Sea lice management measures for farmed salmon production: research

5. Results of participatory workshop: wider implications of sea lice control

The participatory workshop on sea lice control in salmon primary production took place on the 20^th of January 2020, 11 am – 4 pm at SRUC, Inverness Campus.

Workshop participants (ten) included representatives of the different parts of the Scottish salmon supply chain (salmon producer association, salmon processing and retail, input related – cleaner fish, health practitioner), academia (salmon health and environmental aspects) and policy (disease modelling). Workshop organising team (four) comprised of social (economics) and non-social (aquaculture veterinary) science expertise. 

The aim of this participatory workshop was to explore how factors leading to sea lice infestation and choice of sea lice control options can be mitigated and, respectively, influenced through incentives to producers and collaboration with others along the salmon supply chain. 

The foundation of the participatory approach to follow at the workshop was system dynamics (SD). SD models map the flows, processes, decision rules and relationships between actors that operate within a complex system. Group model building (GMB) is used to develop SD models jointly through participation and direct collaboration between the actors involved in the system to identify leverage points and interventions (and potential delivering mechanisms) which may lead to more effective sea lice control in the system (salmon supply chain). GMB is ideally suited to SD language and concepts and particularly relevant when the system involves diverse types of actors, when many different control options exist, and when it is difficult for actors to understand individually the possible consequences of a collective decision made within a complex system. 

Based on findings from previous studies we developed a process flow diagram that represents the flow of salmon through the supply chain from producer to consumer. It described a primary flow representing healthy salmon reaching the market, but also secondary flows to account for sea lice infested salmon and potential impact pre- and post- farmgate. The first step of the workshop was to validate the diagram with workshop participants. Subsequent sessions discussed the causes and consequences of salmon being infested with sea lice, ranked alternative control options and their effects on supply chain (primary production, transport, processing, retail, consumption), welfare and the environment. Incentives for multicriteria effective measures of sea lice control were identified and linked to causes of and control measures within causal loops. Causal loops help us to identify the options for intervention and their potential consequences in the system. The workshop followed the structured presented in the schedule (Appendix).

The scope was confined to the primary salmon flow from farm to processing, with main focus on the causes/destinations/consequences of sea lice control measures on the salmon supply chain, environment and fish welfare where any externalities are due to causes originating in primary production and sea lice management measures identified include those currently used in the Scottish salmon industry.

The participants identified the following potential factors influencing the choice of sea lice preventative/control measures:

• Farm health management: (previously tested) efficacy of preventative/control measure; (previously tested) cost-effectiveness of preventative/control measure; sea lice numbers and dynamics linked to different sequences of (combined) control measures; salmon overall health status; suitability of sea lice control measures within farm holistic health management/disease mitigation plan; sea lice preventative/control measures used on (neighbouring) farms; site/location suitability (location related sea lice prevalence).
• Farm economic factors: business scale/biomass level/production stage/fish size/harvest plan; compatibility to farm environment; farm type/practice - organic/standard/best practice; access to technology/medicines/equipment such as boats; skilled staff availability/time/knowledge, experience, understanding; access to information and training; access to financial resources; resource prioritisation.
• Environmental, salmon welfare, and health concerns: producers’ perceptions re impacts of preventative/control measures on salmon welfare; producers’ perceptions re impacts of preventative/control measures on cleaner fish welfare; environmental impacts of control measures such as residues affecting wild salmonid populations; potential of control measures such as medicines to induce resistance.
• Markets & consumers perceptions: impact of control measure on product quality (stress leading to lower quality flesh)/price/sales; consumers perceptions re welfare/environmental impacts of ('sea lice as a problem') control in salmon industry; consumers perceptions re human health impacts of sea lice control in salmon industry.
• Regulatory framework: compliance with environmental standards/regulations; compliance with food safety regulations; compliance with welfare regulations/welfare act/accreditation schemes/VMD standards.
• Other: weather/seasons.

The discussion focused on a set of sea lice control measures that included the following: 

1 in-feed medicines

2 bath medicines

3 using cleaner fish during the seawater cycle

4 using skirts during (part of the) seawater cycle

5 area management / inter-producer collaboration

6 larger smolts at sea stocking 

7 physical removal: hydrolicer

8 lowering biomass (farm/area)

9 physical removal: thermolicer

10 freshwater bath

11 breeding & genetics/ using lice-resistant salmon strains

12 functional feeds

13 healthy fish

14 reduced cycle length/ early harvest

15 adjusting stocking time

16 site location control

17 adjusting fallowing periods

18 stocking at favourable year classes

The stakeholders’ perceived effects of the use of different sea lice control measures on the supply chain and externalities i.e. environment and welfare, are presented in Table 12. 

The workshop participants have identified a number of potential effects of each of the sea lice preventative/control measures, at times contradictory and thus not always straightforward to summarise. Table 11 information is complemented by Table 12 (Appendix). The following points are based entirely on the opinions of stakeholders.

1 In-feed medicines may have negative impact on the environment in the short term, however positive long term due to disease eradication and lower/no need for in-feed medicines. Most likely low to no impact as in-feed medicines are targeted at smaller fish and thus will not be used for larger fish which are nearing harvest so that they interfere with neither harvest plans when residues have to be cleared from fish nor the subsequent processing and retail.

2 Bath medicines may have negative impact on farm as the measure is time consuming and requires increased staff & equipment resources. Negative impact on the environment through e.g. effect on marine invertebrates and on salmon welfare due to stress from handling & exacerbation of underlying health conditions. Both welfare and environmental impacts are overall negative in the short term, however there will be a positive impact in the long term depending on the efficacy of bath medicines to control sea lice. Welfare of cleaner fish may be negatively affected. The impact on overall health will be either positive or negative depending on underlying conditions, such as water temperature and fish health. Sea lice management measures may reduce the tolerance to transport and potentially increase mortality during transport. Sea lice management measures may impact processing and subsequently retail stages through reduced flesh quality, potential medicine residues in flesh and lower supply due to medicine withdrawal period. Retail and consumption stages may be affected due to perceptions linked to use of medicines and implicitly may affect the image of the salmon industry. 

3 Using cleaner fish as sea lice management measure may impact on the farm economic situation with regard to increased requirement for staff and equipment. However that may be compensated by reduced need for other measures, overall it is very cost-effective if the seasonal aspects of cleaner fish are well managed as part of the overall fish health management. It may affect the environment negatively through impact on the wild populations/knock on effect on other species. However, the reduced need for sea lice management measures and efficacy of sea lice control may lead to positive impacts on the marine environment in the long term. Using cleaner fish has moderate to strong positive impacts on salmon health and welfare relative to salmon with baseline lice counts, however the opposite effects with regards to the welfare of cleaner fish themselves. The presence of cleaner fish may cause minor disruptions to transport, however subsequent impacts on processing and retail, consumption are overall positive due to no need for medicinal or other sea lice management measures that may affect salmon welfare. Negative effects at the demand side of the supply chain may occur based on consumers’ perceptions as regards the welfare of cleaner fish.

4 The use of skirts to control sea lice has light environmental and welfare effects, with positive impacts at the retail side of the supply chain. Negative impacts on salmon welfare and overall health may occur due to stress through reduced oxygen flow in the pens. No specific positive or negative effects were identified at any other stages of the supply chain. 

5 The use of area management to control sea lice has moderate to strong environmental and welfare effects, with positive impacts also at the retail side of the supply chain. No specific positive or negative effects were identified at any other stages of the supply chain. It is very effective as a sea lice control measure and thus has strong positive impacts on salmon health. 

6 While strong in terms of sea lice control and related impact on salmon health, using larger smolts quality as a sea lice control measure has a high cost to the farm. Smolts often come from freshwater recirculating aquaculture system (RAS), which is a very controlled environment, therefore costly to run. Salmon’s shorter presence in the marine environment may lead to lower levels of waste and thus an overall positive impact on the marine environment. Also, a reduced duration of exposure of salmon to the environment including to sea lice reduces exposure to factors that impede health and welfare of the salmon. Overall, the effects at the demand side of the supply chain are positive, not affecting industry image due to no specific negative perceptions of the consumers related to the different aspects of this sea lice control measure. 

7 Use of hydrolicer as a sea lice control measure involves high equipment costs to the business. It has overall a strong positive impact on the marine environment through reduced need for licenced veterinary medicines, however the equipment involved has a high carbon footprint. The short term impact on salmon welfare from using hydrolicers is strongly negative as this is a stressful method involving significant risks, however as any other measure of control, when effective in controlling sea lice, it may have a positive long term impact on salmon welfare. While effective in controlling for sea lice, the method has a negative damaging impact on the overall health of salmon (exacerbating underlying conditions through increased stress and high mortality) and the health and welfare of cleaner fish, if used on farm. The negative health and welfare effects may transfer to the processing stage and the method has overall negative effects at the retail/consumption end of the supply chain through mostly public perceptions. Depending on the information available to the public, perceptions may focus on reduced use of medicines with its subsequent environmental effects, however they are mostly negative due to direct impact on salmon health and welfare. 

8 Reducing biomass (farm/area) as a measure of sea lice control has overall positive impacts at supply chain level, on the environment and salmon welfare and health.

9 Use of thermolicer as a sea lice control measure involves high equipment costs to the farm. It has overall a strong positive impact on the marine environment through reduced need for licenced veterinary medicines, however the equipment involved has a high carbon footprint. The short term impact on salmon welfare from using hydrolicers is strongly negative as this is a stressful method involving significant risks, however as any other measure of control, as effective in controlling sea lice, it may have a positive long term impact on salmon welfare. While effective in controlling for sea lice, the method has a negative damaging impact on the overall health of salmon (exacerbating underlying conditions through increased stress and high mortality) and the health and welfare of cleaner fish, if used on farm. The negative health and welfare effects may transfer to the processing stage and the method has overall negative effects at the retail/consumption end of the supply chain through mostly public perceptions. Depending on the information available to the public, perceptions may focus on reduced use of medicines with its subsequent environmental effects, however they are mostly negative due to direct impact on salmon health and welfare. 

10 The use of freshwater as a sea lice management measure involves a high cost to the farm and has mixed environmental and welfare impacts depending on management of the method e.g. it can be challenging to maintain water quality for the whole duration of the measure, and this may represent a moderate risk to salmon welfare. It is overall effective in controlling sea lice, particularly for free living or recently attached lice, however management of control i.e. duration has a direct influence on efficacy and subsequently overall salmon health. The impact on overall health will be either positive or negative depending on underlying conditions. The method has positive effects on processing and retail stages with strong positive impact on consumers perceptions. 

11 Use of breeding and genetics to improve salmon resistance to sea lice has strong positive effects on salmon health and welfare, the environment and supply chain from production to processing. Selecting for a specific trait i.e. resistance to sea lice may compromise others. Due to the general lack of public knowledge and confusion generated on genetically modified organisms, production of sea lice resistant salmon may meet with negative perceptions of consumers and thus marketing/retail may be negatively affected by use of this control method. 

12 Use of functional feeds to control for sea lice has positive impacts on salmon health and welfare, it is cost-effective and these effects are transferred throughout the supply chain. There may be negative impacts on the marine environment, e.g. through waste. 

13 Use of healthy fish as a sea lice control measure has strong positive impacts on supply chain from production to retail, salmon health and welfare and the environment. 

14 While there may be a financial and potentially environmental cost to producing smolts either in freshwater or closed systems, this method is overall cost efficient through reduced duration of the saltwater cycle by producing larger smolts and overall higher productivity. It has a positive effect on the environment and salmon health and welfare due to reduced need for intervention measures (licenced veterinary medicines or physical removal measures) and if timing of cycle is managed to reduce wild-farm interactions. The positive impacts are transferred to the demand end of the supply chain. There is an overlap between this and 'larger smolts' control measure however we have not blended them into one as there are other ways to reduce cycle length e.g. at the end of the saltwater cycle through earlier harvest.  

15 The use of a more favourable stocking time as a sea lice control measure has positive effects on the environment and salmon welfare. No specific effects were mentioned at production stage, however it has positive effects on processing and further on retail and consumers.   

16 Use of site location as a sea lice control measure has positive effects on the supply chain, the overall salmon health and welfare, and the environment, resonates well with consumers perceptions and thus positively affects retail. However it may involve high equipment and production costs in offshore or high velocity sites. 

The linkages between the causes and effects of current sea lice control measures and identified incentives for improved control are presented in the causal loop diagram (CLD^[5]) (Figure 10). 

Participatory analysis identified potential incentives for further improving control of sea lice on farm, many of these are already taken into account in the Scottish salmon sector. These include: 

• better balancing of science-based evidence and precautionary principle based policies (health, environment, welfare)
• public sector driven positive incentives such as subsidised access to technology
• research on consumers’ willingness to pay for sustainably farmed salmon
• media campaigns and education to the public on implications of disease control in aquaculture
• market based incentives (price differentiation through labelling re sustainable disease control)
• market based incentives (traceability)
• development of health monitoring/preventative technologies
• development of delicing technologies from product/flesh at packing
• research on salmon welfare linked to sea lice control
• research on cleaner fish welfare linked to sea lice control
• media campaigns to maintain/improve industry image to the public
• private driven stick type incentives such as higher environmental/welfare standards required under processor/retail contracts
• research on efficacy of disease control
• improved collective action to sea lice control along supply chain

The causal relationships between causes and effects of sea lice control, effects of sea lice control and incentives for improved control, incentives for control and effects of improved control can be followed in the CLD diagram (Figure 10). An example of a causal loop is presented in Figure 11 Balancing loop. 

The example depicts the effect of developing health monitoring technologies combined with subsidised access to the technology on sea lice control on farm and subsequently on salmon health and welfare, and public perceptions. The loop is balancing with the system converging on a target i.e. improved salmon health and welfare through reduced use of suboptimal measures of sea lice control. 

Unlike this, the use of incentives such as development of delicing technologies at later stages e.g. packing/processing as opposed to sea lice control at source may create a reinforcing loop (and potentially leading to a vicious cycle) as it creates the possibility of reducing sea lice count and maintaining quantity and quality required by processors by means other than improved sea lice control at source. 

The effects on health and welfare are mixed. The decision to delay a sea lice management measure when close to harvest will be a mix of the observed effect of the lice load on the animals at that time (i.e. salmon can take a minimal lice load without affecting appetite or behaviour etc.) and the potential for having additional stress and mortalities as a result of any sea lice management measures. The business decisions follow an even more complex set of factors e.g. when adding the commercial recognition that the fish, when close to harvest, are at maximum size and maximum cost to the business.