  The paper investigates the coexistence and interplay of spin and mass
superfluidity in a ferromagnetic spin-1 Bose-Einstein condensate. Superfluidity
is possible only in the presence of uniaxial anisotropy (linear and quadratic
Zeeman effect). This follows from the topology of the order-parameter space
(vacuum manifold). According to the Landau criterion, the critical phase
gradients, both for mass and spin supercurrents, vanish at the phase transition
from the easy-plane to the easy-axis anisotropy. However, mass superfluidity is
still possible at the phase transition. This is because the Landau criterion
signals instability only with respect to nonsingular vortices with special
ratio between circulations of mass and spin currents. Phase slips produced by
these vortices are not sufficient for complete decay of supercurrents. Full
decay of supercurrents requires phase slips with vortices of another
topological class and larger energy. These phase slips are suppressed by
energetic barriers up to the upper critical velocity (gradient) exceeding the
Landau critical velocity. The upper critical velocity does not vanish nor has
any anomaly in the critical point at the phase transition from the easy-plane
to the easy-axis anisotropy.
