Closing in on closed cages

Two main drivers behind the recent years with development of alternative farming technologies have been the increasing problems with salmon lice and increased focus on the possible genetic introgression from escaped farmed salmon. Industrialized farming of Atlantic salmon and rainbow trout in seawater has been developed for marine net-pens with a free exchange of water, pathogens, parasites and organic effluents with the marine ecosystem outside the cages. In this context, aquaculture production depends on available local ecosystem services (FAO, 2007), e.g. areas for location of sites, clean water and a large recipient capacity. Alternatives to traditional

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net-pens are (1) floating, closed confinement systems (CCS) with rigid walls or with flexible walls, (2) offshore constructions, (3) land-based flow-through systems and (4) land-based recirculating aquaculture systems (RAS). The Norwegian management system of aquaculture is complex, involving County authorities, the Norwegian Directorate of Fisheries and the Ministry of Trade, Fisheries and Aquaculture. Between 2000 and 2015, the Norwegian government issued new licenses for salmon farming through six different allocating rounds (Hersoug et al., 2019). From 2002 to 2009, 155 new licenses were issued, with no environmental strings attached. In the licensing round in 2013, 45 green and so-called ‘super-green’ licenses were issued. The idea was to incite development of new farming technologies and to reduce the environmental impact caused by traditional, net-pen farming (Hersoug et al., 2019). Annual reports from some of these projects are published at the Directorate website⁵. As the pressure towards access to more licenses increased, the government issued a new allocation round already in 2015, referred to as ‘Development licenses’, again with environmental issues as the most important drivers. This round was, unlike the previous, not restricted to a specific number of licenses, but encouraged new and ambitious projects to apply for the number of licensed they could envisage necessary to implement the new technology.

‘Development licenses’ were also supposed to support in resolving the environmental and area-related challenges addressed by the new ‘traffic-light system’ (Hersoug et al., 2019). Little information has been aggregated about the performance of the implementation of ‘Development licenses’ so far, besides the project brochures presented at the Directorate’s website⁶. A controversial aspect of these licenses is how such licenses (as with previous rounds) can be converted to standard, commercial licenses after finishing a specified technical and biological test program (Hersoug et al., 2019). The price for converting ‘Development licenses’ is NOK 10 million, less than 10%

of their assumed present market value. The possibility of harvesting such profit margins through converting licenses could be possible driver behind some of the largest and most spectacular technological projects. The large offshore projects have been suggested to increase the available area for fish farming (Anonymous, 2018b), but it is

5 https://www. fiskeridir.no/Akvakultur/Delt-kunnskap-og-erfaring/Groene-loeyve

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https://www.fiskeridir.no/Akvakultur/Tildeling-og-tillatelser/Saertillatelser/Utviklingstillatelser/Kunnskap-fra-utviklingsprosjektene

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also a risk with large offshore farming projects that problems of lice and emissions are moved to new and until now pristine areas outside the coastline.

The CCS described in this thesis belonged to group (1): floating CCS with flexible walls.

These CCS were floating tarpaulin bags (Figure 7), with single flow-through of seawater, and with oxygen supplied through diffusors or ejector systems. So far, there has been no aeration or removal of CO2 in these systems. In the outlet, particles were separated, but the remaining outlet water was left untreated. The inlet water was pumped from a 25 m depth and neither filtered nor disinfected to remove viruses, bacteria or parasites. Less sea lice and microbial pathogens could be an advantage when using water from such depths. However, for other parasites or for potentially troublesome pathogens or opportunistic marine pathogens such as Moritella viscosa or Aliivibrio spp. the risk might even increase. Filtration and disinfection of intake water has been suggested as a measure to improve the biosecurity of closed containment systems (Rosten, 2011, Espmark, 2019).

Social and environmental impact of CCS technology

Salmon lice, release of chemicals during lice treatments, escaped fish, organic emissions, energy use, emissions of CO2, and the environmental impact of feed production for farmed fish are examples of negative externalities, on both a local and a global scale. Life cycle assessment (LCA) (Finnveden et al., 2009) is a tool widely used to assess the sum of environmental impacts and resources used throughout a product’s life cycle. In an LCA of Canadian aquaculture systems, including CCS cages, land-based systems had the poorest environmental performance, mainly because of the energy needed to pump and treat water (Ayer and Tyedmers, 2009). In the case of the marine cages, CCS cages had a smaller environmental footprint compared to net-pens, if given access to low-CO2

energy sources like hydroelectricity. If the extra energy needed to run CCS was supplied via fossil fuel-based electricity, the balance would shift in favour of net-pens. However, this analysis was executed without considering the environmental impact of sea lice and sea lice treatments and without the technological possibility of collecting organic emissions from CCS or land-based flow-through systems.

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Figure 7. Above: Schematic illustration of a floating, tarpaulin cage (2870 m³) with water intake from a 25 m depth, described in Papers I, II, III (Illustration: AkvaDesign AS). Belowt: Picture of a site with ten floating, tarpaulin cages (6000 m³) of the same basic design, used for trials described in Paper II (Photo: AkvaFuture AS and Visual 360).

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Thus, the outcome of their analysis is of limited value for evaluating such systems in a Norwegian context. In a comparison of the carbon footprint of marine net-pens (Norway) and land-based freshwater RAS (US) (Liu et al., 2016) concluded that freshwater RAS located in the US released twice as much CO2 during the production period as salmon production in Norwegian net-pens. After adjusting for the airfreight needed to transport Norwegian salmon to the US, the balance would be reversed, with RAS releasing less than 50% of the CO2 emitted by Norwegian net-pens. This is an interesting twist to the discussion about the ecological sustainability of salmon production in clean Norwegian coastal areas. It also highlights how land-based RAS is a technology that may have greater global potential than cage-based farming systems.

Salmon farming based on marine cage systems is today mainly located in Northern Europe, Canada, Chile and Oceania. With more effective land-based technology available, this picture could change. However, poor system designs, water quality issues and mechanical problems have so far been important constraints on the development of commercial-scale RAS production worldwide (Badiola et al., 2012).

Outside the scope of this thesis, there are several important environmental issues that should be included in assessments of the sustainability of intensified salmon farming.

Several research projects are now initiated to explore the possibility of using CCS salmon farming technology to develop more diversified aquaculture systems, so-called Multitrophic Aquaculture (MTA) (Stedt, 2018). CCS farms close to mainland infrastructure could exploit more environment-friendly energy sources (Ayer and Tyedmers, 2009). Collection and reuse of faeces and surplus feed could contribute to reduce the environmental footprint of industrialized fish farming in vulnerable coastal areas. An increased demand for protein-rich and high-energy feed for carnivore salmonids could increase the competition for important feed inputs like captured fish and vegetable oils. Emission of greenhouse gases is also a challenge, through energy-consuming production systems and through trans-continental transport of both feed ingredients and the salmon products. The salmon farming industry in Norway often present increased volumes of salmon production as a means of improving the global supply of fish for human consumption (Anonymous, 2018c). However, it could be argued that a further expansion of the aquaculture industry without a shared vision between public and private sectors on how to develop fish farming with less negative external

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costs could be a threat, not only to the surrounding environment, but also to itself (Naylor et al., 2000).

Closed containment systems: Where are we and where are we going?

In the period from 2012-2015, when the projects leading to my thesis were developed, very few studies had been published on the actual production capacity and the possibilities and pitfalls of fish welfare in commercial-scale closed cages. As I finish this thesis (April 2019), knowledge about the management and biological performance of large, closed containment systems is still scarce. A thorough review of the literature on the biological requirements for post-smolt Atlantic salmon in closed containment systems was published in 2011 (Thorarensen and Farrell, 2011), together with a Norwegian report on the possibilities of CCS technology (Rosten, 2011). Since 2011, several CCS projects have been implemented. The most profiled projects with activity in the years from 2011 to 2019 are:

1. The Neptun cage, 21,000 m³ solid wall CCS, Mowi AS 2. Preline, 2,000 m³ raceway CCS, Lerøy AS

3. Aquadomen, 5650 m³, solid wall CCS, Cermaq AS 4. Flexible and solid wall CCS, different volumes, Nekton AS 5. Flexible wall CCS, 2870 and 6000 m³ volumes, AkvaDesign AS

Projects 1, 2, 3, 4 are incorporated in the CtrlAqua research consortium, headed by NOFIMA (Espmark, 2019), while the projects developed by AkvaDesign AS and AkvaFuture AS that are described in this thesis are not. Between 2011 and 2014, few new studies were published on CCS-related topics, but from 2015 onwards, more information became available from experimental studies and from the first field trials involving CCS technology projects (nos. 1-3 from the list above). Two doctoral theses (Calabrese, 2017; Sveen, 2018) have been published, together with a few papers with reference to CCS-technology: hydrodynamic studies (Gorle et al., 2018; Klebert et al., 2018; Maximiano et al., 2018; Gorle et al., 2019) and a survey of technical specifications of large land-based tanks and one pilot CCS (Summerfelt et al., 2016). Growth, mortality, muscle development and cardiac development in net-pens and a raceway CCS has been compared (Balseiro et al., 2018). The microbiota in recirculating aquaculture systems

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(RAS) and the 21,000 m³ Neptun cage is described (Rud et al., 2017), and development of the skin barrier of Atlantic salmon after sea transfer to the raceway CCS (Karlsen et al., 2018). Several experimental studies of stocking density and specific water consumption have been published, with special reference to implementation in CCS or in RAS systems (Sveen et al., 2016; Calabrese et al., 2017; Sveen et al., 2019). The effect of swimming exercise in CCS model cages is described in this thesis (Paper IV) and exercise in combination with salinity by Hvas et al. (2018) and the effect of different temperatures on swimming capacity of salmon by Hvas et al. (2017a). The impact of intensification on levels of CO2 in large-scale CCS cages from AkvaDesign AS is described in this thesis (Paper III), and the effects of CO2 in RAS in two recent publications (Good et al., 2018; Mota et al., 2019). The effect of CO2 on post-smolt Atlantic salmon has been described (Fivelstad, 2013; Fivelstad et al., 2003; Fivelstad et al., 2015; Fivelstad et al., 2018), it has been shown a diurnal variation of CO2 and TAN excretion of post-smolt at different water flow (Kvamme et al., 2019). The effect on sea lice infestations is described in this thesis (Paper I). A few master theses describe different aspects of CCS-based farming (Chen, 2015; Pedersen, 2016; Haaland, 2017; Stedt, 2018). A large number of important scientific studies with relevance to CCS technology were conducted in the late 1980’s and early 1990’s describing the ongrowing of post-smolt salmon in land-based, flow-through tanks supplied with oxygen-enriched seawater. These studies are still very relevant and important for the understanding of closed confinement farming (Kjartansson et al, 1988; Fivelstad et al., 1990; Fivelstad et al., 1991; Fivelstad and Smith, 1991; Forsberg, 1994; Fivelstad et al., 1995; Forsberg 1995a,b; Forsberg, 1996; Forsberg and Bergheim, 1996; Sanni and Forsberg, 1996; Forsberg, 1997;

Fivelstad et al., 1999). In addition, an early pilot study on the on-growing of post-smolt salmon in closed, tarpaulin covered cages (CCS) was performed in Southwestern Norway (Skaar and Bodvin, 1993).

Studies on stocking density, specific water consumption and salinity and exercise from experimental studies with post-smolt were described in a doctoral thesis (Calabrese, 2017). One of the conclusions was: ‘Large scale CCS studies are needed to verify results in this thesis’ (p. 34). This thesis is an attempt to provide more detailed insights about rearing conditions, production capacity and fish welfare in such systems.

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