The numbers of crustaceans who are farmed worldwide every year are estimated at 21 to 40 billion crayfishes, crabs, and lobsters and 150 to 380 billion shrimps and prawns.
Scientific evidence suggests that it’s highly likely that decapod crustaceans can feel pain and suffer. They have nociceptors (pain receptors), central nervous systems, and opioid (painkiller) receptors. They show physiological responses to pain, such as a change in heart rate, and behavioral responses, like prolonged rubbing of areas that are in pain. In one study, glass prawns groomed their antennae and rubbed them on the side of the tank significantly more after an acidic substance was applied, and those given painkillers did not groom them as much as those who did not receive them.
Pain influences their decision making: crabs will trade a valuable commodity (a dark shelter) for a bright shock-free tank. In one study, crabs who had been shocked in a shell evacuated and moved away from the shell for 15 minutes, even though they are extremely vulnerable and typically quickly move into any shell that is available. Some crabs got out of the shell and investigated it for a longer period of time than usual, suggesting that they were attempting to locate and remove what caused them pain.
Crustaceans show an excellent ability to gather, manipulate, and use information from multiple sources. Because they can learn and remember complex information, they are capable of suffering. Some may argue that we do not have conclusive evidence that crustaceans feel pain. But given the evidence we do have, we can conclude that we farm, transport, and kill them in ways that likely cause them immense suffering.
In the US, crustaceans are not protected by the federal Humane Methods of Slaughter Act, which requires that some non-human animals be rendered insensible to pain before being slaughtered, or the Animal Welfare Act, which sets some standards for non-human animals who are exhibited for entertainment or used in research. They are offered some legal protections in Norway, Switzerland, Austria, New Zealand, some Australian territories, and some regions in Germany and Italy.
Transport, Storage, Slaughter
Crustaceans are often farmed, transported, stored, and sold alive, where they suffer from stress, injuries, overheating, and dehydration. Some are mutilated on farms: eyestalk ablation is the removal of one or both eyestalks from a crustacean that is routinely practiced on female shrimps and prawns in almost every shrimp maturation or reproduction facility in the world. This is done as it increases the crustaceans’ total egg production and increases the percentage of females who will reproduce. The eyestalk is removed by pinching, slicing with a razor blade, or cauterization.
Crustaceans are often sold alive. When for sale at restaurants and grocery stores, lobsters are often kept in crowded bright tanks – but they like dark conditions and are solitary animals.
During commercial slaughter, crustaceans often have their limbs, head, or tail removed when still alive, are boiled or chilled alive, or put into fresh water to kill them via osmotic shock. One study estimated that a crab who is boiled alive may remain conscious for 2.5 to 3 minutes. Crabs and lobsters violently thrash, whip their tails, try to escape, convulse, and lose their limbs (a symptom of stress) when they are boiled alive. Crabs who are chilled alive likely suffer tremendously – they stay conscious for 30 to 40 minutes, and usually lose their legs before they’re unconscious. When chilled, they may only become paralyzed, not anesthetized, so they are alive and sensing pain when they are boiled. Crabs who are put into fresh water to die via osmotic shock suffer for very long, at least 30 minutes, but up to 3 to 5 hours.
Motivational trade-offs and potential pain experience in hermit crabs by M. Appel & R. Elwood in Applied Animal Behaviour Science Vol. 119, No. 1-2 (120-124) (2009).
Nociception or pain in a decapod crustacean? by S. Barr, JTA Dick, P. Laming, & R. Elwood in Animal Behaviour Vol. 75 (745-751) (2008).
Shock avoidance by discrimination learning in the shore crab (Carcinus maenas) is consistent with a key criterion for pain by R. Elwood & B. Magee in the Journal of Experimental Biology Vol. 216 (353-358) (2013).
Stunning and killing of edible crabs (Cancer pagurus) by B. Roth & S. Øines in Animal Welfare Vol. 19 No. 3 (287-294) (2010).
Trade-offs between predator avoidance and electric shock avoidance in hermit crabs demonstrate a non-reflexive response to noxious stimuli consistent with prediction of pain by B. Magee & R. Elwood in Behavioural Processes Vol. 130 (31-35) (2016).
Welfare during killing of crabs, lobsters and crayfish, Fish Count (2019).