Crustacean Welfare

It is well documented that crustaceans have a negative response to noxious stimuli. The question is, does this response involve pain perception or is it simply a reflex? Scientists commissioned by the European Food Safety Authority (EFSA) concluded that based on the current literature, decapod crustaceans (crabs, lobsters, crayfish, prawns etc.) can feel pain and as such their welfare must be managed accordingly. New Zealand, Norway and Switzerland have already changed their legislation to include crustaceans in their animal welfare act. This legislation stipulates that the slaughter of crustaceans must be humane and must only be done on unconscious animals.

Pain Perception

Morphology & Physiology

Unlike vertebrate animals, crustaceans don’t have a single complex brain structure; however, they do have nociceptors (pain receptors) and a central nervous system (CNS). The CNS comprises of a double ventral nerve cord linking a series of ganglia, with the largest ganglia found at the head and functioning as the brain. Their nociceptors are in cuticular extensions of the shell, called sensilla, these relay information about noxious stimuli to the CNS. Despite the reduced complexity of the crustacean brain and central nervous system compared to vertebrates, they have all the necessary components for pain perception. Studies have shown that the anatomical structures in crustaceans perform the same function as different structures in vertebrates, for example, crustaceans have well developed visual ability despite having a completely different eye structure. There is no indication that the simplified CNS of crustaceans precludes their ability to feel fear and pain.

There is physiological evidence for pain perception in crabs, lobsters and prawns. These crustaceans produce the stress hormone Crustacean Hyperglycaemic Hormone (CHH), which functions similarly to cortisol in vertebrates, in response to painful and stressful stimuli. They also show decreased responses to noxious stimuli when treated with analgesics or opioids – handling lobster anaesthetised with AQUI-S^® reduced mortality and limb casting, and administration of opioids reduced the sensitivity of crabs to electric shock.

Behaviour

Crustaceans respond to noxious stimuli with adverse behaviours including trying to escape the stressor, thrashing and autotomy (limb loss). Crustaceans have also shown learned behaviours which is indicative of a certain level of intelligence and sentience. Examples of learned behaviour include:

A hermit crab choosing a new shell and deciding whether to fight for it or not.
Lobster learning that a light signal is associated with an electric shock and avoiding it.
Shrimp responding to acid applied to their antennae by grooming the specific area, but not when water is applied in the same manner. This indicates a pain response rather than merely a reflex.
Hermit crabs trading off the protection of their shell against getting an electric shock.

Note: these studies were not performed or endorsed by AQUI-S New Zealand Ltd. in any way. We are committed to good animal welfare. More information can be found at fishcount.org.uk.

How Can We Reduce Pain & Improve Welfare?

In acknowledging that crustaceans are sentient beings with the capacity to experience pain, fear and suffering, we must consider their welfare on a similar level to other animals.
AQUI-S^® is a convenient and effective way to reduce pain relating to husbandry practices. Unlike many common fish sedatives, AQUI-S^® is a true anaesthetic in that it has analgesic (pain reducing) properties as well as reducing activity and the physiological stress response. This 3-fold benefit means greatly improved welfare as AQUI-S^® not only reduces the animals short-term experience of pain and stress, but also the potential handling damages due to avoidance behaviour, struggling and attempting to escape. The long-term detrimental effects of the physiological stress response are also reduced, resulting in strong and healthy animals after live transport.

Not only is humane slaughter necessary from a welfare perspective, but it also provides many quality advantages including:

• Reduced autotomy – improved sale price
• Easier handling – less risk of limb loss, improved sale price
• Reduction in physiological stress response – meat is sweeter and more tender

Learn how AQUI-S^® can reduce stress during transport of crustaceans.

Humane Slaughter

Welfare regulations stipulate that crustaceans must be unconscious prior to slaughter. There are only two approved humane stunning methods – AQUI-S^® anaesthetic and electrical stunning.

Electrical Stunning

Electrical stunning is the most humane stunning method for crabs, as it can cause immediate unconsciousness. The animals should, however, be killed immediately after stunning to prevent recovery of consciousness (e.g. by boiling or spiking). Only purpose-built electrical stunning equipment should be used, in accordance with the manufacturer’s instructions. There may be serious welfare concerns, including a high rate of autotomy, if an inadequate electrical current is applied. Electrical stunning equipment can be bulky and may not be a practical option for some commercial operators and recreational fishers.

AQUI-S^® Anaesthetic

Studies have shown that crab and lobster can be slaughtered humanely using AQUI-S^®. The animals do not show aversive behaviour or autotomy, despite the extended time to death. Measures of stress hormones, lactate and muscle pH in AQUI-S^® euthanised animals also indicate that the process is not stressful. AQUI-S^® is the only food-grade anaesthetic with zero with-holding period, allowing it to be used for harvesting fish and crustacea.
Visit our members section or contact us directly to access the crustacean sedation protocol.

Chilling - Not Recommended

Chilling in ice slurry or air is recommended by some welfare groups as a method to immobilise and render animals unconscious prior to being slaughtered, however it is not universally approved. Chilling is slow and likely imparts limited metabolic advantage for the animal, with evidence suggesting that the animals are not anaesthetised but merely paralysed, preventing them from reacting to negative stimuli. Lobster exposed to cold shock show negative behavioural changes including autotomy, and chilling can even prolong the killing process during boiling, with the animal being sensible to heat for up to 3 minutes and autotomy frequently observed. Sedation with AQUI-S^® prior to cold shock is a common industry practice. This improves both the welfare of the animal, and the quality of the product.

Mechanical Slaughter

Both AQUI-S^® anaesthetic and electrical stunning, when applied appropriately, can be used alone for killing. More often, stunning followed by immediate slaughter of the animal is recommended to prevent it regaining consciousness. Stunning followed by mechanical killing is generally considered the most humane slaughter technique. Stunning followed by boiling is also common practise when a whole product is desired.

The only acceptable method to mechanically kill crustaceans is by destroying all nerve centres. This involves splitting (lobster) and spiking (crab).

Splitting

After stunning, the lobster is split – cut in half lengthwise, through the head, thorax and abdomen with a large, sharp knife. This destroys the nerve centres which run down the length of the body. This process takes 10 -15 seconds when performed by a skilled person. Splitting is considered the most human method of killing lobster when stunning methods are not available. You can learn more about the RSCPA approved splitting method here.

Figure 2: Lobster showing line of cut for splitting

Spiking

Crabs have two main nerve centres, which can be destroyed by spiking with an iki jime tool or sharp knife, from the underside of the crab. Both nerve centres must be destroyed in quick succession. Again, this process takes 10 -15 seconds when performed by a skilled person, and is considered the most human method of killing crabs when stunning methods are not available. You can learn more about the RSCPA approved spiking method here.

Figure 3: Underside of crab showing points for spiking