Laser cooling and trapping of neutral mercury is performed in a single-stage ${}^1{S}_0\leftrightarrow {}^3{P}_1$ 3D magneto-optical trap. We give a detailed account of the atom cloud size and temperature for both bosonic ( ${}^{200}\mathrm{Hg}$ and ${}^{202}\mathrm{Hg}$ ) and fermionic ( ${}^{199}\mathrm{Hg}$ and ${}^{201}\mathrm{Hg}$ ) isotopes. The bosonic isotope temperatures are in close agreement with Doppler cooling theory, while temperatures obtained for the fermionic isotopes are lower, suggesting the presence of sub-Doppler cooling. A minimum temperature of $29\pm 4\mathrm{\mu K}$ is achieved for ${}^{201}\mathrm{Hg}$ .