Most countries have legislation covering the welfare of mammals and birds, however few have detailed legislation applying to fish, although this is rapidly changing.
Farmed fish welfare at slaughter is of special importance as this has potential to cause significant, stress, pain and suffering. A slaughter method is considered to be humane when unconsciousness is induced immediately by stunning and is irrecoverable. The slaughter of wild fish represents an area of growing concern because most fisheries do not consider slaughter of their fish as a step in the process, but more a by-product of the capture and chilling process, with fish dying of anoxia before or during chilling without bleeding. This is slowly changing as fishermen and retailers gain knowledge in the benefits of applying modern welfare and quality practices.
There is a wide variety of slaughter techniques used between and within farmed fish species with some methods very clearly superior to others, and performance is easily measurable from KPIs like rigor time, gaping, bloodspotting, yield and shelf life. Common methods include the following, with some combined:
- Exposure to air
- Ice slurry
- Carbon dioxide
- Ike Jime (Spiking)
- Percussive stunning
In general, the slaughter methods that are slower result in more movement by the fish that is generally perceived as being aversive. The only movement seen using the faster methods, (i.e. percussive stunning and spiking) occurs during pre-slaughter handling. While some believe that there is a developing consensus that fish feel pain, and respond to this pain with aversive movements, this is yet to be decisively proven, say Smart Aqua. However, there is a strong perception of concern from people viewing slaughter operations when they observe fish exhibiting aversive behaviour. The perception of fish retailers reflect this attitude and many have set standards for suppliers that focus on minimising stress and suffering. In the UK, the RSPCA have developed Welfare Standards for Farmed Atlantic Salmon enabling salmon farmers to receive Freedom Food accreditation, and the Freedom Food logo on their products identifies them as conforming to these standards.
These standards state that: The method of killing used must rapidly, and without pain and distress, render the fish insensible, until death supervenes. An efficiently applied percussive blow is the only permitted killing method at present. This method is highly effective when applied properly. Humane mechanical percussive devices are now available commercially and these must be used in preference to a manual percussive blow for slaughter (except emergency killing).
Mechanised percussive stunning and bleeding is creeping into certain wild cod fishery operations and the fishermen and buyers are amazed at the quality difference. It is only a matter of time before it becomes commonplace with wild fisheries catching cod, haddock, saithe, salmon, etc. In the meantime, the early players are reaping the rewards for being industry leading.
Substantial progress has been made in the development of commercially viable pneumatic stunning machines and these are now widely used by the farmed salmon industry, and are also present in cod, yellowtail, basa, channel catfish, trout, and barramundi slaughter operations. Fish can now be directed to machines without manual handling, in water, up to the point of stun. The quality and welfare benefits of this technology, and in many cases logistical improvements, have attracted interest from many farmed and wild fishery operations, and this method of slaughter shows most promise at present to develop and spread over a range of fish species and locations.