  Dual canonical bases of the quantum general linear supergroup are constructed
which are invariant under the multiplication of the quantum Berezinian. By
setting the quantum Berezinian to identity, we obtain dual canonical bases of
the quantum special linear supergroup ${\s O}_q(SL_{m\mid n})$. We apply the
canonical bases to study invariant subalgebras of the quantum supergroups under
left and right translations. In the case $n=1$, it is shown that each invariant
subalgebra is spanned by a part of the dual canonical bases. This in turn leads
to dual canonical bases for any Kac module constructed by using an analogue of
Borel-Weil theorem.
