Fish do feel pain
Fish have a nervous system and pain receptors like all other animals. Twenty-five years ago the RSPCA’s Medway Report (1981) concluded that fish are capable of suffering and feeling pain, yet the slaughter regulations which offer some level of protection to other farmed animals still do not apply to fish. A 2004 review evaluated the scientific evidence for the existence of sentience (the ability to feel or perceive subjectively) in farmed fish. It was concluded that pain, fear and psychological stress are likely to be experienced by fish. This implies, like other vertebrates, that fish have the capacity to suffer and that welfare consideration for farmed fish in this instance should be taken into account(6).
Fish have nociceptors (receptors that preferentially respond to noxious stimuli) and their forebrain & midbrain areas are active during noxious stimuli. Rainbow trout, for example, display adverse behavioural and physiological responses during potentially painful procedures that are similar to responses shown by higher vertebrates (7). Studies of shellfish have shown that they too are also capable of experiencing pain. One particular study in 2009 looked at investigating whether decapods, in this case the hermit crab, feel pain. The overall results obtained were consistent with the idea of pain in these animals(8).
The Welfare of Animals (Slaughter or Killing) Regulations 1995 legislation states that; (4.1) No person engaged in the movement, lairaging, restraint, stunning, slaughter or killing of animals shall— (a) cause any avoidable excitement, pain or suffering to any animal; or (b) permit any animal to sustain any avoidable excitement, pain or suffering. There are also specific rules on handling, stunning, slaughter or killing of animals(2). The basic act of removing a fish from water causes severe pain and distress, even before the killing begins.
Farmed fish may not be endangered but they are caged in cramped and unhealthy conditions, causing great stress and rendering them susceptible to disease. Farmed salmon, for example, can grow up to 2.5 feet long and yet are only given space equivalent to a bathtub of water. Sea lice pose a huge problem to the welfare of farmed fish. They feed on their blood and underlying tissues causing skin and scale loss. Lice damage around the head can be so severe that the bone of the living fishes’ skulls can be exposed, a condition referred to as the "death crown"(9). Aquaculture relies on the artificial breeding of fish. Females have their eggs extracted on several occasions under anaesthetic. Most of them are then eventually killed as their recovery process from the anaesthetic is considered to be uneconomic. Males are milked several times for their semen before slaughter(10). Farmed fish are normally starved for about 7 to 10 days before slaughter.
There are a number of methods used to kill farmed fish (mostly salmon and trout), these include;
Carbon dioxide stunning
The fish are placed in a bath saturated with carbon dioxide. This environment causes changes to behaviour, with fish being observed to shake their heads and tails vigorously trying to escape(11). Movement ceases after 30 seconds, but sensibility may not be lost for 4 to 9 minutes. Bleeding after CO2 stunning is essential to avoid fish recovering. If fish are removed early from the stunning tank, they are likely to have their gills cut when immobile but still conscious(12).
Suffocation on air / ice
The fish may be taken out of the water and allowed to die through suffocation in air. Alternatively, fish are removed from water onto ice. This method prolongs suffering as the cooling effect of the ice can lengthen the time to unconsciousness with fish aware of what is happening to them 15 minutes after being taken out of water. The Farm Animal Welfare Council (FAWC) recommended 10 years ago that this method should be prohibited(9). Fish farmers have admitted that ‘letting tens of millions of fish die of suffocation each year as unacceptable(12).
Gill Cutting and Percussive Stunning
Gill cutting without prior stunning has shown that certain responses of fish are not immediately lost and vigorous movements occurred. Percussive stunning involves the fish being hit on the head with a rapidly moving, manually applied club. When sufficient force is applied the concussion can be irrecoverable, however in practice the stun is often not immediate and fish are hit more than once(13).
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