Inland Fisheries

3.4.6.1 Types of Fish passes / Fish ways

The following types of fish passes have been used for the migration of fishes in freshwaters in foreign countries.

1) Natural: In this type of fish passes the approach routes of fish may be strengthened with concrete to the natural rock with the natural rock with the object of concentrating flows previously diffuse, reducing turbulence and deepening pools.

2) The Pool design (Fish ladder) : It consists of a series of pools arranged in a ladder-like manner from downstream to upstream. The flow of water from pool to pool may be over solid obstacles or through passages between obstacles or a combination of two types. Each pool is designed in such a way that it provides adequate resting grounds for the ascending fishes.

3) Deep baffled channel: This is a modified Deniel type of fish way designed for low gradient and is suitable for extreme variations in inflow and water level. Actually, it is a single slot vertical baffle fish way.

4) Simple sluice or inclined chute: The chute is an inclined channel or a sort of waterfall with deep descent. The effective width of the channel is actually much less than the width of sluice and many sharp turns cause cross currents that are very difficult to be counteracted by large fishes.

5) The Deniel design: It is a narrow channel with closely spaced baffles set at an angle with the axis of the channel. In this kind of fish way, the force of fast flowing water is minimized and fishes can negotiate them easily.

6) The Fish lock: It is an arrangement for the regulation of flow of water with the help of mechanical gates. The inflow and outflow can be regulated thus providing fishes with the passage to move either way.

7) Other types include fish lifts, dished channel, submerged orifice and roughened channel