Abstract
European eel ( Anguilla anguilla ; Teleostei) is a valuable commercial species. However, over the past 25 years, the population of European eel has been declining to such a degree that major concerns have been raised for its long‐term conservation. Since little information is available on the life‐cycle and genetic structure of European eel, it has been difficult to evaluate the existence of any population substructuring. Molecular genetic methods contribute to a better knowledge of the demography and population structure in marine fish. In addition, management strategies and conservation goals must consider information on genetic substructuring as well as on life history patterns. The aim of the study is to provide more detailed knowledge on the genetic variability, demography and population substructuring of European eel by analysing and comparing natural and farmed individuals. Natural eel samples have been obtained in two geographical sites (Netherlands, France) including temporal samples in a short‐scale (within years) and a long‐scale (between years). Simultaneously, farmed glass eels have been grown in two separate batches during one year. Batches have been monitored and genetic samples have been obtained during the year. A combination of selection‐sensitive (allozymes) and selection‐neutral markers (microsatellites) has been used in the study since selection seems to play an important role in the determination of the quality of future eel spawners. Results suggest a positive correlation between growth and genetic variability since individuals attaining a large length and mass present significant higher heterozygosities.