Crustaceans show responses consistent with signs of pain and distress [1–5]. They also have the cognitive capacity to remember and learn to avoid unpleasant stimuli [6–8]. The RSPCA thinks that crustaceans that can feel pain and suffering should be treated humanely when they are caught, handled, transported, stored, and killed. This goes for all crabs, crayfish, lobsters, Moreton Bay bugs, prawns, shrimp, and yabbies, as well as other decapod crustaceans. It doesn’t matter if the animal is cooked or eaten raw (sashimi). Electrical stunning/killing is effective and humane.
The RSPCA recommends that live crustaceans are not made available for purchase by the public. Instead, they should be humanely killed by trained and competent personnel before purchase.
Shrimp are one of the most popular seafood options worldwide. In 2020 alone, around 440 billion farmed shrimp were killed for food production globally. But have you ever wondered how these small crustaceans are actually killed before ending up on your dinner plate? The slaughter of shrimp involves some controversial methods that have raised concerns around ethics and animal welfare. This article will provide an in-depth look at the most common techniques used to kill shrimp in the seafood industry.
An Overview of Shrimp Slaughter Methods
There are several ways in which shrimp are killed on an industrial scale for human consumption. These include:
- Splitting/Spiking
- Chilling
- Boiling
- Gassing
- Drowning
- Using chemicals
- Electrocution
The choice of slaughter method depends on factors like efficiency cost and ideas around ethics. However, all techniques ultimately cause the death of the animal.
Shrimp have a decentralized nervous system unlike vertebrates which have distinct central neural structures. So destroying one part of their body does not kill them instantly. This raises questions around whether certain killing techniques cause pain or distress.
Splitting and Spiking
One of the most common slaughter methods is splitting or spiking. This involves driving a spike through the shrimp’s head and body to destroy the neural tissues and organs A specialized mechanical tool is used to perform splitting efficiently on an industrial scale
The shrimp are impaled on the spikes and may still display reflex reactions even after the spiking due to their decentralized nervous system. This has led to debates around whether splitting and spiking causes unnecessary suffering. The industry maintains it is a humane slaughter method.
Chilling
Chilling is another prevalent shrimp slaughter technique. The shrimps are plunged into ice slurry or very cold water, dropping their body temperature so rapidly that tissues freeze. This cold shock paralyzes the shrimp and leads to death.
Proponents state that chilling causes a swift, painless death. But some argue that the sudden extreme temperature change is inhumane. From an industrial perspective, chilling is an efficient slaughter method.
Boiling
Simply boiling shrimp in hot water is a common practice, especially for small-scale kitchen preparation. The shrimps are dropped live into boiling water, which cooks them. The high temperature denatures proteins and kills the animals.
Boiling can kill shrimp humanely if the water temperature is high enough. But there are concerns that slow heating may gradually cook the animal alive, causing unnecessary pain. Some chefs prefer to stab or split shrimp before boiling to ensure a swift death.
Gassing
Gassing with carbon dioxide is a slaughter method sometimes used on an industrial scale. Shrimp are placed in a sealed chamber and exposed to high concentrations of CO2 gas which renders them unconscious and ultimately kills them.
Proponents argue that CO2 gassing is fast, humane and does not affect meat quality. But there are debates around whether it causes distress to the shrimps before they lose consciousness. There are also worker safety issues involved in handling the gas.
Drowning
Drowning is a controversial old slaughter practice where shrimps are simply placed in freshwater, leading to eventual death by osmotic shock. They are unable to tolerate the sudden drop in salinity.
This method takes a long time, sometimes hours before the shrimp finally die. Many consider it an inhumane practice that should not be used today given more efficient and faster options available. There are campaigns to stop drowning of shrimp.
Chemicals
Certain chemicals like chlorine solutions have historically been used to kill shrimp. The shrimps are immersed in chlorinated water which leads to eventual death, but this process can take time.
Use of chemicals raises concerns around residue retention and impact on meat quality. Most operations avoid this today due to the availability of faster mechanical and physical slaughter methods.
Electrocution
Passing an electric current through water to electrocute shrimp is an instant killing method sometimes utilized. The electric shock stuns the nervous system leading to death.
Electrocution is considered humane if sufficient current is used to kill the shrimp immediately. But getting the parameters exactly right can prove technically challenging. There are also chances of pre-stun shocks if the setup is improper.
The Debate Around Shrimp Slaughter
There is ongoing debate around which methods of shrimp slaughter are truly humane and ethical. Some practices clearly cause more distress and suffering than others. However, there are issues with making definitive conclusions.
The main problem is the lack of scientific consensus around whether shrimps actually feel pain or are conscious in a manner comparable to humans. Their physiology is very different. More research is needed to accurately determine their capacity for suffering.
However, the principle of precaution suggests that potentially painful techniques should be avoided till clarity emerges. There are also ethical arguments around avoiding all slaughter of animals for food, though this remains a niche view currently.
In conclusion, killing shrimp for the seafood industry involves some controversial practices. But there is scope for improving slaughter methods and making them more humane as our scientific understanding evolves. As consumers, being aware of how our food is sourced and advocating against potentially unethical techniques can potentially drive positive change.
Skills and experience required
Humane killing requires skills and experience. Those competent to humanely kill crustaceans know how to:
- Handle and care for live crustaceans in the right way to keep them from suffering and stress.
- apply the method of stunning to induce insensibility
- recognise signs of insensibility
- recognise signs of stress
- apply the method of killing
- apply a back-up stunning and/or killing method
- operate and maintain any equipment involved in the killing process.
The goal of stunning is to make sure the crustacean is unconscious and can’t feel any pain, suffering, or distress before it is killed.
A specialist piece of equipment and the right electrical stunning settings for each species can effectively and humanely stun (within one second) decapod crustaceans (e.g. g. , crabs, crayfish, lobsters, prawns/shrimps) [5, 9].
Only purpose-built electrical stunning equipment (e. g. , the ‘Crustastun’ for lobsters, crabs, and crayfish) should be used, and in accordance with the manufacturer’s instructions. Failure to adequately electrically stun may have serious welfare consequences, including a high rate of autotomy (i. e. , where the animal casts off of limbs or other body parts) [10].
If an animal is stunned with electricity, it must be killed humanely, unless the shock is kept on until the animal is dead.
Signs of insensibility and therefore effective stunning, vary from species to species but generally include [10]:
- no resistance to handling—for example, the belly or tail is easy to move, and the outside parts of the mouth can be moved without any trouble.
- no control of limb movement
- no eye reactions when tapping on the shell
- no reaction when touching around the mouth parts.
Signs of stress include [10]:
- thrashing
- autotomy (casting off of limbs or other body parts).
Following stunning, the unconscious animal must be immediately humanely killed. The RSPCA says that an animal is killed humanely when it is either killed right away or made unconscious until it dies, without pain, suffering, or distress (see Policy G1 Humane killing).
For large decapod crustaceans (e.g., crabs and lobsters), acceptable methods are [5, 9]:
- electrical stunning followed by ‘spiking’ of crabs only
- Only lobsters and other similar decapod crustaceans can be shocked with electricity and then “split.”
- electrical stunning followed by boiling.
Spiking is suitable for stunned (i. e. , unconscious) crabs. Crabs have two main nerve centres. One is located at the front of the animal, under a shallow depression. The other one is near the back of the animal and might have a small hole over it (Figures 1 and 2). Crabs can be killed by rapid destruction (i. e. , “double spiking”) of both nerve centers by sticking a sharp spike through both ganglia from the crab’s underside (e.g. g. , a thick, pointed pithing instrument, an awl, or a sharp-pointed knife).
Lobsters should not be spiked because they have a long chain of nerve centers that can’t be quickly damaged by piercing.
Splitting is suitable for pre-stunned lobsters and similarly shaped species. Lobsters have a chain of nerve centres running down their central length (ventral longitudinal midline) (Figure 3). The nerve centers are all below the longitudinal midline on the underside of the animal. The first nerve center, the supraoesophageal ganglion, is at the very end of the nerve chain and can only be reached through the head.
When you split someone, you quickly cut through the middle of their head, chest, and abdomen with a big, sharp knife. Cutting must occur along the longitudinal midline (lengthways) to destroy all the nerve centres (Figure 4).
Stunning and killing methods requiring further research
Anaesthetic agents (e. g. , AQUI-S clove oil) are not included as acceptable methods for the humane killing of crustaceans. Studies have not been able to tell the difference between anesthesia (and insensibility) and paralysis, and more studies are needed to figure out how it works [5]. There is no anaesthetic compound currently registered in Australia for use for the purpose of humanely killing crustaceans.
how Japanese kill shrimp to eat
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