WO2011019288A2

WO2011019288A2 - Device for aquaculture

Info

Publication number: WO2011019288A2
Application number: PCT/NO2010/000304
Authority: WO
Inventors: Kjell L. Risnes
Original assignee: Vevos As
Priority date: 2009-08-12
Filing date: 2010-08-12
Publication date: 2011-02-17
Also published as: NO20092824A1; CL2012000360A1; WO2011019288A3; NO335067B1

Abstract

A float (10) is described which comprises a number of light sources (12) for lighting control of aquatic organisms in a farming net cage wherein the float is arranged to float on, or adjoining to, the surface of the water in the net cage. The underside of the float is equipped with a number of downwardly directed and/or tilted downwardly directed light sources arranged to throw light in defined directions from an area at the surface and down into the net cage for control of the lighting of the aquatic organisms lying below. An application of the device is also described.

Description

Device for aquaculture

The present invention relates to a float comprising a number of light sources for lighting control of aquatic organisms in a farming net cage wherein the float is arranged to float on, or adjoining to, the surface of the water in the net cage. The present invention also relates to a use of a float.

It is known that the natural changes during the daylight period (the length of the day) control different

physiological processes in fish. One of these processes is sexual maturation. In fish farming sexual maturation happening too early is one of the biggest challenges for cod, among others, but the problem is also well known for other farmed species such as, for example, salmon.

A fish that is sexually matured before it reaches its slaughter weight is difficult to sell to the consumers and thereby represents an economic loss. It has been shown that sexual maturation at an early age can be

prevented/delayed by controlling the light in the farming cages. The idea all light control is based on in this context is that by exposing the fish to a constant light condition, the changes in natural daylight are not noted and the sexual maturation process is thereby not

initiated. Different day lengths can also be simulated to counteract sexual maturation.

Today' s solutions that are applied in connection with control of lighting in fish farm net cages comprise different types of light sources and devices. However, these have not been found to be optimal with respect to light distribution, biological effects on the fish, particularly early sexual maturation and ease of use.

Available products are in general submergible underwater light systems, where the light source or light sources are placed down in the water column of the sea cage. The light is spread in all directions in order to achieve a

physiologically effective high light input on the fish (e.g. Nytt fra Havbruk, Nr. 2/2007, p.1-4).

Light regulation in connection with cod farming is not a new idea. However, present knowledge regarding optimal solutions in terms of placement of light sources, light intensities and the most effective light spectra is still very limited and insufficient (e.g. Nytt fra Havbruk, Nr. 2/2007, p.4, 2nd column). There are several companies in the market that supply products within this field. Common for all these is that their products are, in the main, developed with salmon farming in mind. The results that have been achieved indicate clearly that light regulation has a positive effect on the delaying of sexual maturity for cod as well. At the same time one sees that cod behave in many contexts very differently from other farmed species such as salmon. Salmon is a fish which normally swims near the surface and which seeks light. Cod spend much of their lives down at the sea bed. It basically seeks to be away from light sources and is much more sensitive to light than salmon. Under completely controlled light conditions, as can be achieved in land-based farming systems, it is possible to get a delay of the sexual maturity with a success rate of close up to 100% for cod too. In addition, in these tests a growth increase of 60% compared to the control group experiencing natural light was achieved.

The growth increase of the cod is assumed to be a result of the delayed sexual maturity. It is not clear if there were other physiological factors that were affected by the ^•light control for the cod that can have a more direct effect on the weight increase.

The use of additional light in the farming of salmon in net cages resulted in increased growth for the fish compared to fish that was exposed to natural light only in certain periods (see for example Endal et . al. 2000.

Effect of continuous additional light on growth and sexual maturity in Atlantic salmon, Salmo salar, reared in sea cages, Aquaculture, 191, 337-349) . However, it seems that the light control can also have a more direct effect on the weight increase of salmon than it being a result of delayed sexual maturity only.

Species such as salmon and cod are farmed from a certain size/life state, in the main, in sea-based farming cages. In contrast to land-based installations, with today's lighting technology for sea-based net cages one never achieves full control of the lightning conditions. The ideal situation is today that even with extensive use of light, the desired control of the sexual maturation process is normally not achieved because of the

"competition" with the sunlight.

With light regulation related to salmon many lighting points that are hung into the net cage are normally used. The fish swim both over, under and around the light sources. For salmon, which is a surface fish, it does not seem that this leads to so pronounced challenges as it does for cod.

However, it seems that multi-point lighting creates unwanted effects for cod. That the fish gets the light from several different angles and from several light sources seems to disturb the fish. In a number of cases changes in the behaviour pattern can be documented, among other things, in that the cod forms circles around each individual light source. Scientists have suggested that the cod can come to regard the light sources as several different suns.

The lights that are used in connection with both salmon and cod today are either built around the principle with lamps that hang down into the water in the net cage or based on surface lights that are fastened to the edge of the net cage.

Reflectors are, by and large, not used in underwater lights, the bulb shines directly out into the net cage in all directions, including upwards. This is effective when it comes to creating a light field in all directions around the lamp. In salmon farming this principle has been found to function relatively well. However, for cod, one of the problems is that to achieve a desired light intensity a number of lamps must be lowered deeper down in the net cage. This results in that the light also shines on the cod from below. It has been registered that this is experienced as stressing for the cod. A challenge is also when the cod pulls away from these light sources, the result is poor utilisation of the light and an unwanted behaviour pattern. In addition, blindness has been observed in cod as a result of the light intensity being too great.

The placing of light above the surface of the water that shines down into the net cage was used by many fish farms for a while and is still used by some. However, this is associated with two large challenges:

• The ocean surface reflects 70 - 80% of the light so that one achieves very poor utilisation of the supplied energy. In addition, the frequency spectra are affected so that the light that reaches through is not optimal for the purpose.

• The lights appear disturbing to the sea traffic and have gradually been banned.

Research data in connection with control of the lighting of cod also suggest that natural daylight can have a negative effect if one wishes to have a controlled light regime. An unwanted effect of daylight is that it induces sexual maturation. Attempts to remedy this have been made by placing an opaque tarpaulin on the surface of the water or a shade net over the edge of the net cage. However, it is difficult to carry this out in practice. The tarpaulin on the surface of the water does not function together with the air feeding systems that are common in many installations today. Besides, the many lights in each net cage means that there are many ropes down into the sea, something which makes it difficult to get the tarpaulin to lie correctly. It has also been found that growth on tarpaulins occurs rapidly which means they must be taken up to be washed.

A shade net is a solution that can, to some extent, function but it has been found to be problematic with regard to wind and daily inspections. Many light units also have the disadvantage that there are too many ropes that extend down into the net cage. This results in the ordinary maintenance operations and the daily operation of the installation becoming more

complicated. Growth on the ropes that reach the lamps must regularly be removed. In this connection each lamp must be pulled up, something which means that both this operation and general maintenance of the lamps are time consuming and cumbersome. Activity in the net cage also causes vibration that leads to the bulbs going dead and having to be replaced.

From prior art WO 2005/090860 Al that relates to an underwater lamp suspended down in the net cage to improve the growth of the fish in the net cage shall be mentioned, among others. Correspondingly, WO 2006/137741 shows a lamp that hangs down into the net cage, but which comprises LED light instead of ordinary lamps with halogen light.

US 6203170 Bl describes a device for attracting farmed fish or wild fish comprising an array of visible light emitting diodes encased in a submergible water resistant housing, which can also be connected to a float. The light system is developed in order to attract fish in a fish cage during feeding and the diodes emit light in all directions .

The object of the present invention is to provide a device for light control that, for example, simulates an

approximately natural daylight for the fish, and then especially cod, to delay the sexual maturation of the fish and where the above mentioned disadvantages are avoided.

Another object is also a use such a device to delay and/or prevent sexual maturation in aquatic farmed organisms such as fish. Another object is also a use to achieve increased growth and welfare for the fish through an optimal control of the lighting.

These objects are achieved with a float and a use of the float as defined in the independent claims 1 and 10.

Alternative embodiments are given in the dependent claims.

Thus, the present invention relates to a float comprising a number of light sources for lighting control of aquatic organisms in a farming net cage wherein the float is arranged to float on, or adjoining to, the surface of the water in the net cage, wherein the underside of the float is equipped with a number of downwardly directed and/or tilted downwardly directed light sources arranged to throw light in defined directions from an area at the surface and down into the net cage for control of the lighting of the aquatic organisms lying below.

Said light sources can comprise symmetrical and/or asymmetrical reflectors.

Said light sources can be arranged to provide a frequency spectrum, light distribution and/or light intensity that affect the organisms concerned, such as fish, in the net cage .

It is preferred that said light sources are arranged to provide a frequency spectrum, light distribution and/or light intensity that prevent sexual maturation, increase the growth, increase the tolerance to diseases, reduce infections by ectoparasites and/or reduce stress for the fish. The light sources can be placed girth wise inside the float and possibly centrally in the float.

One or more of the light sources can be arranged at an angle .

The float can be equipped with a rack for a shade net and/or a bird net.

Furthermore, the float can be equipped with a feeding sweeper/spreader.

Said light sources can be arranged to give an

approximately natural frequency spectrum and a light distribution that prevent sexual maturation of farmed fish, especially salmon and cod.

The present invention also relates to use of a float comprising a number of light sources for control of lighting of a farmed aquatic animal in a net cage to delay/prevent sexual maturation, to reduce ectoparasite infections, to reduce stress of the animal, to increase the disease tolerance and/or to increase the growth of the aquatic animal, in which the float is arranged to float on, or adjoining to, the surface of the water in the net cage and in which the underside of the float is equipped with a number of downwardly directed and/or tilted downwardly directed light sources arranged to throw light from an area at the surface and down into the net cage for control of the lighting of the aquatic animal lying below.

In a preferred embodiment the float according to any of the paragraphs above is used.

Preferably, the aquatic animal is chosen from the group comprising fish, molluscs and crustaceans. More preferably, the fish is a species chosen from the group comprising salmon (Salmonidae) , flatfish, cod

(Gadiformes) or any fish species that can be farmed.

Most preferred the farmed fish is Atlantic salmon, Salmo salar or Atlantic cod, Gadus morhua.

The invention shall now be described in more detail with the help of embodiment examples shown in the enclosed figures, in which:

Figure 1 shows a principle diagram of the present invention.

Figure 2 shows a further embodiment of the present invention .

Figure 3 shows a side outline of the float according to the present invention.

Figure 4 shows a cut along the line A-A in figure 3.

Figure 5 shows a ground plan of the float according to the present invention.

Figure 6 shows a cut along the line B-B in figure 5.

Figure 7 shows a cut along the line C-C in figure 5.

As it can be seen in the figures, the float 10 according to the present invention comprises a floating house body that floats on the water in the net cage (not shown) .

Basically, it is intended that the float shall float on the surface of the water, but the float can also be formed with regulation of the buoyancy so that it can float somewhat below the surface of the water if this is wanted. The float is moored, for example, in the centre of the net cage with the help of several lines or ropes (not shown) .

All cable distributions and electronics can lie inside the float, thus only one or more cables are needed for this. Installation of a feed sweeper 16 for connection to an air feeding appliance (not shown) can be made on the float. In addition, a possibility to mount a rack 18 for a bird net 20 is provided. Furthermore, all sensors (temperature, oxygen, cameras, etc) can, for example, be built-in or equipped in connection with the float, and also technical installations/equipment on the float, so that everything is collected at one location. This will make the net cage much tidier and simplify the daily operations

considerably.

Inside or on the underside of the float 10 a number of light sources 12 are located in the form of lamps, preferably supplied with symmetrical or asymmetrical reflectors which thereby throw the light directionally down into the net cage. By using modern symmetric or asymmetric reflector technology it will be possible to achieve that the lamps throw the light downward more efficiently in the whole circumference of the net cage - but without light being thrown upwards to any extent. A small part of the upper light will come up along the water surface and will be reflected down in the water mass. It is assumed that this will be a considerable advantage. Thereby, the light comes from a point high up in the net cage. For the cod this will be understood in the same way as when the sun shines on the ocean surface. A "lighting sky" will be achieved. At the same time a distance between the light source and the fish will be achieved something which has repeatedly been pointed out as important as the cod is basically rather sensitive to strong light. The cod can then use the lower part of the net cage as it normally will do, at the same time as greater control of the light conditions will be achieved.

A very large fraction of the light will be sent down into the net cage with the use of symmetrical or asymmetrical reflectors. This means that one achieves a very high utilisation of the energy which is supplied. At the same time leakage of light to other net cages is avoided, something that makes it possible to run an individually- adapted light regime in each net cage. It is also expected that the heat production in the float will heat up the glasses and thereby prevent growth on the underside of the glasses. This is contrary to traditional solutions where the light is sent out in all directions and one gets both poor utilisation of energy and also an overlap and leakage of light to other net cages.

The downwardly directed and/or tilted downwardly directed light sources 12 are arranged to throw light in defined directions from an area at the surface and down into the net cage for control of the lighting of the aquatic organisms lying below.

Lamps that provide exactly the frequency spectrum that has been found to affect the fish physiologically can be used. The effect of the lighting control of, for example, the light intensity, light distribution, frequency spectra and length of the day can be registered by measuring the level of the hormone melatonin in the fish. With the help of such measurements, and also by, for example, registering the percent fraction of fish that have become sexually mature, it will be possible to document the effect the light sources and/or the lighting device has on the cod and other species .

Such a lighting device and an optimised control of the light will thereby be less stressing for the fish than the known lighting devices with many different light sources distributed in the net cages, which spread the light in substantially all directions in order to achieve the desired high light input on the fish. Thus, the float of the present invention can contribute to increased fish welfare and less stress for the fish in that it is stimulated in a better way, for example, by simulating the natural conditions. It is known that increased fish welfare and less stress also increase the tolerance to diseases and can positively contribute to the behaviour and appetite of the fish, something which can be very favourable in the context of fish farming.

It is also known that an optimised control of the lighting- can result in an increased growth of the fish compared with a less optimal control of the lighting or a natural light regime. Therefore, it is assumed that it is possible to achieve a higher growth for the fish by the use of the present invention.

Additionally, there are indications from preliminary trials using the lighting float of the present invention, that infections by ectoparasites, such as by sea lice in cod, can be reduced. Without knowing the exact mechanism behind it, this could be a result of the light avoiding behaviour of the fish. As described previously, cod preferably seeks away from light sources. By using the light float of the present invention, the fish are mainly staying in the lower part of the sea cage where the parasitic density might be lower than at the surface. This is a further advantage of the present invention.

As figure 4 shows, the lamps 12 can be arranged girth wise on the float 10, and also centrally in the float. The number of lamps that are used inside each float is

dependent on factors such as type of lamp, the species of fish, the biomass that shall be lit up, and also the sizes of the net cages, and so on. Furthermore, the float 10 can be equipped with a hatch 14 for inspection and maintenance purposes, for example, for the replacement of the light bulbs. Ordinary light bulbs, fluorescent tubes, high pressure steam lights, halogen lights or LED light sources can be used, or any other suitable light source depending on the circumstances and what is desired.

In a traditional lighting arrangement it is not unusual that 10 - 12 lamps hang in each net cage. Each of these are normally connected to one cable and at least two ropes. In addition there is a hose(s) for air feeding which normally runs from its own float in the net cage where the sweeper/spreader is equipped. This results in a relatively high number of installations in the net cage which often gives an untidy set up in the net cage and causes challenges and problems with respect to practical farming work and maintenance. In addition, it has been found that the ropes are very susceptible to fouling, something that leads to a need for frequent washing and care. With the present concept, the above mentioned disadvantages are reduced to a few ropes and one cable. All cable distributions can lie inside the float so that one does not need many distribution boxes and electrical installations scattered around the installation. In addition one can also fit, if necessary, the

sweeper/spreader 16 for the air feeding on the float 10 so that the need for a separate float for the feeding in the net cage is eliminated.

The present invention is also suited to achieve a new method for delaying/preventing of sexual maturation of farmed fish such as salmon and cod, in net cages by control of the lighting in the net cage using a float according to the present invention.. Control of the lighting - control of the lighting means in connection with the present invention, the control of light in a farming installation with regard to control, regulation and/or changing the distribution of light, light level (intensity, strength), period of lighting and/or distribution of spectra, to influence an aquatic organism in a farming installation, such as

delaying/preventing sexual maturation of fish, in

particular salmon and/or cod.

Claims

C L A I M S

1. Float comprising a number of light sources (12) for lighting control of aquatic organisms in a farming net cage, wherein the float (10) is arranged to float on, or adjoining to, the surface of the water in the net cage, c h a r a c t e r i s e d in that the underside of the float (10) is equipped with a number of downwardly directed and/or tilted downwardly directed light sources (12) arranged to throw light in defined directions from an area at the surface and down into the net cage for control of the lighting of the aquatic organisms lying below.

2. Float according to claim 1,

c h a r a c t e r i s e d in that said light sources (12) comprise symmetrical and/or asymmetrical reflectors.

3. Float according to claim 1 or 2,

c h a r a c t e r i s e d in that said light sources (12) are arranged to provide a frequency spectrum, light distribution and/or light intensity that affect the organisms concerned, such as fish, in the net cage.

4. Float according to claim 3,

c h a r a c t e r i s e d in that said light sources (12) are arranged to provide a frequency spectrum, light distribution and/or light intensity that prevent sexual maturation, increase the growth, increase the tolerance to diseases, reduce infections by ectoparasites and/or reduce stress for the fish.

5. Float according to any of the claims 1-4,

c h a r a c t e r i s e d in that the light sources (12) are placed girth wise inside the float (10) and possibly centrally in the float (10) .

6. Float according to claim 1,

c h a r a c t e r i s e d in that one or more of the light sources (12) are arranged at an angle.

7. Float according to claim 1,

c h a r a c t e r i s e d in that the float (10) is equipped with a rack (18) for a shade net and/or a bird net (20) .

8. Float according to claim 1,

c h a r a c t e r i s e d in that the float (10) is equipped with a feeding sweeper/spreader (16).

9. Float according to any of the claims 1-8,

c h a r a c t e r i s e d in that said light sources (12) are arranged to give an approximately natural frequency spectrum and a light distribution that prevent sexual maturation of farmed fish, especially salmon and cod.

10. Use of a float (10) comprising a number of light sources (12) for control of lighting of a farmed aquatic animal in a net cage to delay/prevent sexual maturation, to reduce ectoparasite infections, to reduce stress of the animal, to increase the disease tolerance and/or to increase the growth of the aquatic animal, in which the float (10) is arranged to float on, or adjoining to, the surface of the water in the net cage and in which the underside of the float (10) is equipped with a number of downwardly directed and/or tilted downwardly directed light sources (12) arranged to throw light from an area at the surface and down into the net cage for control of the lighting of the aquatic animal lying below.

11. Use according to claim 10 in which the float

according to any of the claims 1-7 is used.

12. Use according to any of the claims 10-11,

wherein the aquatic animal is chosen from the group comprising fish, molluscs and crustaceans.

13. Use according to claim 12,

wherein the fish is a species chosen from the group comprising salmon (Salmonidae) , flatfish, cod (Gadiformes) or any fish species that can be farmed.

14. Use according to claim 13, wherein the farmed fish is Atlantic salmon, Salmo salar or Atlantic cod, Gadus morhua .