Farming in the open sea is very demanding

Global aquaculture has to face some major challenges in the coming years. On the one hand it has to produce more fish and seafood to meet the rising needs of a growing world population. And on the other hand we are already now reaching the limits of what the available locations can offer for new farms. One way out of this dilemma would be to shift farming into the offshore region but this necessitates new concepts, independent systems, more robust technology – and more risk capital.

Piscicoltura del Golfo di Gaeta/Mercator Media
Delegates to the offshore mariculture conference visited an offshore fish farm, the Piscicoltura del Golfo di Gaeta. The farm is located within the Gulf of Gaeta and consists of 72 floating cages with an annual output of approximately 2,000 tonnes of seabass and seabream.

Anyone who has followed developments in the aquaculture sector in recent years will likely have realised that there is no way around the expansion of mariculture and the shifting of farming from the relatively protected coastal zones into the offshore region. At present, most of the fish that are produced in aquaculture come from land-based ponds and tanks or from net cages that float in rivers and freshwater lakes. Nearly 88% of the total volume of farmed fish are freshwater species! The only aquaculture segment in which marine species dominate is molluscs. The further extension of land-based aquaculture is hardly going to be possible, nor would it be responsible. Land is becoming scarcer, suitable locations are lacking. Drinkable freshwater has become a valuable food over which hefty disputes prevail in some parts of the world. But producing fish in the sea is currently still not a satisfactory solution. Up to now it has been carried out almost without exception directly off the coasts which in many places leads to conflicts with other potential user groups such as tourism, shipping, fishing, energy industry and others.

So wouldn’t it be a good idea to move the farm cages further out to sea and so avoid these tiresome disputes? After all, the environmental conditions prevailing there are mostly better than those closer to the coast. Up to now, however, only a few companies have dared to make the step into the offshore region, and there are a lot of good reasons for this. Aquaculture in high-energy, wind and wave swept offshore waters where the farms cannot be reached for days and so have to be left to themselves as it were, requires completely new techniques, innovative production methods and good staying power if the commitment is also to be socio-economically successful, environmentally sound and sustainable. Based on cautious estimates the costs of the offshore investment required to produce the same volume of fish are at least twice as high as they would be in the inshore region. Anyone who has hopes of economic success under these conditions needs original ideas, sound concepts and perhaps also new fish species that can cope with the particular farming conditions. Apart from that it should not be forgotten that offshore installations always require a land-based unit, too, for example as a quarantine station for fry, for feed storage or as a landing stage for the service and supply vessels.

Although the first real marine farms have already been set up and there are more plans and projects for new ones underway, offshore aquaculture continues to be a haven for dreamers and visionaries who with their sometimes quirky ideas awaken interest and fascinate the public. One only has to think of the popular and frequently rumoured utopia described in media reports: ocean enclosures that drift freely between the continents, stocked with fry months ago and now full of fish that are ready to harvest in some far-away place. Unfortunately journalists hardly seem to question the feasibility of such scenarios, for example whether the effort, costs and benefits of these systems are in reasonable proportion to each other, who is liable for the damages in the event of accidents or wreckage and, indeed, whether it is possible at all to insure such facilities. Not to mention problems of feeding the fishes, checking and controlling their growth. A lot of the problems of offshore aquaculture are still unsolved. And there is as yet no satisfactory answer to many of them.


A lot of investors still put off by high costs and risks

One of the illusions that persists, for example, is that through moving into the offshore area aquaculture will be able to get around many of the problems that currently exist due to its present location close to the coast. This might be true in certain regions but in many areas there is already severe competition for "offshore" locations. During planning procedures aquaculture projects are often in a rather weak position because aquaculture frequently comes under the criticism of the public and some NGOs. Offshore aquaculture is more than the mere relocation of the current farms to areas that are further away from the coasts. It is a paradigm shift that requires a huge research and development effort, and it is costly. As with almost any new technology, mistakes will be difficult to avoid in the initial phase and this will have to be accepted by society. The risk of financial loss is much higher than in current aquaculture, it can take much longer for a commitment to pay off for the investor.

Just how many problems and questions related to offshore aquaculture are still open and what possible solutions there might be became apparent at the international “Offshore Mariculture Conference 2014” which took place in Naples (Italy) from 9 to 11 April 2014. The lectures held there looked at legal, biological and technical issues; scientists and hands-on experts talked about the design of offshore farms, possibilities for maintaining and controlling the different systems, investment options, technical equipment and important findings from existing offshore farms.

Katherine Hawes from the Australian legal office Aquarius Lawyers that has specialised in legal problems in aquaculture and fishing reminded listeners in her lecture that the geopolitical and legal framework for marine aquaculture is dealt with in two conventions: international maritime law in the Law of the Sea, LoS, and the International Environmental Law. The LoS creates a legal order for fair and peaceful utilisation of the seas, the conservation of biological resources and the protection of the marine environment. Interestingly, aquaculture is not mentioned in the Convention, apparently because the issue was at that time not yet considered to be of international importance. But the LoS regulates the sovereign rights of coastal states and divides the oceans into areas of responsibility to which the 200 nautical mile economic zones (EEZ) belong. That is probably the location of the majority of offshore aquaculture farms. Article 60 of the LoS entitles the coastal states to permit, build and regulate “installations and structures” in their own EEZ. What exactly the term "systems and structures" means is defined in Article 56, where aquaculture facilities are not explicitly mentioned, however, which leaves plenty of room for interpretation in the event of disputes. The vague wording makes it easier for each coastal state to prevent the establishment of aquafarms of other states in its EEZ.

Josef Melchner, SUBflex
Four SUBflex systems are currently in operation at locations up to 12 km off Israel's coast. They were eco-friendly, could be lowered into the sea when necessary, and had already survived 12 m high waves in the Mediterranean.

The International Environmental Law (Part XII of the Convention, Article 118) narrows the scope for marine aquaculture further. It demands that aquafarming should neither threaten nor destroy marine wild animal stocks. Article 192 additionally commits coastal states to the protection and maintenance of the marine environment. States have to ensure that their offshore activities will neither pollute nor damage the environment either in their own waters or the waters of other coastal states. Articles 207 to 213 list in detail which laws and regulations the states have to pass for the protection of the marine environment.


Offshore technology has to be robust, independent and affordable

One of the conference’s lecture blocks examined the design of offshore aquaculture facilities in detail and looked at the special demands that these systems have to fulfil in the open sea. These are understandably much higher than those for systems directly off the coast. Most speakers favoured integrated systems that are largely independent and can be left on their own, so to speak, for longer periods. There are still a lot of design propositions for the net cages but it would certainly be helpful if this area of business would agree on system “standards” as quickly as possible so that larger numbers could be produced which would reduce costs. A lot of technology manufacturers favour spherical net cages for offshore regions because these constructions are particularly stable and have an optimal surface/ volume ratio. However, they are mostly relatively expensive and also rather heavy which makes handling and maintenance of the facilities as well as the control and care of the fish stock more difficult.

That inshore cages are of little use in the offshore region was one of the things that Terry Drost (President Four Links Marketing Ltd) made clear in his conference paper. Conditions in the open sea demanded a completely new approach, net materials had to be more stable, long-lasting, reliable antifoulants were needed to prevent growth on the nets, and automatic washing facilities for cleaning the nets were required on site. Much of what had become routine work for the staff of inshore farms would have to be done remotely or automatically in offshore farms. For example feeding, or necessary controls and the removal of dead fishes from the cage. Josef Melchner, Vice President of the Israeli technology company SUBflex, pointed out that tried and tested offshore net cages already existed. Four of his company’s SUBflex systems were currently in operation at four locations up to 12 km off Israel's coast. They were eco-friendly, could be lowered into the sea when necessary, and had already survived 12 m high waves in the Mediterranean. What is special about the Subflex system, in which several net cages are movably connected to each other like pearls on a chain, is their single point mooring, i.e. attachment to a single anchor. This meant that the whole installation could rotate freely 360° around the anchor point. Faeces and uneaten food were spread over this circular area whose diameter was sometimes more than 1,000 m. And it was also a kind of sanctuary for wild fishes and plants, said Melchner, because the casting of nets and fishing were impossible there.

Just how important anchoring is for the stability of the farms was made clear by Ludvig Karlsen from the Department of Marine Technology (Trondheim, Norway). The net cages of the salmon farms in Norway were mainly kept in shape through the anchoring, making this ‘anchor frame’ the fundamental element of the farm: without the stabilising effect of the anchor frame the cages would be a plaything of the force of currents and waves, and the enclosure could quickly be deformed. It was, however, rarely possible to install a complex anchoring system in the offshore area. The cages have to be stabilized mainly by the shape, material and structural design of the floating support structures that keep the net in position at the surface. However, that alone is seldom sufficient to resist the destructive effects of wind and waves during severe weather and so many facilities can in such situations be lowered beneath the water surface. The technicalities and possible problems encountered during this process were explained by an Italian team led by Alessandro Ciattaglia (Badinotti Group). In their opinion, floating and submerged systems both have their advantages and disadvantages. Floating cages can, for example, be more easily maintained and controlled, feeding is easier and it is also easier to recognize the fishes’ condition. However, a disadvantage of these systems is their strong dependence on the weather, which increases the risk of a total loss. In addition, plastics age faster in strong sunlight (UV light). Submerged cages are one way to get around these problems. The fish are disturbed less, there are fewer fish thefts and temperature conditions are more constant. But even submerged cages have certain disadvantages: the fish stock is harder to control and feed, in some species (e.g. seabass), problems with the swim bladder can arise due to differences in pressure when changing the depth. And a further drawback: submersible systems cost more, compared to floating installations around 20%.

TLC cage,
The Tension Leg Cage system minimises the strain on cage components by moving with the waves rather like seaweed, and enabling the principal net-pen to remain stable under all condition.


Multi-use platforms to concentrate marine activities

The Ciattaglia Team develops and tests various methods for submerging floating facilities if necessary quickly to greater depths in the offshore region. These techniques are basically similar to those known from the submerging and surfacing of submarines. To submerge, ballast water is pumped into the floats, to surface it is forced out again by pumping air in. The selective lowering of the cage has the additional advantage that the fish can be positioned in particularly favourable temperature zones in the sea. A research group led by Carlos Andrade from the Centro de Maricultura da Calheta (Madeira, Portugal) has calculated using a model that fish growth and the profitability of the farming facility can be significantly improved by selectively moving the mobile cages to areas with optimal temperature conditions. The calculations were based on gilt-head seabream (Sparus aurata), but similar results were to be expected for red porgy (Pagrus pagrus) or amberjacks (Seriola sp.)

A particularly detailed, complex and almost futuristic design proposal for offshore farms was presented at the conference in Naples by Aquaculture Consultant Siegfried Beck. It is far removed from the cage shapes used previously in aquaculture, proposing instead an elongated cylindrical structure which is somewhat reminiscent of the hull of a submarine. In the standard version, the cylindrical cage, divided into ten cross sections, measures 100 m in length with a diameter of 16 m, giving a volume of 20,000 cubic meters. Air chambers in a pipe that runs longitudinally through the construction like a spine forming the central axis of the cage and contains various cables from the sensors, aeration, feed and other supply lines, make it possible to lower the installation 20 m deep into the sea and bring it back up again to the surface. Siegfried Beck seems to have thought of everything in his design proposal. Feed pellets are fed into a 6 bar water current by an injector and distributed between the sections; for the removal of dead fish or for harvesting the system rotates around the longitudinal axis like a lottery drum, and when the outer net skin is in need of cleaning the pipe rises to the surface where the sun and wind dry away any growth or fouling. Beck's ideas culminate in a concept for a "Marine Aquaculture Center" (MAC), in which one or more of the 100 m long net pipes is attached to a ship which serves as a hatchery and feed store. Wind power and photovoltaic systems on board ensure sufficient energy supply.

Karl Iver Dahl-Madsen and Lisbeth Jess Plesner from Danish Aquaculture looked at offshore aquaculture a little more soberly: they calculated that through the expansion of the offshore farms in Danish territorial waters alone it could be possible to produce about 120,000 tonnes of fish and seafood annually instead of today’s 10,000 tons. And they believe that in the whole of the Baltic approximately 500,000 t / year are possible. It would make sense, they said, to combine aquaculture with other offshore activities such as energy production (wind, waves). This would result in significant cost savings because transport, maintenance and all the logistics could be better coordinated and at the same time it would reduce environmental impacts by focusing on just a few sites. Exactly what such multi-use offshore platforms might look like was being investigated in the three projects TROPOS, H2Ocean and MERMAID which were receiving financial support from the EU.

Erik Damgaard Christensen from the Technical University of Denmark, who is coordinating the EU project MERMAID, reported on the state of developments at the multi-use platform at Krieger's Flak in the Baltic, east of the island of Møn. There, apart from a 600 MW wind power plant the first offshore power grid is being built including the necessary transformer stations. Christensen believes that aquaculture could also be carried out at the site. Due to the abiotic conditions he particularly favours salmonid cultures (rainbow trout and salmon) and shellfish farms. Macroalgae such as the commercially valuable red alga Furcellaria lumbricalis that used to be used for the production of Danish agar would flourish there, too. The combination of the three species groups to Integrated multi-trophic aquaculture would thus be possible at the site.