I am having trouble making the distinction, i thought mass flux was the flow of fluid through a unit area per second in kg/s. The volume flow was the rate of volume flow in m^3/s,

In several questions i am working on relating to poiselle and couette flow they define Q as the integral of v.dz, where v is the velocity,in some cases they refer to this quantity as the mass flux and in other questions as the volume flux with the same integral, is mass flux and volume flux the same thing?