A system for filtering a flow of water comprises a movable filter strainer 11 comprising a plurality of filtering elements 18 arranged in succession to form a closed filtering surface which can be set in movement such that each element can be displaced between a low point (P1) and a high point (P2) along a first path. A plurality of lifting scoops 30 are arranged on the upstream side of the filtering surface； each scoop having, in a plane perpendicular to that of said filtering surface, a cross-section in the form of a cup. Each scoop is of a shape and a depth which make it possible to contain a sufficient store of water to transport live fish during the displacement of the scoop between the high and low points and is of a sufficiently flared shape at the opening thereof so as to be washable by supplying water tangentially from a washing device 23 to one of the two side walls 30b, 30c thereof.
