Poster 19: The use of genetic tools for the management and conservation of the endangered bullhead (Cottus gobio l., 1758) in Flanders

The European bullhead ranges from North Spain to Scandinavia, excluding only Scotland and Ireland. In Flanders, the bullhead is regarded as highly vulnerable, and is therefore fully protected by law in Belgium. Bullheads are known to have low dispersal capabilities. In addition, vertical migration barriers higher than 20 cm are impassable for bullheads. Consequently, human activities can have a large impact on the viability of bullhead populations. In Flanders, all remaining bullhead populations are confined to the upper courses of some rivers and streams, where conditions are favourable. As a result, Flemish bullhead populations are highly fragmented and isolated. In order to evaluate the problem, we studied genetic variation in the remaining populations using microsatellites. We also examined the longitudinal extent of the populations, and measured the populations' physiological condition. Small patch size appears to act limiting on genetic variation. This could be caused by inbreeding and/or genetic drift. Low genetic variation was associated with a low physiological condition, which in turn was related to fitness. As a result, fragmentation of the bullhead's habitat can jeopardize the long-term survival of this species. Several conservation strategies can be considered: (a) Removal of migration barriers in order to enlarge the populations' patch size, (b) Restauration of the original habitat, (c) Breeding programmes, (d) Translocation of individuals from other populations. However, translocations from other populations should be carried out with care! Several evolutionary bullhead lineages are found in Flanders. Mixing these lineages could break up existing adaptations, which would reduce the evolutionary flexibility of the populations.