  In a thin film of superconducting YBCO the impact of surface acoustic waves
(SAWs) traveling on the piezoelectric substrate is investigated. A pronounced
interaction between the ultrasonic waves and the vortex system in the type II
superconductor is observed. The occurrence of a SAW-induced dc voltage
perpendicular to the sound path is interpreted as {\em dynamic pinning} of
vortices by the piezoacoustic SAW, which acts as a conveyor for the fluxquanta.
Its antisymmetry with respect to the magnetic field directly evidences the
induced, directed flux motion.This dynamic manipulation of vortices can be seen
as an important step towards flux-based electronic devices.
