Fish welfare at slaughter Flashcards
The HAS – humane slaughter association specialises in?
The welfare of food animals, specifically during:
- transport
- marketing
- slaughter for human consumption
- killing for disease control or other welfare reasons, e.g. injury
Define humane
To cause the least amount of suffering
Why is animal welfare important?
- Scientific research
- Ethical/moral reasons
- Legislation
- EFSA reports, OIE, NGOs, codes of practice, producer groups
- Meat quality
- Retailer demands
- Public perception and customer acceptance/ satisfaction
- Human health and safety: stressed animals can behave uncontrollably and can cause injury to themselves and handlers
Describe the potential for fish to experience fear and pain
- Nociceptors detect heat, toxins and pressure – head, lips, gill covers
- Neurones convey nociceptive signals to brain
- Behavioural evidence
What are some external examples of carcass damage that indicate animal welfare and meat quality
- Eye damage
- Bruising
- Cuts
- Scale loss
- Net marks
What are some internal examples of carcass damage that indicate animal welfare and meat quality
- Early rigor
- Gaping: holes in the fillet, reduced yield
- Flesh texture
- Flesh colour: appears opaque and whiter
- Haemorrhages
- Blood splash/spots
What are some examples of potential stressors for fish during slaughter and related operations?
- Decreased oxygen
- Rising stocking density
- Food withdrawal
- Ineffective stunning and killing
- Removal from water
- Human presence
- Increased light intensity
- Abrasions
What is the aim of humane killing?
The aim of humane slaughter is to make an animal unaware of its surroundings and unable to feel fear or pain (insensible). This can be achieved if one can cause an animal to become unconscious. This is the intention with “stunning”.
For stunning to be humane what must occur?
Animals must remain stunned until death occurs
Not all stunning methods reliably result in death, how can death be ensured?
Non-fatal stunning must be quickly followed by a killing method, e.g. bleeding. This will prevent an animal recovering from a stun, regaining consciousness and the ability to feel fear and pain.
Describe dry stunning
Being removed from water is a major stressor for fish
Require less power – more electrical power to the fishes brain to stun it
Stun parameter selection depends on which factors?
Species, size, stress levels, temperature, water conductivity, number of fishes in the stun tank, orientation of the fish
What are the indicators of an effective electrical stun in fish?
- Fish swimming as normal before application
- Electric current applied → fish becomes rigid
- Loss of balance, may turn upside down in the water
- No rhythmic movement of opercula (gill covers)
- Absence of eye-roll reflex – are the eyes moving as you move the fish? Are the eyes fixed on the horizon?
- Small involuntary muscular twitches, tail may flutter
- No reaction to tail pinch
Describe the Vestibulo-ocular (eye-roll) reflex test for fish following stunning
- Negative eye roll = unconscious
- Positive eye roll = conscious/recovery
Describe exsanguination (bleeding) after stunning fish
- The process of killing an animal by stopping the supply of oxygen to the brain, through loss of blood
- After checking a stun has been effective, cut the animal immediately
- It is necessary to sever all of the gill arches on at least one side of the head, and preferably both sides
- Bleeding should be rapid, profuse and complete
What is the maximum stun to stick time for fish?
10-15 seconds
How can you check for, and prevent recovery even after cutting?
- Employ a back-up slaughter man to stun any mis-stunned fishes
- Transport fishes to a processing plant in solid ice, rather than ice-water slurry, to reduce the risk of fish regaining consciousness – reduces oxygenated water from washing over the gills
- Immediately after gill cutting, to prevent recovery, hypoxia-resistant species may need to be immersed in ice or chilled deoxygenated water (e.g. saturated with CO2 or nitrogen)
How does percussive stunning work?
- Severe, mechanical or manual, impact to the head
- Disrupts normal electrical activity within brain
- Physical damage if bolt knocker head fractures skull, particularly if bolt or skull fragments penetrate brain tissue – helps to reduce the risk of recovery of consciousness
Which slaughter methods cause concern for fish welfare when used without prior stunning?
- Asphyxia in air or ice: cheap, minimal expertise, very negative experience, can take some species a long time to die
- Hypothermia in ice-water slurry
- Gill cut or pull
- Immersion in water containing high concs of carbon dioxide
- Decapitation
- Salt or ammonia baths
- Inappropriate electrical parameters, e.g. that cause conscious paralysis
