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Environmental Impact Assessment of Salmon Farm

Paper Type: Free Essay Subject: Environmental Studies
Wordcount: 3521 words Published: 23rd Sep 2019

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Environmental Impact Assessment of Salmon Farm

Non-technical summary

Table of Contents

1)     Background ……………………………………………………………………………………………..2

2)     Operations ………………………………………………………………………………………………3

3)      Receptors ………………………………………………………………………………………………..4

a)     Sea Lice Wild Fish

b)     Other Aquaculture

c)      Waste and Pollution

d)     Maritime Traffic

e)     Marine Mammals

f)       Birds

g)      Tourism

h)      Receptor Severity Chart.

4)     Mitigations ………………………………………………………………………………………….. 7

a)     Sea Lice

b)     Wild Fish

c)      Waste and Pollution

d)     Maritime Traffic

e)     Marine Mammals

f)       Birds

g)      Receptor Survey Chart

5)     Consultations ……………………………………………………………………………………….9



The aim of this report is to assess the potential impacts of the proposed salmon farm by SAMS Fine Salmon Ltd. This salmon farm will be located to the south-west of Shuna (56o35.028’ N 5o24.352’ W) (red) and will run concurrently with the preexisting farm (blue) located to the north-east ran by the same company (locations shown in figure 1 below). This new fish farm will share shore facilities such as docks and processing facilities already in place and licensed by the Scottish Environmental Protection Agency (SEPA). Due to this the impact of this new farm is smaller than a normal application.


The Isle of Shuna is sparsely populated and is only accessible to boat. It is located in Loch Linnhe which runs from Fort William to the Sound of Mull. It is a well circulated loch with a rich biodiversity and good water quality. The proposed farm will be on the more exposed side of the island and will be anchored in depths of roughly 90 meters. There will be 10 cages in total arranged 5×2. A single cage will be 100 meters in circumference and 20 meters deep. This allows for a maximum weight of 800 tonnes to be harvested at the site. It is important to note that the stock density will not exceed 15kg/m3


SEPA (the governing body) have issued a CAR (Controlled Activities Regulation) licence to this Atlantic Salmon (Salmo salar) fish farm based of a report of projected impact to the water quality of the area. This projection is generate using AutoDEPOMOD, a simulation programme produced specifically for this licence. The site will then be inspected up to 3 times a year and the sea bed will be monitored once every two years by SEPA. This will include monitoring on the edge of the nets and 100 meters away to monitor for medicine levels. Nets must be checked regularly for damages to prevent escapees. This is vitally important before crowding the fish for harvesting. Any damage must be recorded and fixed. If the licence is breached, then SEPA can revoke the licence and take legal action.

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The farm will operate on a 22-month cycle excluding the hatching and raising of fish to smolts. The raising stage is excluded as this will be carried out at pre-established sites which currently serve the existing site. Smolts will be added to the cage to be fed to adulthood before being harvested. This stage will take 20 months and will require daily feeding and periodic treatments. Harvesting will take up to a week and nests will be fully inspected before corralling the fish to ensure there is no space for escape. The cages will then remain empty for two months following this. The reason for them being empty is to allow any disease or parasites to die out to stop an infestation occurring. Six jobs will be generated by this project and all staff will be correctly trained including risk assessments, standard operation protocols and health and safety. This training will be validated both internally and externally.

Cages will be anchored to the seabed and will remain under tension for the full lifetime of the farm. It will also include several safety measures to ensure operation runs smoothly. The first of these are at the surface level and are LED lights for visibility at night and a bird to reduce the nuisance of birds. Underwater, acoustic deterrent devices (ADD), dead fish cages and false bottom nets will be added. ADD’s and false bottom nets are used as non-lethal methods of handling marine mammals. The ADD’s scare off the mammals using sound while false bottom nets stop them for getting too close to the stock. The dead fish cages collect any fish that die during the growing period and must be emptied daily. If the fish remain in the bottom net, they will attract predators to the farm.

The fish will be assessed by a veterinarian on a predetermined schedule to measure any health problems or sea lice damage. If fish are found to be injured, they will be tagged and monitored to ensure recovery. If fish are found to be too gravely injured or recovering slowly, they will be humanely euthanised and the corpses burned. Any damage or deaths will be correctly recorded which will be available to authorities on request.


Sea lice

Sea lice is a major problem for fish farms as it is very easy for them to spread throughout cages if not treated. Sea lice are a parasitic organism that attach and feed off the host, in this case the salmon. The sea lice leave lesions on the salmon which have a range of severity depending on the fish. These sea lice can also lead to the spread of disease as the fish can become stressed to the louse. This stress can cause a weaker immune response to disease as well as decreasing growth rates. Sea lice will thrive in a fish farm as the high concentration of fish is ideal for their planktonic stage as it very likely they can attach onto a host and feed off it to grow into an adult.

Wild Fish

Wild fish can be put at risk by fish farms for numerous reasons. The first of which is sea lice. As the lice thrive in the farm, juveniles can be released into the open water. This increases the risk of the wild fish picking up a parasite and suffering the issues as fish in the farm. Young wild fish are even more susceptible to damage from these lice as they have thinner skin than the adults making it much easier for the louse to feed off them. This is of particular importance to this site as there are numerous river mouths within the area of the suggested farm. The closest of these is to the south-east of the island as shown in figure 1. Wild fish can also be affected by escapees. Farmed fish have been selectively bred similarly to cattle. The problem with this is that if a fish escapes and reproduces with a wild fish, then genetic diversity can be lost. Farm fish can also be carriers for diseases that may not affect them but may be deadly to wild fish due to genetic differences.

Other Aquaculture

Other aquaculture can raise serious issues to the area if not properly managed. If farms are too close together then they may amplify issues caused by one farm. The use of chemical treatments may have minimal impact on the environment however if another is added then it may become too much. The same rational can be applied to waste and runoff from a farm. This is a very big issue if one farm is downstream from another as this will cause a huge rise in nutrients available in the water and can cause algal blooms or eutrophication (over saturation of nutrients). Close proximity can also lead to the easy spread of sea lice or disease from one farm to another leading to large economic loss due to lost stock. The operational farm is situated on the other side of the island to the proposed farm and is in a different channel therefore while this issue is important to consider, it is very unlikely to occur here.

Waste and Pollution

Waste is the most well know issue with fish farms. It is an unavoidable part of the growing period. Faecal matter and undigested feed make up the majority of it and cause large problems. Faecal matter can be processed by benthic organisms such as mussels living in the area however if the volume is too much it can smother and kill the organisms. Organic nitrogen is a large threat to the environment underneath the cages as it leads to eutrophication. Due to the influx of nutrients, ecosystems can collapse in these areas and can take many years to recover after the farm is no longer in use. Chemicals used for medication can also be problematic to wild organisms if not properly managed. Chemicals can be bioaccumulated by organisms leading to harmful consequences to them, or to predators that eat them. While fish have been bred to grow quicker and process feed better causing there to be less nitrogen waste, it is still a large factor that must be considered.

Maritime Traffic

Boats that sail in the area will be at risk of collision with the newly placed cages. This will be particularly dangerous at night or weather with reduced visibility. Boats crashing into the cages will not only damage the vessel but could also rupture the net leading to the release of stock into the wild. As previously stated this would be detrimental to the wild populations.

Marine Mammals

As figure 3 shows, there is an area of conservation the south of the site (blue stripped zone). This area is protected due to its importance to seal populations that feed and raise young here.  Seals pose a threat to farms as they can not only steal fish from cages but can also damage cages in doing so leading to a large loss of stock. Porpoise have also been reported in the area however are less common. Porpoises pose the same threats as seals to the farm. Seals raise pups on land and use flat shorelines to do this. The shoreline closest to the farm has suitable conditions for this. This may lead to the displacement and loss of raising grounds for seal pups. 


Birds in the area, specifically sea birds can quickly become pests to fish farms as they provide easy food with little energy expenditure. Young fish freshly released into the cages are susceptible to being stolen by large birds and carried away, however this is not the only issues caused. Birds will try to steal feed pumped to the fish. If this becomes an issue, financial loss will occur as there is less feed making it to the fish while more birds will flock to the new food source.


The proposed site is in a tourist hotspot for Scotland. The natural beauty and Castle Stalker attract people from all around the world. As a result, the coast line is a National scenic area coastal site. The implication of this means that the site cannot detract from the natural beauty of the area more than is absolutely necessary. Due to the distance to the other farm and the lack of need for additional structures this factor is negligible as there will only be the 10 cages which are low to the surface of the water. Additionally, there will be very few boats at the farm at any given point.

Receptorseverity chart




Overall risk

Sea Lice

Wild fish

Other Aquaculture

Waste and pollution

Maritime Traffic

Marine mammals



Table 1: Receptor severity chart

Very low to no potential impact

Moderate potential impact

Serious potential impact


Sea lice

 In order to stop sea lice becoming a problem for the proposed site, a monitoring system will be put in place as well as a treatment plan. For the monitoring plan, a veterinary surgeon will oversee the assessment of the stock for sea lice by trained staff once a week. Stock will be randomly selected, and the extent of the damage recorded. As there are 10 cages at this site, 50 fish should be randomly selected and assessed. The sex and life stage of the louse should also be recorded as this provides valuable information as to the extent of the issue. If a fish is found to be too badly affected it must be removed and humanely euthanised.  All euthanised fish must be recorded. For medical treatments, in-feed treatments will be used only when lice are identified as a problem and will be used as soon as possible. The frequency and dosage will be decided by the veterinary surgeon. Using medication in this manor allows for very little to accumulate on the sea bed. In cases of large infestations, fish should be transferred to a well boat and given larger dosage of the in-feed medication. This reduces contamination to the environment drastically as the well boat is a controlled system. This method can also be used for the treatment of other diseases requiring restricted medication.

Wild fish

As previously mentioned nets must be regularly checked to ensure that there is no escape for the fish. Nets must also remain properly secured and tight to minimise opportunity of escape. Similarly, nets must be designed to withstand storms or any harsh weather conditions to ensure they function as intended without fail.

Waste and pollution

The projected module submitted with the CAR licence will be used as the expected impact of the farm. Samples will be taken by divers in different locations as previously stated. If the impact is worse than expected, then the farm will have to readjust its operation to reduce the environmental impact or risk legal implications from SEPA.

Maritime traffic

To avoid collisions, lights should be attached to the top of the cages to ensure there is a level of visibility to their location even is harsh conditions. In addition to this, warning buoys should be anchored at a safe distance from the farm in case the lights are not visible. 

Marine Mammals

The most effective way of deterring these organisms from trying to eat stock is to use an acoustic deterrent device (ADD). This device emits noise at a level that deters mammals that get too close to the farm. In the event this does not work, tensioned nets or false bottom nets can be used to make it harder to get to the fish. Dead fish baskets should also be emptied daily to stop them becoming an attraction to the mammals. In addition to this the basket should have seal blinds to stop access to the basket between emptying. While licences can be given to shoot seals if they become too much of a problem this is very much a last resort. Given the location of the farm, the licence would also only allow for a very small number to be shot. If this number was exceeded there would be very serious legal repercussions.


Birds can be easily restricted by installing bird nets onto the top of cages. These nets stop the birds getting to the fish or the feed that is being used to feed them. Additionally, licences can be granted to shoot birds however, like seals it is very restricted and only a designated number can be shot. All shootings must be recorded.


Local authorities were invited to raise any concerns to the proposed site so that they could be also considered. The groups that responded are shown below in the table as well as their opinion.



Scottish Natural Heritage

This organisation was concerned as to the effect the farm would have on the seals and cetaceans nearby. They expressed that shooting should be used as a very last measure after everything else had been used. They also felt that the impact on the seabed was of concern. This was only a minor concern as similar habitat is common around this area and no rare species (such as flame shells) would be negatively affected by the farm.

Marine Scotland (Science)

Concerns arose from two major areas, sea lice and external environment impact. While sea lice will always be a concern, sufficient treatment plans as well as the low reported numbers from the nearby farm dispelled these concerns. For the impact on the external environment, it was agreed that the simulation would provide an adequate base to estimate the impact while monitoring schemes would provide enough data so that any issues could be caught and dealt with early.

Arygll and District fishing board

This organisation objected to the farm as they felt it put natural stocks at too much risk. The presence of a second farm in close proximity to many river estuaries was too great of risk to wild fish in the area.

Council’s marine and coastal manger

The possibility of eutrophication was raised as this would leave the area in bad condition after the farm was removed. Benthic organisms were once again raised as they support ecosystems around the area. The proximity to the other sea farm was also an issue as it takes away from the scenic beauty of this are of coast. This was dispelled however as the distance between the two is quite large and it would be very hard to see both from one view point.

Council’s biodiversity officer

The use of ADD’s in proximity to the protected area caused concern and it was suggested they should operate on license basis from Scottish Natural Heritage. The possible impact of wild fish also caused concern as it is important that they must not be affected. The benthic organisms were also of concern however their abundance in the surrounding area made this of least concern

Image refences

Figure 1: Screenshot form google maps and from Iboating (http://fishing-app.gpsnauticalcharts.com/i-boating-fishing-web-app/fishing-marine-charts-navigation.html?title=Loch%20Linnhe%20Southern%20Part%20boating%20app&#13.71/56.5828/-5.4006)

Figure 3: A screenshot from Marine Scotland interactive map (https://marinescotland.atkinsgeospatial.com/nmpi/)


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