Mass marking of juvenile diadromous fish: common requirements from the recovery plans of Allis shad Alosa alosa and North Sea Houting Coregonus oxyrinchus in the Rhine basin
Résumé
Most of the diadromous fish species encountered in Europe are now threatened. Conservation of this component of the aquatic biodiversity needs a hydromorphological and physicochemical improvement of the hydrosystems but also often requires stocking measures. This practice is at last quite properly mastered for salmonids but we have now to set up or improve methods fitted to other species e.g. Allis shad (Alosa alosa) (Fig. 1), Nord sea Houting (Coregonus oxyrhinchus) (Fig. 2), common sturgeon (Acipenser sturio) (Lochet et al., 2004), or even European eel (Anguilla anguilla) for transfer actions.