  Recent ALMA observations have found many protoplanetary discs with rings that
can be explained by gap-opening planets less massive than Jupiter. Meanwhile,
recent studies have suggested that protoplanetary discs should have low levels
of turbulence. Past computational work on low-viscosity discs has hinted that
these two developments might not be self-consistent because even low-mass
planets can be accompanied by vortices instead of conventional double rings. We
investigate this potential discrepancy by conducting hydrodynamic simulations
of growing planetary cores in discs with various aspect ratios ($H/r=0.04$,
0.06, 0.08) and viscosities ($1.5 \times 10^{-5} \lesssim \alpha \lesssim 3
\times 10^{-4}$), having these cores accrete their gas mass directly from the
disc. With $\alpha < 10^{-4}$, we find that sub-Saturn-mass planets in discs
with $H/r \le 0.06$ are more likely to be accompanied by dust asymmetries
compared to Jupiter-mass planets because they can trigger several generations
of vortices in succession. We also find that vortices with $H/r = 0.08$ survive
$>6000$ planet orbits regardless of the planet mass or disc mass because they
are less affected by the planet's spiral waves. We connect our results to
observations and find that the outward migration of vortices with $H/r \ge
0.08$ may be able to explain the cavity in Oph IRS 48 or the two clumps in MWC
758. Lastly, we show that the lack of observed asymmetries in the disc
population in Taurus is unexpected given the long asymmetry lifetimes in our
low viscosity simulations ($\alpha \sim 2 \times 10^{-5}$), a discrepancy we
suggest is due to these discs having higher viscosities.
