et al, 2007), and pollution (Robinet and Feunteun, 2002) have all been implicated
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