Because of the lack of information on the genetic structure of fishes on the Belgian Continental Shelf, the Laboratory of Aquatic Ecology of the Katholieke Universiteit Leuven initiated a large-scale survey of the genetic structure of selected marine animals in 1992. Species were chosen on the basis of their abundance and role in the food web (gobies of the genus Pomatoschistus), as ecological indicator (parasites of the flatworm genus Gyrodactylus) or their significance for fisheries (European eel and sole). Monogeneans of the genus Gyrodactylus differentiate in a group parasitising the fins of gobies and a group parasitising their gills. In the first group molecular differentiation precedes morphological adapation, while the reverse is true in the gill group (Zietara et al, 2000 and 2001; Huyse and Volckaert, in prep). The results have been used over the past years by the Working group on eel (EIFAC/FAO). Fisheries management of eel was optimised by introducing a marine perspective and the isolation-by-distance genetic structure. Expertise of the Laboratory of Aquatic Ecology has also been shared with ICES at the annual meeting (Brugge, 2000), with the Belgian and regional government, with the EU (expert evaluation), the media (TV appearance on exotic species in Flanders; radio interview on transgenics) and the public (voluntary teaching to high school pupils and the public).