  We calculate the conductance through rings with few sites $L$ described by
the $t-J$ model, threaded by a magnetic flux $\Phi$ and weakly coupled to
conducting leads at two arbitrary sites. The model can describe a circular
array of quantum dots with large charging energy $U$ in comparison with the
nearest-neighbor hopping $t$. We determine analytically the particular values
of $\Phi$ for which a depression of the transmittance is expected as a
consequence of spin-charge separation. We show numerically that the equilibrium
conductance at zero temperature is depressed at those particular values of
$\Phi $ for most systems, in particular at half filling, which might be easier
to realize experimentally.
