  High-resolution sub-mm observations of some protoplanetary discs reveal
non-asixymmetric features, which can often be interpreted as dust
concentrations in vortices that form at the edges of gaps carved out by the
embedded planets. We use recent results on the timescale for the planet-driven
vortex development in low-viscosity discs to set constraints on the mass and
age of a planet producing the vortex. Knowledge of the age of the central star
in a vortex-bearing protoplanetary disc system allows one to set a lower limit
on the planetary mass at the level of several tens of $M_\oplus$. Also, an
independent upper limit on the planetary mass would constrain the planetary
age, although given the current direct imaging detection limits this constraint
is not yet very stringent (it is also sensitively dependent on the disc scale
height). These results can be extended to account for the history of planetary
mass accretion if it is known. We apply our calculations to several
protoplanetary discs harbouring vortex-like features as revealed by ALMA and
set limits of $(30-50)M_\oplus$ (for disc aspect ratio of $0.1$) on the minimum
masses of putative planets that could be responsible for these vortices. Our
vortex-based method provides an independent way of constraining the properties
of embedded planets, complementary to other approaches.
