Basic conditions of fishways for freshwater amphidromous shrimps, two
atyids Caridina japonica and Paratya compressa and a palaemonid Macrob
rachium japonicum, which migrate to upstream habitats by walking at ni
ght, were studied using an experimental apparatus comprised of ten dis
tinct flooring materials. As a result, effective fishway conditions we
re defined as follows: three-dimensional mesh structure (0.5 mm in mes
h sizes), e.g.,cellular concrete, in the flooring, less than or equal
to 50 degrees at the inclination, and less than or equal to 65 cm/s at
the surface current velocity in the fishway. A plan for modifying and
improving existing fishways and a proposal for preserving populations
of amphidromous shrimps above dams are discussed.