The “European Eel Investigation and Assessment of their Decline” project (or EELIAD), funded under the seventh framework programme (FP7) which is a grant funding programme, provides scientific knowledge to allow the recovery of European eel populations. The initiative is characterised by scientific collaboration and the deployment of networking activities to establish a network of excellence throughout Europe. It aims to increase the understanding of the behaviour, biology and ecology of eels, particularly by bringing together numerous external (i.e. environmental) and internal (i.e. biological) factors that may influence their migration. To reach this goal, large-scale monitoring and sensing technologies, such as automatized and remote sensing devices supported by numerical models, are being used.
The ecological and economic role of eels is significant in many European countries (e.g. Spain, Portugal, France, Sweden and the United Kingdom), but the recruitment of eels in Europe, in common with recruitment of eels in Japan and in northern America, has dramatically decreased since the 1960s. While factors contributing to this decline can be studied relatively easily in the freshwater or ‘continental’ environment, there is speculation that the causes of the decline may also exist in the marine environment. However, the marine environment monitoring of eels is technically challenging, and can be very expensive. Undertaking a large-scale study with traditional means, that aim to reveal migration routes, spawning sites or population mixing of species, is neither technologically suitable nor cost-efficient. As a consequence, despite more than a century of research, the oceanic phase of eel biology is poorly understood, and much of it remains a mystery.
To increase our understanding of eels, the project delivers a multidisciplinary approach designed to integrate the relationship between different life-stages of eels (i.e. glass eels, yellow eels and silver eels). Thus glass eels (so-called because of the transparency of their body), for example, are sampled and analysed in order to increase the knowledge concerning the several factors explaining the way that populations mix and the larval migration history: the researchers wonder in particular if the spawning of eels is random mating (panmixia) or whether there are spatial or temporal substructures in the spawning population. To do so, the analysis relies on an identifying technique (i.e. isotopic and genetic analysis) performed on eels collected from several sampling sites across Europe. In addition, the project makes use of recently developed tagging technologies to determine what the relevant factors that lead silver eels to define their migration routes and their spawning sites consist of. To do so, in-situ physical sensing devices are attached to numerous adult eels. Satellite communicating tags (i.e. connected to satellites) and drift archival tags (i.e. collected at the end of life of the host) allow the researchers to gather various data to determine connections between the marine environment (e.g. water temperature) and migratory behaviours (e.g. depth of movement). Finally, the quality of eels (such as size, fat content, toxic load) at several life stages is being assessed by quantifying specific in situ indicators (such as biomarkers). The relationship between the eel’s quality and habitats they come from is also assessed. To achieve this task, an exhaustive data analysing approach is carried out by gathering numerous information extracted from information and observation system databases (e.g. Global Information System or map-based resources).
The global characterisation process, which provides several technologies and methodologies, is complete (the technology readiness level is 9 on the TRL scale) so that information is available.
The data collected within the project will be used to inform fishery policies at regional and pan-European scales by providing recommendations for implementing the most suitable measures, i.e. by opting for the most effective fishery / stock support ratio, or for identifying uncertainties in the Eel Management Plan. For example, accurate awareness of the downstream movement of silver eels is extremely relevant with regard to small hydroelectric power plants of which managers must not impede the escapement of eels. The information provided by the project will therefore help to determine sustainable exploitations as well as identify how to achieve efficient recovery plan, and therefore contribute to stem the tide of the stock’s decline.