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As the eel is a long-lived, carnivorous, benthic and lipid-rich species, it is particularly prone to the accumulation of noxious chemical compounds, especially lipophilic contaminants like polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) and brominated flame retardants (BFRs). At the Research Institute for Nature and Forest (INBO), a monitoring network was set up to measure contaminants in the eel over Flanders during a 15-year research programme, starting from 1994. More than 3000 eels from 376 locations were analysed for PCBs, OCPs, heavy metals and some other compounds.The data showed clearly that eels in their yellow stage are excellent chemical bioindicators; contaminant profiles in the studied eels are fingerprints of the contamination pressure on the site where they grow up.Results generated status reports and distribution maps of eel pollution for some 30 substances. Most substances are present all over Flanders, but there is considerable variation between river basins, dependent on land use. Contaminant analysis in eel is able to pinpoint specific pollution sources, like some volatile organic compounds in very specific locations, very high BFR levels in eels from areas with intensive textile industry, or high lindane levels in some rivers under agricultural pressure. We could demonstrate that banned chemicals like DDT are still in use in some places. Within the study period, trend analysis indicated significant reductions in PCBs and many OCPs. Also for some heavy metals (lead, arsenic, nickel and chromium), concentrations decreased in the eel, but this was not the case for cadmium and mercury.Self-caught eels are much esteemed by fishermen, but considering the eel’s high contaminant body burden, consumption constitutes a potential risk for human health. On many sites levels of specific compounds exceed legal maximum levels.Several contaminants were assessed for their potential impact on the eel population. Contaminants may impact on various levels of biological organisation from molecular, individual to population and community, hence the nature of the effects varies to a very wide extent. Despite a very high internal load of endocrine disrupters, we did not find any effects on vitellogenin levels in immature yellow eel. However, a significant negative correlation between heavy metal pollution load and condition was observed, suggesting an impact of pollution on the health of sub-adult eels. In strongly polluted eels a reduced genetic variability was observed. New advances in gene expression profiling, using either microarrays or RNA-seq, offers the opportunity to investigate the effects of pollutants at the genome-wide level and also showed significant impacts.It was further demonstrated that fat stores and condition decreased significantly during the last 15 years in eels in Flanders and The Netherlands, jeopardizing a normal migration and successful reproduction of this long-distance migrator. Belpaire et al (2009) hypothesized that pollution is a major driver for this decrease in fat reserves.Part of the work presented here has been summarized in two reviews. Geeraerts and Belpaire (2010) reviewed the potential effects of contamination on the eel and Belpaire et al. (2016) presented a simplified concept describing how reprotoxic chemicals may influence the status of the stock of the European eel.Belpaire C.G.J., G. Goemans, C. Geeraerts, P. Quataert, K. Parmentier, P. Hagel and J. De Boer. 2009. Decreasing eel stocks: Survival of the fattest? Ecol. Freshw. Fish. 18(2):197-214.Belpaire, C., Pujolar, J.M., Geeraerts, C., and Maes, G., 2016. Contaminants in Eels and their Role in the Collapse of the Eel Stocks. in press. In Biology and Ecology of Anguillid Eels T. Arai (Ed.)Geeraerts, C. and C. Belpaire. 2010. The effects of contaminants in European eel: a review. Ecotoxicology (2010) 19: 239–266

The Planning Group on the Monitoring of Eel Quality met at the Research Institute Nature and Forest (INBO) Brussels, Belgium, on the 20–22 January 2015 during its first Workshop (WKPGMEQ) under the subject “Development of standardised and harmonised protocols for the estimation of eel quality”, chaired by Claude Belpaire (Belgium) and Olga Haenen (The Netherlands). There were 31 participants (21 attendees and 10 remote participants) representing 13 countries.Reliable assessment of the eel stock quality and its quantitative effect on the reproductive stock is currently not possible, due to insufficient spatial and temporal data coverage (ICES 2009). This has emphasised the urgent need to establish a comprehensive overview with improved spatial coverage of the quality of the eel population across Europe as an essential and urgent requirement. Understanding the reproductive potential of the international spawning stock is a key component to predicting the effects on stock recovery of changes to silver eel escapement, arising from management actions implemented within Eel Management Plans.To address this need, ICES 2012 recommended that Member States implement routine monitoring of lipid levels, contamination and diseases. Many countries have started compiling data on the health status of eels in their water bodies. Objectives for these monitoring actions are diverse and are not restricted to the framework of eel recovery. Eel quality is also monitored for different purposes, which include human health considerations and to meet requirements of the Water Framework Directive. Hence, there is a large amount of information collected by EU member countries. However, procedures with respect to sampling, analysis and reporting are not harmonised, hindering stock wide assessments and risking inefficient use of resources. Consequently, ICES (2009) identified the need to develop standardised and harmonised protocols for the estimation of eel quality, so that national data would be comparable between Member States and could be reliably incorporated in international stock assessments.The objective of WKPGMEQ was to document standardised and harmonised protocols for the estimation of the quality of the European eel Anguilla anguilla, with regard to the bioaccumulation of contaminants and the presence of diseases, including parasites.WKPGMEQ took advantage of the preparative work of the participants who in advance of the workshop drafted reports describing the framework and methods used in their countries for the assessment of contaminants and diseases in the eel. At the start of the meeting Member States’ country reports were presented. Two subgroups, covering contaminants and diseases respectively, further discussed the practical issues surrounding the sampling, assessment procedures, diagnostic approaches and reporting related to measuring contaminants and diagnosis of eel parasites and other diseases. As far as possible, common procedures and guidelines were described.The report starts with an overview of the current eel quality assessments in the Member States, and further discusses general issues on sampling of eel quality assessments. It includes a chapter on the assessment of eel condition in terms of fitness and lipid levels. In further chapters best practices to (sub)sample, analyse, report and visualize contaminants in the eel are described. The disease sections focus on parasitic diseases (including the swimbladder parasite Anguillicoloides), and on viral and bacterial diseases. Possible ways to integrate data and to implement them into eel quality indices have been suggested. The workshop also discussed the future perspectives of using biomarkers of effects to assess eel health. Finally the report concludes describing the international context and future perspectives in eel health assessments.Several recommendations were made to facilitate the further development of a framework to integrate eel quality assessments into the quantitative management of the eel stock. Member States should apply harmonised methods for eel quality assessments and reporting, and routine monitoring and reporting of lipid levels, contamination and diseases needs to be integrated in the requirements within the Eel Regulation. Raw data should be made available to the international community and the management of the Eel Quality Database needs a structural basis. There is an urgent need for an internationally coordinated research project aiming at improving the understanding and quantification of the effects of contaminants on the reproductive success of the European eel, to allow integration of quality indicators in stock wide assessments.ICES, 2009. Report of the 2009 Session of the Joint EIFAC/ICES Working Group on Eels, FAO European Inland Fisheries Advisory Commission; International Council for the Exploration of the Sea, Göteborg, 7–12 September 2009, EIFAC Occasional Paper No. 45, ICES CM 2009/ACOM: 15. Rome, FAO/Copenhagen, ICES. 2010. p. 540 (Online).ICES, 2012. Report of the 2012 Session of the Joint EIFAAC/ICES Working Group on Eels, Copenhagen, Denmark, 3–9 September 2012; ICES CM 2012/ACOM:18, EIFAAC Occasional Paper 49, 828 pp.ICES, 2015. Report of the Workshop of a Planning Group on the Monitoring of Eel Quality under the subject “Development of standardized and harmonized protocols for the estimation of eel quality” (WKPGMEQ), 20–22 January 2015, Brussels, Belgium. ICES CM 2014/SSGEF:14. 274 pp.