WO1992019100A1

WO1992019100A1 - Method of leading and trapping fish in the sea, and equipment for use in carrying out the method

Info

Publication number: WO1992019100A1
Application number: PCT/NO1992/000082
Authority: WO
Inventors: Harald Hov; Inge LADEGÅRD
Original assignee: Hov Maritim A/S
Priority date: 1991-04-29
Filing date: 1992-04-28
Publication date: 1992-11-12
Also published as: AU1686392A; NO911686D0; NO911686L

Abstract

A method, and equipment for the execution thereof, of leading and trapping fish, e.g., fish/salmon escaped from a breeding farm, with the aid of pressure hoses with air jets distributed along the length thereof and connected to a source of compressed air. The pressure hose is equipped with means for maintaining it at the desired depth below the water surface for the production of an air curtain. A generator for producing sound frequencies in the water may also be connected to the equipment. The above components are arranged on at least two vessels (B, C) which tow the pressure hose (1) through the water. The two vessels (B, C) are positioned near/moved along the land on opposite sides of a fjord (inlet), bay, etc., in order, by slow movement of the pressure hose inward toward the base of the fjord or end of the bay with the aid of the vessels and by simultaneous provision of the air curtain and, optionally, sound frequencies in the water along the pressure hose (1), to gather and lead the fish to, and to confine them in, said fjord base/bay end, for subsequent collection of the fish with the aid of suitable means.

Description

METHOD OF LEADING AND TRAPPING FISH IN THE SEA, AND EQUIPMENT FOR USE IN CARRYING OUT THE METHOD.

The present invention relates to a method of leading and trapping fish, e.g. , fish escaped from a breeding farm, and specifically escaped farmed salmon, which method is of the type disclosed in the preamble to the following independent method claim 1.

The invention also relates to equipment for use in carrying out the method, which equipment is of the type disclosed in the preamble of the following equipment claim 8.

It is well known that there are major problems relating to farmed fish, e.g., salmon, that have escaped from breeding farms and enclosures along the coast. Escaped salmon which in some cases may be diseased have created a major ecologi¬ cal catastrophe in fjords (inlets) and watercourses and, as far as I can see, could bring about enormous and widespread damages. The escaped and possibly diseased farmed fish infect wild fish, laying waste the marine life in the fjords and water systems. It could take decades to repare such damage. At the present time we have no known tools for trapping escaped and diseased farmed fish that have become spread over large areas. By large areas we mean entire fjord (inlet) systems or parts of a fjord, cove or bay.

There do, however, exist equipment and means for leading/ frightening fish in the sea, for example as disclosed in Norwegian patent no. 164.812. This shows use of air curtains and sound signals in the water to lead the fish or confine them in an area of the sea.

It is also known to use electrical fields of varying strength in addition to light to prevent the fish from swimming into areas or waterways, or to arrange and use these to lead the fish positively into desired paths, for example as disclosed in TJS patents no. 2,709,984 and no. 2,761,421.

These publications, however, relate to equipment/installa¬ tions in a local region and are not suitable for use in the sea to drive or lead escaped fish across a wide area, toward a predetermined and suitable location such as a bay or cove, where the gathered-together escaped and possibly diseased fish may be confined without being injured, and may sub¬ sequently be picked up with the aid of known equipment.

The purpose of the present invention is to provide a method, and the equipment to be used for the execution thereof, of leading and trapping fish, e.g, fish escaped from a breeding farm, and specifically escaped farmed salmon, as mentioned above, which is achieved by means of the characterizing features disclosed in the characterizing clause of the following method claim 1 and the subsequent dependent claims.

The equipment for use in the method is characterized by the features disclosed in the characterizing clause of the following equipment claim 5 and the subsequent dependent claims.

Hence, it is apparent from the method according to claim 1 that a pressure hose is towed through the water with the aid of at least two vessels connected thereto. The two vessels are positioned near and/or are moved along the land on opposite sides of a fjord, bay, etc., in which area the escaped fish are located, in order by slow movement of the pressure hose inward toward the base of the fjord or the end of the bay with the aid of the vessels, and by simultaneous provision of the air curtain and, optionally, sound frequen¬ cies in the water along the pressure hose, to gather and lead the fish to, and to confine them in, said fjord base/bay end for subsequent collection of the fish with the^" aid of suitable means.

The equipment which is used for carrying out the method, and which is of the type mentioned in the introduction, is comprised of the pressure hose connected to two vessels spaced apart, where at least one said vessel is equipped with a source of compressed air and, if desired, sound frequency generators. In order to adapt the length of the pressure hose relative to the width of the fjord or bay, a winch is provided on one of the vessels for drawing in or letting out the pressure hose, in such manner that through the supplying of compressed air, it maintains an air curtain across the fjord/bay while, optionally, there are also provided sound signals that contribute toward leading or frightening the escaped fish in the desired direction.

The invention will be described in more detail in the following, with reference to the drawings, where

Figures 1, 2 and 3 illustrate schematically the method and the equipment used for execution of the method,

Figure 4 shows a more detailed picture of the parts of the equipment which are adapted for placement in the sea and on the boat,

Figure 5 shows details of the equipment, with the sound frequency generator located on the suspension line between the pressure hose and buoy, and

Figure 6 shows a section of a sound frequency generator with a bell chamber and electromechanical hammer disposed therein.

Figure 1 shows equipment for leading and trapping fish, e.g. fish that have escaped from a breeding farm and specifically escaped farmed salmon, comprising a pressure hose 1 having air jets 2 distributed along the length thereof, to be positioned at the desired depth below the water surface A with the aid of suitable means and connected to a source of compressed air and, optionally, a generator 4,5 for produc¬ ing sound frequencies in the water. The pressure hose 1 is connected to two vessels B,C, spaced apart, the one vessel B being equipped with the source of compressed air and, optionally, the sound frequency generators 4 and/or 5. A winch 6 for drawing in or letting out the pressure hose 1 is provided on the second vessel C situated at a distance from the first vessel B.

As is clearly apparent from Figure 4, pressure hose 1 is connected to a pipe D for supply of compressed air from a compressed air source.

A sound frequency generator 4 is pneumatically driven and is disposed in the compressed air passage between pipe D from the compressed air source and pressure hose 1. Sound frequen- ^c generator 4 is composed of a diaphragm 4a prestressed by means of a spring 4b against a seat 4c having a smaller diameter than that of the passage, in a direction counter- current to that of the air stream. Spring 4b in the form of a helical pressure spring or, optionally, spring washers, is disposed on a spindle 4d, the free end of which projects out of the compressed air passage formed as a chamber 7, and is provided with threads for engagement with a tightening/ adjusting nut 4e. The nut 4e may, for example, be provided with a control arm 4f for regulation of the sound frequency and sound level by adjustment of the pressure of spring 4b. Said sound frequencies are intended to be transmitted in the air stream in pressure hose 1 and further into the air bubbles out through the air jets 2 in the pressure hose and out into the surrounding water.

In addition to said sound frequency generator 4, or as a replacement therefor, there may be provided a sound frequency generator 5 composed of an acoustic hammer disposed on/near a sink line 8 of wire with sinkers 9, for producing, when said wire is struck, sound signals in the wire and thereby in the surrounding water. The acoustic hammer may be hydrauli- cally or electrically driven.

Said sink line 8 with sinkers 9, as shown in Figures 1, 3 and 4 as well as 5, is designed to be connected with the pressure hose 1 to keep said pressure hose submerged in the water. To maintain pressure hose 1 at the desired depth below the water surface, there is also used a buoy 13 with suspension line 12 attached to pressure hose 1. By regulating the length of suspension line 12, one determines the desired depth for the pressure hose and for the air curtain in the water provided by means of said hose. Such buoys 13 with suspension lines 12 are spaced apart along the length of pressure hose 1.

An alternative form for sound frequency generator 5' in the form of a sound head having a bell chamber 10 with an electromechanical hammer 11 as shown in Figure 6, is attached to the suspension line 12 at the desired distance from buoy 13, as shown in Figure 5.

Here the sound frequency generator 5' is provided with upper and lower ears 10a, 10b for attachment to the respective buoy 13.

The bell chamber 10 in sound frequency generator 5' is cylindrical with a lower base and an upper open end covered with a screw cap 10c provided with threads lOd and a seal lOe. As shown, the upper ear 10a is attached to lid 10c. Inside the bell chamber 10 is the electromechanical hammer 11 and a battery 14 for operation thereof, placed in free¬ standing position relative to the walls of the bell chamber 10 with the aid of a support bolt 16 attached to the underside of lid 10c. Battery 14 is connected via a circuit breaker 15 and wires 14a,b to the driving motor 11a for the electromechanical hammer 11. Circuit breaker 15" may be pressure controlled, in dependence on the depth of the water, for engaging driving motor 11a when the equipment is brought into its operational position in the water.

On activation of driving motor 11a, hammer lib swings back and forth and hits the inside of bell chamber 10, which vibrates and transfers sound frequencies to the surrounding water.

The bell chamber 10 is provided at its upper sector directly below lid 10c with a flange lOf for conducting the generated sound frequencies outward and downward in the water.

The equipment described above is towed through the water with the aid of said two vessels B,C and at the desired depth below the water surface, depending on the depth at which the escaped fish are estimated to be. The two vessels are moved along the land on opposite sides of the fjord, bay, etc., where the fish are located, and with the pressure hose at a depth corresponding to the depth where experience has indicated that the fish will be found. By slow movement of the pressure hose inward toward the base of the fjord/end of the bay with the aid of vessels B,C, and with simultaneous provision of the air curtain 3 and, optionally, sound frequencies in the water along pressure hose 1, the fish are gathered and led to and confined in said fjord base/bay end, for the subsequent collection of the fish with the aid of suitable means.

Pressure hose 1 and the means for maintaining the hose at the desired depth, namely buoys 13 and suspension lines 12, are drawn in and let out, respectively, with the aid of a winch 6 from one of the vessels B,C in order to vary the length of pressure hose 1 between the vessels as they follow the land on each side of the fjord/bay, etc. To relieve the tension under pressure hose 1 during use in wide fjords, inlets, etc., there may be employed, for example, a third vessel D, optionally several, which is/are connected to pressure hose 1 between the two first-mentioned vessels B,C, as indicated in Figure 3.

4

In that case, pressure hose 1 may optionally be divided and supplied with compressed air from the intermediate vessel D while the pressure hoses 1 are drawn in and let out, respectively, on one or both of the two other vessels B,C. This may optionally be accompanied by production of sound frequencies from generators 4,5 on preferably the interme¬ diate vessel D, or by means of the sound frequency generators 5' on suspension lines 12.

With the aid of the method described above for leading and trapping escaped fish, and the equipment for carrying out the method, there are provided possibilities, to a much greater extent than previously known, for leading and trapping escaped fish over large regions and guiding the fish into collection areas.

Claims

P a t e n t C l a i m s

1.

A method of leading and trapping fish, e.g., fish that have escaped from a breeding farm and specifically escaped farmed salmon, with the aid of pressure hoses having air jets distributed along the lengths thereof and connected to a source of compressed air, and equipped with suitable means for maintaining the pressure hose at the desired depth below the water surface for production of an air curtain, and optionally a generator for producing sound frequencies in the water, c h a r a c t e r i z e d i n that the pressure hose (1) is towed through the water with the aid of at least two vessels (B,C) connected to the pressure hose, which two vessels (B,C) are positioned near/moved along the land on opposite sides of a fjord (inlet), bay, etc., in order by slow movement of the pressure hose inward toward the base of the fjord or end of the bay with the aid of the vessels, and by simultaneous provision of the air curtain and, optionally, sound frequencies in the water along the pressure hose (1), to gather and lead the fish to, and to confine them in, said fjord base/bay end, for subsequent collection of the fish with the aid of suitable means.

2.

The method according to claim 1, c h a r a c t e r i z e d i n that the pressure hose (1) with means for maintaining it at the desired depth, is drawn in and let out, respectively, e.g., with the aid of a winch (6), from at least one of the vessels (B,C) in order to vary the length of the pressure hose (1) between the vessels as they follow the land on each side of the fjord/bay, etc.

3.

The method according to claim 1 or 2, c h a r a c t e r i z e d i n that a third vessel (D), optionally several, is/are positioned or connected to the pressure hose (1) to relieve the tension thereof during use in wide fjords, inlets, etc.

4

4.

The method according to claim 3, c h a r a c t e r i z e d i n that the pressure hose (1) is optionally divided and supplied with compressed air from the intermediate vessel (D), while the pressure hose(s) (1) is/are drawn in or let out, respectively, on one or both of the two other vessels (B,C), optionally accompanied by production of sound frequencies from the generator(s) (4,5) on preferably the intermediate vessel (D).

5.

Equipment for use in carrying out the method according to at least one of the preceding claims, comprising a pressure hose (1) having air jets (2) distributed along the length thereof, to be positioned at the desired depth below the water surface (A) with the aid of suitable means, and connected to a source of compressed air, and optionally a generator 4,5 for produc¬ ing sound frequencies in the water, c h a r a c t e r i z e d i n that the pressure hose (1) is connected to two vessels (B,C), spaced apart, and where at least one said vessel (B) is equipped with the source of compressed air and optionally with the sound frequency generator (4,5).

6.

Equipment according to claim 5, c h a r a c t e r i z e d i n that a winch (6) for drawing in and letting out, respec¬ tively, the pressure hose (1) is provided on the second vessel C, which is situated at a distance from vessel (B) where the source of compressed air and the optional sound frequency generator (4,5) is/are located.

7.

Equipment according to one of the claims 5 and 6, c h a r a c t e r i z e d i n that a sound frequency generator (4) is pneumatically driven and is disposed in the compressed air passage between the compressed air source and the pressure hose (1).

8.

Equipment according to claim 7, c h a r a c t e r i z e d i n that the sound frequency generator (4) is made up of a diaphragm (4a) prestressed by means of a spring (4b) against a seat (4c) having a smaller diameter than the diameter of the passage, in a direction countercurrent to that of the air stream, and where the spring (4b) in the form of a helical pressure spring or spring washers, is disposed on a spindle (4d), the free end of which projects out of the compressed air passage, e.g., a chamber (7), and is provided with threads for engagement with a tightening/adjusting nut (4e), optionally having a control arm (4f), for regulation of the sound frequency and sound level by adjustment of the pressure of the spring (4b), which sound frequencies are intended to be transmitted in the air stream in the pressure hose (1) and in the air bubbles out through the jets (2) and out into the surrounding water.

9.

Equipment according to one of the claims 5 and 6, c h a r a c t e r i z e d i n that a sound frequency generator (5) is composed of an acoustic hammer disposed on/near a sink link (8) of wire with sinkers (9) for producing, when said wire is struck, sound signals in the wire and thereby in the surrounding water.

10.

Equipment according to claim 9, c h a r a c t e r i z e d i n that the acoustic hammer is hydraulically or elec¬ trically driven.

11.

Equipment according to claim 5, c h a r a c t e r i z e d i n that sound frequency generators (5') in the form of sound heads having a bell chamber (10) with an electromechan¬ ical hammer^' (11) in the bell chamber, are attached to suspension lines (12) which, at a mutual distance apart, are connected to the pressure hose (1) and buoys (13), which sound frequency generators (5') are connected to a source of electrical current, preferably a battery (14) placed in the bell chamber (10), via a circuit breaker (15) for activating the driving motor (11a) for the electromechanical hammer (11) and operation of its hammer (lib) for striking against the inside of the bell chamber (10).

12.

Equipment according to claim 11, c h a r a c t e r i z e d i n that the circuit breaker (15) is pressure controlled, in dependence on the depth of the water, for engaging of the driving motor (11a) when the equipment is brought into its operational position in the water.