  Tsallis has proposed a generalization of Boltzmann-Gibbs thermostatistics by
introducing a family of generalized nonextensive entropy functionals with a
single parameter $q$. These reduce to the extensive Boltzmann-Gibbs form for
$q=1$, but a remarkable number of statistical and thermodynamic properties have
been shown to be $q$-invariant -- that is, valid for any $q$. In this paper, we
address the question of whether or not the value of $q$ for a given viscous,
incompressible fluid can be ascertained solely by measurement of the fluid's
hydrodynamic properties. We find that the hydrodynamic equations expressing
conservation of mass and momentum are $q$-invariant, but that for conservation
of energy is not. Moreover, we find that ratios of transport coefficients may
also be $q$-dependent. These dependences may therefore be exploited to measure
$q$ experimentally.
