RISK ASSESSMENT IN SCALEAQ

Biological risk assessments have been implemented in ScaleAQ’s quality system in line with HSEQ and escape risk assessments in accordance with the Regulations on requirements for technical standards for aquaculture facilities for fish in seas, lakes and watercourses (NYTEK23). Based on the underlying risk assessment, a biological user manual is prepared. In Norwegian legislation, specific requirements must be followed in the production of fish (Chapter 3 of the Aquaculture Operations Regulations¹). Specific requirements also apply to the development of new production methods or other relevant equipment in accordance with Norwegian legislation. These requirements are set out in the Norwegian Food Safety Authority’s guide of 2020: Guidelines on fish welfare in the development and use of methods, equipment and technology, etc. in aquaculture².

ScaleAQ wants to offer a complete and user-friendly system for risk assessments that is compliant with both user requirements and government legislation. As part of our overall system, we have categorised severity, consequence and probability within the category of biology and animal welfare. We aim to recognize all trade-offs between welfare and environmental outcomes in our efforts to invent and improve technology used for the rearing and handling of aquaculture animals, in line with recommendations from the scientific community³.

Figure 1. System for risk assessment in ScaleAQ (2024)

Our goal is to combine the best available knowledge from scientific literature and practical aquaculture production with technology-specific challenges and site-specific environmental conditions to accurately identify and manage all relevant risks in our risk assessments and subsequent biological user manuals. We have addressed risks and measures using categories from Noble et al. (2018)⁴, adapted to subject categories proposed by the Norwegian Food Safety Authority.

Figure 2. Fish welfare needs based on categories from Noble et.al., (2018)

A relevant basis for comparison is often known risks and results of current production methods. We include current standard monitoring systems in our descriptions under a separate column, to emphasise that all risk mitigation measures are in addition to, and sometimes as a result of, monitoring. In addition, we seek to identify and implement positive welfare measures⁵ to promote optimal utilization of our products.

Not all categories are relevant to the current biological risk assessment. Only conditions that are relevant to the method’s area of use are included.

DESCRIPTION OF TECHNOLOGY, CONCEPT OR METHOD

In the development of its concept for submerged operation, ScaleAQ has carried out a biological risk assessment according to an extended methodology in relation to the Norwegian Food Safety Authority’s recommendations⁶, that address all known and imagined aspects of submerged operation and animal welfare. The risk assessment forms the basis for measures described in the biological user manual designed in accordance with current requirements and best practice. ScaleAQ’s concept for submersible operation is based on experience with components already used in several submerged projects and related concept development, as well as several decades of experience and improvement of traditional sea-based production systems.

Scientific work to document the effect of submerged concepts on health, welfare and biological parameters during production has been ongoing intensively for a decade, although testing of submerged concepts dates back to the 70s (Sievers et al, 2021⁷). Experimental studies on salmon have mainly been carried out by the Institute of Marine Research and their R&D partners. Different types of snorkel cage concepts with air access via the water surface, and fully submerged concepts with air access via air dome and/or air bubbles have been evaluated. Snorkel cages have been shown to significantly reduce lice infestations (Oppedal et al, 2017)⁸, where deeper snorkel gave the best results. Key welfare and production parameters were unchanged in this study. Lower lice infestations and less AGD (amoebic gill disease) problems were also detected. Stien et al. (2016⁹) and Geitung et al. (2019¹⁰) both reported significant reductions in lice infestations when using snorkel cages. Normal growth rates and welfare scores have been observed by providing weekly access to surface for swim bladder filling (Korsøenet al, 2009¹¹, Glaropoulos et al, 2019¹²), and when accessing air via a submerged air dome, behaviour and biological performance are reported similar to traditional surface operation (Oppedal et al, 2020¹³). The scope of this documentation has resulted in the development of tools that farmers are encouraged to use to choose technology for their specific locations (New app gives farmers lice help | Institute of Marine Research (hi.no)).

Operation in submerged systems and adjacent technology on a commercial scale has been tested over the years through Development Licences and continued in regular production at several locations. Published summary of full-scale operations (Warren-Myers et al, 2021¹⁴) indicates reduced lice infestation, normal swimming behaviour and impact on animal welfare due to suboptimal environmental conditions (oxygen). The importance of adequate water exchange is emphasized as an important factor. The establishment of submerged operations at existing sites has accelerated over the past year and will probably represent a significant share of production in a few years.

ScaleAQ experience with components and concepts for submerged operation

Own investigations of production conditions at existing sites indicate that a significant proportion of these sites are suitable for deep farming when we consider depth and general suitability such as water current and water exchange. It must be noted that site-specific conditions should be mapped and risk assessed when it comes to suitability. The same is true for bottom currents and the ability to spread particles. Main components from ScaleAQ have been tested at deep farming and adjacent technology such as iFarm (development license). Main components and monitoring tools (camera etc.) have also been used in submerged production. ScaleAQ’s overall design for submerged operation has also been extensively tested in tank simulations (Marintek).

ScaleAQ Subsea – System Overview

Subsea is made up of a floating collar (FR500, FR560 or FR630) with a circumference of 120-200 m and a cylindrical net bag with a net roof. The net is lowered so that the net roof is at a depth of 20-25 metres, where the risk of being infected with salmon lice is significantly reduced. In the centre of the net roof, an air dome with an air mirror of 10-15 cm has been installed, to ensure access to air to fill the swim bladder. For illustration of the system see Figure 3. Figure 4 illustrates the air dome mounted in the centre of the net roof.

Figure 3: Overview image Subsea

Figure 4: Image of the air dome

Main Components and Features

Net and net roof: Standard net bags are used that connect the net roof. A standard net bag is used, which also ensures the same volume in all phases of operation, both submerged and in surface operation. The net roof has a design that ensures that the highest point in the net is the centre where the air dome is mounted.

Air dome: Located in the centre of the net roof and at the highest point in the net volume. The area under the dome and the air mirror is illuminated with specific lights to ensure that the fish find access to the air mirror and can fill the air bladder.

Lining: Feeding will take place from several pipes that are placed in the outer perimeter of the air dome, this is to ensure distribution of the feed in the net volume. The area is well lit by lights mounted on the air dome.

Lighting: Lights are installed at the bottom of the net roof in addition to lights that illuminate the area around the air dome. Both the placement of light and the amount of light can be adjusted as needed.

Camera and sensors: To monitor the conditions in the net, a camera is installed that can observe e.g. fish behaviour and feeding. The cameras are mounted on winches to be able to move in the cage volume. In addition, there are oxygen sensors that will monitor the O2 conditions.

Winches: Winches are mounted on the floating collar to ensure safe and efficient lowering and raising of the net.

RISK ASSESSMENT, PREVENTION AND MEASURES

For specific implementation of the recommended monitoring, prevention and measures resulting from the risk assessment, please see the technical user manual for the relevant components in each specific case.

FEED AND FEED ACCESS

Description of risk assessment including prevention: Long-term loss of feeding will result in starvation. Modern feeding systems are designed to provide stable daily feeding, and long-term deviations resulting in reduced feed availability are rare. Salmonids have a high tolerance for prolonged periods without access to feed¹⁵ up to 8 weeks without observed negative effects on otherwise healthy fish, and salmonids are routinely starved for 2-5 days before processing operations and slaughter. In normal operations, daily feeding is common¹⁶, and meeting this requirement provides a very good safety margin against negative effects of hunger on health and welfare. Depending on temperature, fish size and other relevant factors, it is therefore unlikely to end up in a situation where feed availability is a critical factor in deep farming. Deep farming involves a switch of technology from traditional airborne feeding to waterborne feeding, to be able to deliver the feed at the desired depth. This is currently a tested and implemented technology that does not seem to have any greater potential for downtime than traditional airborne feeding. Camera-based monitoring also ensures enough feed in deep operation, in combination with adequate lighting.

Monitoring: Camera-based monitoring of feeding behaviour, traditional or camera-based average weight measurements

Measures:

Improve lighting conditions
Improve feed dispersion

NUTRITION

Description of risk assessment including prevention: We assume that the feed composition meets all requirements set in current regulations. There is little reason to assume changes in the nutritional needs of salmonids during deep farming, but adequate adaptation of feed composition to waterborne feeding is assumed.

Monitoring: Feed companies’ food declarations and other documentation are used as a basis, together with any monitoring data from relevant authorities, and relevant regulations are updated with new knowledge in the area. Disease status of certain diseases (PD) may indicate an increased risk of reduced nutritional status. Camera-based monitoring of welfare indicators related to nutrition.

Measures:

Camera-based monitoring of welfare indicators related to nutrition

WATER ENVIRONMENT

Oxygen

Description of risk assessment including prevention: In open cage system production, oxygen access is ensured through water exchange driven by water flow. Location, farm dimensions in relation to biomass and the farm’s barrier function that can reduce the water exchange are therefore of significant importance. The oxygen consumption of fish depends on temperature, swimming speed, feeding status and stress state. Several diseases and production disorders can reduce the fish’s ability to absorb oxygen from the environment by affecting the uptake capacity of the blood (e.g. anaemia, reduced gill health) or circulatory capacity (heart disease). Submerged systems in most cases result in reduced water velocities and thus reduced water exchange in the unit. The actual water exchange rate should be calculated and weighed against the planned biomass in the plants in each individual case. Experience shows that oxygen saturation in deeper water layers can vary somewhat over time, often linked to biodegradation of organic matter. Oxygen saturation in relevant water layers should be mapped throughout a season prior to the establishment of deep farming, and assessments of sites regarding current conditions, threshold depth and distance to the bottom should all be included in a specific assessment of biomass per unit and in total at a site with deep farming.

Monitoring: Online oxygen measurements continuously in camera platform. Site surveys.

Measures: ScaleAQ recommends that limit values for measures follow the LAKSVEL protocol (Figure 5)¹⁷.

Reduce or stop feeding
Surface operation
Oxygen supply

Figure 5: Outline of principles for risk assessment of oxygen

Temperature

Description of risk assessment including prevention: In deep farming, temperature variation will be significantly reduced, and both critically high and suboptimal low temperatures will most likely be avoided at relevant locations. Layers (thermocline) formed due to heating by solar radiation are under Norwegian conditions usually limited to the top 20 m of the water column.

Monitoring: Online continuous monitoring in relevant positions in the device

Salinity

Description of risk assessment including prevention: In deep farming, the variation in salinity will be minimized, and the fish will experience almost full salinity (<30 ppt) continuously. The brackish water layer in Norwegian fjord areas very rarely deeper than 20 m, and only in exceptional cases will periods of low salinity occur in the vast majority of Norwegian localities.

Monitoring: Online continuous monitoring in relevant positions in the device

Particles/faeces in the water

Description of risk assessment including prevention: The amounts of particles from external sources will be low due to the nature of the sites. Somewhat increased amount of particle with organic origin will probably occur during periods of high photosynthetic activity during algal blooms, which typically occur in spring and autumn. Internally generated particles from crushed pellets etc. will most likely be low, since waterborne feeding will result in less crushing and dust formation compared to airborne feeding. The amount of faeces that sinks and settles under the facility will depend on the amount fed and eaten, completely comparable to traditional net-based aquaculture production. Depending on current conditions in the water column and along the bottom, as well as the distance to the bottom under the cages, faeces and feed waste may accumulate on a smaller bottom area (see other water chemistry conditions).

Monitoring: Camera-based visual particle determination, standard MOMB/C bottom condition monitoring.

CO₂, nitrogen compounds (NH3, NO2)

Description of risk assessment including prevention: Given a production concept that is based on natural water exchange without a large degree of oxygenation or reuse of water, CO₂ and nitrogen compounds will never be able to accumulate to harmful levels, given that oxygen availability in the water will be a limiting and dimensioning factor for production.

Monitoring: If necessary, monitor pH (for CO₂ calculations) or water samples for TAN analysis.

Other water chemical conditions

Description of risk assessment including prevention: Sedimentation of faeces and feed waste on a concentrated area under the cages due to low current velocities and short distance between the bottom of the net and the seabed could potentially result in anoxic bottom sediments, with the formation of CH₄ and H₂S as potential problems that need to be monitored and considered.

Monitoring: Site surveys, standard MOMB/C monitoring of bottom conditions.

Measures: Surface operation

FISH HEALTH – PHYSICAL

Risk of mechanical damage from sharp edges during production

Pelvic injuries, skin and impact injuries, snout injuries, eye injuries, stress and fatigue

Description of risk assessment including prevention: In general, the design of the cage ensures a stable volume and physical shape of the net. Compared to a traditional cage, new elements for a submerged cage are a net roof and an air dome in connection with the net roof. The same design conditions as with traditional cages are considered, as well as specific considerations in the design of the air dome. Other structures include ropes and cables for camera and lights. These have rounded edges and smooth surfaces. In the design phase, care is generally taken to avoid sharp edges and that the material surfaces are smooth. Adequate artificial lighting may also be necessary to avoid collisions with structures.

Stress and exhaustion are associated with relatively long-term stress, and often combinations of various negative influencing factors. Some of these may be new challenges that we do not have enough knowledge about in submerged production. A known factor is the risk of inadequate filling of the swim bladder with gradual loss of buoyancy consequently. Increased swimming speed and changes in tilt to maintain depth in the event of negative buoyancy are common compensatory behaviours that, over time, can lead to fatigue over several weeks. Salmonids need to fill their swim bladder by swallowing air about once a week.

Monitoring: Camera-based monitoring of behaviour, wounds and injuries. Camera-based or hydroacoustic method for monitoring swimming behaviour related to stress.

Measures:

Filling of the air dome according to consumption.
Surface operation.
Avoid excess ropes and cables in your production volume.
Ensure adequate lighting in the cage.

Risk of mechanical damage during manual and mechanical handling

Pelvic injuries, skin and impact injuries, snout injuries, eye injuries, stress and fatigue

Description of risk assessment including prevention: The expected overall picture is less manual and machine handling (e.g. delousing operations) during submerged production. In such operations, the additional elements for raising and lowering the structure, as well as the removal of the net roof and air dome, must be considered. The pace of raising and lowering must be adjusted to avoid panic reactions, and sufficient time must be allowed for adjustment. Salmonids have physoclist swim bladders, which allows them to release excess air as they rise from deeper water, significantly reducing the need for low velocity when rising. Removal of the air dome and net roof may be necessary after raising, and this must be done carefully to avoid injury to the fish.

During operations, there is a risk of panicked behaviour and crowding. The speed of operations must be adjusted accordingly, and crowding must be carefully monitored. Interruption of operations upon observation of negative behaviour or exhausted individuals should always be a possibility.

Surveillance: Camera-based monitoring during raising/lowering with a focus on panicked behaviour. Camera-based behaviour monitoring and oxygen monitoring.

Measures:

Speed adjustment of raising/lowering
Follow procedures and precautions during removal of air dome and net roof
Speed adjustments of operations
Stop feeding and/or add O₂ or air to the unit’s water volume.

Increased mortality

Description of risk assessment including prevention: Increased mortality can be observed either because of infectious diseases or other health conditions, or as a result of adverse biological and abiotic factors in the environment that may occur without warning.

Monitoring: Health monitoring, daily mortality monitoring (and sampling), camera surveillance for behavioural changes.

Measures:

Limit or stop feeding
Go to surface operation

FISH HEALTH – INFECTION – AND DISEASE RISK

Increased external exposure to infection

Viral diseases, bacterial diseases and parasites

Description of risk assessment including prevention: Some known viral diseases such as ISA and PD have the potential to spread in water between facilities of up to several days. Water contact between facilities and so-called “water contact networks”, where oceanographic modelling is combined with the infectivity of the various viruses is a known methodology for quantifying the potential for infection. With deep farming where current velocities are generally lower, and the spread of infection via surface transport is reduced due to water layering, a reduced external infection potential is expected. However, the disease situation of viruses should be closely monitored with all available tools.

Some of the so-called “environmental bacteria” such as moritella viscosa and Tenacibaculum spp, which give rise to “winter ulcers”, are often associated with low temperatures, and outbreaks often occur after different handling situations¹⁸. Both generally low temperatures in submerged operation, as well as the bacteria’s somewhat uncertain association with bottom substrate and decomposition of organic matter, may give rise to an increased risk in submerged operation compared to surface operation. The external infection picture is uncertain, as various “clones” (genome ovars) have been detected in disease outbreaks, and that the origin of these as mainly environmental bacteria or infection from other aquaculture facilities is somewhat unclear. At the same time, fewer treatment operations are expected in the event of submerged operation, which may reduce the risk of subsequent outbreaks.

Salmon lice infections are expected to be significantly reduced, due to reduced exposure to infectious stages. AGD (amoebic gill disease) is a widespread problem that can potentially occur since fish are prevented from using upper water layers with periodically lower salinity.

Monitoring: Fish health monitoring, daily monitoring of mortality (and sampling), camera-based monitoring of behavioural changes.

Measures:

Reduce or stop feeding
Surface Operation
Vaccination
Health feed
Freshwater Treatment

Increased internal infection exposure

Viral diseases, bacterial diseases and parasites

Description of risk assessment including prevention: A shared air dome for filling the swim bladder and generally reduced water flow velocity are factors that can increase the internal infection pressure.

Monitoring: Fish health monitoring, daily monitoring of mortality (and sampling), camera-based monitoring of behavioural changes.

Measures:

Refill the air dome regularly with air
Reduce or stop feeding
Surface Operation
Vaccination
Health feed
Freshwater Treatment

Increased degree of treatment difficulties

Viral diseases, bacterial diseases and parasites

Description of risk assessment including prevention: Preventive health measures such as vaccination etc. are unaffected by the production method compared to traditional surface operation. The same applies to all treatments related to feed and feed components. If handling operations become necessary, the farming system can be converted to traditional surface operation within a very short time (hours), and thus the degree of difficulty in carrying out planned operations is not significantly increased.

Monitoring: Fish health monitoring, daily monitoring of mortality (and sampling), camera-based monitoring of behavioural changes.

Measures:

Reduce or stop feeding
Surface Operation

Other possible negative effects on the fish when using the method or equipment in relation to infection and disease risk.

Description of risk assessment including prevention: Experience with deep farming has been obtained from a few sites over a few production cycles. The experience base will be expanded in the future, and it’s expected that site-specific conditions and rarely occurring phenomena may arise that may pose disease challenges. Both new potential pathogenic organisms can be discovered and larger organisms such as various jellyfish can pose challenges with e.g. gill health. It is therefore important to prepare for monitoring of “the unknown” based on environmental samples and fish behaviour.

Monitoring: Fish health monitoring, daily mortality monitoring (and sampling), camera-based monitoring of behavioural changes, environmental monitoring

Measures:

Profiling environmental monitoring throughout the cage (O2, temperature)
Reduce or stop feeding
Surface farming/changed operating depth

BEHAVIOR

Behaviour control

Description of risk assessment including prevention: In submerged operation, the fish are prevented from surface contact and filling the swim bladder with atmospheric air. This is compensated for by offering an air-filled dome in the net roof that provides the same opportunity for air filling, but in a smaller area. Research has demonstrated the need to fill the swim bladder from the surface in salmon (at least weekly), where loss of buoyancy leads to increased swimming speed, and a change in swimming position to compensate for this. It is therefore necessary to offer the fish the opportunity for air filling, as well as optimize this so that the fish learn to use the opportunity. Both feeding points and lighting help to ensure that the air dome is easily retrievable, as well as its location at the top of the roof structure.

Monitoring: Air-filling activity using cameras or sonar, swimming speed and tilt.

Measures:

Lighting control
Surface Operation
Camera in dome area

Social contact

Density and available volume

Description of risk assessment including prevention: Density in kg per volume interacts with water exchange rate in defining safe limits. In production from smolt to slaughter, the density in large parts of the production will be far lower than the recommended limit values. Real density also depends on the fish population’s use of the available volume, as well as how stable this volume is under various environmental parameters such as currents and waves. Physical integrity of available volume is ensured in the design phase.

Monitoring: Behaviour monitoring.

Rest and lighting

Current velocity, variation in current velocity in time and space, light intensity, and variation in light intensity

Description of risk assessment including prevention: Current velocity will depend on site-specific conditions, but generally decreases with depth. It can therefore be assumed that lower current velocities will apply during submerged operation compared to surface operation. Swimming capacity in salmon has been shown to be good, and rarely limiting for production at coastal locations¹⁹ ²⁰.

Inshore current velocity is in most places significantly affected by the tidal cycle, so a variation throughout the day and over time will be the norm in most places. The amplitude of this variation will vary geographically and cyclically, and more stochastic variation in the form of wind and wave-driven currents is also common, although this will probably affect less in deep farming than in surface farming.

Natural light is effectively filtered in water, and mainly blue light of relatively low intensity is left at depths above 20 m. This requires the introduction of artificial light sources to be able to provide enough light intensity to make observations on camera. For the fish, it will also be advantageous to have light sources that facilitate orientation and food search, as well as provide the opportunity to experience variation in the cage environment over days and over time. Lighting control to prevent sexual maturation is also a key element in the welfare context. Proper lighting therefore becomes an important element of the design of submerged systems.

Monitoring: Behaviour monitoring. Site surveys to avoid unsuitable sites.

Measures:

Surface drift/changed operating depth
Lighting control

Explore

Environmental Enrichment and Environmental Variety

Description of risk assessment including prevention: Significantly less natural environmental variation in temperature, light, current and oxygen saturation can be expected in deep farming compared to surface farming. This is basically positive to avoid environmental extremes that challenge the animals’ capacity. However, the need for introduced environmental variation should be considered as a factor of well-being and opportunity for exploration.

Monitoring: Behaviour monitoring.

Measures:

Lighting control

POSITIVE EFFECTS ON FISH

The most important positive welfare effect of the submerged system is reduced exposure to sea lice infections, which reduces the need for both non-medical and medical treatments. The non-medical treatments are a major contributor to reduced health, physical injuries and mortality in today’s salmon fish farming.

Additionally, reduced exposure to adverse environmental conditions during surface operations, such as strong currents, waves, and elevated temperatures above critical limits, can contribute to significant improvement in fish welfare.

Avoidance of high concentrations of algae, jellyfish, and surface predators is another potential factor in improving welfare.

Increased biosecurity through reduced external infection pressure for several waterborne viruses that are transmitted between farming sites can also be a positive welfare effect.

Positive welfare measures that can be implemented in a more controlled environment include active feeding signals (air bubbles and/or light signalling) and daily predictable variation in environmental conditions, e.g. light conditions.

REFERENCES

Manuals

Biological User Handbook – Subsea

Scale Aquaculture AS