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.
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.
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.