GB2472035A - Open ocean fish farm - Google Patents

Abstract

An open ocean fish farm based around existing offshore facilities A such as oil or gas rigs which may be active or otherwise. The system contains farmed fish using a bubble curtain and acoustic transponders D, E which also serve to keep out predators. The fish are fed by algae which are grown on site F, G. The system is designed as a whole to have minimal environmental impact, and to substantially reduce, or even eliminate net CO2 emissions from the production of farmed fish, and to substantially increase the availability of fish over and above that which can be harvested using traditional fishing methods.

Description

I

Open Ocean Fish Farm

Introduction

Globally, there is a massive demand for fish which is currently largely supplied by catching wild fish. Most fish stocks are currently under stress, with many over-fished, and most of the rest fished at maximum sustainable capacity.

As well as wild caught fish, there are also an increasing number of fish farming operations both sweet and salt water. Whilst sweet water fish fanning largely concentrates on species which feed on vegetation, so allowing the possibility of increasing the overall fish production, salt water fish fanning tends to concentrate on species such as Salmon which eat other fish. Whilst this upgrades the financial value of low value fish, it does nothing to increase overall fish biomass. Salt water fish farms are now largely confined to estuaries, fords, and other shallow water where any pollution tends to remain localised causing various problems.

Human populations are still rising, as is the demand for fish with the result that wild fish stocks cannot support the increasing demand. The current model of salt water fish farming has poor sustainability and does nothing to meet this increasing demand. Current fish fanning techniques suffer from a number of problems, including high levels of pollution due to the stocking density of farmed fish. This damages fish health -both to farm and wild populations, degrades the local environment, threatens eutrophication, and can result in loss of biodiversity of wild populations as they interact with the fish farms. The current generation of salt water fish fanns also require expensive physical infrastructure which is not robust enough to be placed in exposed situations in the open sea.

The purpose of this invention is to offer solutions to all of the difficulties of current fish farms, and to allow efficient fish farming out in exposed areas of the open ocean.

Rather than build a heavy conventional cage, this invention uses a combination of a bubble wall -which most fish are reluctant to swim through, and acoustic transponders giving off noise directionally at frequencies which repel fish. Each fish species responds to different sound frequencies, so that the sound curtain will contain transponders both inward directed and outward directed to perform the twin tasks of containing farmed fish and scaring off predators. Whilst this system is likely to repel and contain fish, it may not be sufficient to deter mammals such as dolphins and seals which could well learn to associate the transponder noises with concentrations of fish, and which are unlikely to be deterred by standard continuous noises. It is therefore proposed to use sound detection technology to alert the fish farm to the approach of these mammals, and to specifically give off warning calls similar to those used by the animals to deter them from closely approaching the fish farm.

A vast amount of data on fish sounds are available as a result of a US military program (now declassified) to detect and track potentially hostile submarines. In order to achieve this task, it was necessary to identify and subtract natural sounds arising from fish and other sea creatures, hence the availability of data.

The invention The open ocean fish farm concept seeks to use redundant or in use offshore infrastructure such as oil and gas rigs as anchoring point and fixed location for building un-caged fish farms at significant distances from the shore, and in relatively deep water.

Each fish farm encloses a large area of the sea surface in an acoustic and bubble curtain, which can be several hundreds of meters wide. Further transponders direct sound downward to the seabed in relatively shallow locations, or horizontally across the base of the virtual cage enclosed by bubble and acoustic wall in deep locations to prevent predators from entering the enclosed area from beneath. The fish farm might also be subdivided into age groups, so that intermediate dividing acoustic and bubble curtains would keep young and older fish apart -reducing the risk of cannibalistic predation. The systems indicated so far, are designed to contain farmed fish and exclude predatory fish. Birds and mammals also pose a threat to the farmed fish, particularly dolphins and whales which are likely to be attracted to the sounds of the bubble curtain and the acoustic transponders due to their similarity to dolphin and whale techniques for concentrating fish whilst hunting. The system therefore needs to be able to detect and identify such creatures and deter them by using the transponders to specifically put out warning signals when they approach. This is necessary as due to their intelligence, they will quickly become accustomed to continuous sounds. In regards to birds, water depth together with realistic models of predatory birds such as eagles and hawks and the use of bird cries can be used to limit the amount of fish removed.

By avoiding the use of cages or nets, the risk of injury to fish would be reduced, as would the cost of the structure, and its vulnerability to storm damage. As a result of the use of deep water -with very large farm areas and relatively modest stocking density, and exposed to the effects of wind and current, any fish faeces and other pollutants would rapidly disperse preserving water quality and avoiding many of the pollution and infection problems which plague coastal fish farms.

The fish species selected for farming in these farms would primarily feed on algae, and hence being lower on the food chain than most wild caught commercial species would allow an overall increase in fish production -especially if algae are cultivated to feed them. This would help to ensure that fish farming results in an overall increase in the quantity of food available to humans from the ocean rather than simply upgrading low value fish such as sand eels into high value fish such as salmon without increasing the total fish yield.

As light only penetrates to around 15-30 meters from the surface, the virtual containment system need only cover the depth to which the farmed species swim and feed, hence no more than around 30 meters. The bottom containment would be provided by transponders set to contain / exclude fish as per requirements. An optional horizontal net could be placed across the bottom made highly visible to fish to avoid unwanted catch and strung across the bottom of the structure for containment. This net would have the secondary function of an attachment structure for the cultivation of marine macro-algae (seaweed) as a source of food for the fish. The overall size of the enclosure could be as large as desired, requiring only more perforated pipe -to supply the bubble wall, and more transponders to generate the acoustic wall (and a larger horizontal net where used).

As part of the overall system of fish cultivation system, micro-algae will be cultivated on site in photo-bioreactors which may be floating or otherwise, whilst macro-algae (seaweed) will be encouraged to grow on suspended growth platforms in which the algae are attached to ropes or similar below the surface. Growth of said algae will be encouraged and enhanced by aeration from the sunken bubble curtain, and may in certain cases be naturally encouraged by nitrate and phosphate pollution in estuarine waters. Within a closed photo-bioreactor, active application of fertilizer and C02 would also be acceptable, as said fertilizer would be removed from the water rapidly by growth of micro-algae, and so could not be considered to be dumping at sea which is prohibited by international treaty.

In order for this system to function, it will require a constant source of power, which may be sourced from waves, current, ocean thermal energy, offshore wind farms, solar photovoltaic power -all with battery or other back up as needed, or by cable from the shore.

Power generated by on site renewable energy devices or otherwise will serve the photo-bioreactors, aerators, transponders, and such navigation lights as might be necessary to prevent collision together with any instrumentation, and will meet the needs of such staff as might from time to time visit the site. Protection against collision can be further enhanced by the installation of radar reflectors on floats around the perimeter of the farm.

Such a system has many benefits, a major one being increased net productivity of fish due to farming of species lower down the food chain. In this way, less food is required per kg of edible fish than would be the case farming carnivorous species. Culture of algae within the same fish farm area allows nutrient runoff from rivers to be utilised within a controlled environment, so removing pollutants from the sea. Use of a bubble screen aerates the water, enhancing algal growth rate, whilst preventing the build up of oxygen deficit and stagnation.

All this feeds through to high fish productivity and clean sea water.

As large numbers of fish can be grown in an area enclosed by acoustic and bubble curtains, far less fuel need be expended catching fish, and with enhanced algal production, the C02 balance of the whole operation is highly favourable.

Figures 1 & 2 A. Adapted oil/gas platform or other offshore structure B. Perimeter buoys C. More Perimeter buoys D. External transponder E. Internal transponders F. Mesh supporting marine algal (seaweed) growth 0. Seaweed cultivation H. Anchorage 3. Photo bioreactors mounted on platform K. Power supply for transponders & bubble screen generator from renewable energy devices or by other means L. Perimeter bubble screen generator.

Claims (22)

1. Claims 1. Using a combination of a bubble wall and transponder generated sound; farmed fish will be contained in an area of Open Ocean without physical containment.
2. 2. Using a combination of a bubble wall and transponder generated sound; predator fish will be excluded from an area of Open Ocean without physical barriers to prevent entry.
3. 3. The system reuses existing offshore structures permitting them to remain as production facilities and avoiding the need for decommissioning.
4. 4. The system permits fish farming far from the coast in deep water reducing greatly the concentration of pollution which occurs in conventional fish farming.
5. 5. The system permits fish more room to move, improving their welfare 6. The system detects whales and dolphins and deters them with warning sounds as they approach.7. The system utilises models of predatory birds such as eagles or hawks complete with bird cries to limit the amount of fish taken by birds.8. The system design allows farm areas to be far larger than conventional cages.9. The system is designed for a high degree of natural flushing, reducing disease and pollution.10. The system produces farmed algae allowing herbivorous fish to be fed without bringing in food from outside.11. The overall fish farm system including algal cultivation and aeration serves to reduce the degree of pollution experienced in estuarine water.12. The system excludes trawlers so reducing disturbance of the seabed.13. The overall fish farm system can be installed in high nutrient locations to help clean up effluent improving bathing water quality on nearby beaches.Amendments to the claims have been filed as follows Claims 1. An open ocean fish farm that contains farmed animals by means of an integrated bubble screen and transducer generated sounds which create virtual walls in the ocean without the need for a physical containment structure, allowing low cost construction, avoidance of contamination, free flow of nutrients, specific delivery of photobioreactor delivered phytoplankton as a fish feed, as well as a defensive facility preventing predators from availing themselves of the contained fanned fish, whilst also providing for the harvesting of fish crops on an age related basis by means of separate containment areas within the overall perimeter.2. The bubble screen according to claim 1 that acts as a deterrent to contained fish escaping into the open ocean and as the bubble screen is generated by the pumping of air into submerged tubing at the bottom of the open ocean fish farm in a perimeter pattern, the resultant delivery of the bubbles of air ensures the delivery of carbon dioxide in the air to phytoplankton within the contained farm area thereby ensuring maximum reproduction of micro algae and the optimum generation of fish food.3. The acoustic sound barrier in the open ocean fish farm in claim 1 that is generated by tranducers is ananged in two parts on either side of the bubble screen by means of Q variable wave length transducers. 4. The variable wave length transducers of claim 3 that generate inward directed sound waves to carall fish of a selected species and discourage them from trying to escape the containment area.5. The variable wave length transducers of claims 3 and 4 that are mounted in such a way that they can be outward directed on the external side of the bubble screen to be activated and repel predators upon their approach to the open ocean fish farm.
6. 6. Arranging a floating platform or buoy to mount a solar powered bioreactor to allow the open ocean fish farm according to claim 1 to generate in situ energy that can be used to pump air down to a perforated pipe device that releases the bubble wall at the same time as powering the acoustic screens for inward containment and outward repelling of predators and the continuous fermentation of micro algae in the photo bioreactor.
7. 7. The perforated pipe device according to claim 6 that is mounted on the subsurface floor of the open ocean fish farm either in a circular perimeter track around the solar powered bioreactor or such other shape as may be deemed convenient in order to deliver a totally encompassing flow of air bubbles pumped underwater using energy from the photobioreactor.
8. 8. The photobioreactor according to claim 1 that is designed to be powered primarily by solar energy but for periods where sufficient sunlight is not available, power can be further generated by wave energy or by wind.
9. 9. The open ocean fish farm according to claim 1 that is totally scalable allowing a flexible range of sizes and shapes whose depth does not exceed the maximum depth to which sunlight will adequately penetrate the top layers of the sea with enough energy to enable photosynthesis to be undertaken by micro algae, typically no more than thirty meters.
10. 10. The open ocean fish farm according to claim 1 that protects the bubble screen and acoustic transducers from damage by storms or rogue waves by virtue of it being some thirty metres below the surface of the sea.
11. 11. The photobioreactor according to claim 8 that has tracking devices and marine warning lights powered by its own self generating power systems to enable the apparatus to be tracked in the event that it were to break loose in a storm or other emergency.
12. 12. The open ocean fish farm according to claim 1 that enables man to harness the food producing capabilities of the seventy percent of the earth's surface that are covered by the oceans but which are not exploited as an intensive farming facility.
13. 13. The open ocean fish farm according to claim 1 that allows mankind to give up its traditional hunter gatherer system of gathering up fish from the ocean and replacing it with a determined type and quantity of animals to avoid the inadvertent capturing of Q juveniles that never grow up to become mature animals and reproduce and to prevent I-the over fishing of naturally occuning fish stocks which would otherwise result in the oceans being turned into sterile waste lands.
14. 14. The absence of physical containment within the virtual structure of the open ocean fish farm in claim 1 so that there is no build up of faecal waste, poisoning the animal stocks intended for food usage.
15. 15. The positioning of the open ocean fish farm in claim 1 in the sea rather than close onshore so that dead or diseased fish will fall to the sea bed or be washed away, thereby avoiding contamination of the other animals being husbanded.
16. 16. The open ocean fish farm in claim 1 that can be adapted for mounting around a fixed offshore structure such as a disused oil or gas platform thereby saving the cost of the removal of such a platform at the end of its economical life cycle in the oil and gas sector.
17. 17. The open ocean fish farm in claim 1 that lends itself to secure operation in that various warning systems can be incorporated into a top surface mounted floating perimeter track designed to warn off approaching ships and such defensive mechanisms can be further supported by the use of web cams mounted on the photo bioreactor or floating platform to monitor on a real time basis the day to day operation of the farm without the need for human presence.
18. 18. The open ocean fish farm in claim 1 that avoids overpacking of fish in too tightly contained an area, so that the animals are able to grow naturally without stress and they benefit from this in their ability to resist diseases caused by stress, thereby enhancing the quality of the harvest collected.
19. 19. Acoustic subdivisions within the open ocean fish farm according to claim 1 that allow for planned harvesting of specifically aged fish. Improving homogeneity and commercial value whilst avoiding waste and cross contamination.
20. 20. The open ocean fish farm in claim 1 designed for a high degree of natural flushing brought about by current flows bringing fresh nutrients to the farm facility whilst reducing the incidence of disease.
21. 21. The open ocean fish farm in claim 1 that is not dependent on the use of trawlers and excessive man power and is therefore a cost effective way of producing food.
22. 22. The open ocean fish farm in claim 1 that can be used to replenish depleted fish stocks by the controlled release of mature farmed animals, thus avoiding overfishing resulting in sterile marine areas and the wiping out of hitherto abundant species of fish. r (4 r (0