Experiments on Fishways for Freshwater Amphidromous Shrimps.

Abstract

Basic conditions of fishways for freshwater amphidromous shrimps, two atyids Caridina japonica and Paratya compressa and a palaemonid Macrobrachium japonicum, which migrate to upstream habitats by walking at night, were studied using an experimental apparatus comprised of ten distinct flooring materials. As a result, effective fishway conditions were defined as follows: three-dimensional mesh structure (0.5mm in mesh sizes), e.g., cellular concrete, in the flooring, ≤50° at the inclination, and ≤65cm/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.