APPARATUS AND METHOD FOR COLLECTING LOOSENED FISH PARASITES IN A FISH PEN

Abstract

A sweep net is for crowding fish in a fish-farming pen. The sweep net has a fine-mesh net. A collecting device is for free fish parasites in a fish pen, a system is for collecting free fish parasites in a fish pen, and a method is for calculating the effect of a treatment against an external fish parasite in which the fish is treated outside a fish pen.

Claims

1.-13. (canceled)

14. A sweep net for crowding fish in a fish pen, wherein the sweep net comprises a fine-mesh net having a mesh size between 1.1 mm and 10 mm.

15. The sweep net according to claim 14, wherein the sweep net comprises a soft material.

16. The sweep net according to claim 14, wherein the mesh size is more particularly between 1.1 mm and 5 mm.

17. A collecting device for free fish parasites in a mass of water in a fish pen, the collecting device comprising a sweep net, and the sweep net comprising a fine-mesh net having a mesh size between 1.1 mm and 10 mm.

18. A system for collecting free fish parasites in a mass of water, wherein the system comprises a sweep net for crowding fish in a fish pen, the sweep net comprising a fine-mesh net having a mesh size of between 1.1 mm and 10 mm, wherein the sweep net forms an outer side and an opposite crowding side, and wherein the system further comprises a collecting apparatus for an external fish parasite.

19. The system according to claim 18, wherein the collecting apparatus comprises a collecting device for an external fish parasite positioned on the crowding side of the sweep net.

20. The system according to claim 19, wherein the collecting device comprises a perforated pipe.

21. The system according to claim 20, wherein the perforated pipe is in fluid communication with a suction side of a pump.

22. The system according to claim 20, wherein the system comprises a handling unit for a crustacean parasite, the handling unit being in fluid communication with a pump on the pressure side of the pump.

23. The system according to claim 18, further comprising: a fish pump arranged to carry fish, water and free fish parasites in the water from the sweep net; a treatment unit for fish infected with a fish parasite; and a collecting unit arranged to retain the free fish parasites in the water and fish parasites that have loosened from the fish in the treatment unit.

24. A method for calculating an effect of a treatment against an external fish parasite in which the fish is treated outside a fish pen, the method comprising the steps of: a) catching a representative number of fish from the fish pen; b) counting the number of external fish parasites and calculating an average number of fish parasites per fish; repeatedly: c) crowding the fish together in the fish pen with a sweep net; d) guiding the crowded fish through a suitable treatment unit; e) guiding the treated fish into a suitable receiving tank; and f) picking a representative number of fish after the treatment unit, counting the number of remaining external fish parasites and calculating an average number of remaining fish parasites per fish, wherein in step c, the method comprises using a sweep net comprising a fine-mesh net.

25. The method according to claim 24, wherein the sweep net comprises a soft material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In what follows, an example of a preferred embodiment is described, which is visualized in the accompanying drawings, in which:

[0030] FIGS. 1A-B show schematically a sweep net in two prior-art embodiments; and

[0031] FIG. 2 shows schematically a system for collecting a fish parasite in accordance with the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0032] In the figures, the reference numeral 100 indicates a prior-art sweep net. The sweep net 100 comprises a net 110. At an edge, the sweep net 100 comprises a top line 120 which is provided with a plurality of buoyant bodies 122. On the opposite side from that of the top line 120, the sweep net 100 comprises a bottom line 130. The bottom line 130 may be provided with weights (not shown), or the bottom line 130 may comprise a lead line (not shown). The sweep net 100 is provided with a lifting lug 140 at each corner. Traces (not shown) are attached to the lifting lugs 140.

[0033] The sweep net 100 may be of a rectangular shape, as shown in FIG. 1A. The sweep net 100 may be formed with truncated corners, as shown in FIG. 1B.

[0034] According to the invention, the sweep net 1 is formed in the same way as known sweep nets 100, the difference being that the net 110 is replaced with a fine-mesh net 10. The mesh size of the fine-mesh net 10 is chosen to be such that external fish parasites, such as pre-adult and adult crustacean parasites (not shown), cannot move through the fine-mesh net 10. The crustacean parasite may be a salmon louse (L. salmonis). The mesh size may be smaller than 10 mm, such as smaller than 7.5 mm, such as smaller than 5 mm, such as smaller than 4 mm, such as smaller than 3 mm. The mesh size may be larger than 1.1 mm, such as larger than 1.5 mm, such as larger than 2 mm.

[0035] The sweep net 1 comprises the net 10. At an edge, the sweep net 1 comprises a top line 12 which is provided with a plurality of buoyant bodies (not shown in FIG. 2). On the opposite side from that of the top line 12, the sweep net 1 comprises a bottom line 13. The bottom line 13 may be provided with weights (not shown), or the bottom line 13 may comprise a lead line (not shown). The sweep net 1 is provided with a lifting lug 14 at each corner. Traces (not shown) are attached to the lifting lugs 14. The net 10 forms an outer side 11 and a crowding side 19. The crowding side 19 faces the fish during crowding. The outer side 11 is the opposite side of the net 10 relative to the crowding side 19.

[0036] The invention also relates to a system 2. The system 2 comprises the sweep net 1 and a collecting apparatus 3 for collecting fish parasites which have fallen off fish (not shown) during crowding in a fish-farming pen (not shown).

[0037] The collecting apparatus 3 comprises a collecting device 4 which is positioned on the crowding side 19 of the sweep net 1. In one embodiment, the collecting device 4 is formed of a perforated pipe 42. The perforated pipe 42 may be closed in a free end portion 40. At an opposite end portion 49, the perforated pipe 42 may be connected to a hose 44. The system 2 comprises a pump 5 in fluid communication with the hose 44 on the suction side of the pump 5.

[0038] The system 2 comprises a handling unit 6 for fish parasites. The handling unit 6 is in fluid communication with the pump 5 on the pressure side of the pump 5. A channel 64 carries water containing fish parasites from the pump to the handling unit 6. In one embodiment, the handling unit 6 may comprise a filter unit 62. The fish parasites are retained by the filter unit 62 while water passes through the filter unit 62. In another embodiment, the handling unit 62 comprises a chamber 66 provided with electrodes (not shown). The electrodes are supplied with electrical energy from a source (not shown). An electric field is formed between the electrodes inside the chamber 66. Fish parasites flowing through the chamber 66 are subjected to the electric field. The electric field has a strength and a character that at least inflict lasting damage on the fish parasites so that they are no longer infectious. The electric field may be lethal to the fish parasites. The water that flows through the chamber 66 then flows to a drain 7.

[0039] The handling unit 6 may comprise the water flowing first through the filter unit 62 and then through the chamber 64 before the water flows to the drain 7. The handling unit 6 may comprise the water flowing first through the chamber 64 and then through the filter unit 62 before the water flows to the drain 7.

[0040] The pump 5 and the handling unit 6 may be positioned on a vessel (not shown).

[0041] In an alternative embodiment (not shown), the pump 5 may be submerged and positioned between the collecting device 4 and the handling unit 6. In another embodiment (not shown), the pump 5 may be submerged and positioned at the free end portion 40 of the collecting device 4. In this embodiment, the collecting device 4 will be positioned on the pressure side of the pump 5.

[0042] In an alternative embodiment (not shown), loosened fish parasites may be sucked up in the water together with the fish that are crowded together in the sweep net 1. Water, fish and fish parasites are carried through a fish pump (not shown) into a suitable treatment unit (not shown) for fish with external fish parasites such as crustacean parasites to be treated. Free fish parasites will be separated from the sucked-up water together with fish parasites that are separated from the fish inside the treatment unit and be collected in a suitable collecting unit, such as a filter (not shown).

[0043] A fish pump like that creates such a strong current through the fine-mesh sweep net that free fish parasites will not manage to swim against the current, and the fish parasites will be carried into the fish pump and then into the treatment unit. Since the sweep net 1 is puckered up as it is being emptied of fish, most of the loosened parasites will be sucked up. The sweep net according to the invention is therefore also a collecting device for free fish parasites, such as pre-adult and adult crustacean parasites, in a mass of water.

[0044] The sweep net 1 is used for crowding fish in a fish-farming pen in a known manner. After each crowding or after the fish pen has been emptied of all the fish, the sweep net 1 may be hoisted and immersed in a vessel (not shown) containing a solution which is lastingly harmful to fish parasites. The solution may be lethal to fish parasites.

[0045] It should be noted that all the above-mentioned embodiments illustrate the invention, but do not limit it, and persons skilled in the art may construct many alternative embodiments without departing from the scope of the attached claims. In the claims, reference numbers in brackets are not to be regarded as restrictive.

[0046] The use of the verb “to comprise” and its different forms does not exclude the presence of elements or steps that are not mentioned in the claims. The indefinite article “a” or “an” before an element does not exclude the presence of several such elements.

[0047] The fact that some features are indicated in mutually different dependent claims does not indicate that a combination of these features cannot be used with advantage.