 All of the terminology is quite vague, leaving it largely up to the farmer as to what constitutes ‘suitable quality’. This could be easily improved by integrating the RSPCA’s standards for water quality, as well as possibly providing additional advice on what actions to take to improve different parameters in different systems.
Scale: Medium. All ~50 million Scottish salmon per year are affected by water quality during all stages of their lives. The current state of water quality on Scottish salmon farms is unclear.
Severity: High. Water quality is one of the most important aspects of finfish welfare.
Strength of current CoGP guidance: Weak. Guidance is very vague, leaving interpretation largely up to the farmer.
The barren interior of salmon pens differs from the natural environment that wild salmon would be living in. Provision of structures and objects that attempt to create an environment on a farm that more closely mirrors the challenges and variety experienced by wild animals is often known as ‘environmental enrichment’.
Current research on the impact of enrichment on salmon welfare, and which kinds of enrichment are best, is still limited. One study found that the provision of shelter (shredded material) decreased aggression between salmon smolts, as well as levels of stress hormones following disturbance. However, the same study found that the provision of shelter reduced the growth rate of fish at high densities (Rosengren et al. 2017). Another study used shredded plastic bags and plastic tubes as enrichment for juvenile salmon and found that in the barren tanks, fish showed higher cortisol levels and more fin damage than fish reared in the enriched environment (Näslund et al. 2013). However, the current lack of literature means that more research is needed to determine how enrichment could be best used to improve farmed salmon welfare.
No mention of environmental enrichment for salmon was found in the current industry CoGP.
Scale: Large. All ~50 million Scottish salmon per year could potentially benefit from environmental enrichment.
Severity: Unclear. Further research needs to be conducted to fully understand the extent of the benefits of enrichment for salmon.
Strength of current CoGP guidance: No guidance exists. The Code does not mention environmental enrichment for salmon.
Handling and transport can be two of the most acutely stressful events for farmed fish. There is significant evidence that handling, crowding, and grading cause stress responses in fish (P. J. Ashley 2006). As well as causing high levels of stress, handling can also result in physical damage, such as the removal of scales. Handling of farmed salmon occurs at multiple different stages in their lives, including during vaccination, grading (a process to separate fish into groups according to their size), disease/lice treatment, and transport.
Live fish should only be removed from water and handled when absolutely necessary.
If fish are handled, adequate support should be given to the body - live fish should never be held by the gills or tail only.
Different species have different tolerance to being out of water, but the time out of water should never be so long as to produce signs of distress.
In all cases, fish should be kept wet, except where blotting dry is essential to avoid contamination of gametes during stripping.
A written procedure for crowding of fish should be prepared.
The frequency and duration of crowding should be kept to the minimum.
Farmers should monitor fish behaviour during crowding and take action if fish show signs of stress or damage.
Farmers should remove and cull any moribund or damaged fish.
Farmers should ensure that enclosure nets and screens are kept clean in order to avoid water quality problems during crowding.
Farmers should monitor oxygen levels during crowding and take corrective action if levels fall below a critical point for that species.
The avoidance of injury and stress to fish should be a primary consideration when deciding on the method of grading to be employed.
Grading equipment should be designed and maintained so as not to damage the fish.
Crowding of fish before collection for transport should be kept to a minimum.
Fish should be transported in such a way that possible adverse effects on their welfare are minimised.
Biosecurity and fish welfare should be considered before transporting fish populations.
For transport, oxygen monitoring should be carried out with sufficiently frequent monitoring intervals to ensure that oxygen levels remain within safe limits at all times.
Supplementary oxygen or air supply should be sufficient to last longer than the anticipated length of the journey, including helicopter transport.
Excessive or rapid changes in water temperature or pH in transport tanks should be avoided.
Any fish that die during transportation should be separated from live fish as soon as possible after arrival and the cause of death determined by a competent person.
It is positive that the CoGP frequently refers to the welfare of fish in these sections. However, the guidance is generally very weak. For example, although crowding should be kept to a ‘minimum’, no specific time durations are given as limits. Fish must also not be kept out of water ‘so long as to produce signs of distress’, but again no time limit is given. Stronger guidance providing these limits would mean that farmers could be held accountable. Standards from the RSPCA could be adopted to achieve this. For example, RSPCA standards require that fish must not be crowded for more than two hours and that a conscious fish must not be out of water for more than 15 seconds (RSPCA 2021).
Scale: Large. All ~50 million Scottish salmon each year are affected by handling and transport processes.
Severity: Moderate. Handling and transport can cause severe acute stress that may take several days to recover from (and could also have long-term effects). However, the suffering caused by these procedures is probably of shorter duration than some other welfare issues in salmon farming, such as sea lice or stocking density.
Strength of current CoGP guidance: Weak. The Code provides very general welfare guidance on protecting fish welfare and is severely weakened by the lack of concrete limits.
95% of salmon in Scotland are slaughtered using percussive stunning followed by bleeding, which is thought to be the most humane method. The remaining 5% are killed using electrical stunning before bleeding (SSPO n.d.).
In order to minimise suffering, a stun should be instantaneous and unconsciousness should remain until death (i.e. the fish must not become conscious while it is bleeding out). The use of a stunning machine in a facility is therefore not enough on its own to guarantee that welfare is protected. For suffering to be minimised, the stunning and killing process must be closely monitored to ensure that unconsciousness is maintained throughout and that appropriate steps are taken in any instance where a fish is seen to be conscious.
Concerningly, a recent Animal Equality investigation of a slaughter facility operated by The Scottish Salmon Company (Animal Equality 2021) found that many salmon experienced highly stressful and painful deaths despite the use of stunning machines.
This problem has been observed in other fish species where lab-proven humane slaughter methods are difficult to implement in practice. A study on the pre-slaughter stunning of common carp in German slaughterhouses illustrates how prevalent unsuccessful stunning can be. The study found that across the three slaughterhouses that were monitored, percussive stunning resulted in 46.2% of fish displaying behavioural indicators of consciousness at the time of slaughter (Retter et al. 2018). Caution is required in considering these findings in the Scottish salmon context. Practices may differ between Scotland and Germany, while separate studies on the efficacy of percussive studies for carp and salmon indicate carp may be more difficult to stun than salmon (Lambooija et al. 2010; Robb et al. 2000; Lambooij et al. 2007). However, it demonstrates the importance of identifying the optimal parameters for stunning machines, as well as effectively monitoring fish for signs of consciousness.
ii) made available on request.
And a specified maximum length of time between the stunning and bleeding of fish.
Scale: Medium It is difficult to establish what percentage of Scottish salmon currently suffer unnecessarily at slaughter. However, all of the industry uses a stun before slaughter.
Severity: Moderate. Slaughter while conscious causes severe acute pain and stress. Poor harvesting procedures may also cause short-term stress. In comparison to some other welfare issues, the duration of potential suffering caused by harvesting and slaughter is relatively short.
Strength of current CoGP guidance: Very weak. The Code provides extremely minimal guidance on how to perform these technically complicated procedures without compromising welfare.
Salmon are carnivorous. The composition of their diet varies throughout their life stages, with younger freshwater salmon eating more insects while adult salmon subsist on other marine animals. In aquaculture, salmon feed is carefully formulated for each life stage by varying protein, lipid, and nutrient content (“FAO: Feed Production” n.d.). This provides the salmon with the nutrients they need to grow and develop into the next stage. The ingredient composition used to achieve these goals has changed in recent decades. One recent study has produced estimates of the ingredients used in salmon feed in Norway (Aas, Ytrestøyl, and Åsgård 2019). In the figure below you can see the general trend, with the percentage of marine oil and protein sources reducing dramatically over the past 30 years. Although this data is from Norwegian salmon farms we expect this to generalise to the Scottish context.
The main benefit of this reduction in the use of marine ingredients in salmon feed is the lower demand for other, mostly wild-caught, fish. The most straightforward benefit this has to wild fish is sparing them the experience of capture and slaughter. As there are no protections for wild-caught fish, this is usually a very stressful process culminating in death by asphyxiation - a process that can take more than 30 minutes for some species.  However