Development of the fish stock and its manageability in the deep, stratifying Wupper Reservoir

AbstractToday's fish fauna of Wupper Reservoir is the result of natural development in combination with management. Manageability of the fish stock, a prerequisite for continuing biomanipulation, was limited. Despite protection and stocking, the abundance of the stocked predatory fishes (pike, pikeperch) did never exceed 10% of the total fish biomass since filling in 1988. Contrary to predictions, the “juvenile” cyclical perch population that became dominant after flooding, with the disappearance of gigantic perch in 1997, was not replaced by cyprinids (>60% of total fish biomass). Instead, a strong, non-cyclical piscivorous perch population, plus cyprinids (