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Keeping an open mind over closed containment

Rob Fletcher
Rob Fletcher
02 May 2017, at 1:00am

Salmon farmers and equipment providers are backing the value of using closed containment systems both on land and in at sea just over a year into a project which is investigating the potential pros and cons of such technology.

The CtrlAQUA project, which is now entering its second year and involves scientists, farmers and technology suppliers, has already launched several large-scale trials which have demonstrated – amongst other things – that closed-containment aquaculture systems can be a solution to the sea lice problem. Very few lice, in most cases none, have been found in the large portfolio of systems tested to date. These include land-based recirculation systems (RASs) as well as different types of floating closed-containment aquaculture systems in the sea (CCS).

Geir Magne Knutsen, Development Manager the Norwegian salmon producer Bremnes Seashore , is involved in the project and has been impressed by the results to date. Originally, the idea was that Bremnes should contribute to CtrlAQUA with semi-closed facilities in the sea. But they decided against that and went for land-based, as Knutsen believes such systems allow infection to be more easily controlled, require less maintenance and make it easier to meet increasingly stringent cleaning legislation.

“Whatever the results, I believe that by 2023 [the end of the project], quite a large number of hatcheries will be built with the technology that we are now developing,” says Knutsen.

He reflects that the jury is still out on whether they will grow post-smolts up to 1000g in land-based systems in the future, but he is sorely tempted.

“I will need to prove my case if I am to get acceptance to expand the production of 1000g [post-smolts] on land. But the gains to be realised by cutting down on the production time are so great that I believe it will pay,” he says.

Another of the project’s key commercial partners is Magnus Stendal, from Botngaard System AS. He has been impressed with the progress made to date and predicts that closed-containment systems will become the norm in the salmon industry.

“I believe that, in a few years, we will see post-smolt in closed cages where they will grow up to a kilo in weight. The time in open cages will be reduced to seven to eight months,” says Stendal.

Even though he is a supporter of closed systems, he nevertheless believes that in the future 85-90 percent of salmon growth will still take place in marine cages.

“We believe that halving the time in the sea using closed systems will generate great value for industry and for society,” says Stendal. “Less lice is one of the advantages of closed technology; less mortality is another. We believe this is definitely the right way to go, I am convinced of that. And it is possible.”

Survival and growth

Writing up the project’s first annual report, CrtrlAQUA centre leader Bendik Fyhn Terjesen notes the impressive survival and growth rates that occur in closed systems.

“We have found again that when salmon are kept in closed systems…they still result in high survival of the fish, good growth rate and no or very little sea lice,” he reflects.

Meanwhile he is looking forward to collating the results of a number of studies into microparasite activity in such facilities.

“We also studied microparasites (eg viruses and bacteria) in two different types of floating closed-containment systems in the sea, over two consecutive production cycles, and in a commercial-scale land-based RAS for post-smolts. When completed, this dataset will be a valuable tool for directing the later research efforts in the centre on how to avoid and control disease outbreaks in closed systems,” he writes.

Intriguingly, he notes that the results relating to levels of particulate matter in the water and their impact on fish health were not as expected.

“We performed experiments to find the maximum concentration of particles that salmon can handle when reared in RAS, and surprising results turned up,” Terjesen observes. “Some fish performance data (feed conversion, survival) and oxygen consumption were adversely affected by very high particle loads in the water but, surprisingly, gill scores and external welfare indicators indicated better fish health and welfare when exposed to high particle loads.”

As for the potential stocking densities that such systems can support, Terjesen notes: “We found that in land-based facilities the choice of technology and water quality significantly influences the tolerance of the fish to high density, before it starts to affect health and welfare.”

He also believes that the project will help create a range of designs which will make it easier for more producers to adopt closed systems.

“The results bode well for the goal that CCS should reach a level of reliability equal to an off-the-shelf product within the lifetime of CtrlAQUA, meaning that it is a technology that is proven, predictable and gives the fish a good welfare and health,” he reflects.

Hydrodynamics

One of the areas that has attracted the most interest from commercial partners in the project has been the hydrodynamics that take place in large tanks.

“[Tanks] of several thousand [cubic metres in] volume can offer challenges in terms of hydrodynamics. This can be seen in models and measurements as whirlpools and dead-zones in the large tanks, which may cause problems for the fish and for the self-cleaning of feed remnants and faeces from the tanks,” Terjesen explains.

“In order to develop solutions to these challenges we have created advanced computer-based flow models, [similar to those that are] being used for the construction of new aircraft and ships. This tool will be valuable for the continued research on large culture tanks, on land and floating in sea, in the centre in 2017,” he adds.

Background

CtrlAQUA is a centre for research-driven innovation (SFI). Nofima , in Norway, is the host institution and there are six research partners from Norway, Sweden and the United States, as well as 14 industry partners. It is co-financed by the Research Council of Norway and its partners. It began operations in 2015 and will continue to 2023.