Cable screen for fish protection purposes

Abstract

An apparatus for holding back, and diverting, fish in bodies of water by the arrangement of parallel cables (S) braced between two or more abutments (W), wherein the distance between the cables is small enough to prevent fish from swimming through the apparatus.

Claims

1. Method for holding back fish in a body of water, comprising horizontally bracing cables (S) essentially parallel below the surface of a body of water between two or more horizontally spaced abutments (W) such that the cables are not connected together below the surface of the body of water, a vertical spacing between the cables being such that the fish that are to be held back are prevented from swimming through.

2. Method according to claim 1, further comprising relaxing the cables (S) for opening.

3. Method according to claim 1, further comprising vibrating the cables (S).

4. Method according to claim 1, further comprising illuminating the cables (S).

5. Method according to claim 1, further comprising applying electric current to one or more of the cables (S).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the Figures:

(2) FIG. 1 shows a cable screen for fish protection having cables horizontally braced below the surface of a body of water between two abutments in a normal position;

(3) FIG. 2 shows the fish protecting cable screen of FIG. 1 in an open position; and

(4) FIG. 3 shows a further developed fish protecting cable screen with cable sections comprising linear light elements, said cable sections being braced horizontally between two abutments, in a normal position.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(5) The fish protection cable screen differs from the gratings previously used in its fundamental construction and mode of operation. The mechanical barrier required for fish protection is achieved by a plurality of cables S braced parallel or substantially parallel to one another. Typically, the cables are braced horizontally below the surface of the body of water between two or more abutments W (FIG. 1). In this way, large span widths can be achieved inexpensively and making the best possible use of the material properties. Each individual cable S can be braced at one or more abutments W, and also cast off from them, independently of the other cables S. For this reason, a tension device for each individual cable is attached on at least one of the abutments W for repeatedly stretching tight and relaxing the corresponding cable S. The tension device can be a winch.

(6) The fish protection cable screen can easily be opened completely by casting off the individual cables S (FIG. 2). This is particularly important with high outflows to avoid log jams and harmful interactions with the bed load. Also the fish protection cable screen is cleaned by partially or completely laying the cables S flat and then stretching them tight.

(7) The effect of the fish protection cable screen can be further enhanced by setting the cables S vibrating. For this reason, at least one vibration device is attached on at least one of the abutments W for making the cables S to vibrate. Alternatively or additionally, it is possible to integrate other fish-repelling measures, such as, for example, the arrangement of linear light elements LL (FIG. 3), in the fish protection cable screen. As another example, some embodiments are configured to apply electric current to one or more of the cables S. These measures constitute a behavioural barrier that may deter even smaller fish from swimming through the apparatus.

LIST OF REFERENCES

(8) W abutment

(9) S cables

(10) LL linear light element