Eels at the Edge: Science, Status, and Conservation Concerns

<em>Abstract.</em>—A new checklist of 36 metazoan parasites recorded in European eels <em>Anguilla anguilla </em>in Ireland is presented and reviewed. Some of these parasite taxa are eel specialists but most utilize a range of fish hosts. Many were accidentally brought to Ireland during fish introductions. Changing distributions of preferred intermediate hosts have affected some parasite species. Commercial transport of eels has been implicated in the introduction and spread of several potentially pathogenic parasites, including the Asian nematode <em>Anguillicola crassus</em>. The current status of this and two <em>Pseudodactylogyrus </em>species, similarly introduced to Ireland, is discussed. Analysis of parasite assemblages of Irish eel populations indicates that individual host characteristics, such as size and diet, are important at the infra-community level. Likewise, variation in biotic and abiotic features of ecosystems is reflected in composition and structure of eel parasite component communities. Environmental changes, such as eutrophication and species introductions, were found to affect eel parasite assemblages. Better regulation of fish introductions and translocations is needed to protect the ecological integrity of Ireland’s freshwater systems and to avoid economic damage by nonindigenous parasites. Restrictions on live eel transport and on eel stocking programs may be necessary to protect recreational fisheries and the Irish aquaculture industry.