NO20201047A1

NO20201047A1 - Trawl device

Info

Publication number: NO20201047A1
Application number: NO20201047A
Authority: NO
Inventors: Stefan Paulsen
Original assignee: Geiga As
Priority date: 2020-09-23
Filing date: 2020-09-23
Publication date: 2022-03-24
Also published as: CL2023000780A1; WO2022063935A1; CA3192157A1; NO346570B1

Description

Field of the invention

The present invention relates to a device for reducing and removing the amount of ectoparasites such as salmon lice and other undesired organisms in a floating fish farm facility. The invention further concerns a method for reducing and removing the amount of ectoparasites such as salmon lice from a floating fish farm facility using said device.

Background of the invention

Ectoparasitic copepods such as sea lice of the genus caligus and lepeophtheirus, particularly Caligus elongatus and Lepeophtheirus salmonis, constitute a problem in the fish farming industry and also constitute an animal welfare issue. The salmon lice infest salmonids such as Atlantic salmon (Salmo salar L) and trout (Salmo trutta) in seawater, the salmon lice attach to the fish and lead to skin ulcers which in turn may lead to bacterial infections. The attached fish loose appetite and growth leading to substantial economic loss for the fish farmer. The fish is reduced in size and the quality of the fish is also affected. The abundance of salmon lice in the environment is increasing and leading to infestation in the wild fish population as well.

The economical loss related to sea lice infestation in fish farming in Norway, Canada, Scotland and Chile is substantial and several different approaches have been made to reduce or eliminate the problem.

Chemical treatments with pesticides have been used to kill the sea lice. Examples of such anti-parasitic drugs used to treat sea-lice infested salmon are organophosphates (trichlorvos, dichlorvos and azamethiphos) and permethrins (cypermethrin and deltamethrin). Also, chitin synthesis inhibitors such as diflubenzuron and teflubenzuron have been used.

Chemical treatments used in the fish farming industry are affecting other organisms living in the area near and around the fish farms. Particularly crustaceous animals have been adversely affected by chemicals used against salmon lice. Further, the salmon lice have over time build resistance to the chemicals and the efficacy of the treatment have decreased. This has left such chemotherapeutic treatments less attractive, both with respect to environmental acceptability and from an efficacy point of view.

Biological methods such as use of wrasse that feed on salmon-lice they pick off salmon skin. This method does not have the local side effects as the chemical treatment, it has however the effect of overfish of the wrasse species in their natural habitats and the welfare of the wrasse used in this way have been questioned.

Other methods involving handling of the fish to be treated have been used, but the physical handling of the fish is stressful for the fish and not desirable.

Mechanical barrier solutions preventing the sea lice from contacting the farmed fish have been developed. The principal of these solutions is arrangements enclosing the fish cage with a tarpaulin or fine-meshed fluid-permeable net keeping the sea lice outside the cage. The disadvantages with such solutions are fouling and maintenance with respect to cleaning and mending of damages to the tarpaulin/ finemeshed net.

There is a constant need in the art for new efficient solutions to resolve the problem that salmon lice constitute in the fish farming industry.

Prior art

WO2009136797 (A1) concerns a trawl for harvesting calanus or other organisms in a body of water. The trawl comprises an outer net and an inner net located inside it, where the inner net is divided into a number of sections. Each section has its own attachment point to the outer net, whereby the towing forces are distributed over the different attachment points, with the result that each of the sections absorbs a load. In addition to better distribution of the towing forces, the independence of the different sections will facilitate repairs and/or replacements of the inner net, reduce problems resulting from different lengths between the outer and inner nets during towing of the trawl, simplify inclusion of selection devices and offer better possibilities for use of differentiated aperture, strand thickness and different materials in the inner net.

WO2018062999 (A1) discloses a device for trapping and killing marine organisms such as animal plankton, salmon lice and other parasites, which comprises a body configured for submersion in water. The body comprises at least one light source configured and controlled for attracting said marine organisms, and an internal cavity having an opening for fluid communication with at least a portion of the water. The light sources are arranged inside the cavity and arranged and controlled to emit light waves through said opening and into at least a portion of the water. At least one positive electrode is arranged in the cavity and electrically connected to a low-voltage power source, and at least one negative electrode is arranged in the water and electrically connected to said power source. The device generates, by means of electrolysis with the water, chlorine gas at or in a region near the at least one positive electrode, and the chlorine gas reacts with water inside the cavity to form hypochlorous acid and hydrochloric acid. NO 344590 and NO 20140640 also concerns devices for capture and discharge of parasites like salmon lice using light to lure the parasites into a trap where e.g. a power pulse with a voltage high enough to destroy or weaken the parasites is arranged.

WO2005000017 (A1) concerns an arrangement for a plankton net, for collecting plankton-containing water from arbitrary ocean depths. It has a net compartment , which can be lowered to a desired water depth and which has closing member that is arranged to enclose a collected amount of water. A sieving member is attached to the net compartment for discharge of water. The arrangement includes a member , which is arranged to keep the inlet of the entrance of the net compartment closed until the sampling is to be conducted.

Brief description of the figures

Fig. 1 an illustration of the front view (i.e. towing direction) of a trawl according to the invention.

Fig. 2 shows a trawl frame in a folded position.

Fig. 3 and 4 are illustrative side views of a trawl according to the invention.

Fig. 5 is a sidelong perspective illustration of a trawl.

Fig. 6 is a front view of a trawl frame according to the invention.

Fig. 7 illustrates a trawl frame in a folded position.

Fig. 8 and 9 are side view illustrations of a trawl according to the present invention.

Fig. 10 shows an embodiment of the present invention including a device for towing or pulling a trawl inside a fish farm cage.

Objective of the invention

An object of the present invention is to provide a device and system for collecting salmon lice in a floating fish farming facility, and further to provide a method for use of said device.

The terms salmon lice and sea lice are used interchangeably herein and refers to copepods of the genus caligus and lepeophtheirus, particularly Caligus elongatus and Lepeophtheirus salmonis.

Detailed description of the invention

One aspect of the present invention concerns a trawl device for collecting and destroying marine organisms such as animal plankton, salmon lice and other parasites, particularly salmon lice. The trawl device comprises a trawl frame 1 supporting a fine meshed trawl bag 8 having a mesh width from 100 µm to 1000µm, preferably 300 µm to 500 µm. The trawl bag 1 is evenly tapered in the length direction and is ending in a removable collecting bag 10.

The collecting bag 10 is comprised of a fine meshed fabric similar to or the same as the material of the trawl bag and is connected to the trawl bag 1 through a release mechanism. In an embodiment of the invention the colleting bag is 0.25 meters to 1 meter long, preferably about 0.5 meter having a diameter of 0.1 meters to 0.4 meters, preferably about 0.2 meter.

In one embodiment of the invention, the trawl frame 1 has a pentagonal shape wherein the upper horizontal side of the pentagon is 2-3.5 meters, preferably about 3.5 meters. The sides stretching vertically downwards from the ends of upper side are 1.2-2 meters, preferably about 1.8 meters. These vertical sides continue in an inward angle to meet such that the frame forms a pentagon. From the upper side to the bottom of the trawl frame 1 the depth is 1.0 to 4 meters, preferably about 3 meters.

The trawl frame shape is not limited to the pentagonal shape, and may have a rectangular, square, circular or oval design.

The size of the trawl device and frame is adapted for a fish farming cage having a diameter in the range of 120-160 meters. It is obvious that the size of the trawl device and frame can be adapted to any fish cage size without diverting from the present invention.

The trawl frame 1 is equipped with folding mechanisms 6 enabling the folding of the frame 1 for easier handling and transport and storage.

In one embodiment of the invention a netting 7 is mounted in the outline opening of the trawl frame 1. The netting having a mesh width of 30-100 mm. The mesh with is adapted to the size of the fish in the fish cage i.e. from sea-ready smolt to fish of about 3-6 kg. The netting 7 prevents fish, and foreign objects entering the trawl bag. Further the netting 7 is equipped with ribs 4, where the ribs are mounted in the trawl frame 1 to form a cross with a tension so that the netting 7 is kept in a position forwardly directed away from the trawl bag. The tension keeps the netting 7 in position an facilitate that any foreign objects are pushed away to the sides and away from the trawl bag opening.

In other embodiments the trawl device according to the invention the trawl frame can be equipped with one or more thruster modules 5, one or more camera 5, and/or one or more light source 5. The one or more thruster modules 5, one or more camera 5, and/or one or more light source 5 are mounted on the vertical sides of the trawl frame 1 and should be installed such that the balance of the frame is maintained.

In another embodiment of the invention a control unit 3 comprising a sender/receiver unit for remote control, and one or more power sources 2, preferably battery packages are mounted on the upper horizontal side of the trawl frame 1.

The trawl device according to the invention may be dragged, pulled or towed at the water surface or near the water surface, preferably at a depth of 0-3 meters of the fish farming cage to remove sea lice found in the water volume. A bridle 12 system is mounted at the five corners of the trawl frame 1 and joined together and continued in a tow line 13. The system comprising the bridles and the tow line can be denoted “cock feet”.

In another embodiment of the invention the tow line 13 is connected to a dragging, pulling or towing device 11. The dragging, pulling or towing device 2 can be any suitable device known in the art, preferably a Remotely Operated Vehicle, ROV, 11.

In another aspect of the invention a method for removal of sea lice in a fish cage is provided wherein a trawl device as described above is moved inside said fish cage by use of manual power or a dragging or pulling or towing device, in a pattern that covers the whole surface area of the fish cage.

In a particular embodiment of the invention the dragging, pulling or towing device is a ROV. The dragging, pulling or towing device, e.g. the ROV or winch, is moved at a speed of about 15 to 35 centimeter/second, 15 to 25 centimeter/second.

Reference numbers in the drawings

1. Trawl frame

2. Power source; Battery package

3. Control unit and sender/receiver for remote control, camera system and light 4. Rib to prevent seine from curling into the trawl

5. Thruster modules, camera, light

6. Folding mechanism for trawl frame

7. Netting

8. Trawl bag

9. Release mechanism for collecting bag

10. Collecting bag

11. ROV – Remotely Operated Vehicle

12. Bridle

13. Tow line

12 and 13 taken together are also denoted “Cock foot” or “Crow foot”.

Claims

1. Trawl device for collecting sea lice characterised in that the device comprises a trawl frame (1) supporting a fine mashed trawl bag (8) having a mesh width from 100µm to 1000µm, wherein said trawl bag is evenly tapered ending in a removable collecting bag (10).

2. Trawl device according to claim 1 wherein the trawl frame (1) is foldable through folding mechanisms (6).

3. Trawl device according to claims 1 to 2, wherein a netting (7) is mounted in the outline opening of the trawl frame (1) and wherein the mesh width of the net is 30-100 mm.

4. Trawl device according to any one of the preceding claims wherein the netting (7) is equipped with ribs (4).

5. Trawl device according to any one of the preceding claims wherein the trawl frame is equipped with one or more thruster modules (5), one or more camera (5), and/or one or more light source (5).

6. Trawl device according to any one of the preceding claims wherein the trawl frame is equipped with a control unit (3) comprising a sender/receiver unit for remote control, and one or more power sources (2), preferably battery packages.

7. Trawl device according to any one of the preceding claims wherein a bridle (12) system is mounted at the corners of the trawl frame (1) and joined and continued in a tow line (13).

8. Trawl device according to any one of the preceding claims wherein the tow line (13) is connected to a dragging or pulling device (2), preferably a Remotely Operated Vehicle (11) or winch.

9. Method for removal of sea lice in a fish cage wherein a device according to any of the claims 1-8 is moved inside said fish cage by use of a dragging or pulling device, in a pattern that covers the whole surface area of the cage.

10. Method according to claim 9 wherein the dragging or pulling device is a Remotely Operated Vehicle or a winch.