Introduction Filter-feeding fish separate food particles from the surrounding water by cross-flow filtration in which a suspension flows parallel to a porous filter medium, thereby transporting particles along the surface. Methods Here, we investigate cross-flow filtration in five ram-feeding fish species from two groups, Scombridae ( Scomber scombrus and Rastrelliger kanagurta ) and Clupeidae ( Clupea harengus , Sardina pilch...