CA2711191A1 - Treatment system for fish - Google Patents

Abstract

The present invention provides a system for bath treatment of fish afflicted by exterior infections wherein said system includes at least one first cage for raising fish, the said cage being adapted to retain fish in a body of water. The improvement of the present invention wherein said system comprises at least one non-porous treatment bath cage for placement in an aqueous medium adapted to receive infected fish from said at least one first cage for treatment of said infected fish contained within said at least one said first cage, the said at least one treatment bath cage having a closed loop water recirculating and filtration system adapted to maintain water quality and remove solids during treatment of said fish.

Description

TREATMENT SYSTEM FOR FISH

This invention relates to a method and system for the treatment of fish parasites.
Background Parasites such as sea lice (predominantly Lepeophtheirus sahnonis) are large ectoparasitic copepods having a pan-global distribution and are found on salmonid fishes (e.g. Atlantic salmon) in marine waters. These host-specific parasites are extremely pathogenic to salmonid species, especially populations retained in cage culture where the stocking density is unnaturally high. Large numbers of sea lice can quickly cause severe skin and tissue damage resulting in significant fish stress and mortality. The global economic impact associated with loss of stock, product downgrades at harvest, and the cost involved in monitoring and managing sea lice infection is estimated to exceed US$ 100M annually (see Johnson et al.
Zoological Studies 43:229-243). Other fish species in culture and/or ectoparasites/gill infections can be equally costly to the global finfish aquaculture industry (e.g., Atlantic salmon in Tasmania are exposed to Amoebic Gill Disease requiring constant bathing in freshwater; amberjack species contend with external parasites that plague aquaculture operations etc.).

By way of example only, Atlantic salmon aquaculture represents an important employment factor in Canadian Provinces such as British Columbia, New Brunswick, Nova Scotia and Newfoundland & Labrador. Sea lice infections occur annually in all of these areas, resulting in direct losses of fish and frequent need for repeated treatment to reduce infection levels. An early strategy in the art to attempt to control sea lice infection in some areas involved bath treatments in full tarps with hydrogen peroxide.
This strategy allowed bathing with an environmentally benign compound;
however, inconsistent water volumes with hydrogen peroxide did not provide the efficacy required to adequately treat sea lice infection (i.e., successful removal of 60-80% of mobile sea lice compared with the chemical pesticide Deltamethrin which kills 90-95% of all mobile pre-adult and adult sea lice).

Also, in general, applying bath treatments to cultured fish held in sea cages can be a low-tech proposition. At minimum the treated cage net is shallowed to reduce the rearing volume and increase fish density during treatment and surrounded by a non-porous skirt at which time the prescribed pesticide is added. The treatment lasts for the required dose duration and then the skirt is removed from the treated cage and the net lowered to its original depth. This method has obvious limitations associated with escapement of the prescribed pesticide through the bottom open net. A complete non-porous tarp might be deployed after the net is shallowed to ensure none of the pesticide escapes through the open skirt bottom. However, this operation is much more time consuming and labour intensive typically requiring disconnection of the bottom weight ring before completely enclosing the treatment cage. This method is also limited to areas having low energy and current speed, by unknown total water volumes and numbers of fish to be treated, and less effective in treating large circumference (diameter) grow-out cages that the industry has tended to evolve towards over time.
Even while using complete non-porous tarps to complete the bath treatment, the pesticide is released to the environment after the treatment period is ended thereby providing environmental concerns. Deploying either a skirt or tarp is greatly affected by the site current speed in the tidal cycle and a good crew can only expect to treat up to two cages per day in ideal weather/tidal conditions.

In addition to the above methods, another method that has been used in the industry involves moving fish from grow-out cages to treatment vessels to grow-out cages. In certain locations, such as Norway, well boats have been used to apply pesticides to treat sea lice infections. However, the capital costs involved with this approach are very high if not prohibitive and there is no environmental gain from using this method as the treatment pesticide is still discharged to the environment following treatment.

Not only is the treatment pesticide water in all three of the above treatment methods released to the environment so too are sea lice or other ectoparasites that are removed from the treated fish but not killed during the treatment process and therefore can quickly re-infect the treated fish stock. A further complication exists with these three methods in that the local grow-out water might be heavily laden with natural organic

2 particles that readily bind with some treatment pesticide compounds. This in effect ensures that the dose concentration can never be reached in the absence of filtering the treatment water to remove these natural organic particulates prior to adding the treatment pesticide.

Effective treatments available globally that actually kill and remove an acceptable number of sea lice are all chemical and frequently pesticide-based. Until very recently Ivermectin (a large-animal anti-tick medication used through off-label veterinary control) and Ememectin benzoate (trade name "Slice") were the only pesticides used extensively in some areas and administered through in-food treatments. In-food treatment requires that each infected fish consume the medicated feed in sufficient quantity to treat the contained fish population or risk sea lice resistance to the drug over time. As early as 2004, Westcott et al. (see Burka, 2004. Aquaculture Research 35:784-792) indicated a concern that reduced sensitivity in the fish will develop to "Slice" due to the widespread use of the chemotherapeutant in the industry.

Widespread resistance to "Slice" in certain areas finally occurred in 2009, and a sea lice epidemic ensued. Addressing sea lice resistance to in-feed treatments requires the industry to change its focus to include bath treatment options, such as Deltamethrin (trade name, AlphaMa) ). Hydrogen peroxide and all chemical treatments require bathing the infected fish in treated water for a required dose time to remove and kill sea lice. Environmental concerns are present when bathing occurs (using techniques such as either by skirting/tarping infected cages or "well" boats) as the treatment bath water is released into the environment along with removed sea lice that may or may not be dead and the treatment pesticide. Skirting/tarping infected cages is very difficult and can only be accomplished in a water area during periods of slower current when carried out in a tidal cycle, and requires addition of the entire dose concentration to each individual cage as treatments occur, which can be impacted by natural organic particulates binding with active pesticide compounds. Further, sea lice that are not killed during the removal treatment process can quickly re-infect the treated fish stock thereby rendering the treatment ineffective.

3 The salmon aquaculture industry recognizes the immediate need to develop an integrated pest management plan that includes a system of multiple treatment solutions to reduce the likelihood for sea lice resistance to develop for any single treatment option. Such a system should include access to in-food treatments (using e.g., "Ivermectin", "Slice", "Teflubenzuron", etc.) and bath treatments (e.g., hydrogen peroxide, AlphaMax and other pesticides such as Cypermethrin (trade name, "Excis"), and Azamethiphos (trade name, "Salmosan") or the like). However, industry and government representatives also recognize that application of these chemical pesticides to treat sea lice must be performed in an eco-friendly, safe and cost-effective manner, with minimum environmental concerns from the treatment protocols and reduction in the likelihood for easy re-infection of treated fish stocks.

Given the above, it would be desirable to provide innovative technology and management solutions that will administer sea lice pesticide bath treatment in an eco-friendly, safe and cost-effective manner. Desirably, any new technique will provide a low-cost yet effective eco-friendly solution to sea lice infection which will permit the development of an integrated pest management plan with a range of treatments which will most desirably reduce or eliminate discharge to the environment of any pesticide approved for use in such treatments and collect sea lice that have simply been removed from the fish to prevent quick re-infection.

In the patent art, in addition to the above common or known practices, reference can be made to the following US patents dealing with the general issue of treatment of parasites in fish.

United States Patent 3,116,712, Ogden et al., January 7, 1964 discloses a closed cycle fish rearing system to remove or destroy organisms in a fish holding tank for the purpose of reducing or preventing water-borne infections and diseases of fish in the tank. United States Patent 7,052,601, Arve Gravdal, May 30, 2006 discloses a bath system for the treatment/cleaning of water in a main tank for marine organisms. The water for the main tank is recirculated and the system includes a filter unit, a disinfection chamber and an aeration chamber. United States Patent 7,631,615, Dennis L.
Mast,

4 December 15, 2009 discloses a recirculating aquaculture system comprising a tank or pond, a filter, an oxygenator, a main mixer and a recyle pump. Biological contaminants are removed by the filter, and oxygen is provided to the tank or pond by the oxygenator.
Summary of Invention With this present invention, applicant has developed an improved method and system which overcomes the problems associated with prior art techniques.

More particularly, applicant has developed an improved system for the treatment of infected fish which includes at least one first cage for raising fish, which cage is adapted to retain fish in a body of water; the system comprises at least one non-porous treatment bath cage for placement in an aqueous medium adapted to receive infected fish from at least one first cage for treatment of infected fish contained within the at least one first cage, and wherein at least one treatment bath cage includes a closed loop water recirculating and filtration system which is adapted to maintain water quality and remove solids including ecto-parasites that are removed from treated fish but still living during treatment of infected fish.

In another embodiment of the present invention, the system includes means for returning treated fish to at least one first cage following treatment.

In a further embodiment of the invention, the system includes means for returning treated fish to a second cage other than the at least one first cage.

In another preferred embodiment of the present invention, there is provided at least two separate treatment bath cages each adapted to receive fish in alternating fashion to increase the speed of treatment while ensuring the required therapeutant bath soak time for treatment from at least one treatment bath cage.

In another preferred embodiment of the present invention, water that is pumped with the infected fish during the transfer process from the initial raising cage is removed by dewatering to the exterior of the bath cage while pesticide water in the bath cage that is pumped with the treated fish during the transfer process from the bath cage is removed

5 by dewatering and returned to the bath cage water for further treatment. A
screen can be added below the incoming dewatering system to collect parasites that are removed during the transfer process.

In another preferred embodiment of the present invention, a fish counter and/or size estimator is included in the transfer process either from the initial raising cage to the bath cage or during transfer following treatment to allow estimation of treatment fish number and therefore biomass estimate being treated.

In another preferred embodiment of the present invention, a platform or barge having sufficient deck space is positioned to carry all peripheral equipment to operate the bath system including pumps, dewatering, and recirculating and filtration components.

In yet a further preferred embodiment of the present invention, at least one treatment bath cage includes means for providing a controlled atmosphere system associated with the at least one treatment bath cage.

In another preferred embodiment of the present invention, the at least one treatment bath cage includes means for filtering the aqueous medium within the treatment bath cage for removal of solids therefrom including ecto-parasites that might be removed but remain alive following treatment.

A preferred embodiment of the present invention provides means for introducing a treatment chemical that is dosed in the required concentration within the bath cage water that might include a pre-mixing tank and mixed in a thorough and widespread manner within the at least one treatment bath cage. Further, there is provided means for removing the treatment chemical after fish have been treated in the bath treatment cage.

A preferred embodiment of the present invention includes a means for automatic treatment chemical measurement and reporting from one to numerous locations within each bath cage (e.g., peroxide autotitration system).

6 In yet another preferred embodiment of the present invention, the at least one treatment bath cage includes means for providing an oxygen source for introduction to the at least one treatment bath cage. The means for providing an oxygen source comprises means for infusing oxygen into an aqueous medium within the at least one treatment bath cage.

In another preferred embodiment of the invention, there is provided means for removing nitrogen from the aqueous medium in the at least one treatment bath cage.

In another preferred embodiment of the invention, fish that have been treated in a bath cage are initially transferred to a fish grading table so that efficient separation of large and small fish into separate grow-out cages can be achieved. Alternatively, fish removed for treatment from the at least one first cage can be initially graded and transferred to either bath cages based on size to complete size grading prior to treatment.

In greater detail of the above, and according to preferred embodiments, the method and system of the present invention in one form will include the use of two fish cages, one cage being for initially retaining fish to be treated (such as a stocked cage); together with one empty cage adapted to receive treated fish from at least one, desirably two, treatment bath systems. Such a method and system will also include a closed loop recirculation and filtration system.

The above-described system, which desirably includes two modified fish containment systems will ensure a constant bath volume; desirably, the system will utilize internal smolt nets, non-porous tarps and external smolt skirts as required in order to decrease external current effects. In practising the invention, fish will be seined and pumped into bath units until the initial cage containing the fish to be treated is emptied while dewatering occurs exterior to the bath units during the fish transfer process.
Counting/sizing/grading of fish to be treated can be performed during the transfer process from the initial cage to each bath cage. Treatment chemicals are dosed in the required concentration within the bath cage water or initially in a pre-mixing tank, mixed in a thorough and widespread manner within the treatment bath cages when treatment

7 fish are present and possibly automatically measured and reported during the treatment process. Operating in conjunction with the bath units is a closed loop recirculation and filtration system (such as a bead filter or drum filter) utilized to maintain water quality and remove solids during treatment including any ecto-parasites that might be removed but not killed during treatment. After the required treatment period, treated fish will be seined and pumped into the same initial cage or another cage until the bath units are emptied while dewatering occurs interior of the bath units during the transfer process.
The final transfer action might involve fish size grading such that large and small fish are separated into either the initial cage or another cage to continue further grow-out.
Chemical pesticides may be removed from the bath cage after the treatment period is completed through binding the chemicals with suitable organic compounds.

Removal of solids from the treatment system is highly desirable since pesticides such as "Deltamethrin" have been found to bind with natural organic material in the cages in order to render the pesticides inactive. Removal of ecto-parasites that remain alive following removal from the fish is highly desirable as they can otherwise quickly re-infect treated fish. Removal of the solids including living ecto-parasites and any bound pesticides will then permit their safe disposal in a land-fill.

The above-described system also can incorporate controlled atmosphere technology to ensure that oxygen is not limited while the fish are contained within the treatment cages.
Such technology may include suitable methods to infuse gas into liquids to produce high levels of oxygen and at the same time remove nitrogen. Such technology will be incorporated into the method and system of the present invention in a manner such that it is effective for the purposes desired and to this end, direct infusion of oxygen into the treatment water is preferred, desirably after solids have been removed from the treatment water. By utilizing such a system, fish stress will be lowered since the fish density in the treatment cage will be quite dense.

Desirably, the method and system of the present invention can be coupled with known and future effective pesticides to remove sea lice during treatment. Typical pesticides known for use in bath treatments include hydrogen peroxide, Deltamethrin (trade name,

8 AlphaMax ), Cypermethrin (trade name, "Excis"), and Azamethiphos (trade name, "Salmosan") or the like. Total pesticide use will be greatly reduced in treating sea lice on infected fish when used in the described system. Some applications might suitably use water of varying degrees of salinity to remove ecto-parasites (e.g., bathing salmon in freshwater to remove sea lice).

The present invention has many advantages over the technology described above in the prior art; in particular, applicant's method and system can reduce fish stress and mortality of fish being treated; the present invention also provides an effective means to remove sea lice from infected fish at a cost-effective level and remove living sea lice following treatment to prevent quick re-infection of the fish stock. Reduction in the total amount of pesticides required to treat fish can be obtained and safe and effective disposal of spent pesticides can be achieved to lower total treatment costs and environmental impacts of treatment. Further, desirable farming practices can be achieved during the treatment process while using advanced embodiments of the system including fish sizing/counting to acquire a more accurate biomass estimate and grading of fish sizes to more effectively continue grow-out following treatment.
Applicant's invention utilizing the system described herein fully contains the treatment bath water and as well, contains removed sea lice (dead and living) and bound pesticides after fish treatment, for safe disposal.

Having thus generally described the invention, reference will now be made to the accompanying drawings illustrating preferred embodiments, and in which:

Figure 1 is a schematic plan view of one embodiment of the present invention;
and Figure 2 is a schematic plan view of another embodiment of the present invention.
Referring initially to Figure 1 there is illustrated a bath treatment cage system utilized in conjunction with a fish cage which normally retains fish being raised. The volume of fish cage indicated by reference numeral 10 is reduced and fish are seined towards the fish pump and outlet 12 which passes from the interior to the exterior of the cage;
as well, the cage 10 includes a clean fish return inlet 14.

9 In accordance with the present invention, there is provided a bath treatment cage 16 operating in conjunction with (in this embodiment) a treatment barge 50. The barge, as well as the fish cage 10, are conventional systems known to those skilled in the art.

The present invention, with respect to the bath treatment cage 16, includes a recirculating system 18 which includes a water filtering system inlet 18a located in the middle of the bottom of the bath cage 16 (in this embodiment) operatively associated via a connecting conduit 20 to a water filter pump 22 which includes a further water filter 24.
The system of the present invention also includes an oxygen injection device operatively associated with the bath treatment cage 16.

Referring to the filtering system, a return line 28 returns filtered water to the bath treatment cage.

Following treatment of the fish in the bath treatment cage 16, fish are returned to the fish cage 10 via a return inlet 30. The clean fish return inlet also includes a dewatering system 32 operatively associated with the clean fish return line which also includes a bath water return line 44.

The fish to be treated, once in the inlet 12, are placed in the bath treatment cage 16 using a conduit system terminating in an outlet 34 which may also include a dewatering system 36 and a fish pump 42.

Referring to Figure 2, similar components shown in Figure 1 bear the same reference numerals as in Figure 1.

In Figure 2, the system utilizes two treatment cages 16 and 16' in order to increase efficiency.

As shown in Figure 2, the clean fish return outlet can supply either one or both of the bath treatment cages 16 and 16'. In addition, as shown in dotted lines in Figure 2, this option can be utilized for faster removal of the fish from the treatment cages. Likewise, the oxygen injection system 26 can be used to feed oxygen to either one or both of the treatment cages as desired or required.

In the drawings, the cages 10 can be of any conventional structure and typically hold several hundred to thousands of fish.

Treatment baths 16 is provided with non-porous full tarps applied to the interior or exterior of the treatment bath containers in order to prevent the escape of pesticides and waste solids. Their structure also includes the use of internal smolt nets to ease removal of fish following treatment and external skirts as necessary to reduce the effects of strong external currents.

In operation, the infected fish are seined from the initial cage to the bath cage to ease transfer to the bath cage preferably by pumping. As is seen from the drawings, water that is pumped with the infected fish during the transfer process from the initial raising cage is removed by dewatering to the exterior of the bath cage. Sea lice that are removed during the pumping transfer process can be collected under the dewatering system by means of screen filtration.

In the preferred embodiments shown, the bath treatment cages 16 are shown as being operatively associated with a closed loop recirculation filter system which may be any suitable filter such as a bead filter or drum filter, for removing solids during treatment including removed sea lice that remain alive following treatment. The treatment cages 16 are also associated with an oxygen infusing system for adding oxygen into the treatment water preferably after solids have been removed from the treatment water.
Introduction of a suitable amount of pesticide into the treatment baths may be carried out by any suitable pesticide dosing and dispensing system and may involve use of a pre-mixing tank as necessary.

Following treatment in the treatment cage 16, the treated fish are then removed and returned to the fish cage 10. Preferably, the treated fish are returned to cage 10 preferably by seining and pumping while pesticide water in the treatment cages 16 is removed by dewatering and returned to the bath cage water to treat additional infected fish. Cage 10 can remain in its present location or be then moved to a suitable location to permit the fish to continue growing.

Claims (21)

WHAT IS CLAIMED IS:

1. In a system for treatment of infected fish wherein said system includes:

at least one first cage for raising fish, said cage being adapted to retain fish in a body of water;

the improvement wherein said system comprises at least one non-porous treatment bath cage for placement in an aqueous medium adapted to receive infected fish from said at least one first cage for treatment of said infected fish contained within said at least one said first cage, said at least one treatment bath cage having a closed loop water recirculating and filtration system adapted to maintain water quality and remove solids during treatment of said fish.

2. The system of claim 1, wherein there are included means for returning treated fish to said at least one said first cage following treatment.

3. The system of claim 1, wherein there are included means for returning treated fish to a second cage other than said at least one said first cage.

4. The system of claim 1, wherein at least two separate treatment bath cages are provided each adapted to receive fish for treatment from said at least one treatment bath cage.

5. The system of claim 1 or 2, wherein said at least one treatment bath cage includes means for providing a controlled atmosphere system associated with said at least one treatment bath cage.

6. The system of claim 1, 2 or 3, wherein infected fish are seined in the first cage to ease transfer to the bath cage.

7. The system of claim 1, 2 or 3, wherein said at least one treatment bath cage includes means for filtering the aqueous medium within said treatment bath cage for removal of solids therefrom.

8. The system of claim 1, 2 or 3, wherein there is included means for introducing a treatment chemical at the required dose concentration and rate with proper mixing throughout the at least one treatment bath cage.

9. The system of claim 7, wherein there is included means for removing said treatment chemical after fish have been treated in said bath treatment cage.

10. The system of claim 1, 2 or 3, wherein said at least one treatment bath cage includes means for providing an oxygen source for introduction to said at least one treatment bath cage.

11. The system of claim 10, wherein said means for providing an oxygen source comprises means for infusing oxygen into an aqueous medium within said at least one treatment bath cage.

12. The system of claim 1, 2 or 3, including means for removing nitrogen from the aqueous medium in said at least one treatment bath cage.

13. The system of any of claims 1 to 12, wherein water and infected fish are pumped from said first cage to said at least one treatment bath cage, and water from said first cage when placed in the said at least one treatment bath cage is removed by dewatering to the exterior of said treatment bath cage.

14. The system of claim 13, wherein fish, after treatment in said treatment bath cage, are removed from treatment bath cage by seining and removal preferably by pumping.

15. The system of claim 13 or 14, wherein water containing pesticide in said treatment bath cage is removed by dewatering and returned to the treatment bath cage to treat additional infected fish or for proper disposal following all treatments.

16. The system of any one of claims 1 to 12, wherein the system includes dewatering means having a source of incoming water adapted to collect parasites removed from the treatment of fish.

17. The system of any one of claims 1 to 16, wherein said system is mounted or associated with a mobile platform or barge.

18. The system of any one of claims 1 to 17, wherein there is included at least one of fish counting means and fish size-estimator means in or associated with said first cage.

19. The system of any one of claims 1 to 18, wherein the system includes fish grading means operatively associated with said system for sorting fish into large and small fish sizes.

20. The system of claim 8, wherein the proper treatment chemical is initially dosed into a pre-mixing tank prior to introduction to the treatment bath cage.

21. The system of any one of claims 1 to 20, wherein said system includes means for automatic treatment chemical measurement and reporting, from at least one location in a treatment bath cage.